HPV38-SIRT6-自噬轴及其下游分子群促进皮肤鳞癌发生发展的作用及机制研究

The occurrence of cutaneous squamous cell carcinoma (cSCC) is extremely relevant to the persistent infection of human papilloma virus (HPV). Despite the fact that its etiology is not fully understood, our previous data show that elevated level of autophagy in HPV38 positive cSCC is the key component of the occurrence. However, how the HPV38 triggers the autophagy process remains unclear. Silent information regulator 2 related enzymes (Sirtuins), a family of class III histone deacetylases, which are confirmed to directly or indirectly regulate autophagy through the deacetylation reactions of autophagy related molecules and pathways, are crucial upstream modulators of autophagy. Latest reported studies suggested that SIRT6, a member of the Sirtuins family, can regulate the proliferation and differentiation of keratinocytes for the promotion tumorgenesis of cSCC. These data together with our study which show that the expression level of SIRT6 in HPV38 positive cSCC is consistent with that in autophagy, consequently infer that autophagy positively activated by SIRT6 in HPV38 positive cSCC leads to tumorgenesis and development of cSCC. Nonetheless, the concrete molecular mechanism and the downstream molecules of autophagy are still not fully explained. We therefore conduct the application of this project to elucidate the mechanism of HPV38-SIRT6-autophagy axis and its downstream molecules promoting the pathogenesis of cSCC, which are to be investigated on tissue, cellular, molecular and animal levels. In this way, the pathogenesis of HPV-induced cutaneous squamous cell carcinoma mediated by HPV38-SIRT6-autophagy will be evaluated systemically from both in vitro and in vivo perspectives. Therefore the study will contribute to setting up SIRT6 as a new and a more precise therapeutic target in HPV inflection diagnosis and treatment as an evaluation of feasibility in terms of theoretical rationale.

皮肤鳞癌与人乳头瘤病毒持续感染密切相关，然而机制不明。我们一直致力于HPV与皮肤鳞癌发病机制的研究，近来发现细胞自噬水平升高是HPV38阳性鳞癌发生的关键环节，但机制不清。去乙酰化酶类分子Sirtuins家族可直接或间接调控自噬相关分子及通路,是自噬上游的关键调节分子。新近研究表明，SIRT6作为其中一员，可调控角质形成细胞增殖与分化，促进鳞癌的发生。我们发现，HPV38阳性鳞癌组织中SIRT6与自噬表达水平相一致，提示HPV38可能通过SIRT6激活细胞自噬，促进皮肤鳞癌的发生与发展。然而，SIRT6如何调控细胞自噬，及自噬下游促癌的具体分子机制，均是尚待明确的重要问题。因此，本项目拟于前期工作基础上，在组织、细胞及动物水平系统阐释HPV38-SIRT6-自噬轴及下游分子群促进皮肤鳞癌发生发展的具体机制，为HPV感染的诊治及SIRT6作为新的生物标志物及治疗靶点的可行性评估提供理论依据。

皮肤鳞癌与人乳头瘤病毒（HPV）持续感染密切相关，然而机制不明。我们一直致力于HPV与皮肤鳞癌发病机制的研究，近来发现细胞自噬水平升高是HPV38阳性鳞癌发生的关键环节，但机制不清。Sirtuins 被认为是自噬上游的关键调节分子。SIRT6 作为Sirtuins 家族的一员，在皮肤鳞状细胞癌的发生发展中具有重要作用。我们研究发现，SIRT6 分子在HPV38 阳性的鳞状细胞癌组织中，表达水平升高，且与自噬水平相一致。提示HPV38可能通过SIRT6激活细胞自噬，促进皮肤鳞癌的发生与发展。然而，SIRT6如何调控细胞自噬，及自噬下游促癌的具体分子机制，均是尚待明确的重要问题。本项目初步证明在HPV38 持续感染条件下，SIRT6及自噬表达水平均升高，且二者呈线性正相关；Western blot、电镜、免疫荧光结果显示：SIRT6可正向调控黑素瘤细胞内自噬水平；Microarray及Western blot结果显示：HPV38 持续感染条件下，IGF-Akt信号通路活化水平均降低，SIRT6与IGF-Akt信号通路二者之间呈线性负相关；Western blot结果显示：SIRT6可通过负向调控IGF-Akt信号通路上调鳞癌细胞内的自噬水平；裸鼠实验显示：过表达SIRT6可抑制IGF-Akt信号通路，上调细胞自噬水平；干涉SIRT6可进一步活化IGF-Akt信号通路，抑制自噬水平。通过本课题的研究，我们首次发现HPV38阳性鳞癌中SIRT6高表达，并且其通过负向调控IGF-Akt信号通路介导鳞癌细胞自噬水平的表达，SIRT6可促进鳞癌细胞自噬水平的升高。这一机制参与SIRT6调控鳞癌细胞生长的过程。我们的发现加深了SIRT6对自噬调控的认识，拓展了二者参与调控的疾病谱。并为HPV38阳性鳞癌的临床诊疗提供新的思路及治疗靶点，对鳞癌临床选择用药具有重要意义。