Identification of anti-invasive but noncytotoxic chemotherapeutic agents using the tetrazolium dye MTT to quantitate viable cells in Matrigel

Screening methods for chemotherapeutic agents usually rely on the cytotoxic properties of the drugs. However, agents that inhibit invasion may have more efficacy and cause fewer side effects. Various cellular invasion assays have been used to evaluate these types of compounds, including the modified Boyden chamber, monolayer wound models and Matrigel outgrowth assays. In this report, we have combined the use of the Matrigel outgrowth assay with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) visualization and cell viability dye to visualize invasive cells on Matrigel without magnification. Extraction of the dye's formazan byproduct allows cell viability to be assessed. Using several invasive and noninvasive cell lines, the utility of the method for various target cells was verified. Several established chemotherapeutic agents were also screened for their anti-invasive and/or cytotoxic effects when cultured on Matrigel. Our results suggest that this method may be an easy, inexpensive and nonradioactive alternative for both enumerating cells on Matrigel and screening various tumor cell lines treated with chemotherapeutic agent to look for compounds with noncytotoxic but anti-invasive properties.