A simple quantitative assay for studying the invasive potential of high and low human metastatic variants.

This paper presents a more reliable model for studying the extent of tumor cell migration and invasion in vitro. Polycarbonate filters were uniformly coated with a reconstituted basement membrane material and allowed to dry; each filter measured 0.035 mm in thickness when hydrated with media. Subsequently, the membrane-coated filters were suspended in Membrane Invasion Culture System (MICS) chambers, and high (A375M) and low (A375P) metastatic variants of human melanoma cells were seeded onto the membranes and allowed to incubate for 3 days. At the end of this period, cells were examined morphologically, and the invasive cells of both metastatic variants were collected, stained and counted microscopically. The tumor cells could be seen attached to the reconstituted basement membrane, buried within it, and forming colony-like aggregates in the matrix. It was determined that approximately twice as many A375M cells invaded the artificial biological matrix compared with the A375P cells (P less than 0.0005). Substantially more cells from each variant invaded uncoated polycarbonate filters, thus indicating the selective barrier imposed by the Matrigel. The utilization of such a reconstituted matrix for in vitro invasion studies allows one the opportunity to examine tumor cell attachment, migration and invasion of a uniform matrix over an extended period of time.