Synergistic Antitumor Effect of Recombinant Adeno-Associated Virus-Mediated Pigment Epithelium-Derived Factor with Hyperthermia on Solid Tumor

Adeno-associated virus (AAV) is an ideal choice for gene delivery; however, its further development has been limited owing to its low transduction efficiency. DNA-damaging agents can improve AAV-mediated transgene expression. Hyperthermia, as one of the oldest documented tumor treatment modalities, can cause DNA damage as well. However, combined treatment consisting of hyperthermia and AAV-mediated gene therapy has not been reported yet. In this work we investigated whether therapy consisting of AAV-mediated pigment epithelium-derived factor (PEDF) delivery combined with hyperthermia has synergistic antitumor effect on established solid tumors. We produced the recombinant AAV encoding PEDF (rAAV-PEDF). The therapeutic effect of rAAV-PEDF plus hyperthermia was evaluated in a subcutaneous fibrosarcoma mouse model, and the possible mechanism of antitumor effect was investigated. We found that rAAV-PEDF could infect a murine fibrosarcoma cell line (Meth-A) and express PEDF protein with bioactivity in vitro. In addition, in vivo experiments suggested that the combination of rAAV-PEDF with hyperthermia could significantly suppress tumor growth and prolong survival time of treated mice. Immunofluorescence studies indicated that the combination therapy could inhibit angiogenesis and induce apoptosis in tumor tissues. An immunohistochemistry assay of tumor tissue showed that PEDF expression in the combined treatment group was significantly higher than in the rAAV-PEDF group, which implied that hyperthermia could improve the expression of PEDF protein in vivo. No significant differences were observed in each group by hematoxylin-eosin staining of major organs, serum chemistry test, and complete blood assay. These results indicate that the combination of rAAV-PEDF with hyperthermia has synergistic therapeutic effects on established solid tumors, with no side effects. In addition, hyperthermia could improve AAV-mediated transgene expression, which suggests that hyperthermia could serve as a promising adjunctive therapy for AAV-mediated gene therapy.