Background: Colorectal carcinomas (CRC) express high levels of insulin-like growth factor-I/II (IGF-I/II) and the receptor (IGF-IR). We hypothesized that selective inhibition of IGF-IR would inhibit hepatic growth of human CRC in mice.
Methods: Human CRC cells were treated in vitro with anti-IGF-IR monoclonal antibody (MoAB) with and without oxaliplatin to assess cytotoxicity. The effect of anti-IGF-IR MoAB on IGF-I-induced vascular endothelial growth factor (VEGF) production in human CRC cells was assessed by Northern blot and ELISA. We injected human CRC cells intrahepatically in nude mice, and then administered anti-IGF-IR MoAB with and without oxaliplatin. We delayed treatment in one group until large hepatic tumors were present. We assessed tumors for apoptosis, proliferation, and angiogenesis.
Results: Anti-IGF-IR MoAB and oxaliplatin inhibited CRC cell growth in vitro and combination treatment was even more effective. IGF-I stimulation of CRC cells resulted in significant upregulation of VEGF and this was completely inhibited by pretreatment with anti-IGF-IR MoAB. Anti-IGF-IR MoAB significantly inhibited hepatic growth of tumors in mice. Anti-IGF-IR MoAB plus oxaliplatin led to a significantly greater inhibition of tumor growth. Anti-IGF-IR MoAB plus oxaliplatin was just as effective at inhibiting growth of larger, more advanced liver tumors. Anti-IGF-IR MoAB, alone and in combination with oxaliplatin, led to a significant increase in tumor cell apoptosis, and a significant inhibition of tumor cell proliferation and angiogenesis.
Conclusions: These findings suggest that IGF-IR is a potential target for therapy in patients with advanced CRC.