PIK3CA-E545K突变通过下调SIRT4诱导谷氨酰胺代谢重编程促进宫颈癌放疗抵抗的机制研究

Cervical cancer is one of the most common cancer in women worldwild. Radiation resistance has a strong impact on overall survival of cervical cancer. It is reported that the abnormal activation of PI3K/AKT pathway can reduce radiation efficacy in a variety of ways. Our primary study demonstrated that PIK3CA was the most frequently mutated gene in cervical cancer, and the most common PIK3CA mutation in cervical cancer is E545K. Furthermore, our study manifested that ectopically expressed PIK3CA E545K led to radioresistance in cervical cancer cells. Recently, more and more studies have indicated a closed relationship between glutamine metabolism and radiation resistance, and SIRT4 regulates the cellular metabolic response to DNA damage by inhibiting glutamine metabolism. Given that PI3K/AKT signaling pathway is involved in regulating glutamine metabolism, whether PIK3CA E545K enhances radiation resistance via glutamine metabolism induced by inhibiting SIRT4 in cervical cancer is less researched, however. Therefore, the current study will focus on the following questions. Firstly, to illuminate the experimental phenomenon that PIK3CA E545K mutation enhances radiation resistance via increased glutamine metabolism induced by inhibiting SIRT4. Secondly, to demonstrate how PIK3CA E545K increases glutamine metabolism by transcriptional regulation of SIRT4. Lastly, to screen for effective PI3K/AKT pathway inhibitors to improve the radiation efficacy in cervical cancer with PIK3CA E545K. On the one hand, the study could provide a new perspective to increase radiaotherapy from the point of glutamine metabolism; on the other hand, it could demonstrate the transformational significance of PI3K/AKT pathway inhibitors in cervical cancer.

宫颈癌是最常见的女性恶性肿瘤之一。放疗抵抗是影响宫颈癌疗效的重要因素。PI3K通路异常活化参与对抗放疗损伤，我们前期研究明确PIK3CA是宫颈癌中突变率最高的基因，且突变主要发生在E545K。进一步研究发现PIK3CA-E545K突变促进宫颈癌细胞放疗抵抗。近年来，研究表明放疗通过上调SIRT4抑制谷氨酰胺（Glutamine,Gln）代谢介导细胞周期阻滞。考虑到PI3K通路调控Gln代谢，但PIK3CA-E545K是否通过Gln代谢促进宫颈癌放疗抵抗，目前尚无报道。因此本课题重点探讨：1.阐明该突变可能通过抑制SIRT4增强Gln代谢促进宫颈癌放疗抵抗；2.探讨宫颈癌中该突变转录调控SIRT4参与Gln代谢的分子机制；3.筛选出增强宫颈癌放疗疗效的PI3K通路抑制剂。该研究既为Gln代谢干预在宫颈癌放疗中的应用提供科研基础，又可阐明PI3K通路抑制剂在宫颈癌治疗中的临床转化价值。

宫颈癌是最常见的女性恶性肿瘤之一。放疗抵抗是影响宫颈癌疗效的重要因素。PI3K通路异常活化参与对抗放疗损伤，我们前期研究明确PIK3CA是宫颈癌中突变率最高的基因，且突变主要发生在E545K。本研究首次从体内外研究水平阐明PIK3CA-E545K突变降低宫颈癌放疗敏感性。近年来，研究表明放疗通过上调SIRT4抑制谷氨酰胺（Glutamine, Gln）代谢介导细胞周期阻滞。考虑到PI3K通路调控Gln代谢，但PIK3CA-E545K是否通过Gln代谢促进宫颈癌放疗抵抗，目前尚无报道。本项目首先从细胞及组织水平揭示宫颈癌中PIK3CA突变通过EP300负向调控SIRT4表达；过表达SIRT4可以增加携带PIK3CA-E545K突变细胞的放疗敏感性，并阐明谷氨酰胺剥夺主要通过SIRT4影响宫颈癌放疗敏感性；通过RNA测序明确GPT1为SIRT4调控放疗敏感性的下游效应分子，进一步揭示GPT1降低宫颈癌放疗敏感性的作用。此外，发现相比于mTOR抑制剂，PI3K抑制剂具有更强的放疗增敏效果。本研究首次从谷氨酰胺代谢角度阐明PIK3CA E545K-EP300-SIRT4-GPT1信号轴降低宫颈癌放疗敏感性的作用及分子机制，为谷氨酰胺抑制剂及PI3K通路抑制剂在宫颈癌放疗增敏中的临床应用提供必要的研究基础。