Characterization of early events in bulge McSCs and their progeny during melanoma

描述（由申请人提供）：该基金的目标是研究黑色素细胞干细胞（McSCs）及其后代的黑色素瘤形成潜力，从而了解黑色素瘤发生的初始事件。黑色素瘤的发病率在美国正在增加，可能是由于皮肤暴露于紫外线辐射的增加。目前，没有办法治愈黑色素瘤时，它成为转移。开发早期干预的靶点和早期诊断和预防的有效策略是必要的，然而涉及黑素瘤起始的机制是难以捉摸的。在小鼠黑色素瘤模型中，我们可以诱导黑素细胞中的致癌突变。然而，小鼠的黑素细胞主要存在于毛囊中，并且它们的行为在毛发周期中发生变化，使得很难区分致癌突变引起的变化。目前，还没有研究解决这些致癌突变何时以及如何在体内对黑素细胞产生影响。尽管人们相信干细胞可能是肿瘤起源细胞的最佳候选细胞，但McSC参与黑色素瘤的情况仍然未知。由于McSC位于毛囊中，并且它们的主要功能是产生毛发黑色素细胞，而大多数黑色素瘤产生于毛囊间表皮，因此该群体在黑色素瘤研究中研究不足。我们发现，毛囊中的MCSCs引起表皮黑素细胞在成年小鼠UVB辐射后。我们推测隆起处的McSCs可能是导致黑色素瘤的表皮黑素细胞的来源。在目标1中，我们将使用遗传小鼠模型在McSCs中诱导致癌突变（BRAF激活和PTEN缺失，这通常在人黑色素瘤中发现）。我们还将利用一种遗传上易于处理的荧光报告基因来追踪 变异的黑素细胞利用这些小鼠，我们将仔细描述突变如何诱导毛囊周期的每个阶段的隆起和表皮中的黑素细胞的增殖，分化和迁移状态的变化。这些分析将是第一个捕捉 由致癌突变驱动的黑素细胞的初始改变，并确定来自不同黑素细胞群体的黑素瘤发生率。在目标2中，我们将从不同位置分离黑素细胞，以检查它们在免疫缺陷小鼠中移植和诱导突变后产生黑色素瘤的潜力。通过分析每个特定人群中黑色素瘤的发病率，我们将确定是否存在导致黑色素瘤形成的内在差异。通过这些原位和离体研究阐明起源细胞将最终有助于确定预防黑色素瘤发生的新策略。

DESCRIPTION (provided by applicant): The goal of this grant is to investigate the melanoma-forming potential of melanocyte stem cells (McSCs) and their progeny, thereby understanding initial events of melanomagenesis. The incidence of melanoma is increasing in the United States, presumably due to increased skin exposure to UV radiation. Currently, there is no way to cure melanoma when it becomes metastatic. Developing targets for early intervention and effective strategies for early diagnosis and prevention are necessary, however the mechanism involved in melanoma initiation is elusive. In mouse melanoma models, we can induce oncogenic mutations in melanocytes. However, melanocytes in mice primarily reside within the hair follicle and their behavior alters during the hair cycle, making it difficult to distinguish te changes caused by oncogenic mutations. Currently, no study has addressed when and how these oncogenic mutations exert its effect on melanocytes in vivo. Despite the belief that stem cells may be the best candidate for the cell of origin in tumors, the involvement of McSCs in melanoma remains unknown. Since McSCs are located in the hair follicle and their primary function is to generate hair melanocytes whereas most melanomas arise from inter-follicular epidermis, this population has been under-studied in melanoma studies. We found that follicular McSCs give rise to epidermal melanocytes in adult mice following UVB-radiation. We hypothesize that McSCs in the bulge may be the origin of epidermal melanocytes that are responsible for melanoma. In Aim 1, we will use genetic mouse models to induce oncogenic mutations (BRAF activation and PTEN loss that are often found in human melanoma) in McSCs. We will also utilize a genetically tractable fluorescent reporter to trace the fate and behavior of the mutated melanocyte. Utilizing these mice, we will carefully delineate how mutations induce change in proliferation, differentiation and migration status of melanocytes in the bulge and epidermis at each stage of the hair follicle cycle. These analyses will be the first to capture the initial alterations in melanocytes driven by oncogenic mutations and to determine the incidence of melanomagenesis from distinct populations of melanocytes. In Aim 2, we will isolate the melanocytes from distinct locations to examine their potential to produce melanoma upon transplantation and induction of the mutations in immunodeficient mice. By analyzing the incidence of melanoma in each specific population, we will determine whether there are intrinsic differences that cause melanoma formation. Elucidating the cell of origin through these in situ and ex vivo studies will ultimately help identification of novel strategies to prevent melanomagenesis.