FOXD3 up-regulation and ERBB3 signaling as an adaptive response to RAF inhibitors

描述(由申请人提供)：黑色素瘤是最致命的皮肤癌形式，代表了化疗耐药的范例。我们的目标是了解黑色素瘤的耐药机制，为改进靶向治疗策略提供基础。丝氨酸/苏氨酸激酶B-RAF在40-60%的黑色素瘤中发生体细胞突变。突变型B-RAF过度激活MEK-ERK1/2信号，是黑色素瘤生长和侵袭所必需的。RAF抑制剂PLX4032(RG7204/Vemurafenib)的I期临床试验在突变的B-RAF黑色素瘤患者中产生了令人振奋的结果。然而，19%的患者对B-RAF抑制剂有内在耐药，大多数初始应答者现在因获得性耐药而复发。在体内模型中，RAF/MEK抑制剂有效地抑制突变的B-RAF驱动的黑色素瘤生长，但停止治疗会导致肿瘤快速再生长，因此无法根除肿瘤也是显而易见的。B-RAF抑制剂耐药的潜在机制尚不清楚，必须加以阐明，以优化未来的临床试验。我们的研究将集中在干细胞因子FOXD3，它是在B-RAF抑制突变的B-RAF黑色素瘤细胞后上调的。在这项应用的目标1中，我们将在体内确定FOXD3在黑色素瘤生长和对B-RAF抑制剂的耐药性中的作用。在目标2中，我们将确定在突变的B-RAF黑色素瘤中调节FOXD3的机制。在目标3中，我们将确定ERBB3，FOXD3的直接靶点，在诱导RAF抑制剂的作用中的作用。我们的实验方法是创新的，我们使用临床分级抑制剂和分子生物学方法在生理相关的体外和体内模型中调节B-RAF的活性。在我们的实验完成后，我们预计已经确定了一种新的耐药促进机制，并为利用FOXD3和/或ERBB3作为B-RAF抑制剂耐药黑色素瘤细胞的生物标志物提供了证据。

DESCRIPTION (provided by applicant): Melanoma is the deadliest form of skin cancer and represents a paradigm for chemo-resistance. We aim to understand resistance mechanisms in melanoma in order to provide the basis for improved targeted therapeutic strategies. The serine/threonine kinase, B-RAF, is somatically mutated in 40-60% of melanomas. Mutant B- RAF hyper-activates MEK-ERK1/2 signaling and is required for melanoma growth and invasion. A phase I clinical trial with the RAF inhibitor, PLX4032 (RG7204/Vemurafenib) yielded promising results in mutant B-RAF melanoma patients. However, 19% of patients were intrinsically resistant to B-RAF inhibitors and most initial responders are now relapsing from acquired drug resistance. An inability to eradicate tumors is also evident using in vivo models in which RAF/MEK inhibitors potently inhibit mutant B-RAF-driven melanoma growth but treatment cessation results in rapid tumor re-growth. The mechanisms underlying resistance to B-RAF inhibitors are unknown and must be elucidated to optimize future clinical trials. Our studies will focus on the stemness factor, FOXD3, which is up-regulated following B-RAF inhibition in mutant B-RAF melanoma cells. In Aim 1 of this application, we will determine the role of FOXD3 in melanoma growth and resistance to B-RAF inhibitors in vivo. In Aim 2, we will identify mechanisms regulating FOXD3 in mutant B-RAF melanomas. In Aim 3, we will determine the role of ERBB3, a direct target of FOXD3, in eliciting the effects of RAF inhibitors. Our experimental approaches are innovative in that we modulate B-RAF activity using clinical grade inhibitors and molecular biology approaches in physiologically relevant in vitro and in vivo models. At the completion of our experiments, we expect to have identified a novel resistance-promoting mechanism and provided evidence for utilizing FOXD3 and/or ERBB3 as a biomarker for B-RAF inhibitor resistant melanoma cells.