Skin Cancer Chemoprevention by Silibinin: Mechanisms and Efficacy

项目摘要 基底细胞癌（BCC），一种非黑色素瘤皮肤癌（NMSC）类型，是美国的主要健康问题。 美国（US）; BCC年发病率高于所有其他癌症发病率的总和（1.67 年）。大多数基底细胞癌病例可以通过手术/放疗治愈，但这些手术/放疗可能会带来疼痛，并严重毁容。 并且对于患有局部晚期和转移性疾病的BCC患者不是可行的治疗选择， 化疗也没有证明有效。由于Hedgehog（Hh）信号在BCC中起着核心作用， 开发和进展，最近FDA批准了GDC-0449和LDE-225（Hh通路抑制剂）， 治疗BCC;然而，获得性耐药和毒性是限制。综合来看，显然有一个 迫切需要制定更多的无毒战略，以防止和干预BCC。 在过去的20年里，我们广泛研究和报道了水飞蓟宾对UVB的化学预防功效， 在NMSC的鳞状细胞癌（SCC）模型中诱导皮肤癌;目前，我们处于晚期阶段 用于人体皮肤的水飞蓟宾配方。基于显示水飞蓟宾在以下方面具有强大功效的发现： 小鼠皮肤SCC模型，在初步研究中，我们还评估了其对UVB诱导的BCC的影响。使用 Ptch1 +/−小鼠BCC模型，我们观察到水飞蓟宾减少UVB诱导的：环丁烷嘧啶 耳皮肤二聚体（CPD）阳性细胞，显微镜下BCC形成，真皮肥大细胞浸润和骨 皮肤中的形态发生蛋白（BMP）-2基因和蛋白水平。此外，水飞蓟宾降低：MC9肥大细胞 细胞向小鼠BCC ASZ细胞的趋化性迁移和粘膜肥大细胞脱粒。水飞蓟宾还 降低培养物和小鼠同种异体移植物中小鼠BCC细胞的增殖，以及抑制促有丝分裂的 信号通路在最近的研究中，水飞蓟宾显著增加了Hh的生长抑制作用， 通过靶向EGFR/AKT逆转BCC细胞对这些药物的耐药性， hh通路与细胞凋亡的诱导。基于BCC中这些非常重要和令人鼓舞的发现， 模型，我们的假设是，通过靶向UVB诱导的DNA损伤修复和逆转肥大细胞 细胞介导的免疫抑制事件，以及调节相关的信号通路 对于耐药性，水飞蓟宾有可能成为预防和 BCC的辅助治疗。我们的目标是：1）建立和定义水飞蓟宾介导的DNA修复在细胞凋亡中的作用。 其对UVB诱导的BCC的预防功效; II）评估和建立DNA损伤之间的联系 修复、肥大细胞和水飞蓟宾对UVB诱导的免疫抑制的逆转作用 III）进一步确定水飞蓟宾单独和组合对BCC的治疗功效 与FDA批准的抗BCC疗法，并定义相关的机制。

Project Summary Abstract Basal cell carcinoma (BCC), a non-melanoma skin cancer (NMSC) type, is a major health problem in the United States (US); annual BCC incidences alone are higher than all other cancer incidences combined (1.67 million/year). Most BCC cases are curable by surgery/radiation, but these can be painful and highly disfiguring and are not viable treatment options for BCC patients with locally advanced and metastatic disease where chemotherapy has also not proven effective. Since Hedgehog (Hh) signaling plays a central role in BCC development and progression, recently FDA has approved GDC-0449 and LDE-225 (Hh pathway inhibitors) to treat BCC; however, acquired resistance and toxicities are limitations. Taken together, clearly there is an urgent need to develop additional non-toxic strategies towards BCC prevention and intervention. In past ~20 years, we have extensively studied and reported chemopreventive efficacy of silibinin against UVB- induced skin cancer in squamous cell carcinoma (SCC) model of NMSC; currently, we are in advanced stages of developing silibinin formulation for human skin use. Based on findings showing strong silibinin efficacy in mouse skin SCC model, in preliminary studies, we also assessed its effects against UVB-induced BCC. Using Ptch1+/− mouse model of BCC, we observed that silibinin decreases UVB-induced: cyclobutane pyrimidine dimer (CPD) positive cells in ear skin, microscopic BCC formation, dermal mast cell infiltration and bone morphogenetic protein (BMP)-2 gene and protein levels in skin. Furthermore, silibinin decreased: MC9 mast cell chemotactic-migration towards mouse BCC ASZ cells and mucosal mast cell degranulation. Silibinin also decreased proliferation of mouse BCC cells in culture and mouse allografts together with inhibition of mitogenic signaling pathways. In most recent studies, silibinin significantly increased the growth inhibitory effects of Hh pathway inhibitor drugs and reversed the resistance of BCC cells to these drugs via targeting EGFR/AKT and Hh pathway and induction of apoptosis. Based on these highly significant and encouraging findings in BCC models, our hypothesis is that by targeting UVB-induced DNA damage repair and reversal of mast cells-mediated immunosuppressive events, together with modulating signaling pathways associated with drug resistance, silibinin has the potential to be an effective agent for both prevention and adjuvant therapy of BCCs. Our aims are to: I) establish and define the role of silibinin-mediated DNA repair in its preventive efficacy against UVB-induced BCC; II) assess and establish the link between DNA damage repair, mast cells, and reversal of UVB-induced immunosuppression by silibinin in its efficacy against BCC formation; III) further establish the therapeutic efficacy of silibinin against BCC, both alone and in combination with FDA approved anti-BCC therapeutics, and define the associated mechanisms.