The association of Id-1, MIF and GSTpi with acquired drug resistance in hormone independent prostate cancer cells.

Most patients with prostate cancer respond to androgen ablation therapy, but the tumor eventually progresses to an androgen-independent stage with multiple anti-cancer drug resistance. Novel therapeutic strategies for hormone independent prostate cancer need to be developed. The genes for Id-1, MIF and GSTpi were up-regulated in drug resistant cells of hormone independent prostate cancer cells using cDNA microarray gene expression analysis. In this study we aimed to investigate whether constitutive overexpression of these candidate genes in cells can affect cellular resistance to chemotherapeutic agents. The mRNA expression was determined by reverse transcriptase-polymerase chain reaction, and the Id-1, MIF and GSTpi protein contents in these cell lines were measured by Western blotting. Susceptibility of the cells to chemotherapeutic agents including doxorubicin, paclitaxel and cyclophosphamide was determined by microculture tetrazolium bromide assay. The analysis of apoptosis was assessed by annexin V assay. The cytotoxity assay results demonstrated that cells overexpressing the Id-1 gene increased in their resistance to doxorubicin, paclitaxel and cyclophosphamide. MIF expression can drive cells to increase in their resistance to paclitaxel, and GSTpi expression confers drug resistance to doxorubicin and cyclophosphamide. The induction of mdr1 gene expression was noted in up-regulation of MIF and GSTpi. Our findings suggest that overproduction of the Id-1, MIF and GSTpi proteins and coinduction of mdr-1 play an important role in the development of acquired drug resistance to various drugs of prostate cancer cells.