Real-Time Detection and Capture of Invasive Cell Subpopulations from Co-Cultures

Summary

We describe an approach to detect and capture invasive cell subpopulations in real-time. The experimental design uses Real-Time Cellular Analysis by monitoring changes in the electric impedance of cells. Invasive cancer, immune, endothelial or stromal cells in complex tissues can be captured, and the impact of co-cultures can be assessed.

Abstract

Invasion and metastatic spread of cancer cells are the major cause of death from cancer. Assays developed early on to measure the invasive potential of cancer cell populations typically generate a single endpoint measurement that does not distinguish between cancer cell subpopulations with different invasive potential. Also, the tumor microenvironment consists of different resident stromal and immune cells that alter and participate in the invasive behavior of cancer cells. Invasion into tissues also plays a role in immune cell subpopulations fending off microorganisms or eliminating diseased cells from the parenchyma and endothelial cells during tissue remodeling and angiogenesis. Real-Time Cellular Analysis (RTCA) that utilizes impedance biosensors to monitor cell invasion was a major step forward beyond endpoint measurement of invasion: this provides continuous measurements over time and thus can reveal differences in invasion rates that are lost in the endpoint assay. Using current RTCA technology, we expanded dual-chamber arrays by adding a further chamber that can contain stromal and/or immune cells and allows measuring the rate of invasion under the influence of secreted factors from co-cultured stromal or immune cells over time. Beyond this, the unique design allows for detaching chambers at any time and isolating of the most invasive cancer cell, or other cell subpopulations that are present in heterogeneous mixes of tumor isolates tested. These most invasive cancer cells and other cell subpopulations drive malignant progression to metastatic disease, and their molecular characteristics are important for in-depth mechanistic studies, the development of diagnostic probes for their detection, and the assessment of vulnerabilities. Thus, the inclusion of small- or large-molecule drugs can be used to test the potential of therapies that target cancer and/or stromal cell subpopulations with the goal of inhibiting (e.g., cancer cells) or enhancing (e.g., immune cells) invasive behavior.

Introduction

Cell invasion is an important process that allows cells to cross basement membrane barriers in response to environmental cues provided by stromal cells. It is a crucial step during several stages of development for immune responses, wound healing, tissue repair, and malignancies that can progress from local lesions to invasive and metastatic cancers¹. Assays developed early on to measure the invasive potential of cell populations typically generate a single endpoint measurement or require pre-labeling of invasive cells². The integration of microelectronics and microfluidics techniques is now developed to detect different....

Protocol

The study was reviewed and considered as "exempt" by the Institutional Review Board of Georgetown University (IRB # 2002-022). Freshly harvested bone marrow tissues were collected from discarded healthy human bone marrow collection filters that had been de-identified.

1. New chamber design (Figure 2)

1. Open a new dual-chamber cell analyzer plate. Set aside the top chamber with electrodes.
2. Using a milling machine, shave off 2 mm of the U-shaped bottom wells of the cell analyzer plate.
3. Attach a 2 cm x 7 cm polyethersulfone (PES) membrane with....

Results

Using the newly designed three-chambered array, invasion of the cells was tested in the presence or absence of stromal cells such as fibroblasts. MDA-MB-231 cell invasion was enhanced when irradiated Swiss 3T3 fibroblasts (J2 strain) were seeded in the bottom chamber, allowing for the exchange of factors between the two cell lines. Interestingly, MDA-MB-231 invasion increased when 3T3-J2 cells were doubled in number (Figure 3A). On the other hand, the invasion rate of an invasive clone of MC.......

Discussion

We have modified the design of a dual-chambered array to include a third chamber for monitoring cell invasion in real-time in the presence of stromal cells. We have observed distinct effects of co-cultured fibroblasts on invasive and non-invasive cancer cells indicating that the array can be used to distinguish between cancer cell subpopulations that respond differently to factors produced by co-cultured stromal cells. The array was also used to monitor endothelial cell invasion into stromal tissues, a critical step duri.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.05% Trypsin-EDTA	Thermofisher	25300-054
Adhesive	Norland Optical Adhesive	NOA63
Bovine serum albumin (BSA)	Sigma	A9418
Cell lifter	Sarstedt	83.1832
Cholera Toxin from Vibrio cholerae	Thermofisher	12585-014
CIM-plate	Agilent	5665817001	Cell analyzer plate
Collagenase from Clostridium histolyticum	Sigma	C0130
Dispase	StemCell	7913
DMEM	Thermofisher	11995-065
DMEM-F12	Thermofisher	11875-093
Fetal Bovine Serum (FBS), Heat Inactivated	Omega Scientific	FB-12
HEPES	Thermofisher	15630106
Horse serum (HS)	Gibco	16050-122
Human EGF	Peprotech	AF-100-15
Human umbilical Vein endothelail cells (HUVEC)	LONZA (RRID:CVCL_2959)	C-2517A
HUVEC media	LONZA	CC-3162
Hydrocortisone	Sigma	H4001
Insulin Transferrin Selenium Ethanolamine (ITSX) (100x)	Thermofisher	51500056
Insulin, Human Recombinant, Zinc Solution	Sigma	C8052
J2 Fibroblasts	Stemcell (RRID:CVCL_W667)	100-0353
LymphoPrep	Stemcell	7851	Density gradient medium for the isolation of mononuclear cells
Matrigel	Corning	354230	Basement membrane matrix
MCFDCIS.com cells ( DCIS)	RRID:CVCL_5552
MDA-MB-231 cells	RRID:CVCL_0062
Milling machine			Bridgeport Series 1 Vertical
Phosphate-buffered saline (1x)	Thermofisher	10010049
Polyethersulfone (PES) membrane	Sterlitech	PCTF029030
RBC lysis solution	Stemcell	7800
RNeasy Micro Kit	Qiagen	74004
RTCA DP analyzer	Agilent	3X16	Dual purpose cell analyzer
Trypsin	Sigma	T4799