Suppression of tumorigenicity in the human prostate cancer cell line M12 via microcell-mediated restoration of chromosome 19

Previously we immortalized human, nontransformed prostate epithelial cells with SV40 large T-antigen (SV40TAg) and derived increasingly aggressive sub lines from the immortalized line, The progression of the tumorigenic sublin es to metastatic capacity was accompanied by the formation of an unbalanced translocation between chromosomes 16 and 19, resulting in loss of 19p and proximal 19q. To test whether the tumorigenic and/or metastatic phenotype w as causally related to this genetic alteration, we restored a neo-tagged hu man chromosome 19 to M12 cells by microcell-mediated transfer and assessed their growth. In vitro, the resultant hybrids grew more slowly in monolayer culture and showed a significant reduction in anchorage-independent growth as compared to M12neo controls, In vivo, all mice (13/13) injected subcuta neously (SC) with control M12neo cells developed tumors after 9-15 days, In contrast, 9/15 mice injected SC with microcell-transferred chromosome 19 h ybrid cells failed to form tumors, with 6/15 producing very small tumors af ter 120 days. Analysis of three of these six tumors showed consistent, new chromosomal changes, Furthermore, in one of the tumors, loss of a chromosom e 19 was noted in 40% of the cells. After intraprostatic injections of the hybrid cells, only 2/7 mice developed microscopic tumors, with no metastase s. These data suggest the presence of a gene or genes on chromosome 19 that function to suppress growth. (C) 2001 Wiley-Liss, Inc.