Promotion of photocarcinogenesis by the senescent field and mechanisms for field persistence

暴露于阳光中的紫外线（UV）是皮肤癌的主要原因， 每年有20，000名美国人。退伍军人患皮肤癌的风险增加， 在训练和部署期间暴露在阳光下。紫外线照射也会导致光老化， 获得一种叫做衰老的有丝分裂后表型。除了阳光照射，年龄和治疗 免疫抑制剂是皮肤癌发展的最重要危险因素。在本提案中，我们将 研究我们的新的2组分癌症领域模型的皮肤癌发生，联系光老化和 免疫抑制皮肤癌的发展。从历史上看，癌症领域是指多焦点领域， 否则正常上皮细胞的癌症发展风险增加。这个上皮癌区域 以突变的逐步积累为特征，最终导致恶性转化。我们 已经表明，紫外线诱导多灶性皮肤衰老领域，其特征在于炎症 可以通过对真皮血红蛋白（Hb）含量进行成像来可视化和测量血管生成。这 停止UV治疗后，真皮区域持续并扩大，并预测覆盖表皮的部位 克隆扩增和肿瘤形成。在这个建议中，我们提出，真皮领域也存在， 该真皮区域的关键特征是衰老细胞的存在。这些衰老的细胞产生和 分泌特定的促炎、促有丝分裂和免疫调节介质，我们建议这些介质驱动 继续发展的覆盖上皮突变领域。然而，免疫系统可以识别 和清除衰老细胞（衰老监视）。我们预测，这种免疫介导的清除作用， 抑制衰老真皮区对肿瘤形成的影响。我们希望这种治疗 免疫抑制药物会通过阻断免疫介导的真皮清除来促进肿瘤发生 衰老细胞转化生长因子β（TGF-β）是一种细胞因子，在紫外线诱导的细胞凋亡中是必需的。 由衰老细胞产生。这种TGF-β的产生反过来可以导致诱导 旁观者衰老（bystander senescence）我们认为，旁观者衰老，在一个 免疫抑制设置，提供了一个自我永存的机制，驱动衰老领域的持久性 和扩展。最后，并非所有的免疫抑制剂都具有相同的促进皮肤癌的能力 发展环孢霉素A促进皮肤癌发展、TGF-β产生并诱导衰老。 相比之下，西罗莫司对皮肤癌风险的影响有限，已知其抑制TGF-β产生， 抑制衰老细胞形成和分泌活性。在本建议中，我们将确定紫外线- 诱导衰老场是皮肤癌发展所必需的， 治疗促进衰老领域的发展和持久性，并确定是否TGF-β信号转导和 旁观者衰老在这一过程中起着核心作用。这将在三个目标下实现： 目的1：确定衰老清除疗法是否抑制光致癌作用和皮肤领域的持久性。 检查衰老清除治疗和TGF-β信号转导的丧失是否阻断了环孢霉素A增强， 和西罗莫司来抑制UV诱导的肿瘤形成。 目标2.使用单细胞RNA测序（scRNAseq）和真皮全转录组测序， 差异表达分析以表征充血和非充血病灶之间的差异。 目标3：确定环孢素A是否抑制衰老监测和促进旁观者 而西罗莫司起到抑制旁观者衰老的作用。TGF-β在旁观者中的作用 还将评估衰老。

Exposure to the ultraviolet (UV) rays of sunlight is the primary cause of skin cancer, which kills greater than 20,000 U.S. individuals each year. Veterans are at increased risk for skin cancer development due to increased sun exposure during training and deployment. UV exposure also causes photoaging that results in cells acquiring a post-mitotic phenotype called senescence. In addition to sun exposure, age and treatment with immunosuppressants are the most significant risk factors for skin cancer development. In this proposal, we will examine our novel 2 component cancer field model of cutaneous carcinogenesis that links photoaging and immunosuppression to skin cancer development. Historically, the cancer field refers to multifocal areas of otherwise normal epithelium that are at increased risk for cancer development. This epithelial cancer field is characterized by the stepwise accumulation of mutations that eventually lead to malignant conversion. We have shown that UV induces a multifocal dermal senescent field that is characterized by inflammatory angiogenesis that can be visualized and measured by imaging the dermal hemoglobin (Hb) content. This dermal field persists & expands following cessation of UV treatments and predicts sites of overlying epidermal clonal expansion & tumor formation. In this proposal, we propose that a dermal field also exists and that the key characteristic of this dermal field is the presence of senescent cells. These senescent cells produce and secrete specific pro-inflammatory, mitogenic and immunomodulatory mediators that we propose drive the continued development of the overlying epithelial mutant field. However, the immune system can recognize and clear senescent cells (senescence surveillance). We predict that this immune-mediated clearance acts to suppress the effects of the senescent dermal field on tumor formation. We expect that treatment with immunosuppressive drugs would promote tumorigenesis by blocking immune-mediated clearance of dermal senescent cells. Transforming growth factor beta (TGF-β) is a cytokine that is necessary for UV-induced senescence and is produced by senescent cells. This TGF-β production can in turn result in the induction of senescence in nearby cells (bystander senescence). We propose that bystander senescence, in an immunosuppressed setting, provides a self-perpetuating mechanism that drives senescent field persistence AND expansion. Finally, not all immunosuppressive agents have the same capacity to promote skin cancer development. Cyclosporine A promotes skin cancer development, TGF-β production, and induces senescence. In contrast, sirolimus has a limited effect on skin cancer risk, is known to suppresses TGF-β production, and suppresses senescent cell formation and secretory activity. In this proposal, we will determine whether the UV- induced senescent field is necessary for skin cancer development, determine whether immunosuppressive therapy promotes senescent field development and persistence, and determine whether TGF-β signaling & bystander senescence play central roles in this process. This will be done in three aims: Aim 1: Determine whether senolytic therapy inhibits photocarcinogenesis and dermal field persistence. Examine whether senolytic therapy and loss of TGF-β signaling block the ability of cyclosporine A to enhance, and sirolimus to suppress, UV-induced tumor formation. Aim 2. Use single cell RNA sequencing (scRNAseq) and dermal whole transcriptome sequencing and differential expression analysis to characterize the differences between hyperemic and non-hyperemic foci. Aim 3. Determine whether cyclosporine A suppresses senescence surveillance and promotes bystander senescence in wildtype while sirolimus acts to suppress bystander senescence. The role of TGF-β on bystander senescence will also be assessed.