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

描述（由申请人提供）：本资助的目的是研究黑素细胞干细胞（McSCs）及其后代形成黑素瘤的潜力，从而了解黑素瘤形成的初始事件。在美国，黑色素瘤的发病率正在上升，可能是由于皮肤暴露于紫外线辐射的增加。目前，当黑色素瘤发生转移时，没有办法治愈它。制定早期干预的目标和有效的早期诊断和预防策略是必要的，然而黑色素瘤发生的机制尚不明确。在小鼠黑色素瘤模型中，我们可以在黑色素细胞中诱导致癌突变。然而，小鼠的黑色素细胞主要存在于毛囊内，它们的行为在毛发周期中发生变化，这使得很难区分由致癌突变引起的变化。目前，还没有研究表明这些致癌突变何时以及如何在体内对黑素细胞产生影响。尽管人们认为干细胞可能是肿瘤起源细胞的最佳候选细胞，但McSCs在黑色素瘤中的作用仍然未知。由于间充质干细胞位于毛囊内，其主要功能是产生毛发黑色素细胞，而大多数黑色素瘤起源于毛囊间表皮，因此在黑色素瘤研究中对这一群体的研究不足。我们发现，在uvb辐射后，成年小鼠的滤泡间充质干细胞产生表皮黑色素细胞。我们假设凸起处的间充质干细胞可能是导致黑色素瘤的表皮黑色素细胞的起源。在Aim 1中，我们将使用小鼠遗传模型在McSCs中诱导致癌突变（BRAF激活和PTEN丢失，这在人类黑色素瘤中经常发现）。我们还将利用基因易处理的荧光报告来追踪的命运和行为

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.