Impact of Endogenous DOPA Signaling on Melanocyte Homeostasis and Melanoma Susceptibility

摘要 与皮肤浅色的人相比，患黑色素瘤的风险要高得多。 那些有深色皮肤的人。虽然这种差异传统上被归因于紫外线 黑色素的辐射屏蔽作用，有越来越多的证据表明这一点 可能不能解释这些差异的全部。我们的初步数据显示高水平的 黑素细胞的基线色素沉着与增殖抑制和局限性相关 致癌潜力。这种影响似乎不是由黑色素本身造成的，而是由 黑色素合成中间体二羟基苯丙氨酸(DOPA)。在浅色黑素细胞和 黑色素瘤细胞，外源性DOPA诱导更分化的细胞状态 通过增加成熟的黑素细胞分化抗原的表达，增加 色素生成，增殖能力下降，c-Myc和c-Myc表达减少 FOXM1是关键的增殖相关转录因子，在 很多癌症。我们的结果表明，多巴酚A可能抑制胆碱能受体M受体。 1(CHRM1)，这是一种GQ偶联G蛋白偶联受体，似乎促进黑色素瘤 扩散。CHRM1的基因消融阻断了DOPA的抗增殖作用，而 低基线CHRM1促进黑色素瘤细胞系CHRM1过表达 呈现的细胞对DOPA最新敏感。 在目标1中，我们将验证试点数据，这些数据表明CHRM1在初级 黑素细胞和黑色素瘤，并使用一种新的生物发光共振能量转移(BRET) 用于定义CHRM1和DOPA影响的信号机制的生物传感器平台 黑素细胞功能与黑色素瘤增殖。在目标2中，我们将使用与医学相关的 临床前黑色素瘤模型测试药物CHRM1拮抗剂抑制这一想法 体内黑色素瘤，既可作为单一疗法，又可与标准免疫和联合治疗相结合 靶向黑色素瘤疗法。为此，我们将使用茎递送的DOPA/Caridopa，a 目前FDA批准的治疗帕金森氏症的药物组合在试点研究中表现良好 能耐受并有效抑制黑色素瘤生长的小鼠模型。这项工作将共同定义 皮肤色素沉着、黑色素瘤风险、DOPA和CHRM1之间的机制联系，很可能 提供关键的临床前体内数据，支持新的人体试验以测试疗效 将帕金森氏症药物重新用于治疗黑色素瘤。

Abstract The risk of melanoma is substantially higher in people with lightly pigmented skin, compared to those with darkly pigmented skin. While this discrepancy is traditionally attributed to the ultraviolet radiation shielding effect of melanin pigment, there is accumulating evidence suggesting that this may not account for the totality of these differences. Our preliminary data show that high levels of baseline pigmentation in melanocytes correlates with inhibited proliferation and limited tumorigenic potential. This effect appears to result not from melanin itself, but rather, from the melanin synthesis intermediate dihydroxyphenylalanine (DOPA). In light melanocytes and melanoma cells, addition of exogenous DOPA induced a more differentiated cell state as defined by increased expression of well-established melanocyte differentiation antigens, increased pigment production, decreased proliferative capacity, and decreased expression of c-Myc and FOXM1, which are critical proliferation-associated transcription factors that are overexpressed in many cancers. Our results indicate that DOPA likely inhibits the cholinergic receptor muscarinic 1 (CHRM1), which is a Gq coupled G Protein-Coupled Receptor that seems to promote melanoma proliferation. Genetic ablation of CHRM1 blocked DOPA’s anti-proliferative effect, while overexpression of CHRM1 in melanoma cell lines with low baseline CHRM1 promoted and also rendered cells newly sensitive to DOPA. In Aim 1 we will validate pilot data suggesting that CHRM1 mediates DOPA effects in primary melanocytes and melanoma, and use a new bioluminescence resonance energy transfer (BRET) biosensor platform to define the signaling mechanisms by which CHRM1 and DOPA impact melanocyte function and melanoma proliferation. In Aim 2 will we will use medically relevant preclinical melanoma models to test the idea that pharmacologic CHRM1 antagonism inhibits melanoma in vivo, both as monotherapy, and in combination with standard of care immune and targeted melanoma therapeutics. For this we will use stemically delivered DOPA/carbidopa, a currently FDA-approved drug combination for Parkinson’s disease, which in pilot studies was well tolerated and effectively inhibited melanoma growth mouse models. Together this work will define a mechanistic link between skin pigmentation, melanoma risk, DOPA and CHRM1, and is likely to provide critical preclinical in vivo data that would support new human trials to test the efficacy of repurposing a Parkinson’s disease drug as a melanoma therapeutic.