PARTIAL GROWTH SUPPRESSION OF HUMAN PROSTATE-CANCER CELLS BY THE KREV-1 SUPPRESSOR GENE

A series of functional studies were performed to assess the potential role of the ras-related transformation suppressor gene, Krev-1, in sup pressing prostate cancer cell growth. Three human prostate cancer cell lines, PC-3, TSU-Pr1, and DU-145 were transfected with a plasmid cont aining the Kuev-1 cDNA and a neomycin resistance gene. Selected G418-r esistant clones were isolated and expanded into cell lines. All cloned transfectants exhibited a significant reduction in their in vitro gro wth rates, i.e., longer doubling times, when compared to the parental cell lines. Molecular analysis of the Kuev-1 cloned transfectants reve aled that they all contained variable copy numbers of the Krev-1 gene and expressed high levels of Krev-1 mRNA transcript, as shown by South ern and Northern analysis, respectively. To determine whether the biol ogical properties associated with tumorigenicity were changed in these Krev-1 transfectants, their growth characteristics were examined on t he basis of their ability to a) form colonies in soft agar, and b) pro duce tumors in SCID mice. The majority of the Krev-1 transfectants fro m the PC-3 and TSU-Prl cell lines showed a substantially reduced abili ty to form colonies in soft agar and produced significantly smaller tu mors when inoculated into SCID mice. In contrast, there was no signifi cant reduction in the soft agar colony-forming ability or in vivo tumo rigenicity of the DU-145 Krev-1 transfectants. These results suggest t hat the Krev-1 suppressor gene induces partial suppression of the mali gnant phenotype of human prostate cancer cells containing activated ra s oncogenes. (C) 1994 Wiley-Liss, Inc.