Reactivation of tumor suppressor genes by the cardiovascular drugs hydralazine and procainamide and their potential use in cancer therapy.

PURPOSE The purpose of this study is to evaluate the demethylating and tumor suppressor-reactivating activity of hydralazine and procainamide. EXPERIMENTAL DESIGN MDA-231, MCF-7, and T24 cell lines were treated for 5 days with 10 micro M hydralazine or 10 micro M procainamide. 5-aza-deoxycytidine at 0.75 micro M was used as positive control. BALB/c nu/nu mice xenografted with MDA-231 cells were treated with these drugs for 7 days by i.p. route. Methylation was assessed by PCR after digestion with methylation-sensitive enzymes for the ER gene and with methylation-specific PCR for retinoic acid receptor (RAR)beta and p16 genes. Gene expression was evaluated by reverse transcription-PCR and Western blot. The duration of the gene re-expressing effect of hydralazine was analyzed on T24 cells. Functionality of the re-expressed proteins was evaluated by the induction of the estrogen-responsive gene PS2 on MDA-231 cells and by the induction of G(1) arrest on T24 cells. The gene demethylating and re-expressing ability of hydralazine was tested in two patients with cervical and head and neck carcinomas, respectively. RESULTS Hydralazine and procainamide induced de-methylation and re-expression of the ER, RARbeta, and p16 genes in cultured cells. Both drugs also demethylated and re-expressed the ER gene in mice. Hydralazine re-expressed the p16 gene longer as compared with 5-aza-deoxycytidine. The re-expressed genes were functional. In addition, the treatment with oral hydralazine demethylated and re-expressed the RARbeta and p16 genes in the cervical and head and cancer patients. CONCLUSIONS These cardiovascular drugs have a promising tumor suppressor-reactivating action and could potentially be used in clinic as an anticancer treatment, most likely to increase the efficacy of current biological or chemotherapeutic treatments.