Dovitinib synergizes with oxaliplatin in suppressing cell proliferation and inducing apoptosis in colorectal cancer cells regardless of RAS-RAF mutation status

Background: Cancer is the result of a multistep process of genomic alterations, including mutations in key regulatory proteins that result in loss of balanced gene expression and subsequent malignant transformation. Throughout the various stages of colorectal carcinoma (CRC), complex genetic alterations occur, of which over-expression of growth factors, such as vascular endothelial growth factor, fibroblast growth factor and platelet-derive growth factor and their corresponding receptor tyrosine kinases, have been shown to correlate with invasiveness, tumor angiogenesis, metastasis, recurrence, and poor prognosis of colorectal cancer. To evaluate the therapeutic effect, we combined Dovitinib, an orally bioavailable, potent inhibitor of class III-V receptor tyrosine kinases with chemotherapeutic drug, oxaliplatin in preclinical models of colon cancer. Methods: Human colon cancer cells with different RAS-RAF mutation status (HCT-116, HT-29, SW-480, CaCO2 and LS174T) were treated with a combination of Dovitinib and Oxaliplatin at low dosage followed by assays to investigate the effect of the combination on cell proliferation, cell migration, cell apoptosis and signaling pathways involved in molecular mechanism of drug(s). The antitumor effects of either of the drugs were compared to the combination using human colon carcinoma cell line HT-29 xenograft model. Treated vs untreated tumor sections were also compared for proliferation and angiogenesis markers by immunohistochemistry. Results: The combination of dovitinib and oxaliplatin showed higher in vitro cytotoxicity in colon cell lines irrespective of their RAS-RAF status as compared to either of the drugs alone. Simultaneous inhibition of MAP kinase and AKT pathways and induction of apoptosis via activation of caspases 9/caspases 3 contributed to the synergistic effect of this combination therapy. In the xenograft model, the combination showed a significantly higher antitumor activity. Immunohistochemistry of post treatment tumors showed a significant decrease in proliferation and angiogenesis as compared to either of the treatments alone. Conclusions: This study demonstrates the synergistic antitumor activity of combination of dovitinib and oxaliplatin against colon cancer with different RAS-RAF status. The combination also showed its antitumor efficacy in a multidrug resistant phenotype xenograft model. This provides a basis for further investigation for its potential in clinical setting for colorectal cancer.