Targeting the Melanocortin 1 Receptor by Selective Small Analogs of α-Melanocortin for Melanoma Prevention

太阳紫外线辐射(UV)是黑色素瘤的主要病因，黑色素瘤是皮肤癌中最致命的一种。 在退伍军人中被诊断为癌症的人数排名第五。退伍军人的黑色素瘤发病率高于退伍军人 平民，特别是肤色较浅和晒黑能力较差的人。超过65%的退伍军人都有 这种表型。在伊拉克和阿富汗等地理区域部署数百万士兵 增加他们患黑色素瘤的风险，因为在没有最佳保护的情况下，每天不可避免地过度暴露在阳光下。 鉴于黑色素瘤先进治疗方法的局限性，重点开发新的治疗方法是很重要的。 化学预防策略，以减少其发生率。我们的目标是开发黑色素瘤预防策略 基于靶向黑素皮质素1受体(MC1R)，这是一种真正的黑色素瘤易感性的产物 已知是人类色素沉着和黑素细胞对太阳紫外线反应的主要调节基因。我们 是第一个报道MC1R的开创性发现，MC1R是一种膜结合的Gs蛋白偶联蛋白 黑素细胞刺激素激动剂α-黑素皮质素(α-α)表达于黑素细胞的受体 通过增强DNA修复和抗氧化能力来减少紫外线诱导的DNA损伤 刺激光保护真黑素的合成。另一些人则表现出一种失去- MC1R的功能变异与紫外线信号突变增加和常见的体细胞 BRAF中的V600E突变，导致黑色素瘤发生。大约50%的白人，包括大约7% 数百万退伍军人是MC1R变异的杂合子携带者，该基因突变与罹患高血压的风险增加相关 黑色素瘤。这些个人将特别受益于我们的预防战略，该战略将加强 激活MC1R。我们已经开发了α-msh的四肽和三肽类似物，它们模拟了 α-MSH对人黑素细胞有抑制作用，具有稳定性和亲脂性，其独特之处在于对 MC1R.这些多肽的美容用途包含在一项已公布的专利申请中。这些四肽是 在激活Mc1R信号方面，三肽的活性仅为α-msh的10倍 以及它对培养的人类黑素细胞的下游影响。这些多肽增强紫外线诱导的修复作用 DNA照相产物，以及在没有任何紫外线的情况下增加培养的人类皮肤替代品(CS)的色素沉着 曝光。与α-msh不同，这些小肽不应该引起免疫抑制，因为它们缺乏 α-msh的11-13位氨基酸残基(Lys-Pro-Val)与其抗肿瘤活性有关。 炎症和免疫抑制作用。我们提出我们的α-MSH的三肽和四肽类似物 对MC1R具有选择性的药物将被开发为局部药物，以刺激皮肤色素沉着并减少 紫外线诱导的DNA损伤，以维持黑素细胞基因组的稳定性，从而减少 退伍军人患黑色素瘤的风险。我们的具体目标是：I：开发MC1R选择性局部制剂 四肽和三肽，证明它们通过表皮渗透，量化它们的 在皮肤层中的浓度，并在体外验证其对完整的人皮肤或CS的光保护作用 当局部使用时。测试这两种多肽对临床前动物模型的影响，包括 将移植到免疫缺陷小鼠身上的人CS，以及皮肤类似的微型猪模型 人类的生命。终点将包括DNA损伤的测量，色素沉着的变化，增殖和 角质形成细胞和黑素细胞的凋亡。将采集血液样本进行初步药代动力学研究 测试和组织样本将被检查是否有严重的毒理学影响。这个项目的结果应该是 推动我们朝着研究新药申请和临床试验更近一步。

Solar ultraviolet radiation (UV) is the main etiological factor for melanoma, the deadliest form of skin cancer, and the fifth most diagnosed cancer in veterans. The incidence of melanoma is higher in veterans than in civilians, particularly in individuals with light skin color and poor tanning ability. Over 65% of all veterans have this phenotype. Deployment of millions of soldiers in geographical areas such as Iraq and Afghanistan increases their risk for melanoma due to unavoidable daily excessive sun exposure without optimal protection. Given the limitations of advanced therapeutic options for melanoma, it is important to focus on developing new chemoprevention strategies to reduce its incidence. Our goal is to develop a melanoma prevention strategy based on targeting the melanocortin 1 receptor (MC1R), the product of a bona fide melanoma predisposition gene known to be a major regulator of human pigmentation and the response of melanocytes to solar UV. We were the first to report the seminal findings that activation of the MC1R, a membrane-bound Gs protein-coupled receptor expressed on melanocytes, by its agonist α-melanocyte stimulating hormone (α-melanocortin; α-MSH) reduces UV-induced DNA damage by enhancing DNA repair and antioxidant capacities, in addition to stimulating the synthesis of photoprotective eumelanin. Others have shown that expression of a loss-of- function variant of MC1R is associated with increased UV signature mutations and the common somatic V600E mutation in BRAF, that drive melanomagenesis. About 50% of all White Caucasians, including about 7 million veterans, are heterozygous carriers of a MC1R variant, a genotype associated with increased risk for melanoma. These individuals will particularly benefit from our prevention strategy that will enhance the activation of the MC1R. We have developed tetra- and tripeptide analogs of α-MSH that mimic the effects of α-MSH on human melanocytes, and are stable and lipophilic, and unique in their high selectivity for the MC1R. The cosmetic use of these peptides is covered by a published patent application. The tetrapeptides are 100 fold more potent, and the tripeptides are only 10 fold less potent than α-MSH in activating MC1R signaling and its downstream effects in cultured human melanocytes. These peptides enhanced repair of UV-induced DNA photoproducts, and increased pigmentation of cultured human skin substitutes (CSS) without any UV exposure. These small peptides, unlike α-MSH, should not cause immunosuppression, since they lack the COOH-terminal 11-13 amino acid residues (Lys-Pro-Val) of α-MSH that are responsible for its anti- inflammatory and immunosuppressive effects. We propose that our tri- and tetrapeptide analogs of α-MSH that are selective for the MC1R will be developed as topical agents to stimulate skin pigmentation and reduce UV-induced DNA damage, in order to maintain the genomic stability of melanocytes, and therefore reduce the risk for melanoma in veterans. Our Specific Aims are: I: To develop topical formulations of MC1R-selective tetrapeptide and tripeptidepeptide, demonstrate their permeation through the epidermis, quantify their concentrations in the skin layers, and validate their photoprotective effects on intact human skin or CSS in vitro when applied topically. II. To test the effects of the two peptides on pre-clinical animal models, including human CSS that will be grafted onto immunodeficient mice, and a miniature pig model with skin similar to that of humans. Endpoints will include measurement of DNA damage, changes in pigmentation, proliferation and apoptosis of keratinocytes and melanocytes. Blood samples will be obtained for preliminary pharmacokinetics testing and tissue samples will be examined for gross toxicological effects. The outcome of this project should advance us closer towards application for Investigational New Drug and conducting clinical trials.