Suppression activity of pro-apoptotic gene products in cancer cells, a potential application for cancer gene therapy.

Overexpression of anti-apoptotic Bcl-2 and Bcl-XL proteins may play a role in the development of resistance to cancer therapy. We examined the expression of these proteins in prostate, breast, and ovarian cancer cells. We found that some of these cancer cell lines expressed high levels of Bcl-XL or Bcl-2., In order to develop an effective strategy to overcome the potential inhibition of cancer therapy by Bcl-2 and Bcl-XL, we tested the inhibitory ability of several pro-apoptotic or tumor suppressor genes in these cells. The expression of these genes induced apoptosis or suppressed cell growth with variable efficiency in these cells. Harakiri (Hrk) appears to result in the greatest induction of apoptosis or inhibition of cell growth Mtd, bax and bcl-XS were also effective in inhibiting cell growth. Furthermore, transfection of Hrk, bax, or Mtd into these cells caused significantly less colony formation than in cells transfected with p53 or BRCA1. Therefore, these results suggest that Hrk, bax, and Mtd are potent therapeutic agents for cancers expressing high levels of Bcl-2 and Bcl-XL.