The role of Fyn and Srcasm in UVB-induced cutaneous neoplasia

描述(申请人提供)：UVB辐射对皮肤是一种完全的致癌物，并启动信号通路和突变，促进癌症前期光化性角化病(AKs)和皮肤鳞状细胞癌(CSCCs)的形成。AKs和CSCC在有阳光暴露史的老年人中都很常见，这些损害的发生率预计在未来会上升。人类皮肤鳞状细胞癌中常见的突变包括P53功能丧失突变和RAS功能获得突变。在人类AKs和CSCCs中，与非皮损表皮相比，皮损细胞中的Src家族酪氨酸激酶(SFK)被激活，这表明SFK促进皮肤癌的发生；这与SFK Fyn是人角质形成细胞中致癌RAS的效应因子的观察一致。对人类CSCCs和AKs的分析一致显示，sRCasm水平降低，这表明sRCasm下调对于肿瘤可能是必要的。我们先前的研究表明，在K14-Fyn Y528F转基因小鼠中，Fyn下调了P53的表达，并诱导了癌前病变和鳞状细胞的自发形成。这些癌前病变和鳞状细胞癌在组织学和分子水平上与人类相应的病变相似。在这些小鼠中，提高srCasm水平可以使Fyn激酶活性正常化，恢复P53，并抑制肿瘤形成。我们在小鼠中从基因上删除了srCasm，这些小鼠的皮肤中P53水平显著降低。最近的数据显示，UVB治疗srCasm基因缺失的小鼠在5周内就会产生类似于人类AKs的癌前病变。总而言之，这些数据表明，Fyn和SRCasm形成了一个调节皮肤癌的信号网络。这项提议的主要目标是证明Fyn和SRCasm在小鼠模型和转基因重组人皮肤中发挥重要的Fyn作用。提高Fyn活性可以增强UVB诱导的信号转导和DNA损伤，而增加srCasm水平则可以抑制UVB诱导的DNA损伤和皮肤癌。降低Fyn应能抑制RAS诱导的皮肤癌。在这些研究中，我们将展示Fyn和SRCasm如何调控导致皮肤癌的信号通路。在这些小鼠模型中，以促进肿瘤发生的激酶为靶点，局部应用小分子激酶抑制剂可以导致这些肿瘤的消退，这表明这些分子可能在治疗人类病变方面具有潜力。通过这项研究计划获得的数据将进一步加深我们对SFK和SRCasm如何调控UVB诱导的DNA损伤和皮肤癌变的了解。这项工作还将提供新的候选分子，可能会改进局部治疗，以治疗AKS和CSCC患者。

DESCRIPTION (provided by applicant): UVB radiation is a complete carcinogen for skin and initiates signaling pathways and mutations that promote the formation of precancerous actinic keratoses (AKs) and cutaneous squamous cell carcinomas (cSCCs). Both AKs and cSCCs are very common in older individuals with a history of sun-exposure, and the incidence of these lesions is expected to rise in the future. Common mutations in human cSCCs include loss-of-function mutations in p53 and gain-of-function mutations in Ras. In human AKs and cSCCs, Src-family tyrosine kinases (SFKs) are activated in lesional cells compared with non- lesional epidermis, suggesting that SFKs promote skin cancer; this is consistent with the observation that the SFK Fyn is an effector of oncogenic Ras in human keratinocytes. Analysis of human cSCCs and AKs consistently shows decreased Srcasm levels suggesting that Srcasm downregulation may be necessary for neoplasia. Our previous data show that Fyn downregulates p53 and induces the spontaneous formation of precancerous lesions and cSCCs in K14-Fyn Y528F transgenic mice. These precancerous lesions and cSCCs resemble their human counterparts at the histologic and molecular levels. Raising Srcasm levels in these mice normalizes Fyn kinase activity, restores p53, and inhibits tumor formation. We genetically deleted Srcasm in mice and these mice have markedly reduced p53 levels in skin. Recent data show that UVB-treatment of Srcasm null mice produces precancerous lesions that resemble human AKs in 5 weeks. Together, these data show that Fyn and Srcasm form a signaling nexus that regulates skin cancer. The primary goal of this proposal is to demonstrate that Fyn and Srcasm play important Fyn in murine models and in genetically engineered, reconstituted human skin. Promoting Fyn activity should enhance UVB-induced signaling and DNA damage while increasing Srcasm levels should inhibit UVB-induced DNA damage and skin cancer. Decreasing Fyn should inhibit Ras-induced skin cancer. In these studies, we will show how Fyn and Srcasm regulate signaling pathways that contribute to skin cancer. Targeting the kinases responsible for promoting neoplasia in these mouse models with topically applied small molecule kinase inhibitors results in regression of these tumors, suggesting that such molecules may have potential in treating human lesions. The data obtained through this research proposal will further our knowledge of how SFKs and Srcasm regulate UVB-induced DNA damage and skin carcinogenesis. This work will also provide new candidate molecules that may improve topical therapies to treat AKs and cSCCs in patients.