The insulin-like growth factor I receptor/insulin receptor tyrosine kinase inhibitor pqip exhibits enhanced antitumor effects in combination with chemotherapy against colorectal cancer models

Purpose: There is growing evidence implicating the importance of the insulin-like growth factor (IGF) pathway in colorectal cancer based upon the results of population studies and preclinical experiments. However, the combination of an IGF-I receptor (IGF-IR) inhibitor with standard colorectal cancer chemotherapies has not yet been evaluated. In this study, we investigated the interaction between PQIP, the dual IGF-IR/insulin receptor tyrosine kinase inhibitor, and standard chemotherapies in colorectal cancer cell line models. Experimental Design: The antiproliferative effects of PQIP, as a single agent and in combination with 5-fluorouracil, oxaliplatin, or SN38, were analyzed against four colorectal cancer cell lines. Downstream effector proteins, apoptosis, and cell cycle were also assessed in the combination of PQIP and SN-38. Lastly, the efficacy of OSI-906 (a derivative of PQIP) combined with irinotecan was further tested using a human colorectal cancer xenograft model. Results: Treatment with the combination of PQIP and each of three chemotherapies resulted in an enhanced decrease in proliferation of all four colorectal cancer cell lines compared with single-agent treatment. This inhibition was not associated with a significant induction of apoptosis, but was accompanied by cell cycle arrest and changes in phosphorylation of Akt. Interestingly, antitumor activity between PQIP and SN-38 in vitro was also reflected in the human colorectal cancer xenograft model. Conclusions: Combination treatment with PQIP, the dual IGF-IR/insulin receptor tyrosine kinase inhibitor, and standard colorectal cancer chemotherapy resulted in enhanced antiproliferative effects against colorectal cancer cell line models, providing a scientific rationale for the testing of OSI-906 and standard colorectal cancer treatment regimens.