Pathobiology of Interferon-gamma in UV radiation-induced melanomagenesis

 描述（由申请人提供）：皮肤恶性黑色素瘤是最常见和最致命的癌症之一，其发病率继续上升到流行病的比例，以至于它现在是40岁以下女性中最流行的癌症。太阳紫外线辐射（UV）被广泛认为是黑色素瘤的最大风险因素;然而，其潜在的分子机制尚未完全了解。紫外线诱导的致病突变的鉴定长期以来一直是该领域的主要推动力，但非突变和微环境机制的重要性，例如炎症和免疫逃避/免疫抑制，仍然严重不足。在这里，我们提出了一个假设，干扰素-γ（IFNg），这是传统上与抗肿瘤免疫监测机制，在紫外线诱导的黑色素瘤的背景下发挥促肿瘤发生的作用。这项研究将阐明IFNg促黑色素瘤作用的机制。在具体目标1中，将测试IFNg处理通过激活信号转导子和转录激活子3（STAT 3）和小眼症相关转录因子（MITF）对黑素瘤细胞的促转移和耐药性作用的具体机制。UV诱导的黑色素瘤发生实验将在UV诱导的黑色素瘤发生的诱导型BrafV 600 E（BrafCA）小鼠模型中进行，其中IFNg信号传导已通过IFNg受体的黑色素细胞特异性敲除被阻断。特定目标2将表征通过皮肤UV暴露招募到皮肤微环境的分泌IFNg（IFNg+）的巨噬细胞，并将验证这种新的巨噬细胞亚群作为人黑色素瘤易感性和预后的生物标志物。将确定是否遗传阻断紫外线诱导的巨噬细胞流入皮肤抑制黑色素瘤。在具体目标3中，将研究IFN-γ诱导的黑色素瘤细胞中细胞毒性T淋巴细胞抗原4（CTLA 4）表达在黑色素瘤形成过程中的作用。将测试CTLA 4的黑素细胞表达是否保护它们免受T细胞介导的免疫监视，从而导致免疫逃避和黑素瘤的进展，以及在BrafCA小鼠模型中黑素细胞隔室中特异性的Ctla 4的遗传消融是否抑制UV诱导的黑素瘤发生。最后，将研究黑素瘤细胞上的CTLA 4表达作为人黑素瘤患者的临床样品中对抗CTLA 4免疫疗法的应答的预测性生物标志物。拟议项目的总体目标是研究IFNg途径作为一种新的微环境机制与紫外线诱导的黑色素瘤易感性和疾病进展的联系。

 DESCRIPTION (provided by applicant): Cutaneous malignant melanoma is one of the most common and deadliest cancers, and its incidence continues to rise to epidemic proportions, to the extent that it is now the most prevalent cancer among women under forty. The solar ultraviolet radiation (UV) is widely accepted to be the greatest risk factor for melanoma; however, the underlying molecular mechanisms are incompletely understood. Identification of the causal UV-induced mutations has long been the major thrust in the field, but importance of non-mutational and microenvironmental mechanisms, for example inflammation and immunoevasion/immunosuppression, remains severely understudied. Here we have proposed a hypothesis that Interferon-gamma (IFNg), which is conventionally associated with anti-tumor immunesurveillance mechanisms, plays a pro-tumorigenic role in the context of UV-induced melanomagenesis. The proposed research will elucidate the mechanisms of the pro-melanomagenic effects of IFNg. In Specific Aim 1, the specific mechanisms of the pro-metastatic and drug resistance effects of IFNg treatment on melanoma cells via activation of Signal Transducer and Activator of Transcription 3 (STAT3) and Microphthalmia Associated Transcription Factor (MITF) will be tested. UV- induced melanomagenesis experiments will be performed in the inducible BrafV600E (BrafCA)mouse model of UV-induced melanomagenesis, in which the IFNg signaling has been blocked via melanocyte-specific knockout of IFNg-Receptor. Specific Aim 2 will characterize the IFNg-secreting (IFNg+) macrophages that are recruited to the skin microenvironment by erythemal UV exposure, and will validate this novel subpopulation of macrophages as a biomarker of susceptibility and prognosis of human melanoma. It will be determined whether genetic blockade of UV-induced macrophage influx into skin inhibits melanomagenesis. In Specific Aim 3, the role of IFNg-induced expression of the cytotoxic T-lymphocyte antigen 4 (CTLA4) in melanoma cells in the process of melanomagenesis will be investigated. It will be tested whether melanocytic expression of CTLA4 protects them from T-cell-mediated immunesurveillance, leading to immunoevasion and progression of melanoma, and whether genetic ablation of Ctla4 specifically in the melanocyte compartment inhibits UV-induced melanomagenesis in the BrafCA mouse model. Finally, CTLA4 expression on melanoma cells will be investigated as a predictive biomarker of response to anti-CTLA4 immunotherapy in clinical samples of human melanoma patients. The overall goal of the proposed project is to investigate the IFNg pathway as a novel microenvironmental mechanistic link to UV-induced melanoma susceptibility and disease progression.