We are investigating whether the histone deacetylase inhibitor FK228 (FR901228, depsipeptide) can increase the efficiency of adenovirus gene therapy. FK228 is currently in phase II clinical trials for the treatment of patients with peripheral and cutaneous T-cell lymphoma. Previously, we showed that treatment of a diverse group of cancer cell lines with 1ng/ml FK228 caused an increase in the RNA levels of coxsackie adenovirus receptor (CAR) and αv-integrin, two proteins required for efficient adenovirus infection. FK228 treatment prior to adenovirus infection was associated with a 5-10 fold increase in adenovirus transgene expression. Increases in transgene expression were not found in cultured normal cells from breast, liver or kidney following similar FK228 treatment. These results suggest that FK228 treatment may result in preferential enhancement of adenovirus transgene expression in cancer cells in vivo. To further evaluate this differential sensitivity between normal and cancer cells, we examined the effect of FK228 in athymic mice bearing advanced-stage subcutaneous LOX IMVI human melanoma xenografts. Mice were treated with multiple drug doses and schedules. The efficacy of the treatment was evaluated by analyzing the levels of CAR and αv-integrin RNA and protein. The optimum FK228 treatment of those evaluated was a single dose of 3.6 mg/kg administered through the tail vein. Xenografts from mice (n=6) treated with this dose and analyzed at 6 hr following drug administration by semi-quantitative RT-PCR analysis showed an 10.7-fold (±4.9-fold) increase in CAR levels over untreated mice while at 24 hr there was a 13.6-fold (±4.3-fold) increase. By comparison, the levels of CAR in the livers, kidneys and lungs from the same animals remained unchanged. Xenografts from mice (n=6) treated with 3.6 mg/kg and analyzed after 24 hr by western blot analysis showed a 9.2-fold (±4.8-fold) increase in CAR protein over untreated mice while at 6 hr following drug treatment there was no increase in CAR protein levels. Little change in αv-integrin RNA or protein was observed under any condition. Based on these results xenograft-bearing mice (n=10) treated with a single dose of 3.6 mg/kg FK288 were given an intra-tumor injection of adenovirus carrying a GFP transgene (2E+9 VP) 24 hr after FK228 administration. The xenografts were analyzed 24 hr after virus infection. Analysis of RNA from these xenografts by semi-quantitative RT-PCR analysis showed a 7.2-fold (±4.5-fold) increase in expression from the adenovirus GFP transgene in the FK228 treated mice. Thus, as previously observed in vitro, the FK228 induced increase in adenovirus transgene expression also occurs in vivo. These studies suggest that FK228 treatment can increase the efficiency of adenovirus gene therapy in vivo.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]