Targeting the LKB1-AMPK pathway in melanoma: Mechanism and preclinical evaluation

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DESCRIPTION (provided by applicant): Melanoma is a major form of skin cancer and arises from the malignant transformation of melanocytes. One of the most commonly mutated genes in melanoma is B-RAF (~50%), which encodes a member of the RAF protein kinase family and an intermediate in the RAS-RAF-MEK-ERK signaling cascade. Findings from recent clinical trials using B-RAF inhibitors in malignant melanoma have shown great promise for B-RAF-targeted therapy. However, the clinical findings also revealed development of resistance to B-RAF inhibitor as a major therapeutic challenge. We have recently discovered a novel bi-directional crosstalk between B-RAF and the tumor suppressor LKB1-AMPK pathway, another important signaling pathway involved in the regulation of cancer cell growth, proliferation and survival. Activators of the LKB1-AMPK pathway (such as metformin, a common anti-diabetes drug, and its analog phenformin) have recently shown anti-tumor activities in cell culture studies and mouse models. Based on our recent findings, we hypothesize that combination treatment of B- RAF inhibitors and AMPK activators will offer therapeutic advantages for the treatment of melanoma over the B-RAF inhibitor single agent therapy, and holds the potential for overcoming drug resistance to B-RAF inhibitors. The goal of this proposal is to define the biochemical mechanism underlying the attenuation of BRAF-MEK-ERK signaling by AMPK and to assess pre-clinically the therapeutic benefit of combining AMPK activators with B-RAF inhibitors for melanoma treatment. In aim 1, we will further elucidate the biochemical mechanism underlying the regulation of ERK signaling by AMPK and study its role in the regulation of cell proliferation and survival in response to energy stress. In aim 2, we will evaluate the combinatory effect of AMPK activators and B-RAF inhibitors on inhibiting tumor growth in xenografts of human melanoma cell lines and in a B-RAF-driven genetically engineered mouse model. Finally, in aim 3, we will investigate the role of the LKB1-AMPK signaling in defining both acquired and intrinsic resistance to B-RAF inhibitors in melanoma therapy and assess the potential of AMPK activators on delaying the emergence of resistance to B-RAF inhibitors.