Development of a hammerhead ribozyme against BCL-2. II. Ribozyme treatment sensitizes hormone-resistant prostate cancer cells to apoptotic agents

Background: Several lines of evidence strongly implicate a crucial role for the apoptosis suppressing bcl-2 oncogene in the genesis of hormone-refractory human prostate cancer. By efficiently destroying the intracellular bcl-2 mRNA, one might be able to make the prostate cancer cell responsive again to conventional apoptotic stimuli such as androgen withdrawal. To achieve this end, we have devised a catalytic antisense RNA strategy (Ribozyme) for bcl-2 and evaluated its gene therapeutic potential. Methods and Results: Bcl-2 overexpressing LNCaP prostatic carcinoma cells (LNCaP/bcl-2) were transfected with the anti-bcl-2 ribozyme RNA using a ployamine-based transfection reagent and the reduction in the intracellular bcl-2 mRNA levels was followed by a ribonuclease protection assay. Using a cell viability assay, prior ribozyme transfection and subsequent application of apoptotic stimuli such as serum starvation or phorbol ester treatment caused a 30% increase in cell death by apoptosis than with these apoptotic stimuli alone. Conclusions: The results obtained strongly support the ability of a potential anti-bcl-2 ribozyme therapy to synergize with other agents in inducing apoptosis of hormone-resistant human prostate cancer cells.