The Molecular Mechanisms of the Dual Anti-Angiogenic and Anti-Tumor Effects of rAAV-HGFK1

Abstract

The kringle 1 domain of human hepatocyte growth factor (HGFK1) was previously shown to inhibit bovine aortic endothelial (BAE) cell proliferation, suggesting that it might be an anti-angiogenic molecule. Recently, we demonstrated the in vivo efficacy of a recombinant adeno-associated virus carrying HGFK1 (rAAV-HGFK1) for the treatment of hepatocellular carcinoma (HCC) in a rat orthotopic HCC model. We showed that HGFK1 exhibited dual anti-angiogenic and anti-tumor cell effects on hepatocellular carcinoma. To our surprise, HGFK1 did not act through the HGF/HGFR pathway. Instead, it worked mainly through EGF/EGFR signaling, with more minor contributions from VEGF/VEGFR and bFGF/bFGFR signaling in both MECs and tumor cells. To understand the molecular mechanisms and down-stream targets of rAAV-HGFK1, we applied genome-wide expression profiling technology followed by RT-PCR validation, to examine the differentially expressed genes upon rAAV-HGFK1 treatment on mice microvessel endothelial cells (MECs) and rat hepatoma McA-RH7777 cell lines, as compared with rAAV-EGFP (Enhanced green fluorescent protein) treatment. Our results showed that three groups of mechanisms were involved in the anti-angiogenic and anti-tumor signaling network of rAAV-HGFK1: (1) Promotion of apoptosis, (2) Promotion of JNK signaling cascade, and (3) Promotion of cell adhesion and cell migration. In conclusion, this study reveals the pathways regulated by rAAV-HGFK1 and contributes to the further development of HGFK1 cancer gene therapy for the treatment of hepatocellular carcinoma (HCC).