Suppression of C8161 melanoma metastatic ability by chromosome 6 induces differentiation-associated tyrosinase and decreases proliferation on adhesion-restrictive substrates mediated by overexpression of p21WAF1 and down-regulation of bcl-2 and cyclin D3

Metastatic tumors grow under conditions that restrict proliferation of non- metastatic, more differentiated cells. To investigate this prediction, we d eveloped a simple adhesion-restrictive assay which allows proliferation of human metastatic C8161 melanoma, but prevents growth of neo 6.3/C8161 cells in which metastasis is suppressed by introduction of neo-tagged chromosome 6. We show that tyrosinase, a key enzyme in melanocytic cell differentiati on, and expression of chromosome 6-encoded cell cycle modulators like p21WA F1 and cyclin D3 is selectively increased in C8161 tumors in which metastas isis is suppressed by chromosome 6. In the latter cells, growth arrest evid enced only under adhesion-restrictive conditions correlated with down-regul ation of cyclin D3 and anti-apoptotic bcl-2. No comparable growth arrest or down-regulation was detected under comparable conditions in metastatic cel ls, which showed activation of invasion-associated MMP-9 92 kDa gelatinase B. Our data suggests that the metastasis-suppressing effects of chromosome 6 involving increased differentiation-associated tyrosinase and growth arre st on adhesion-restrictive substrates; are partly mediated by modulation of growth regulators, like p21WAF1 and cyclin D3. (C) 2001 Academic Press.