Enhanced transgene expression in urothelial cancer gene therapy with histone deacetylase inhibitor.

Purpose: Efficient adenoviral infection requires the presence of the coxsackievirus and adenovirus receptor (CAR). We determined whether the histone deacetylase inhibitor FR901228 (Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan) increases the efficiency of adenoviral gene therapy in bladder cancer in vivo and in vitro.

Materials And Methods: Cytotoxicity studies were performed to determine a minimally cytotoxic FR901228 concentration for bladder cancer cells. The level of CAR expression was determined by fluorescence activated cell scanning and/or reverse transcriptase-polymerase chain reaction analysis in FR901228 treated bladder cell lines. The in vivo effect on adenoviral gene expression was investigated in athymic mice.

Results: The concentration of FR901228 showing no or minimal cytotoxicity that was selected for these studies was 0.5 ng/ml for bladder cancer cells. Treatment of cancer cells with 0.5 ng/ml histone deacetylase inhibitor increased CAR RNA levels and acetylated histone H3. This increase was associated with a 5 to 10-fold increase in adenoviral infection, as evidenced by increased transgene expression from a beta-galactosidase containing adenoviral vector. Intravenous administration of FR901228 enhanced CAR expression in athymic mice. The combination of p53 adenovirus and histone deacetylase inhibitor resulted in significant tumor inhibition in vitro and in vivo.

Conclusions: Nontoxic doses of the histone deacetylase inhibitor FR901228 increased CAR RNA levels and resulted in the marked enhancement of transgene expression after adenoviral infections. FR901228 pretreatment may increase the sensitivity of tumor cells to adenoviral gene therapy vectors.