Nucleating actin for invasion
See discussions, stats, and author profiles for this publication at: https://https://www.sodocs.net/doc/637812616.html,/publication/49840947 Nucleating actin for invasion
Article in Nature Reviews Cancer · March 2011
DOI: 10.1038/nrc3003 · Source: PubMed
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3 authors, including:
Robert Grosse
Philipps University of Marburg
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Tumour progression is a multistep process involving aberrations in various signalling pathways that result in a survival advantage for transformed cells. In most cases the clinical problem of tumorigenesis is not the primary tumour, as it can be surgically removed, but its malignant transformation and metastatic spread, which is the main cause of death in cancer patients 1. Therefore, understanding the signalling mechanisms underlying the metastatic cascade of cancer is crucial to identifying new treatment options for anticancer therapy that target invasion and metastasis.
Dissemination of cancer cells from the primary tumour, invasion into the local surrounding tissue, intra-vasation into blood or lymphatic vessels, extravasation and the final colonization at distant organs represent the different steps of the metastatic cascade and involve a multitude of changes in cellular behaviour 2. One of the first, and most crucial, steps of the metastatic cascade is the acquisition of invasive capabilities, which is accompa-nied by various changes in gene expression and function; for example, the loss of epithelial and gain of mesen-chymal markers 3. In almost all steps of metastatic spread, the reorganization and reassembly of the actin cytoskel-eton is absolutely necessary for invasive cell behaviour, such as the dissolution of cell–cell contacts, protrusion formation, force generation to overcome physical resist-ance of three-dimensional tissue networks and motility. Depending on the tumour type and the crosstalk with the tumour microenvironment, cancer cells use different invasion modes, which can be roughly separated into amoeboid, mesenchymal and collective mode of inva-sion 4. The amoeboid mode of invasion is defined by an amorphous or round cell shape that can be accompanied by dynamic, non-apoptotic plasma membrane blebbing 5. This motility mode uses high contractility to squeeze through the extracellular matrix (ECM) and can occur
independently of extracellular proteolysis 6, although metalloproteinase activity may still be required for amoeboid migration through a dense crosslinked colla-gen matrix 7. In the mesenchymal invasion mode, cancer cells adopt an elongated morphology, and migration is accomplished by dissolution of the ECM at the cell front, actin-driven leading edge protrusion, the formation of new contacts at the cell front and rear retraction 8. The collective mode of invasion is characterized by invading cell strands or sheets that show intact cell–cell adhesions and requires proteolytic degradation of the ECM 4.
Actin assembly inside cells is directly regulated and enhanced by various proteins that mediate de novo nucle-ation of filaments (FIG. 1), which provide the driving force in the formation of protrusive membrane structures, such as non-apoptotic membrane blebs, invadopodia or pseudopodia (FIG. 2). For a detailed description of actin nucleation factors and their regulation, we refer to recent excellent reviews 9,10. In contrast to the chemotherapeutic agents that target microtubules, which have been used in anticancer treatments for decades, drugs specifically tar-geting actin have not yet been reported. However, many proteins affecting actin cytoskeletal dynamics, such as Rho GTPases 11,12, cofilin and LIM kinase 13, are thought to exert key functions in tumorigenesis and metastasis. This Review focuses on the function of the mechanisti-cally different actin nucleation factors that affect cancer cell motility and metastasis, and highlights new inhibi-tors of actin assembly proteins as future targets for anticancer or anti-invasive therapy.
The substrate actin and its turnover
Monomeric actin is a globular 42 kDa ATP–ADP-binding protein (G-actin) that is abundantly expressed in all eukary-otic cells. In vitro , ATP-actin rapidly and almost completely polymerizes into structurally polarized filaments (F-actin),
*Institute of Pharmacology, University of Marburg, Karl-von-Frisch-Str. 1,
35032 Marburg, Germany. ?
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor NY 11724, USA.
Correspondence to R.G.
e-mail: Robert.Grosse@staff.uni-marburg.de
doi:10.1038/nrc3003Published online 10 February 2011
Structurally polarized filaments
Actin filaments are structurally polarized owing to uniform orientation of asymmetric subunits. As a result, polarized filaments have two ends, a plus and a minus end, which differ in their biochemical properties.
Nucleating actin for invasion
Alexander Nürnberg*, Thomas Kitzing ? and Robert Grosse*
Abstract | The invasion of cancer cells into the surrounding tissue is a prerequisite and initial step in metastasis, which is the leading cause of death from cancer. Invasive cell migration requires the formation of various structures, such as invadopodia and pseudopodia, which require actin assembly that is regulated by specialized actin nucleation factors. There is a large variety of different actin nucleators in human cells, such as formins, spire and
Arp2/3?regulating proteins, and the list is likely to grow. Studies of the mechanisms of various actin nucleation factors that are involved in cancer cell function may ultimately provide new treatments for invasive and metastatic disease.
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e Reviews | Cancer
which are composed of two twisted helices 14,15
. The onset of the reaction is slow owing to the considerable insta-bility of actin oligomers; once an unstable actin trimer, known as the nucleus, is formed, actin polymerization proceeds quickly at the fast-growing plus end, and more slowly at the minus end 14,16 (FIG.1). It is the incorpora-tion of new actin subunits at the plus end that provides mechanical force for the generation of membrane protru-sions in migrating cells. Therefore, actin dynamics must be tightly controlled and regulated in vivo 16. Capping proteins can associate with the plus or minus end, thus
preventing filament elongation or inhibiting depolym-erization, respectively 17,18. Monomer binding proteins control the availability of subunits for filament assem-bly, whereas severing proteins, such as members of the destrin (also known as ADF) and cofilin family, regulate disassembly 18 (FIG.1). The kinetic barrier that prevents spontaneous actin polymerization provides the cell with a flexible instrument for spatial and temporal control of the de novo actin filament assembly.
In response to extracellular signals, actin nucleators can rapidly and efficiently initiate new actin filaments by direct nucleation of actin 9,10. These proteins are tar-gets of multiple intracellular signalling cascades. Most importantly, members of the Rho-GTPase family, such as CDC42, Rac and Rho (reviewed in ReF . 19), are crucial regulators of actin turnover and coordinate the control of actin nucleating activities.
Formin homology proteins in invasive disease Formins are the largest group of directly regulated Rho-GTPase effectors. Mammalian formins are represented by 15 different family members 20,21. They are defined by the presence of the highly conserved formin homology 2 (FH2) domain, which is often necessary and sufficient to promote actin assembly 22,23. The preceding FH1 domain can bind profilin–actin to accelerate the elongation of actin filaments at the plus end 24. The activity of formins is tightly regulated through auto-inhibitory interactions between amino-terminal and carboxy-terminal regions often referred to as the Diaphanous inhibitory domain (DID) and Diaphanous autoregulatory domain (DAD), respectively (TABLe 1). In general, activated Rho-GTPases help to relieve auto-inhibition through specific interac-tion with the GTPase-binding domain (GBD) of form-ins. Once activated, formins form dimers and their FH2 domains can promote the processive incorporation of actin monomers into the plus end of the growing actin filament 25.
As formins are among the most potent actin nuclea-tors they have emerged as potentially valuable candidates for anti-invasive drug targets. sequencing analysis of can-cer genomes from patients with glioblastoma or pancre-atic cancer 26,27 identified missense mutations in several formins, including formin-like 2 (FMnL2; also known as FHOD2) and FMnL3, but their functional consequences have not yet been investigated. Although little is known about the physiological relevance of formin proteins in humans (TABLe 2), several recent reports have described their involvement in cancer cell motility and tumour pro-gression. The first mammalian Diaphanous-related form-ins to be identified, such as diaphanous homologue 1 (Diap1; also known as mDia1), have been implicated in malignant disease through their functional associa-tion with the proto-oncogenic sRC tyrosine kinases 28,29. Human diaphanous homologue 1 (DIAPH1) was shown to be required for invasive cancer cell migration through three-dimensional matrices 30, as well as for invado-podia formation in motile breast tumour cells 31 (FIG. 2). Furthermore, DIAPH1 mediates the pro-migratory phenotype downstream of RHOA that is associated with the loss or the downregulation of the tumour suppressor
Figure 1 | actin nucleation and turnover. Spontaneous actin polymerization is
hampered by the unfavourable kinetics of actin oligomer formation (shown by the thick and thin arrows). Once an actin nucleus is formed, the association of monomers proceeds quickly, with one end, designated the plus end, growing much faster than the other, the minus end. ATPase activity of actin strongly increases on incorporation into the filament. Spontaneous hydrolysis of ATP and the dissociation of phosphate destabilize the filament and render it more susceptible to the action of severing proteins, such as
members of the actin depolymerizing factor (ADF)/cofilin family. Dissociated ADP?actin undergoes nucleotide exchange, which is strongly facilitated by profilin. Profilin binds monomeric actin and controls filament assembly by interacting with formins. Capping proteins, such as gelsolin, can associate with the growing plus end and inhibit filament elongation.
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Capping proteins Ubiquitously expressed proteins that are able to bind to either the plus or the minus end of actin filaments, thereby preventing both association and dissociation of actin monomers.
Profilin–actin
A complex of ATP-actin and profilin, an abundantly expressed actin
monomer-binding protein. Profilin–actin complexes can bind to formins and ena/VASP proteins, thereby delivering actin monomers for incorporation into a growing actin filament.deleted in liver cancer 1 (DLC1)32. Additional evidence
for a role of DIAPH1 in tumour cell motility and inva-
dopodia function stems from recent in vivo findings
of Diap1-deficient, sRC-transformed cells that fail to
form tumours or invade surrounding tissues in nude
mice33. The authors conclude that DIAPH1 may have
a pivotal role in the disease progression of various
cancers overexpressing the SRC oncogene.
In addition to the formation of tumour cell inva-
dopodia, DIAPH1 is also necessary for bleb-associated
cancer cell invasion and amoeboid leukocyte migra-
tion. In this case, DIAPH1 mediates a positive feedback
mechanism through the leukaemia-associated Rho
guanine nucleotide exchange factor (GEF) LARG that
stimulates RHOA–ROCK signalling30,34. Other mem-
bers of the formin protein family, such as FH1, FH2
domain-containing protein 1 (FHOD1) and FMnL1,
are also involved in plasma membrane blebbing, but the
underlying mechanisms remain to be investigated35,36.
By contrast, deletion of DIAPH3 or small interfering
RnA (siRnA)-mediated knock down of DIAPH3, the
human homologue of mDia2, induces potent plasma
membrane blebbing in prostate cancer cells that cor-
relates with oncogenic signalling and metastatic dis-
ease37. Interestingly, the inhibitory role of this formin
for cancer cell bleb formation seems to be conserved
in mouse Diap3(ReF. 38), suggesting that this formin
might function as a tumour suppressor rather than
as a tumour promoter. nevertheless, how and which
formins control plasma membrane blebbing and
bleb dynamics, and whether specific actin nucleation
activities are necessary for certain steps of this process,
remain to be shown.
More evidence for a role of formins in malignant
disease comes from findings that FMnL1 is strongly
overexpressed in T cell non-Hodgkin’s lymphoma39.
Consistent with this, FMnL1 was found to be upregu-
lated in different lymphatic, lymphoblastic and acute
myeloid leukaemias40. Of note, allosteric T cells specific
for a human leukocyte antigen (HLA)-A2-presented
FMnL1 antigenic peptide displayed potent antitumour
effects against various cancer cell types40. Therefore, this
may present a promising concept for targeting formins
for the development of adoptive therapies in cancer. Figure 2 | Typical protrusive structures in invasive cancer cells. Cancer cell invasive phenotypes involve the formation of typical protrusive structures, such as plasma membrane blebs, invadopodia or pseudopodia, which are dependent on the nucleation and assembly of filamentous actin. Non?apoptotic blebs are highly dynamic protrusions in which the plasma membrane bulks out owing to increased hydrostatic pressure on regions of weak cortical actin131. The initial, protruding bleb is devoid of detectable F?actin, which becomes repolymerized during bleb retraction by unknown actin nucleation factors. Ezrin is recruited into the growing bleb, and formins seem to have a role in bleb formation through mechanisms that still need to be defined132. Invadopodia are actin?rich cellular protrusions that are tailored for the degradation of the extracellular matrix. The formation of invadopodia relies on N?WASP–Arp2/3?driven actin assembly (FIG. 4) and requires cortactin for invadopodia initiation and stabilization. Pseudopodia of cancer cells are lamellipodia?like structures and depend on the polymerization and assembly of actin by the WAVE–Arp2/3 nucleation machinery.
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In addition, the closely related FMnL2 was found to be upregulated in patient samples of metastatic color-ectal cancer41, which suggests that FMnL2 might be a useful marker in this disease. In a functional screen for the role of all human formins on cancer cell invasive-ness, FMnL2 was identified as a factor involved in the amoeboid mode of invasion42. In order to identify bind-ing partners between Rho proteins and formins, a coun-ter screen against the human Rho proteins on invasive behaviour was carried out. By this approach, the metas-tasis gene RHOC was found to interact with and regulate FMnL2 (ReF. 42), which points towards a possible role of this Rho–formin module in invasive disease. It will be interesting to elucidate whether FMnL2, like RHOC, is required for metastasis in vivo.
Formins in transcription. One important consequence of actin nucleation and assembly by formins and other actin nucleators is the compartmental and transcrip-tional regulation of the serum response factor (sRF) co-activator MAL through dynamic interactions with actin monomers43(FIG. 3). Release of actin from MAL stimulates sRF-dependent gene expression, which pro-motes cancer cell invasion and metastasis in mice44. Consistently, a novel transcriptional regulator sup-pressor of cancer cell invasion (sCAI) was identified through association with DIAPH1, and it controls β1 integrin expression in motile tumour cells through the regulation of nuclear MAL45. Thus, actin assembly fac-tors, such as formins, may cooperate with transcrip-tional events and have a synergistic effect on invasive cell migration.The Arp2/3 complex and metastasis
The actin-related protein 2 (ARP2; encoded by ACTR2) and ARP3 complex (known as the Arp2/3 complex) was the first actin nucleation factor to be identified. The complex has little nucleation activity and requires the aid of nucleation-promoting factors (nPFs) to initiate a new actin filament10(FIG. 4). In a widely used model46–48, the Arp2/3 complex binds to an existing actin fila-ment and together with an nPF initiates a new filament branch. Another recent model suggests the recruitment of Arp2/3 by a membrane-bound nPF and subsequent filament initiation at the plasma membrane without the contribution of the existing filamentous actin49,50. Actin elongation factors from the enabled/vasodilator-stimulated phosphoprotein (Ena/v AsP) family of proteins, as well as formins, cooperate with nPFs in the assembly of actin filament networks9, as Arp2/3 does not possess elonga-tion activity and remains associated with the minus end of the nucleated filament46,51.
The Arp2/3 complex.In cancer cells, actin nucleation through the Arp2/3 complex is essential for mesenchymal invasion, as the formation of both lamellipodia52 and inva-dopodia53 depends on Arp2/3. The expression of Arp2/3 is strongly increased in a rat model of a metastatic primary breast tumour and correlates with the increased chemo-taxis of these metastatic cancer cells54. similarly, invasive cells collected from mouse primary breast tumours in an in vivo invasion assay show an increased expression of Arp2/3 (ReFS 55,56). Therefore, increased Arp2/3 expression seems to promote tumour invasion in vivo. These findings were further supported by an analysis of
junction?mediating regulatory protein; NTA,N?terminal acidic; NTD, N?terminal domain; PIP
3, phosphatidylinositol?(3,4,5)?trisphosphate; PPP, poly?proline domain;
SH3, SRC?kinase homology 3 domain; SHD, SCAR homology domain; WCA element, G?actin binding WH2?domains (W), connector (C) and acidic (A) domains;
WH1, WASP homology domain 1.
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Association of actin assembly factors with human cancer Array OS, overall survival; OSCC, oral squamous cell carcinoma. *Protein detection method. ?RNA detection method.
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Choroidal
A middle layer of the eye surface located between sclera and retina.human cancers that revealed strong expression of ARP2
and ARP3 in both stromal and tumour cells of colorectal
tumour samples, with ARP2- and ARP3-positive stromal
cells enriched at the invasion front57. Thus, this finding
implicates a role for actin nucleators in the formation of
an invasive tumour microenvironment. Moreover, the
frequency of ARP2 or ARP3 expression in these samples
positively correlates with atypia and invasion depth of the
tumour57. In addition, an association between increased
expression of Arp2/3 complex subunit 1A (ARPC1A) and
ARPC1B and a genomic amplification of the 7q21-q22
chromosomal region, which frequently occurs in pancre-
atic cancers, has recently been reported58. Accordingly,
silencing of ARPC1A in pancreatic cancer cells contain-
ing 7q21-q22 amplification leads to a dramatic decrease
in cell invasion58.
An unexpected finding has come from the study of
choroidal malignant melanoma cells, showing that high
expression of ARPC1B correlates with resistance to
radiotherapy59. The nature of this association remains
unclear, but it might involve a novel role of ARPC1B
in the regulation of cell cycle progression through an
interaction with Aurora A kinase60.
Nucleation-promoting factors.nPFs provide a major
signalling input to the Arp2/3 complex10. Most nPFs
contain the conserved wCA element (TABLe 1), which
is sufficient to initiate Arp2/3-dependent actin nuclea-
tion in vitro (FIG. 4). Currently, eight wCA-containing
nPFs have been identified in mammals10, and the most
important nPFs are the ubiquitously expressed neural
wiskott–Aldrich syndrome protein (n-w AsP; encoded
by WASL) and the wAsP family verprolin homology
proteins (w AvE1–3; also known as w AsF1–3). Another
type of nPF is represented by cortactin, which was ini-
tially identified as a phosphorylation target of sRC61. As
cortactin lacks the wCA domain (TABLe 1), it is by itself
a weak activator of the Arp2/3 complex10. nucleation-
promoting activity of cortactin in vivo probably involves
cooperation with n-w AsP62–64. Alternatively, cortactin
might stabilize actin networks that are generated by the
Arp2/3 complex50,65. n-w AsP and cortactin are essen-
tial for the formation of invadopodia53,66–71, whereas
lamelli p odia formation depends on w AvE2 (ReF. 52,72).
Although neither n-wAsP nor cortactin is required
for lamelli p odia formation53,72, they both contribute to
the sensing of chemotactic stimuli at the leading edge66.
Moreover, cortactin controls lamellipodium persistence,
and consequently overexpression of cortactin results
in the increased migration and invasion of human
fibrosarcoma cells72.
Matrix remodelling is essential for mesenchymal
invasion of cancer cells and there is good evidence
that nPFs are critically involved in this process. Matrix
degradation activity of invading cancer cells requires
wAvE1, wAvE3 and cortactin, which were shown
to regulate the secretion of matrix metalloproteinases
(MMPs)53,67,73–75. Interestingly, w AvE3-dependent MMP
secretion is mediated by the tumorigenic MAPK path-
way74. Accordingly, downregulation of wAvE1 and
w AvE3 expression strongly attenuates invasion of pros-
tate cancer cells76,77. Furthermore, depletion of w AvE3
was shown to suppress lung metastasis in a mouse model
of breast cancer78, and knock down of w AvE2 reduced
the metastasis of melanoma cells79. These studies suggest
that upregulation of nPFs can increase tumour invasion
and metastatic spread in vivo.
There are several reports that provide evidence for
pathophysiological roles of nPFs in cancer progression in
humans (TABLe 2). The coexpression of w AvE2 and ARP2
or ARP3 in cancer cells was identified as a risk factor for
hepatic metastasis in colon carcinoma and as a negative
prognostic factor in breast cancer80,81. Cells coexpressing
w AvE2 and ARP2 or ARP3 are enriched at the invasive
front of these tumours. Apart from cancer cells, high
expression of w AvE2 or the Arp2/3 complex was also
detected in tumour-associated macrophages57,80,81, again
(Pol II) transcription by interaction with the PSF–NONO complex105. N?WASP also
mediates the association of hyaluronan receptor CD44 with ERBB2 and subsequent
induction of β?catenin signalling103. JMY can either activate Arp2/3 or nucleate actin on
its own. Upon DNA damage, JMY translocates to the nucleus where it regulates
p53?dependent transcription. IQGAP is a CDC42?regulated cytoskeletal adaptor protein
that can directly bind to DIAPH1 or N?WASP134. EGF, epidermal growth factor; G?actin,
monomeric actin; GPCR, G?protein coupled receptor; F?actin, filamentous actin; LPA,
lysophosphatidic acid; RTK, receptor tyrosine kinase; S1P, sphingosine?1?phosphate.
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binding
supporting the role of actin nucleators in the formation of a proinvasive and prometastatic tumour microenviron-ment. notably, in breast carcinoma, w AvE2 and ARP2 coexpression is associated with overexpression of ERBB2, but inversely correlates with the expression of oestrogen and progesterone receptors 81. In this case, roundly shaped cells were found to be enriched in high histological grade breast carcinomas, suggesting that certain highly invasive cells use an amoeboid mode of invasion 81.
A comparative analysis of wAvE1–3 expression in breast tumours showed that there is a correlation between high expression levels and poorer prognosis for all three proteins, although only high levels of wAvE2 showed significant correlation 82. Of note in this study, patients who had died from metastasis had higher expression levels of w AvE1. Furthermore, hepatic metastases from patients with colorectal cancer show a strong increase in n-w AsP expression 83, and increased n-w AsP expres-sion has also been linked with lymph node metastasis in oesophageal carcinoma 84.
Cortactin. The gene for the nPF cortactin, CTTN , is located within the 11q13 region, which is frequently amplified in tumours 85. Therefore, cortactin has been extensively studied in the context of tumour progres-sion 86,87. upregulation of cortactin was found to cor-relate with invasion, metastasis and poor prognosis in various tumours (TABLe 2). strong cortactin expression is found in invasive head and neck squamous carcinomas (HnsCCs) but not in non-invasive, lymph node-negative tumours 85,88
. similarly, cortactin is enriched at the inva-sive front of colorectal carcinoma and its lymphatic metastases 89. Consistently, cortactin expression promotes invasion and metastasis in tumour mouse models 90–92. sRC kinase-mediated tyrosine phosphorylation of cort-actin at residues 421, 466 and 482 seems to be important for its pro-metastatic effect, as a non-phosphorylatable mutant that functions as a dominant-negative protein prevents the formation of bone metastases in mice with breast cancer 93. In agreement with this idea, the dual sRC and ABL tyrosine kinase inhibitor saracatinib reduces cortactin phosphorylation and invadopodia formation in vitro , as well as invasion and lymph node metastasis in a mouse model of HnsCC 94.
A recent retrospective clinical study showed that the number of patients with cortactin-positive HnsCC who died from their disease was not significantly different from the death rate in patients with epidermal growth factor receptor (EGFR)-positive and cortactin-positive HnsCC 88. Interestingly, these data imply that patients with HnsCC overexpressing cortactin, as well as EGFR, may not respond to therapeutic strategies targeting EGFR only 88. Consistent with this, in vitro experiments showed that the sensitivity of HnsCC cells to gefitinib , an EGFR inhibitor, is markedly reduced by cortactin overexpression 95. One reason for this observation could be that cortactin was shown to prevent ligand-induced EGFR internalization 96.
Signalling properties of NPFs in metastasis. Besides
their direct action on the cytoskeleton, nPFs are impor-tant signalling molecules that operate at different lev-els of intracellular signalling cascades to modulate the invasive behaviour of cancer cells.In several types of cancer cells w AvE2 was shown to function downstream of the small Rho-GTPase Rac to promote the mesenchymal mode of invasion through inhibition of actin–myosin contractility 97,98, and n-w AsP was shown to promote amoeboid or rounded morphol-
ogy of melanoma cells through the RhoGEF DOCK10 and CDC42 activation 99. Interestingly, downregulation of w AvE3 can result in mesenchymal to amoeboid tran-sition 100, and suppression of w AvE2 and n-w AsP may lead to increased activation of RHOA with subsequent overactivation of DIAPH1 (ReF. 52). Consistent with a counteractive role for w AvE2 on formins, the w AvE2–Arp2/3 complex was demonstrated to bind and inhibit DIAPH3 (ReF . 101).
Figure 4 | Scheme of arp2/3 complex interaction with an actin nucleus. The actin?related protein 2/3 (Arp2/3) complex is a seven subunit protein complex. The ARP2 and ARP3 subunits are structurally similar to actin and form the nucleation core to initiate the growth of a new actin filament. Actin nucleation activity by the Arp2/3 complex is
intrinsically low and is activated by nucleation?promoting factors (NPFs) such as WASP family verprolin homology proteins (WAVE) or neural Wiskott–Aldrich syndrome protein (N?WASP) through the WCA domain, which binds to actin monomers as well as the Arp2/3 complex. Activation of Arp2/3 by an NPF results in the stabilization of the ARP2 and ARP3 subunits and the formation of a nucleation core. For simplicity binding of the Arp2/3 complex to F?actin is not shown.
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Although these findings indicate specific roles of nPFs in distinct modes of cancer cell migration, they also highlight a complex signalling crosstalk between different actin nucleating machineries that is likely to be variable among different types of cancer. Thus, signal-ling interactions between formin and Arp2/3-dependent systems may provide cancer cells with the necessary plasticity during invasive migration through different environments and could therefore represent a consider-able challenge in the development of successful therapies that target actin nucleation factors. To add further com-plexity to this problem, some nPFs may also have func-tions as tumour suppressors. For example, the wAvE complex component CYFIP1 (also known as sRA1) was shown to act as a tumour suppressor by promoting the adhesion of breast cancer cells, and loss of CYFIP1 leads to the disruption of epithelial cell architecture and increased tumour invasion102.
Furthermore, n-w AsP was implicated in the stimula-tion of the oncogenic β-catenin signalling pathway103,104, and was shown to directly regulate transcription by interaction with the PsF–nOnO complex105. Thus, some actin nucleation factors seem to operate in both cytoplasmic and nuclear compartments, thereby link-ing actin assembly and transcriptional activity (FIG. 3). However, whether and how these two processes are coordinated or distinctively controlled during cancer invasion remain to be unravelled.
JMY
Originally identified as a transcription cofactor involved in the p53 response, JMY can shuttle between the nucleus and the cytoplasm, were it functions as an Arp2/3 acti-vator or as an intrinsic actin nucleator106(FIG. 3). when overexpressed or localized in the cytoplasm, JMY strongly facilitates cancer cell motility and invasion, and it seems likely that both its actin nucleating activity and its ability to negatively influence cadherin expression mediate this effect107. Thus, JMY is a dual function pro-tein that may act as a tumour promoter in the cytoplasm or as a tumour suppressor in the stress-induced p53 tran-scriptional response. Interestingly, JMY over e xpression in tumour stroma has been implicated in cancer pro-gression, indicating that JMY-mediated signalling is a promising topic of cancer biology108.
Ena/VASP proteins
In mammals, the Ena/v AsP family109,110 is represented by three ubiquitously expressed proteins — v AsP, mam-malian Enabled (MEnA; also known as EnAH) and Ena v AsP-like (EvL). Ena/v AsP proteins localize at the lead-ing edge where they support the polymerization of nucle-ated actin filaments, function as anti-capping proteins111 or markedly accelerate filament elongation112. In this way, Ena/v AsP proteins can assist the Arp2/3 complex111 and collaborate with formins113. Ena/v AsP proteins are particularly important for the formation of filopodia114 and actin assembly at cell–cell contacts110,115. However, in contrast to formins, Ena/v AsP proteins probably do not nucleate actin in vivo116, although Ena/v AsP-dependent actin nucleation in vitro has been reported117.
The expression of MEnA and EvL is strongly increased in invasive tumour cells collected in vivo55,56. MEnA is known to exist in several splice variants; one of which, MEnA11a, is found in poorly invasive breast cancer cell lines, whereas two others, MEnA++ and MEnA+++ are strongly upregulated in invasive cells118. MEnA++ and MEnA+++ are shown to promote cancer cell motility, invadopodia maturation and sensitivity to EGF and, more importantly, cancer invasion and metas-tasis in vivo119. Although no data on tumour-specific expression of MEnA splice variants in humans have yet been provided, overexpression of total MEnA is observed in breast cancers and breast cancer metastases, as well as in colorectal cancer120,121(TABLe 2).
There is some evidence for the role of two other mem-bers of the Ena/v AsP family in cancer. Overexpression of EvL is shown to increase migration of MCF-7 cells in response to serum122, whereas migration of prostate cancer cells towards lysophosphatidic acid (LPA) seems to depend on the phosphorylation of v AsP by protein kinase A123.
Conclusions and perspectives
Enormous progress has been made in our understanding of actin assembly factors, their modes of action and their role in malignant disease. It seems to be only a matter of time before specific treatments using inhibition of actin regulators or nucleation factors will be added to antican-cer drugs that target microtubule dynamics. In particu-lar, the unsolved problem of invasive cell migration and metastasis is in great need of new concepts, and the large, and expanding, group of diverse and specialized actin nucleation factors seems promising for the future devel-opment of compounds that might be suitable for clini-cal applications. Indeed, it has been shown only recently that actin nucleation factors can be successfully targeted pharmacologically to inhibit distinct actin-dependent cell functions. Compounds that bind and block n-w AsP124 have been identified, as have compounds that inhibit actin nucleation activity of Arp2/3 and the formation of pro-trusive structures, such as podosomes in monocytes125. similarly, isoform-selective compounds that inhibit actin polymerization induced by DIAPH1 and DIAPH3 in vitro have been reported126. As a proof of principle, it was shown that small molecule-mediated suppression of formin127 or Arp2/3 (ReF. 128) activity can be used to inhibit cell motility. Furthermore, pharmacological inhibition of the actin bundling protein fascin129 resulted in a strong reduction of metastatic spread in mice130, demonstrating the effective targeting of actin regula-tory proteins for anticancer therapy. Certainly this is just the beginning, however, what will be needed are drugs that specifically modulate the activity of a single actin assembly factor in vivo. In addition, we still lack detailed information about the physiological expression of these proteins in human cells and tissues, not to mention in pathological situations, such as cancer and inflammation. Indeed, targeting actin nucleation factors might be useful to treat not only cancer cells but also other pro-invasive and pro-inflammatory cells such as tumour-associated macrophages or immune-modulating cells.
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1. Weigelt, B., Peterse, J. L. & van ‘t Veer, L. J. Breast
cancer metastasis: markers and models. Nature Rev.
Cancer5, 591–602 (2005).
2. Nguyen, D. X., Bos, P. D. & Massague, J. Metastasis:
from dissemination to organ-specific colonization.
Nature Rev. Cancer9, 274–284 (2009).
3. Yilmaz, M. & Christofori, G. EMT, the cytoskeleton,
and cancer cell invasion. Cancer Metastasis Rev.28,
15–33 (2009).
4. Friedl, P. & Wolf, K. Plasticity of cell migration: a
multiscale tuning model. J. Cell Biol.188, 11–19
(2010).
5. Wolf, K. et al. Compensation mechanism in tumor cell
migration: mesenchymal-amoeboid transition after
blocking of pericellular proteolysis. J. Cell Biol.160,
267–277 (2003).
6. Sahai, E. & Marshall, C. J. Differing modes of tumour
cell invasion have distinct requirements for Rho/ROCK signalling and extracellular proteolysis. Nature Cell
Biol.5, 711–719 (2003).
7. Sabeh, F., Shimizu-Hirota, R. & Weiss, S. J. Protease-
dependent versus -independent cancer cell invasion
programs: three-dimensional amoeboid movement
revisited. J. Cell Biol.185, 11–19 (2009).
8. Sanz-Moreno, V. & Marshall, C. J. The plasticity of
cytoskeletal dynamics underlying neoplastic cell
migration. Curr. Opin. Cell Biol.22, 690–696 (2010).
9. Chesarone, M. A. & Goode, B. L. Actin nucleation and
elongation factors: mechanisms and interplay. Curr.
Opin. Cell Biol.21, 28–37 (2009).
10. Campellone, K. G. & Welch, M. D. A nucleator arms
race: cellular control of actin assembly. Nature Rev.
Mol. Cell Biol.11, 237–251 (2010).
11. Ellenbroek, S. I. & Collard, J. G. Rho GTPases:
functions and association with cancer. Clin. Exp.
Metastasis24, 657–672 (2007).
12. Sahai, E. & Marshall, C. J. RHO-GTPases and cancer.
Nature Rev. Cancer2, 133–142 (2002).
13. Wang, W., Eddy, R. & Condeelis, J. The cofilin pathway
in breast cancer invasion and metastasis. Nature Rev.
Cancer7, 429–440 (2007).
14. Bugyi, B. & Carlier, M. F. Control of actin filament
treadmilling in cell motility. Annu. Rev. Biophys.39,
449–470 (2010).
15. Holmes, K. C., Popp, D., Gebhard, W. & Kabsch, W.
Atomic model of the actin filament. Nature347,
44–49 (1990).
16. Pollard, T. D. & Cooper, J. A. Actin, a central player in
cell shape and movement. Science326, 1208–1212
(2009).
17. dos Remedios, C. G. et al. Actin binding proteins:
regulation of cytoskeletal microfilaments. Physiol. Rev.
83, 433–473 (2003).
18. Le Clainche, C. & Carlier, M. F. Regulation of actin
assembly associated with protrusion and adhesion in
cell migration. Physiol. Rev.88, 489–513 (2008). 19. Heasman, S. J. & Ridley, A. J. Mammalian Rho
GTPases: new insights into their functions from in vivo
studies. Nature Rev. Mol. Cell Biol.9, 690–701 (2008).
20. Higgs, H. N. & Peterson, K. J. Phylogenetic analysis of
the formin homology 2 domain. Mol. Biol. Cell16,
1–13 (2005).
21. Baarlink, C., Brandt, D. & Grosse, R. SnapShot:
Formins. Cell142, 172, 172 e1 (2010).
22. Pruyne, D. et al. Role of formins in actin assembly:
nucleation and barbed-end association. Science297,
612–615 (2002).
23. Sagot, I., Rodal, A. A., Moseley, J., Goode, B. L. &
Pellman, D. An actin nucleation mechanism mediated
by Bni1 and Profilin. Nature Cell Biol.4, 626–631
(2002).
24. Kovar, D. R. Molecular details of formin-mediated actin
assembly. Curr. Opin. Cell Biol.18, 11–17 (2006). 25. Goode, B. L. & Eck, M. J. Mechanism and function of
formins in the control of actin assembly. Annu. Rev.
Biochem.76, 593–627 (2007).
26. Parsons, D. W. et al. An integrated genomic analysis
of human glioblastoma multiforme. Science321,
1807–1812 (2008).
27. Jones, S. et al. Core signaling pathways in human
pancreatic cancers revealed by global genomic
analyses. Science321, 1801–1806 (2008).
28. Narumiya, S., T anji, M. & Ishizaki, T. Rho signaling,
ROCK and mDia1, in transformation, metastasis and
invasion. Cancer Metastasis Rev.28, 65–76 (2009).
29. DeWard, A. D., Eisenmann, K. M., Matheson, S. F. &
Alberts, A. S. The role of formins in human disease.
Biochim. Biophys. Acta1803, 226–233 (2010). 30. Kitzing, T. M. et al. Positive feedback between Dia1,
LARG, and RhoA regulates cell morphology and
invasion. Genes Dev.21, 1478–1483 (2007).31. Lizarraga, F. et al. Diaphanous-related formins are
required for invadopodia formation and invasion of
breast tumor cells. Cancer Res.69, 2792–2800
(2009).
32. Holeiter, G. et al. Deleted in liver cancer 1 controls cell
migration through a Dia1-dependent signaling
pathway. Cancer Res.68, 8743–8751 (2008).
33. T anji, M. et al. mDia1 targets v-Src to the cell
periphery and facilitates cell transformation,
tumorigenesis, and invasion. Mol. Cell Biol.30,
4604–4615 (2010).
34. Shi, Y. et al. The mDial formin is required for
neutrophil polarization, migration, and activation of
the LARG/RhoA/ROCK signaling axis during
chemotaxis. J. Immunol.182, 3837–3845 (2009).
35. Hannemann, S. et al. The Diaphanous-related Formin
FHOD1 associates with ROCK1 and promotes Src-
dependent plasma membrane blebbing. J. Biol. Chem.
283, 27891–27903 (2008).
36. Han, Y. et al. Formin-like 1 (FMNL1) is regulated by
N-terminal myristoylation and induces polarized
membrane blebbing. J. Biol. Chem.284, 33409–
33417 (2009).
37. Di Vizio, D. et al. Oncosome formation in prostate
cancer: association with a region of frequent
chromosomal deletion in metastatic disease. Cancer
Res.69, 5601–5609 (2009).
This intruiging study shows that genetic loss of the
formin DIAPH3 is associated with prostate cancer
metastasis, possibly through increased plasma
membrane blebbing and oncosome production.
38. Eisenmann, K. M. et al. Dia-interacting protein
modulates formin-mediated actin assembly at the cell
cortex. Curr. Biol.17, 579–591 (2007).
39. Favaro, P. M. B. et al. High expression of FMNL1
protein in T non-Hodgkin’s lymphomas. Leukemia
Research30, 735–738 (2006).
40. Schuster, I. G. et al. Allorestricted T cells with
specificity for the FMNL1-derived peptide PP2 have
potent antitumor activity against hematologic and
other malignancies. Blood110, 2931–2939 (2007).
A very interesting paper describing presentation of
a formin-derived antigenic epitop that can activate
T cell clones to target lymphoma.
41. Zhu, X.-L., Liang, L. & Ding, Y.-Q. Overexpression of
FMNL2 is closely related to metastasis of colorectal
cancer. Intern. J. Colorectal Dis. 23, 1041–1047
(2008).
42. Kitzing, T. M., Wang, Y., Pertz, O., Copeland, J. W. &
Grosse, R. Formin-like 2 drives amoeboid invasive
cell motility downstream of RhoC. Oncogene29,
2441–2448 (2010).
The first comprehensive formin screen on
differently invading cancer cell types, which
identified a RhoC–FMNL2 module for rounded
invasion.
43. Olson, E. N. & Nordheim, A. Linking actin dynamics
and gene transcription to drive cellular motile
functions. Nature Rev. Mol. Cell Biol.11, 353–365
(2010).
44. Medjkane, S., Perez-Sanchez, C., Gaggioli, C., Sahai, E.
& T reisman, R. Myocardin-related transcription factors
and SRF are required for cytoskeletal dynamics and
experimental metastasis. Nature Cell Biol.11,
257–268 (2009).
45. Brandt, D. T. et al. SCAI acts as a suppressor of cancer
cell invasion through the transcriptional control of
β1-integrin. Nature Cell Biol.11, 557–568 (2009).
46. Mullins, R. D., Heuser, J. A. & Pollard, T. D. The
interaction of Arp2/3 complex with actin: nucleation,
high affinity pointed end capping, and formation of
branching networks of filaments. Proc. Natl Acad. Sci.
USA95, 6181–6186 (1998).
47. Pantaloni, D., Boujemaa, R., Didry, D., Gounon, P. &
Carlier, M. F. The Arp2/3 complex branches filament
barbed ends: functional antagonism with capping
proteins. Nature Cell Biol.2, 385–391 (2000).
48. Goley, E. D. et al. An actin-filament-binding interface
on the Arp2/3 complex is critical for nucleation and
branch stability. Proc. Natl Acad. Sci. USA107,
8159–8164 (2010).
49. Urban, E., Jacob, S., Nemethova, M., Resch, G. P. &
Small, J. V. Electron. tomography reveals unbranched
networks of actin filaments in lamellipodia. Nature Cell
Biol.12, 429–435 (2010).
50. Lai, F. P. et al. Arp2/3 complex interactions and actin
network turnover in lamellipodia. EMBO J. 27,
982–992 (2008).
51. Rouiller, I. et al. The structural basis of actin filament
branching by the Arp2/3 complex. J. Cell Biol.180,
887–895 (2008).
52. Sarmiento, C. et al. WASP family members and formin
proteins coordinate regulation of cell protrusions in
carcinoma cells. J. Cell Biol.180, 1245–1260 (2008).
53. Yamaguchi, H. et al. Molecular mechanisms of
invadopodium formation: the role of the N-WASP–
Arp2/3 complex pathway and cofilin. J. Cell Biol.168,
441–452 (2005).
54. Wang, W. et al. Single cell behavior in metastatic
primary mammary tumors correlated with gene
expression patterns revealed by molecular profiling.
Cancer Res.62, 6278–6288 (2002).
55. Wang, W. et al. Identification and testing of a gene
expression signature of invasive carcinoma cells
within primary mammary tumors. Cancer Res.64,
8585–8594 (2004).
56. Wang, W. et al. Coordinated regulation of pathways for
enhanced cell motility and chemotaxis is conserved in
rat and mouse mammary tumors. Cancer Res.67,
3505–3511 (2007).
References 55 and 56 examine the change of gene
expression in invading tumour cells collected in vivo
and further highlight the role of the Arp2/3
complex downstream of the EGF receptor.
57. Otsubo, T. et al. Involvement of Arp2/3 complex in the
process of colorectal carcinogenesis. Mod. Pathol.17,
461–467 (2004).
58. Laurila, E., Savinainen, K., Kuuselo, R., Karhu, R. &
Kallioniemi, A. Characterization of the 7q21-q22
amplicon identifies ARPC1A, a subunit of the Arp2/3
complex, as a regulator of cell migration and invasion
in pancreatic cancer. Genes Chromosom. Cancer48,
330–339 (2009).
59. Kumagai, K. et al. Arpc1b gene is a candidate
prediction marker for choroidal malignant melanomas
sensitive to radiotherapy. Invest. Ophthalmol. Vis. Sci.
47, 2300–2304 (2006).
60. Molli, P. R. et al. Arpc1b, a centrosomal protein, is
both an activator and substrate of Aurora, A. J. Cell
Biol.190, 101–114 (2010).
61. Wu, H., Reynolds, A. B., Kanner, S. B., Vines, R. R. &
Parsons, J. T. Identification and characterization of a
novel cytoskeleton-associated pp60src substrate. Mol.
Cell Biol.11, 5113–5124 (1991).
62. Martinez-Quiles, N., Ho, H. Y., Kirschner, M. W.,
Ramesh, N. & Geha, R. S. Erk/Src phosphorylation of
cortactin acts as a switch on-switch off mechanism that
controls its ability to activate N-WASP. Mol. Cell Biol.
24, 5269–5280 (2004).
63. T ehrani, S., T omasevic, N., Weed, S., Sakowicz, R. &
Cooper, J. A. Src phosphorylation of cortactin
enhances actin assembly. Proc. Natl Acad. Sci. USA
104, 11933–11938 (2007).
64. Kowalski, J. R. et al. Cortactin regulates cell migration
through activation of N-WASP. J. Cell Sci.118, 79–87
(2005).
65. Uruno, T., Liu, J., Li, Y., Smith, N. & Zhan, X.
Sequential interaction of actin-related proteins 2 and
3 (Arp2/3) complex with neural Wiscott-Aldrich
syndrome protein (N-WASP) and cortactin during
branched actin filament network formation. J. Biol.
Chem.278, 26086–26093 (2003).
66. Desmarais, V. et al. N-WASP and cortactin are involved
in invadopodium-dependent chemotaxis to EGF in
breast tumor cells. Cell. Motil. Cytoskeleton66, 303–
316 (2009).
67. Artym, V. V., Zhang, Y., Seillier-Moiseiwitsch, F.,
Yamada, K. M. & Mueller, S. C. Dynamic interactions
of cortactin and membrane type 1 matrix
metalloproteinase at invadopodia: defining the stages
of invadopodia formation and function. Cancer Res.
66, 3034–3043 (2006).
68. Oser, M. et al. Cortactin regulates cofilin and N-WASp
activities to control the stages of invadopodium assembly
and maturation. J. Cell Biol.186, 571–587 (2009).
69. Bowden, E. T., Barth, M., Thomas, D., Glazer, R. I. &
Mueller, S. C. An invasion-related complex of cortactin,
paxillin and PKCmu associates with invadopodia at
sites of extracellular matrix degradation. Oncogene
18, 4440–4449 (1999).
70. Lorenz, M., Yamaguchi, H., Wang, Y., Singer, R. H. &
Condeelis, J. Imaging sites of N-wasp activity in
lamellipodia and invadopodia of carcinoma cells. Curr.
Biol.14, 697–703 (2004).
71. Mizutani, K., Miki, H., He, H., Maruta, H. & T akenawa,
T. Essential role of neural Wiskott-Aldrich syndrome
protein in podosome formation and degradation of
extracellular matrix in src-transformed fibroblasts.
Cancer Res.62, 669–674 (2002).
72. Bryce, N. S. et al. Cortactin promotes cell motility by
enhancing lamellipodial persistence. Curr. Biol.15,
1276–1285 (2005).
REVIEWS
nATuRE REvIEws |CanCer vOLuME 11 | MARCH 2011 |185
4227–4235 (2007).
74. Sossey-Alaoui, K., Ranalli, T. A., Li, X., Bakin, A. V. &
Cowell, J. K. WAVE3 promotes cell motility and
invasion through the regulation of MMP-1, MMP-3,
and MMP-9 expression. Exp. Cell Res.308, 135–145 (2005).
75. Ayala, I. et al. Multiple regulatory inputs converge on
cortactin to control invadopodia biogenesis and
extracellular matrix degradation. J. Cell Sci.121,
369–378 (2008).
76. Fernando, H. S., Sanders, A. J., Kynaston, H. G. &
Jiang, W. G. WAVE1 is associated with invasiveness
and growth of prostate cancer cells. J. Urol.180,
1515–1521 (2008).
77. Fernando, H. S., Sanders, A. J., Kynaston, H. G. &
Jiang, W. G. WAVE3 is associated with invasiveness in
prostate cancer cells. Urol. Oncol.28, 320–327
(2010).
78. Sossey-Alaoui, K. et al. Down-regulation of WAVE3, a
metastasis promoter gene, inhibits invasion and
metastasis of breast cancer cells. Am. J. Pathol.170,
2112–2121 (2007).
79. Kurisu, S., Suetsugu, S., Yamazaki, D., Yamaguchi, H.
& T akenawa, T. Rac-WAVE2 signaling is involved in the
invasive and metastatic phenotypes of murine
melanoma cells. Oncogene24, 1309–1319 (2005).
80. Iwaya, K. et al. Correlation between liver metastasis of
the colocalization of actin-related protein 2 and 3
complex and WAVE2 in colorectal carcinoma. Cancer
Sci.98, 992–999 (2007).
81. Iwaya, K., Norio, K. & Mukai, K. Coexpression of Arp2
and WAVE2 predicts poor outcome in invasive breast
carcinoma. Mod. Pathol.20, 339–343 (2007).
82. Fernando, H. S. et al. Expression of the WASP
verprolin-homologues (WAVE members) in human
breast cancer. Oncology73, 376–383 (2007).
83. Yanagawa, R. et al. Genome-wide screening of genes
showing altered expression in liver metastases of
human colorectal cancers by cDNA microarray.
Neoplasia3, 395–401 (2001).
84. Wang, W. S. et al. The expression of CFL1 and
N-WASP in esophageal squamous cell carcinoma and
its correlation with clinicopathological features. Dis.
Esophagus23, 512–521 (2010).
85. Rothschild, B. L. et al. Cortactin overexpression
regulates actin-related protein 2/3 complex activity,
motility, and invasion in carcinomas with chromosome 11q13 amplification. Cancer Res.66, 8017–8025
(2006).
86. Buday, L. & Downward, J. Roles of cortactin in tumor
pathogenesis. Biochim. Biophys. Acta1775,
263–273 (2007).
87. Weaver, A. M. Cortactin in tumor invasiveness. Cancer
Lett.265, 157–166 (2008).
88. Hofman, P. et al. Prognostic significance of cortactin
levels in head and neck squamous cell carcinoma:
comparison with epidermal growth factor receptor
status. Br. J. Cancer98, 956–964 (2008).
89. Zhang, L. H. et al. Dominant expression of 85-kDa
form of cortactin in colorectal cancer. J. Cancer Res.
Clin. Oncol.132, 113–120 (2006).
90. Clark, E. S. et al. Aggressiveness of HNSCC tumors
depends on expression levels of cortactin, a gene in
the 11q13 amplicon. Oncogene28, 431–444
(2009).
91. Chuma, M. et al. Overexpression of cortactin is
involved in motility and metastasis of hepatocellular
carcinoma. J. Hepatol41, 629–636 (2004).
92. Luo, M. L. et al. Amplification and overexpression of
CTTN (EMS1) contribute to the metastasis of
esophageal squamous cell carcinoma by promoting
cell migration and anoikis resistance. Cancer Res.66,
11690–11699 (2006).
93. Li, Y. et al. Cortactin potentiates bone metastasis of
breast cancer cells. Cancer Res.61, 6906–6911
(2001).
This study demonstrates that cancer cells
overexpressing cortactin show a higher frequency
for metastasis in nude mice, which depends on
tyrosine phosphorylation of cortactin.
94. Ammer, A. G. et al. Saracatinib impairs head and neck
squamous cell carcinoma invasion by disrupting
invadopodia function. J. Cancer Sci. Ther.1, 52–61
(2009).
95. Timpson, P. et al. Aberrant expression of cortactin in
head and neck squamous cell carcinoma cells is
associated with enhanced cell proliferation and
resistance to the epidermal growth factor receptor
inhibitor gefitinib. Cancer Res.67, 9304–9314
(2007).
An intriguing report demonstrating that cortactin
promotes resistance to an anticancer drug
gefitinib.
96. Timpson, P., Lynch, D. K., Schramek, D., Walker, F. &
Daly, R. J. Cortactin overexpression inhibits ligand-
induced down-regulation of the epidermal growth
factor receptor. Cancer Res.65, 3273–3280 (2005).
97. Sanz-Moreno, V. et al. Rac activation and inactivation
control plasticity of tumor cell movement. Cell135,
510–523 (2008).
This elegant paper identifies Rac-regulated WAVE2
function as a key mediator for tumour cell plasticity
from amoeboid to mesenchymal invasion.
98. Yamazaki, D., Kurisu, S. & T akenawa, T. Involvement of
Rac and Rho signaling in cancer cell motility in 3D
substrates. Oncogene28, 1570–1583 (2009).
99. Gadea, G., Sanz-Moreno, V., Self, A., Godi, A. &
Marshall, C. J. DOCK10-mediated Cdc42 activation is
necessary for amoeboid invasion of melanoma cells.
Curr. Biol.18, 1456–1465 (2008).
100. Sossey-Alaoui, K., Bialkowska, K. & Plow, E. F. The
miR200 family of microRNAs regulates
WAVE3-dependent cancer cell invasion. J. Biol. Chem.
284, 33019–33029 (2009).
101. Beli, P., Mascheroni, D., Xu, D. & Innocenti, M. WAVE
and Arp2/3 jointly inhibit filopodium formation by
entering into a complex with mDia2. Nature Cell Biol.
10, 849–857 (2008).
102. Silva, J. M. et al. Cyfip1 is a putative invasion
suppressor in epithelial cancers. Cell137, 1047–1061
(2009).
103. Bourguignon, L. Y., Peyrollier, K., Gilad, E. &
Brightman, A. Hyaluronan-CD44 interaction with
neural Wiskott-Aldrich syndrome protein (N-WASP)
promotes actin polymerization and ErbB2 activation
leading to beta-catenin nuclear translocation,
transcriptional up-regulation, and cell migration in
ovarian tumor cells. J. Biol. Chem.282, 1265–1280
(2007).
104. Lyubimova, A. et al. Neural Wiskott-Aldrich syndrome
protein modulates Wnt signaling and is required for
hair follicle cycling in mice. J. Clin. Invest.120,
446–456 (2010).
105. Wu, X. et al. Regulation of RNA-polymerase-II-
dependent transcription by N-WASP and its nuclear-
binding partners. Nature Cell Biol.8, 756–763
(2006).
106. Zuchero, J. B., Coutts, A. S., Quinlan, M. E., Thangue,
N. B. & Mullins, R. D. p53-cofactor JMY is a
multifunctional actin nucleation factor. Nature Cell
Biol.11, 451–459 (2009).
107. Coutts, A. S., Weston, L. & La Thangue, N. B. A
transcription co-factor integrates cell adhesion and
motility with the p53 response. Proc. Natl Acad. Sci.
USA106, 19872–19877 (2009).
References 106 and 107 identify the p53
transcriptional regulator JMY as a potent actin
nucleation factor that, when expressed in the
cytoplasm, mediates proinvasive cancer cell
motility.
108. Saadi, A. et al. Stromal genes discriminate preinvasive
from invasive disease, predict outcome, and highlight
inflammatory pathways in digestive cancers. Proc. Natl
Acad. Sci. USA107, 2177–2182 (2010).
109. Bear, J. E. & Gertler, F. B. Ena/VASP: towards resolving
a pointed controversy at the barbed end. J. Cell Sci.
122, 1947–1953 (2009).
110. Pula, G. & Krause, M. Role of Ena/VASP proteins in
homeostasis and disease. Handb Exp. Pharmacol.
39–65 (2008).
111. Bear, J. E. et al. Antagonism between Ena/VASP
proteins and actin filament capping regulates
fibroblast motility. Cell109, 509–521 (2002).
112. Breitsprecher, D. et al. Clustering of VASP actively
drives processive, WH2 domain-mediated actin
filament elongation. EMBO J. 27, 2943–2954
(2008).
113. Grosse, R., Copeland, J. W., Newsome, T. P., Way, M. &
T reisman, R. A role for VASP in RhoA-Diaphanous
signalling to actin dynamics and SRF activity. EMBO J.
22, 3050–3061 (2003).
114. Dent, E. W. et al. Filopodia are required for cortical
neurite initiation. Nature Cell Biol.9, 1347–1359
(2007).
115. Scott, J. A. et al. Ena/VASP proteins can regulate
distinct modes of actin organization at cadherin-
adhesive contacts. Mol. Biol. Cell17, 1085–1095
(2006).
116. Bear, J. E. et al. Negative regulation of fibroblast
motility by Ena/VASP proteins. Cell101, 717–728
(2000).
117. Lambrechts, A. et al. cAMP-dependent protein kinase
phosphorylation of EVL, a Mena/VASP relative,
regulates its interaction with actin and SH3 domains.
J. Biol. Chem.275, 36143–36151 (2000).
118. Goswami, S. et al. Identification of invasion specific
splice variants of the cytoskeletal protein Mena
present in mammary tumor cells during invasion in
vivo. Clin. Exp. Metastasis26, 153–159 (2009).
119. Philippar, U. et al. A Mena invasion isoform
potentiates EGF-induced carcinoma cell invasion and
metastasis. Dev. Cell15, 813–828 (2008).
This interesting work examines the role of a MENA
invasion isoform in driving EGF-dependent breast
cancer invasion and metastasis in vivo.
120. Di Modugno, F. et al. The cytoskeleton regulatory
protein hMena (ENAH) is overexpressed in human
benign breast lesions with high risk of transformation
and human epidermal growth factor
receptor-2-positive/hormonal receptor-negative
tumors. Clin. Cancer Res.12, 1470–1478 (2006).
121. T oyoda, A. et al. Aberrant expression of human
ortholog of mammalian enabled (hMena) in human
colorectal carcinomas: implications for its role in
tumor progression. Int. J. Oncol.34, 53–60 (2009).
122. Hu, L. D., Zou, H. F., Zhan, S. X. & Cao, K. M. EVL
(Ena/VASP-like) expression is up-regulated in human
breast cancer and its relative expression level is
correlated with clinical stages. Oncol. Rep.19,
1015–1020 (2008).
123. Hasegawa, Y., Murph, M., Yu, S., Tigyi, G. & Mills,
G. B. Lysophosphatidic acid (LPA)-induced vasodilator-
stimulated phosphoprotein mediates lamellipodia
formation to initiate motility in PC-3 prostate cancer
cells. Mol. Oncol.2, 54–69 (2008).
124. Peterson, J. R. et al. Chemical inhibition of N-WASP by
stabilization of a native autoinhibited conformation.
Nature Struct. Mol. Biol.11, 747–755 (2004).
125. Nolen, B. J. et al. Characterization of two classes of
small molecule inhibitors of Arp2/3 complex. Nature
460, 1031–1034 (2009).
126. Gauvin, T. J., Fukui, J., Peterson, J. R. & Higgs, H. N.
Isoform-selective chemical inhibition of mDia-
mediated actin assembly. Biochemistry48,
9327–9329 (2009).
127. Rizvi, S. A. et al. Identification and characterization of
a small molecule inhibitor of formin-mediated actin
assembly. Chem. Biol.16, 1158–1168 (2009).
128. T o, C., Shilton, B. H. & Di Guglielmo, G. M. Synthetic
triterpenoids target the ARP2/3 complex and inhibit
branched actin polymerization. J. Biol. Chem.285,
27944–27957 (2010).
129. Chen, L., Yang, S., Jakoncic, J., Zhang, J. J. &
Huang, X. Y. Migrastatin analogues target fascin to
block tumour metastasis. Nature464, 1062–1066
(2010).
130. Shan, D. et al. Synthetic analogues of migrastatin that
inhibit mammary tumor metastasis in mice. Proc. Natl
Acad. Sci. USA102, 3772–3776 (2005).
131. Fackler, O. T. & Grosse, R. Cell motility through plasma
membrane blebbing. The Journal of Cell Biology181,
879–884 (2008).
132. Charras, G. & Paluch, E. Blebs lead the way: how to
migrate without lamellipodia. Nature Rev. Mol. Cell
Biol.9, 730–736 (2008).
133. Wu, X., Suetsugu, S., Cooper, L. A., T akenawa, T. &
Guan, J. L. Focal adhesion kinase regulation of
N-WASP subcellular localization and function. J. Biol.
Chem.279, 9565–9576 (2004).
134. Brandt, D. T. & Grosse, R. Get to grips: steering
local actin dynamics with IQGAPs. EMBO Rep.8,
1019–1023 (2007).
135. Martin, T. A., Pereira, G., Watkins, G., Mansel, R. E. &
Jiang, W. G. N-WASP is a putative tumour suppressor
in breast cancer cells, in vitro and in vivo, and is
associated with clinical outcome in patients with
breast cancer. Clin. Exp. Metastasis25, 97–108
(2008).
136. Yang, L. Y. et al. Increased expression of Wiskott-
Aldrich syndrome protein family verprolin-homologous
protein 2 correlated with poor prognosis of
hepatocellular carcinoma. Clin. Cancer Res.12,
5673–5679 (2006).
137. Semba, S. et al. Coexpression of actin-related protein
2 and Wiskott-Aldrich syndrome family verproline-
homologous protein 2 in adenocarcinoma of the lung.
Clin. Cancer Res.12, 2449–2454 (2006).
138. Bringuier, P. P., T amimi, Y., Schuuring, E. & Schalken,
J. Expression of cyclin D1 and EMS1 in bladder
186 | MARCH 2011 | vOLuME 11 https://www.sodocs.net/doc/637812616.html,/reviews/cancer
tumours; relationship with chromosome 11q13
amplification. Oncogene12, 1747–1753 (1996). 139. Hui, R. et al. EMS1 amplification can occur
independently of CCND1 or INT-2 amplification at
11q13 and may identify different phenotypes in primary breast cancer. Oncogene15, 1617–1623 (1997). 140. Hui, R. et al. EMS1 gene expression in primary breast cancer: relationship to cyclin D1 and oestrogen
receptor expression and patient survival. Oncogene
17, 1053–1059 (1998).
141. Lee, Y. Y. et al. Expression of survivin and cortactin in colorectal adenocarcinoma: association with
clinicopathological parameters. Dis. Markers26,
9–18 (2009).
142. Cai, J. H. et al. Expression of cortactin correlates with
a poor prognosis in patients with stages II-III
colorectal adenocarcinoma. J. Gastrointest Surg.14,
1248–1257 (2010).
143. Wang, X. et al. VEGF and cortactin expression are independent predictors of tumor recurrence following
curative resection of gastric cancer. J. Surg. Oncol.
102, 325–330 (2010).
144. Xie, H. L. et al. Differential gene and protein
expression in primary gastric carcinomas and their
lymph node metastases as revealed by combined
cDNA microarray and tissue microarray analysis.
J. Dig Dis.11, 167–175 (2010).
145. T sai, W. C. et al. Association of cortactin and fascin-1 expression in adenocarcinoma: correlation with
clinicopathological parameters. J. Histochem.
Cytochem.55, 955–962 (2007).146. Li, X. et al. Aberrant expression of cortactin and fascin
are effective markers for pathogenesis, invasion,
metastasis and prognosis of gastric carcinomas.
Int. J. Oncol.33, 69–79 (2008).
147. Gibcus, J. H. et al. Cortactin expression predicts poor
survival in laryngeal carcinoma. Br. J. Cancer98,
950–955 (2008).
148. Rodrigo, J. P. et al. Distinctive clinicopathological
associations of amplification of the cortactin gene at
11q13 in head and neck squamous cell carcinomas.
J. Pathol.217, 516–523 (2009).
149. Hsu, K. F. et al. Cortactin, fascin, and survivin
expression associated with clinicopathological
parameters in esophageal squamous cell carcinoma.
Dis. Esophagus22, 402–408 (2009).
150. T akes, R. P. et al. Markers for assessment of nodal
metastasis in laryngeal carcinoma. Arch. Otolaryngol.
Head Neck Surg.123, 412–419 (1997).
151. Xu, X. Z. et al. Cytoskeleton alterations in melanoma:
aberrant expression of cortactin, an actin-binding
adapter protein, correlates with melanocytic tumor
progression. Mod. Pathol.23, 187–196 (2010).
152. Yamada, S. I., Yanamoto, S., Kawasaki, G., Mizuno, A.
& Nemoto, T. K. Overexpression of cortactin increases
invasion potential in oral squamous cell carcinoma.
Pathol. Oncol. Res.16, 523–531 (2010).
153. Lin, C. K., Su, H. Y., T sai, W. C., Sheu, L. F. & Jin, J. S.
Association of cortactin, fascin-1 and epidermal
growth factor receptor (EGFR) expression in ovarian
carcinomas: correlation with clinicopathological
parameters. Dis. Markers25, 17–26 (2008).
154. Wang, G. C. et al. Expression of cortactin and survivin
in renal cell carcinoma associated with tumor
aggressiveness. World J. Urol.27, 557–563 (2009).
155. Dertsiz, L. et al. Differential expression of VASP in
normal lung tissue and lung adenocarcinomas. Thorax
60, 576–581 (2005).
Acknowledgments
The authors are grateful to B. Di Ventura and H. Morrison for
comments on the manuscript and to laboratory members for
helpful discussions. T.K. is a recipient of a DFG fellowship
(KI 1605/1-1). R.G. is supported by grants from the DFG
(GR 2111/2-1), Deutsche Krebshilfe e.V. (108293) and the
LOEWE program T umour & Inflammation.
Competing interests statement
The authors declare no competing financial interests.
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