TGFβ1/Smad与PIKKs/Akt信号转导通路交互作用在紫外线诱导日光性角化病向鳞状细胞癌进展的机制研究

Ultraviolet radiation induces progression of precancerous lesion-actinic keratosis (AK) to cutaneous squamous cell carcinoman(cSCC), which seriously endangers people's lives and health. Domestic and international research showed that UV-induced abnormal activation of signaling pathway is a key pathogenic mechanism. Our previous researches found that inhibition of TGFβ1/Smad signaling pathway in AK would promote progression to cSCC by ultraviolet radiation; and discovered PIKKs/Akt signaling pathway was abnomal activated by ultraviolet, and found DNA-PKcs-mTORC2 complex was a key factor which mediated UV-induced activation of Akt, whose activation would lead to a variety of tumors. But the machnisms of PIKKs/Akt signaling pathway in AK and cSCC are unclear, and whether it cross-talks with TGFβ1/Smad signaling pathway is unkown. This project based on highlands cutaneous cancer sample library and preliminary studies, to explore molecular mechanisms of PIKKs/Akt in AK and cSCC, and the cross-talk between TGFβ1/Smad and PIKKs/Akt signaling pathways, on the platform of lesion tissues, cells and mice, using a variety of molecular biology techniques, to clarify the pathogenesis of AK and cSCC, and the progression of AK to cSCC. The project is important for providing targets to screen medicinal ingredients of Yunnan natural plants.

紫外线照射致癌前病变日光性角化病(AK)向鳞状细胞癌(cSCC)转变，严重危害人民群众生命健康。国内外研究表明紫外线引起信号通路异常激活是关键致病机制。我们前期研究发现紫外线通过抑制AK中TGFβ1/Smad信号通路，促进AK向cSCC进展；发现紫外线异常激活PIKKs/Akt信号通路，找到DNA-PKcs-mTORC2复合物是紫外线活化Akt的关键因子，Akt异常激活可诱发多种肿瘤。但PIKKs/Akt信号通路在AK、cSCC中的机制不清，是否与TGFβ1/Smad信号通路存在交互作用不明。本项目拟在已建立的高原皮肤癌样本库及前期研究基础上，在病损组织、细胞、小鼠水平，运用转基因技术等分子生物学手段，探讨AK、cSCC中PIKKs/Akt信号通路的分子机制及与TGFβ1/Smad信号通路的交互机制，阐明AK发生及向cSCC进展的机制，为后期筛选云南天然药用植物成分提供靶点。

日光性角化病（AK）是皮肤鳞状细胞癌（SCC）的癌前病变，紫外线照射可促进AK向SCC进展。前期发现紫外线通过抑制AK中TGFβ1/Smad信号转导通路促进AK向SCC进展。发现紫外线异常激活PIKKs/Akt信号转导通路，找到DNA-PKcs-mTORC2复合物是紫外线活化Akt的关键因子，Akt异常激活可诱发多种肿瘤。针对PIKKs/Akt信号转导通路在AK、SCC中作用机制不清、是否与TGFβ1/Smad信号转导通路存在交换作用，促进AK向SCC进展不明，本研究检测了正常避光皮肤、正常曝光皮肤、AK和SCC中PIKKs/Akt与TGFβ1/Smad信号转导通路34个相关因子的表达水平，发现PIKKs/Akt信号转导通路相关因子在AK和SCC中表达增加，通过正常角质细胞株HaCaT、UVB-HaCaT细胞和皮肤鳞癌细胞株SCL-1细胞、以及DNA-PKcs敲除转基因小鼠，发现DNA-PKcs、Akt促进细胞克隆形成、促进细胞增殖、抑制细胞凋亡，发现在正常角质细胞中TGFβ1/Smad信号转导通路的经典途径发挥促进细胞凋亡作用，在肿瘤细胞中发挥促癌作用；DNA-PKcs、Akt在正常角质细胞中抑制TGF-βR的凋亡作用发挥促癌作用，在正常细胞和肿瘤细胞中均促进Smad2表达和活化而发挥促癌作用；发现在肿瘤细胞SCL-1中，DNA-PKcs和与TGF-β1、Smad3之间呈现一个正反馈调控，促进SCL-1细胞侵袭和迁徙；证实DNA-PKcs、Akt、Smad2是AK生成并进一步向SCC转化的关键因子。结果为AK发生、向SCC进展机制阐明提供了依据。