The 'chemoinvasion' assay, 25 years and still going strong: the use of reconstituted basement membranes to study cell invasion and angiogenesis.

Invasive and metastatic cells must cross basement membranes (BMs) in order to disseminate to distant sites. The 'chemoinvasion assay' using a reconstituted basement membrane, matrigel, in Boyden blind-well chambers was developed 25 years ago as a tool for invasion and metastasis research. Since then, it was adapted for investigation of how different cells types engage with and penetrate basement membrane, including research in angiogenesis, invasive cell migration, protease functions, and preclinical development of anti-invasive and anti-angiogenic agents. As novel mechanisms of metastasis and angiogenesis come to light and old paradigms are challenged, we examine how the assay can still provide innovative insights. We review established applications and variants of the matrigel invasion assay, highlight key findings derived from it and discuss future developments, including roles for accessory and cancer stem cells.