PIM2介导HSF1磷酸化调控PD-L1表达促进乳腺癌发生发展的分子机制研究

乳腺癌是女性中最常见的恶性肿瘤之一，其发生发展受多种信号通路的调控。热休克蛋白1 (HSF1) 对乳腺癌细胞增殖起到重要的作用，但是翻译后修饰调控HSF1的分子机制尚未明确。本课题通过免疫共沉淀和质谱技术鉴定淋巴瘤病毒插入蛋白2激酶 (PIM2) 是一个HSF1的新结合蛋白。通过体外磷酸化实验研究PIM2可以直接磷酸化HSF1，并研究该磷酸化对HSF1蛋白稳定性及其转录活性的调控。研究PIM2磷酸化HSF1促进细胞内的蛋白质稳态和化疗药卡铂诱导的细胞自噬。利用荧光素酶实验和染色质免疫沉淀实验研究PIM2磷酸化HSF1促进PD-L1基因的表达。利用免疫组化实验研究该磷酸化在乳腺癌组织中的表达。研究PIM2磷酸化HSF1后促进乳腺癌细胞的增殖、侵袭及在裸鼠体内的成瘤。从而阐述PIM2通过磷酸化HSF1促进乳腺癌发生发展的分子机制，为临床靶向PIM2和HSF1治疗乳腺癌奠定理论基础。

Breast cancer is one of the most common malignant tumors in women. The development of breast cancer is regulated by various signal pathways. Heat shock protein 1 (HSF1) transcription factor plays an important role in the proliferation of breast cancer cells. However, the molecular mechanisms of post-transcriptional modification of HSF1 are still unclear. In this study, we study proviral insertion in murine lymphomas 2 kinase (PIM2) as a new binding partner of HSF1 by immunoprecipitation and mass spectrometry. We study PIM2 could directly phosphorylate HSF1 using in vitro phosphorylation and study PIM2-induced regulation of the protein stability and transcriptional activity of HSF1. To study the effect of PIM2 phosphorylated HSF1 on protein homeostasis and autophagy induced by carboplatin. We use luciferase assay and CHIP test to study phosphorylation of HSF1 by PIM2 promotes PD-L1 expression. The expression of this phosphorylation in breast cancer tissues is studied by immunohistochemistry. We also study PIM2 phosphorylation of HSF1 promotes breast cancer cell proliferation and invasion, and promotes tumor growth in nude mice. The molecular mechanisms of PIM2 promoting the development of breast cancer by phosphorylating HSF1 and inducing PD-L1 expression are described, which lays a theoretical foundation for the clinical targeting of PIM2, HSF1 and PD-L1 in the treatment of breast cancer.