Apoptosis of Prostate Cancer by Bax Gene Expression

Kwak, Cheol; Jin, Ren Jie; Ku, Ja Hyeon; Jeong, Hyeon; Lee, Eun Sik; Lee, Sang Eun; Lee, Chong Wook

Abstract

PURPOSE: To evaluate the antitumor effect of the proapoptotic Bax gene in prostate cancer cells, in vitro, using a plasmid vector expressing the human Bax gene.
MATERIALS AND METHODS
cDNA of the human Bax gene, amplified by RT-PCR, was cloned to pCR@3.1. The expression of the cloned Bax (pCR3.1-Bax) was observed by RT-PCR and Western blot analyses. The efficacy of growth inhibition by the cloned Bax gene was tested, in vitro, on PC-3 and DU145 human prostate cancer cell lines using the MTT assay. Immunoblot analysis for the expressions of Bcl-2 and Bcl-xL were performed. Assays were also performed to evaluate the apoptosis, DNA fragmentation and CPP32.
RESULTS
The Bax protein was expressed in the parental PC-3 cells, but not in the DU-145 cells. The expressions of Bax mRNA in the transfected PC-3 and DU-145 cells had increased by 24 hr, and those of Bax protein in the transfected PC-3 and DU-145 cells had increased by 48 and 24 hr, respectively, compared with the control cell lines. The cytotoxicity of pCR3.1-Bax on PC-3 and DU-145 cells increased significantly compared with an empty vector, pCR3.1 (p<0.05, respectively). An increased cytotoxicity of the Bax-transfected cell lines was associated with enhanced apoptosis. The Bcl-2 protein was not expressed in the transfected cells, and the levels of Bcl-xL protein expression in transfected cells were no different to those in the parenteral cells. The Bax/Bcl-xL ratio was increased by the transfection of the Bax expression vector.
CONCLUSIONS
Our results show that the cloned Bax-expression plasmid vector efficiently inhibits the growth of PC-3 and DU145 human prostate cancer cell lines. These data suggest that exogenous Bax expression may have therapeutic applications in prostate cancer.