clincancerres.aacrjournals.org/c … 6.full.pdf
Reactivation of Tumor Suppressor Genes by the Cardiovascular
Drugs Hydralazine and Procainamide and Their Potential
Use in Cancer Therapy1
Abstract
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 M hydralazine or 10
M procainamide. 5-aza-deoxycytidine at 0.75 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) 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 G1 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 demethylation
and re-expression of the ER, RAR, 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 reexpressed
the RAR 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.
In conclusion, we provide evidence that these two cardiovascular
drugs reactivate TSGs silenced by methylation and
may become a potential useful therapy targeting one of the most
common epigenetic abnormality found in cancer cells. Just to
mention some of their potential applications, in the case of
breast cancer, for instance, the re-expression of the ER protein
could make patients with ER-negative tumors responsive to
endocrine management, and in the same way, the efficacy of
retinoid acid treatment of some tumor types could be increased
by re-expressing the RAR through its demethylation.