Adriamycin-induced inhibition of melanoma cell invasion is correlated with decreases in tumor cell motility and increases in focal contact formation.

Tumor cell adhesion to the extracellular matrix (ECM) is closely linked with tumor cell invasion and metastasis. In this study, we demonstrate that low levels of adriamycin, a widely used anticancer drug, can inhibit the invasion of highly metastatic K1735-M2 mouse melanoma cells in vitro through a reconstituted basement membrane extract. Adriamycin-induced inhibition of melanoma cell invasion occurred at levels of the drug (i.e. 1 ng/ml) that did not inhibit tumor cell growth, suggesting that the observed inhibition in tumor cell invasion was not due to the well-documented ability of adriamycin to interfere with DNA and/or RNA synthesis. Rather, these studies indicated that adriamycin-induced inhibition of melanoma cell invasion was accompanied by a corresponding decrease in the ability of adriamycin-treated tumor cells to migrate in response to several isolated ECM components including fibronectin, laminin and basement membrane (type IV) collagen. The decreased migration of adriamycin-treated tumor cells was not accompanied by a decrease in the adhesion or spreading of the adriamycin-treated cells on substrata coated with these ECM components. Instead, adriamycin-treated cells actually exhibited a slightly increased propensity (compared to untreated control cells) to adhere on fibronectin-, laminin-, and type IV collagen-coated substrata. Additionally, adriamycin treatment caused a dramatic increase in focal contact formation by these melanoma cells, as assessed by fluorescent microscopy of actin and vinculin. In addition to providing a useful model for which to study the molecular and cellular basis for focal contact formation, these results further emphasize the results of several other investigators that have suggested an important role for focal contacts in modulating tumor cell motility, invasion and metastasis.