The histone deacetylase inhibitor FK228 increases the efficacy of adenovirus-mediated p53 family gene therapy in in Vitro and in Vivo human cancer models

Abstract

3160 Background: p53 gene therapy is being tested clinically for the treatment of human cancer, however some cancer models (in vivo and in vitro) are resistant to p53. We have shown that p73/p63, the newly discovered p53 family members, is effective in some of colorectal cancer cells resistant to p53-mediated apoptosis. FK228 is a natural histone deacetylase inhibitors that is known to enhance adenovirus transgene expression. Before testing whether a combination of the adenovirus (Ad)-mediated transfer of the p53 family genes with FK228 could be developed in clinical trials, preclinical experiments were performed. Methods: The effect of FK228 on adenoviral transduction, coxsakie-adenovirus receptor (CAR) expression, and acetylation of exogenous p53 family proteins were investigated. Apoptosis was examined by flow cytometry, PARP cleavage, and TUNEL analyses. The Induction of p53-target genes in FK228-treated cells was measured using Western blot. The in vivo effects of FK228 on the anti-tumor activity of Ad-mediated transfer of the p53 family genes were determined by using human cancer xenograft models. Results: Cells treated with FK228 prior to infection had a 3–7-fold increase in transgene expression from a beta-galactosidase- or GFP-expressing Ad. The enhanced viral transduction was due in part to the up-regulation of the CAR protein. Pretreatment with FK228 enhanced apoptosis induced by p53 family through increased expression of exogenous proteins. Additionally, FK228 induced hyperacetylation of exogenous p53 or p63. The levels of certain p53-targets, including NOXA and PIG3, were significantly increased compared with treated with Ad alone. Together, the combination of FK228 and Ad-p53 or Ad-p63 induced Bax translocation to the mitochondria. In human cancer xenograft models, FK228 significantly increased the therapeutic effectiveness of p53 gene therapy. Conclusions: FK228 increased expression of exogenous p53 family gene transfer, apoptosis, and antitumor mechanisms. These results support a clinical combination of FK228 with p53 gene therapy in cancer patients. No significant financial relationships to disclose.