Abstract
Tumors require a vascular supply to grow and can achieve this via the expression of pro-angiogenic growth factors. Many potential oncogenic mutations have been identified in tumor angiogenesis. Somatic mutations in the small GTPase KRAS are the most common activating lesions found in human cancer, and are generally associated with poor response to standard therapies. Biguanides, such as the diabetes therapeutics metformin and phenformin, have demonstrated anti-tumor activity both in vitro and in vivo. The extracellular regulated protein kinases (ERK) signaling is known to be a major cellular target of biguanides. Based on KRAS activates several down-stream effectors leading to the stimulation of the RAF/mitogen-activated protein kinase/extracellular signal-regulated kinase (RAF/MEK/ERK) and phosphatidylinositol-3-kinase (PI3K) pathways, we investigated the anti-tumor effects of biguanides on the proliferation of KRAS-mutated tumor cells in vitro and on KRAS-driven tumor growth in vivo. In cancer cells harboring oncogenic KRAS, phenformin switches off the ERK pathway and inhibit the expression of pro-angiogenic molecules. In tumor xenografts harboring the KRAS mutation, phenformin extensively modifies the tumor growth causing abrogation of angiogenesis. These results strongly suggest that significant therapeutic advantage may be achieved by phenformin anti-angiogenesis for the treatment of tumor.