Enhanced therapeutic efficacy of an adenovirus-PEI-bile-acid complex in tumors with low coxsackie and adenovirus receptor expression

Adenovirus (Ad) is a potential vehicle for cancer gene therapy. However, cells that express low levels of the coxsackie and adenovirus receptor (CAR) demonstrate poor Ad infection efficiency. We developed a bile acid-conjugated poly(ethyleneimine) (DA3)-coated Ad complex (Ad/DA3) to enhance Ad transduction efficiency. The size distribution and zeta potential of Ad/DA3 increased to 324 ± 3.08 nm and 10.13 ± 0.21 mV, respectively, compared with those of naked Ad (108 ± 2.26 nm and −17.7 ± 1.5 mV). The transduction efficiency of Ad/DA3 increased in a DA3 polymer concentration-dependent manner. Enhanced gene transfer by Ad/DA3 was more evident in CAR-moderate and CAR-negative cancer cells. Competition assays with a CAR-specific antibody revealed that internalization of Ad/DA3 was not mediated primarily by CAR but involved clathrin-, caveolae-, and macropinocytosis-mediated endocytosis. Cancer cell death was significantly increased when oncolytic Ad and DA3 were complexed (RdB-KOX/DA3) compared to that of naked oncolytic Ad and was inversely proportional to CAR levels. Importantly, RdB-KOX/DA3 significantly enhanced apoptosis, reduced angiogenesis, reduced proliferation, and increased active viral replication in human tumor xenografts compared to that of naked Ad. These results demonstrate that a hybrid vector system can increase the efficacy of oncolytic Ad virotherapy, particularly in CAR-limited tumors.