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

描述（由申请人提供）：黑色素瘤是皮肤癌的一种主要形式，由黑色素细胞的恶性转化引起。黑色素瘤中最常见的突变基因之一是B-RAF（约50%），其编码RAF蛋白激酶家族的成员和RAS-RAF-MEK-ERK信号级联中的中间体。最近在恶性黑色素瘤中使用B-RAF抑制剂的临床试验结果显示了B-RAF靶向治疗的巨大前景。然而，临床研究结果也揭示了对B-RAF抑制剂的耐药性的发展是一个主要的治疗挑战。我们最近发现了B-RAF和肿瘤抑制因子LKB 1-AMPK通路之间的一种新的双向串扰，LKB 1-AMPK通路是另一种参与调节癌细胞生长、增殖和存活的重要信号通路。LKB 1-AMPK通路的激活剂（如二甲双胍，一种常见的抗糖尿病药物，及其类似物苯丙氨酸）最近在细胞培养研究和小鼠模型中显示出抗肿瘤活性。基于我们最近的发现，我们假设B- RAF抑制剂和AMPK激活剂的联合治疗将为黑色素瘤的治疗提供优于B-RAF抑制剂单药治疗的治疗优势，并且具有克服对B-RAF抑制剂的耐药性的潜力。本提案的目的是确定AMPK减弱BRAF-MEK-ERK信号传导的生化机制，并在临床前评估AMPK激活剂与B-RAF抑制剂联合治疗黑色素瘤的治疗益处。在目标1中，我们将进一步阐明AMPK调节ERK信号转导的生化机制，并研究其在调节细胞增殖和存活响应能量应激中的作用。在目标2中，我们将评估AMPK激活剂和B-RAF抑制剂在人黑素瘤细胞系异种移植物和B-RAF驱动的基因工程小鼠模型中抑制肿瘤生长的组合作用。最后，在目标3中，我们将研究LKB 1-AMPK信号传导在定义黑色素瘤治疗中对B-RAF抑制剂的获得性和内在耐药性中的作用，并评估AMPK激活剂延迟B-RAF抑制剂耐药性出现的潜力。

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.