Cell Migration, Chemotaxis and Invasion Assay Protocol

Cell Migration, Chemotaxis and Invasion

Introduction

Cell migration, the movement of cells from one area to another generally

in response to a chemical signal, is central to achieving functions such as

wound repair, cell differentiation, embryonic development and the

metastasis of tumors. Cell invasion is similar to cell migration; however,

it requires a cell to migrate through an extracellular matrix (ECM) or

basement membrane extract (BME barrier by first enzymatically

degrading that barrier and to then become established in a new location.

Cell invasion is exhibited by both normal cells in responses such as

inflammation and by tumor cells in the process of metastasis, therefore

understanding the underlying mechanisms of this process are important

for a wide array of biological systems.

The advent of disposable permeable supports, such as Transwell? inserts

from Corning Life Sciences, provides a relatively simple in vitro

approach to performing chemotaxis and cell invasion assays. Common

barriers employed for invasion assays include collagen, fibronectin and

laminin coatings as well as more complex extracellular or basement

membrane extracts. More elaborate invasion assays establish a

monolayer of endothelial cells on the permeable support in place of, or in

addition to, the protein coatings or BME listed above. Similarly, cells

that secrete a paracrine growth factor can be cultured in the receiver

wells of the permeable support system to act as the source of

Hilary Sherman, Pilar

Pardo and Todd Upton

Corning Life Sciences

900 Chelmsford Street

Lowell, MA 01851

Assay Protocol

chemoattractant in either simple chemotaxis assays or for more elaborate invasion assays.

This protocol outlines the steps for conducting a cell invasion assay through a BME barrier with special notes for conducting a chemotaxis assay (similar to an invasion assay, however no BME or ECM is present). It is a generalized protocol and should be adapted to suit your needs. This protocol utilizes Corning’s 96 well HTS Transwell?permeable supports, however, tables are provided with the proper volumes and amounts of pertinent materials and reagents to scale the assay for use with large permeable supports.

Materials

Cell lines:

?Noninvasive MCF-7 cells (Human breast adenocarcinoma, ATCC No.

HTB-22)

?Invasive HT1080 cells (Human fibrosarcoma ATCC No. CCL-121) Assay Plates:

?96 well HTS Transwell Permeable Supports with 8 μm pores (Corning Cat. No. 3374)

?96 well black receiver plate (Corning Cat. No. 3583)

?96 well solid black microplates (Corning Cat. No. 3916)

? 6 well Transwell permeable supports with 8 μm pores (Corning Cat. No.

3428)

?12 well Transwell Permeable Supports with 12 μm pores (Corning Cat.

No. 3403)

?24 well Transwell Permeable Supports with 8 μm pores (Corning Cat.

No. 3422)

? 6 and 24 well Ultra-low Attachment plates (Corning Cat. No. 3471 and 3473)

Reagents:

?5x Basement Membrane Extract (BME) coating solution (Trevigen Cat.

No. 3455-096-02)

?10x Coating Buffer (Trevigen Cat. No. 3455-096-03)

?10x Cell Dissociation Solution for preparing the assay dissociating solution (Trevigen Cat. No. 3455-096-05). This solution can not be used to harvest cells.

?HyQtase Dissociation Solution for harvesting cells (Hyclone Cat. No.

JQH2447)

?Calcein AM (Molecular Probes Cat. No. C3100MP) dissolved to

1.67μg/μL in DMSO

?IMDM medium with 10% FBS (Invitrogen Cat. No. 12440046 and 14037036, respectively)

?Serum-free medium (SFM), IMDM medium without serum containing 1x ITS (Invitrogen Cat No. 41400045)

?Wash Buffer – Dulbecco’s Phosphate Buffered Saline (DPBS) with calcium and magnesium

?Sterile deionized water

Instruments:

? 37oC CO 2 incubator ? Laminar flow hood

? Fluorescent plate reader with a 485nm excitation and 520nm emission

filter package

Procedure

Grow enough cells in advance to accommodate the different cell concentrations required to set up assay (Table 2). A separate flask should be set up at a lower concentration in order to run standard curve on day of assay (day 3 of protocol).

Protocol Overview:

? Day 1 – Starve cells and coat Transwell inserts with Basement

Membrane Extract (BME)

? Day 2 – Plate cells in Transwell inserts and stimulate with FBS attractant;

optional setup of standard curve.

? Day 3 – Detect cells that pass through membrane and standard curve.

Day 1

1. Cell Maintenance

a. Cultures should be below 80% confluence, this is important so that cells

are properly starved without becoming confluent during the 24 hr starvation period.

b. Remove serum containing medium from cultures.

c. Thoroughly but gently rinse cultures with PBS to remove all serum.

d. Replace culture medium with serum-free IMDM medium (SFM). Return

cultures to incubator for 24 hours. 2. Basement Membrane Extract (BME) Coating

The concentration of BME necessary for the assay is dependent on the cell line. We recommend testing various BME concentrations (0.1x to 1x, for example) to find the optimal concentration for a particular cell line. The optimal concentration will provide the biggest difference between the invasive and noninvasive cell lines in response to a chemoattractant

a. Under sterile conditions prepare 1x Coating Buffer working solution by

diluting 10x Coating Buffer stock with sterile filtered deionized water. b. Thaw out 5x BME stock solutions by gently swirling vial in a 37o C water

bath. Once thawed dilute immediately or keep vial on ice until ready to use; BME becomes viscous at warmer temperatures. c. Dilute the 5x BME stock to desired working concentration using 1x

Coating Buffer. d. Coat Transwell inserts with BME solution (See Note at left, and Table 1

on page 4) e. Incubate plate overnight in 5% CO 2 incubator at 37o C.

NOTE: In order to properly assess cell

invasion, it is necessary to set up a few wells without an ECM barrier to

determine the percent of cells that would exhibit chemotaxis. This will become important for

analyzing the data in Step 6). See Table 3 for typical layout for a 96 well plate inserts.

NOTE: Read entire

protocol before beginning assay.

NOTE: Using the cell requirements from Table 2, prepare enough cell cultures one day prior in order to accommodate the number of cells required to set up the assay.

Day 2

3. Plating cells for the invasion assay and standard curve

This protocol uses HTS-96 Transwell plates for running a cell invasion assay. The protocol can be adapted for assays using larger permeable supports or fewer wells. As part of the procedure, inserts are setup without a BME barrier (ot differentiate cell invasion from chemotaxis, see Introduction) as a control to calculate total invasion.

a. Harvest cells using HyQtase solution or other suitable cell dissociation

solution. (See Note) b. Quench dissociation solution with serum-free media or serum-free trypsin

inhibitor. c. Spin cells down to remove cell dissociation solution and resuspend in

serum-free medium. d. Determine cell concentration and dilute cell suspension to necessary

seeding concentration with serum free medium (Table 2, below). e. Aspirate excess BME from inserts and plate cells.

f. Leave at least 1 well without cells as a blank to subtract for background

(Table 3). g. Set up some receiver wells with serum-free medium (no chemoattractant)

with the remaining wells receiving medium with serum (plus chemoattractant) as shown in Table 3 on page 5. h. Incubate cultures for 12 to 24 hours depending on the invasiveness of the

cell lines used.

Table 2. Recommended Cell Seeding Concentrations and Volumes

Assay plate format Cells/well (x105)* Seeding volume/ insert (mL) Reservoir volume

(mL/well)

HTS TW-96 0.5 0.05 0.150 24 well 1.0 to 2.0 0.100 0.65 12 well 1.0 to 2.0 0.385 1.0 6 well 3.0 to 4.0

1.5

2.0

NOTE: The migration response using trypsin with these cell lines in this protocol was lower and more variable than when using the HyQtase

solution. Consider trying different dissociating

agents and methods if you want to optimize your protocol.

* These cell seeding

densities have been

optimized for this protocol utilizing MCF-7 and HT-1080 cells. For best results we recommend optimizing cell seeding densities using your cell lines and conditions.

Table 1. Recommended Basement Matrix Extract Coating Volumes

Assay plate format Number of inserts Well bottom area (cm 2)

BME coating/well

(mL)

Total BME coating/plate

(mL)

HTS TW-96 96 0.143 0.050 5 24 well 12* 0.3 0.100 2 12 well

12 1.1 0.3

4

6 well 6 4.5 1 6.5

*Corning ? Transwell ? 6.5mm diameter inserts are packed 12 per 24 well plate.

Day 3

4. Standard Curve Preparation

a. A separate standard curve is required for each cell line and each assay

(see Note at left). b. Harvest cells and collect in a tube.

c. Prepare 1x Cell Dissociation Solution (1x CDS) by diluting 10x Cell

Dissociation Solution with sterile filtered deionized water. d. Thaw out Calcein AM vial (50 μg) and add 30 μL of tissue culture grade

DMSO to it to prepare the working solution. e. Pellet harvested cells and resuspend in 1x CDS.

f. Create a serial dilution of cell suspension (2 mL/dilution) starting with

the highest number of cells plated per well and ending with no cells -1x CDS only. See Table 4 (page 6) for recommended cell dilutions for preparing the standard curve. g. Add 50 μL from each dilution in triplicate to a well from a 96 well solid

black microplate (Corning Cat. No. 3583 if testing a 96 well HTS plate or Corning Cat. No. 3916 for all others).

NOTE: The standard

curve can be run on day 2 using cells harvested for seeding plates. It can also be run on the day of assay using a separate flask set up during the preparation of the cells for the

permeable supports; these cells need to be starved for 24 hours prior to

running assay (from day 2 of study).

Table 4. Recommended cells/well for generating a standard curve in a

96 well plate

Cells/well Desired Cells/mL Required (assuming 50 μL/well)

50,000 1,000,000

25,000 500,000

10,000 200,000

5,000 100,000

2,500 50,000

1,000 20,000

500 10,000

0 0

h.Dilute Calcein AM solution with 1x CDS at a ratio of 2.4 μL of Calcein

AM solution to 1 mL of 1x CDS.

i.Add 50 μL of the Calcein AM/CDS mixture to each well of the standard

curve.

j.Incubate microplate for 1 hour in the dark at room temperature then read using a fluorescent top reader at 485nm excitation and 520nm emission.

k.Average the relative fluorescence units (RFU) values for each

concentration then subtract background (no cells).

l.Plot a standard curve of cell concentration versus RFU .

m.Insert linear trend (set intercept to zero) and solve for cell concentration using y = mx + b, where y = cell number and x = RFU reading for test

sample. See Graph 1 (below) for an example of a standard curve.

5. Assay

a. Prepare 1x Cell Dissociation Solution (CDS) by diluting 10x Cell

Dissociation Solution with sterile filter deionized water. b. Thaw one Calcein AM vial (50 μg) and add 30 μL of tissue culture grade

DMSO to prepare a working solution. c. Combine 1x CDS with Calcein AM solution at a ratio of 1.2 μL of

Calcein AM solution for every 1 mL of 1x CDS. Store solution in dark until ready to use. See Table 5 (below) for recommended volumes.

Table 5. Recommended Calcein AM/1x CDS Solution Volumes

Calcein AM/1x CDS solution Assay

plate

format Recommended receiver plate mL/well mL/plate Multiplication factor

HTS TW-96 96 well black receiver plate 0.1 10 1 24 well 24 well plate 0.35 4.5 3.5 12 well 12 well plate 0.5 6.5 5 6 well

6 well plate

0.8

5

8

d. Aspirate medium from assay/receiver plate and Transwell inserts.

e. Wash apical/inserts once and receiver wells twice with Wash Buffer.

(Table 6)

f. Add Calcein AM/1x CDS solution to each well of receiver plate (Table

5).

g. Place inserts into receiver plate filled with Calcein AM/1x CDS solution.

Make sure there is no trapped air between bottom of insert and solution in the bottom well. Incubate plate at 37o in a 5% CO 2 incubator for 30 minutes. h. After 30 minutes incubation, gently tap sides of microplate and then place

back in incubator for 30 additional minutes. i. Remove insert tray from 96 well receiver plate and gently shake plate to

mix cell solution. Then place receiver plate directly into plate reader for reading (fluorescent top reader with filters set to 485 nm for excitation and 520 nm for emission).

Table 6. Wash Buffer Volumes

Assay plate format Inserts (mL/insert)

Receiver Plate (mL/well)

HTS TW-96 0.1 0.2 24 well 0.2 0.4 12 well 0.5 1.0 6 well

1.0

2.0

NOTE: For all other receiver plate formats remove inserts from receiver wells. Mix cell solution well then transfer 100 μL/well into a 96 well solid black microplate

(Corning Cat. No. 3916) in triplicate. Then read microplate.

NOTE: Cells that pass through membrane attach to the bottom of

membrane or fall to the bottom of the well and attach. In our experience the loss of any cells due to aspiration in step d is negligible.

6. Data Analysis – for simplicity we have omitted the calculations for MCF-7 cells.

a. Prepare data from plate reader. See Table 7a for data.

b. Subtract background from assay readings. The background is uncoated

well with no cells plated (Table 7b; see Note on left).

c. Convert RFU values to cell numbers using equation from standard curve

(Step 4m). See Table 7c below.

d. Determine the total number of cells passing through the membrane of each well by taking the cell numbers generated in step 7c and multiplying

NOTE: If multiple readings are derived from an

individual well (24, 12 and 6 well formats) then those readings should be

averaged first then have background subtracted.

Table 7a. Example of raw RFU data from the plate reader for HT1080 cells using 96 well HTS Transwell Plate (MCF-7 data not shown). No BME, No Serum

No BME + 10% Serum With BME, No Serum

With BME + 10%

Serum

196 218 205 195 216 208 454 348 8518 8569 269 374 300 6391 5284 5051 373

341

8451

7347

289 422 273 8401 8128 6830 394 6776 255 292 258 6522 4459 5635 418 371 586 7159 6279 6863 429

438

293 6876

7577

6199

297

4941

Table 7b. Example of data From Table 7b after the background (blank) is subtracted. No BME, No Serum

No BME + 10% Serum With BME, No Serum

With BME + 10%

Serum

0 0 0 0 200* 0 0 212* 258 152 **** **** 69 174 100 6197 5027 4839 177

145

8233

7128

89 222 73 8189 7916 6618 198 6558 55 92 58 6310 4247 5426 218 171 386 6947 6067 6651 229

238

93 6664

7364

5987

97

4747

* = average of multiple blank wells from table 7a, use for background subtract of test wells .

Table 7c. Cell numbers of each well using standard curve calculations.

No BME, No Serum

No BME + 10% Serum

With BME, No

Serum

With BME + 10%

Serum

Solve for cell number (From Graph 1): y = 5.9673x + 1236.5

2776 2144 50765 51069 1648 2275 1833 38216 31234 30112 2293

2102

50365

43771

1768 2561 1672 50103 48474 40728 2418 40370 1565 1785 1583 38890 26580 33615 2537 2257 3540 42691 37440 40925 2603 2657 1791 41003 45180 36963

1815

29563

it by the multiplication factor from Table 5 on page 7. See Table 7d below.

e. Determine percent invasion

from each well by dividing number of cells (from Table 7c) by the initial number of plated cells (from Table 2). Calculate average % invasion for all wells of each condition. (See Table 7e, on right) and plot results (Graph 2, below).

7. Data interpretation

a. There should be little or no migration/movement of noninvasive cell lines

with or without chemoattractant (serum).

Table 7d. Percent invasion for each well. No BME, No Serum

No BME + 10% Serum

With BME, No

Serum

With BME + 10%

Serum

Calculate % Invasion = (Cell Concentration/Initial cell seed) x Multiplication factor (Table 5)

5.6% 4.3% 101.5% 102.1% 3.3% 4.5% 3.7% 7

6.4% 62.5% 60.2% 4.6%

4.2%

100.7% 87.5% 3.5% 5.1% 3.3% 100.2% 96.9% 81.5% 4.8% 3.1% 3.6% 3.2% 77.8% 53.2% 67.2% 5.1% 4.5% 7.1% 85.4% 74.9% 81.9% 5.2% 5.3% 3.6% 82.0% 90.4%

73.9%

3.6%

59.1%

b. There should be less then 10% movement of invasive cells without the

FBS as a chemoattractant (serum-free medium conditions) c. The difference in percent invasion should be 20% or more between BME

coating (cell invasion) and no coating (cell migration) when using FBS as a chemoattractant.

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