Baculovirus vectors for antiangiogenesis-based cancer gene therapy

Baculovirus is an insect virus that is non-pathogenic to humans and has emerged as a promising gene therapy vector. Since solid tumor growth/metastasis critically relies on angiogenesis and hEA, a fusion protein comprising human endostatin and angiostatin, exhibits potent antiangiogenic and antitumor efficacy in mouse models; this study aimed to evaluate the feasibility of baculovirus for hEA expression and antiangiogenesis-based cancer gene therapy. Toward this end, we constructed Bac-hEA that mediated transient hEA expression and Bac-ITR-hEA that exploited the adeno-associated virus inverted terminal repeats (ITRs) for prolonged hEA expression. Western blot and ELISA analyses showed that both Bac-hEA and Bac-ITR-hEA expressed hEA in transduced mammalian cells, yet Bac-ITR-hEA only marginally prolonged the hEA expression. In comparison with Bac-hEA, nonetheless, Bac-ITR-hEA significantly enhanced the hEA expression level that concurred with augmented antiangiogenic properties, as demonstrated by cell proliferation, migration and tubule network formation assays. Importantly, intratumoral injection of Bac-ITR-hEA into prostate cancer mouse models, when compared with Bac-hEA, exerted stronger antiangiogenic effects in vivo, more potently inhibited tumor growth and significantly prolonged mouse survival. This study collectively supported the notion that hEA is an effective antiangiogenic protein and proved the potential of baculovirus as a vector for antiangiogenesis-based cancer therapy, which may be combined with chemotherapy, radiotherapy or gene therapies using other vectors.