Snail抑制前列腺癌细胞人类I型白细胞抗原(HLA-I)蛋白表达及其机制研究

Human leukocyte antigen class I molecules (HLA-I) are crucial for anti-tumor T cell mediated immunity. However, HLA-I expression defects were frequently induced by prostate cancers to escape the anti-tumor immunity. The latest data have demonstrated that Snail was able to be involved in tumor immune inhibition. However, there was no literature discussing the effect of Snail in HLA-I expression. Our previous studies have suggested that Snail might be able to suppress the HLA-I expression, and our preliminary studies recently demonstrated that Snail over-expression only suppressed the transcription and protein expression of HLA-I heavy chain genes (mainly HLA-A/B/C genes). Thus, we put forward a viewpoint the first time that Snail suppresses the transcription of HLA-I heavy chain genes, thereby leads to the decrease of HLA-I protein level in prostate cancers. In this proposal, we will use Snail over-expression models, clinical samples, and IHC, EMSA, ChIP methods to investigate the following two questions: what is the role of Snail in the HLA-I expression of prostate cancers and what are the underlying mechanisms? This study is expected to provide more evidences for Snail being involved in tumor immune inhibition, give new clues for the mechanism study of HLA-I expression, and provide theoretical basis and potential targets to promote anti-prostate cancer related T cell mediated immunity.

人类I型白细胞抗原(HLA-I)对于抗肿瘤T细胞免疫至关重要。诸多证据表明前列腺癌组织常发生HLA-I表达缺陷，引起免疫逃逸。最新研究显示转录蛋白Snail高表达可诱导肿瘤免疫抑制，而其对HLA-I表达的影响尚无报道。前期研究提示Snail可抑制前列腺癌细胞HLA-I蛋白表达，且本课题预实验发现Snail高表达能且仅能抑制HLA-I重链基因(HLA-A/B/C)的转录及蛋白表达。据此，我们首次提出Snail可通过抑制HLA-I重链基因转录，引起前列腺癌HLA-I表达缺陷的观点。本课题拟进一步采用Snail高表达模型并结合临床样本，使用免疫组化、EMSA和ChIP等方法，旨在回答Snail对前列腺癌HLA-I蛋白表达的影响及其内在关键机制这两个科学问题。本项目有望为Snail参与肿瘤免疫逃逸提供新证据，为HLA-I表达调控提供新线索，为促进抗前列腺癌T细胞免疫反应提供理论依据及潜在靶点。

人体T细胞免疫对于肿瘤的监视和清除至关重要。人类I型白细胞抗原HLA-I（主要为HLA-ABC）为T细胞提呈内源性抗原从而启动肿瘤免疫杀伤，而程序性死亡配体I型（PD-L1）可与T细胞表面受体PD-1结合触发下游负性共刺激信号从而抑制T细胞介导的肿瘤免疫清除。大量研究表明，肿瘤细胞常通过诱导自身HLA-I表达降低及PD-L1表达增加等途径以逃避T细胞免疫杀伤。因此，探讨肿瘤细胞自身HLA-I表达缺陷以及PD-L1异常表达的诱因及机制，将有助于对肿瘤免疫逃逸的临床干预。我们的前期研究发现EGF/EGFR通路激活可诱导Snail高表达，而该Snail高表达可能通过降低HLA-ABC表达引起前列腺癌细胞自身HLA-I表达缺陷，从而实现免疫逃逸。因此，我们从细胞实验和临床标本出发探讨了Snail高表达与HLA-I表达缺陷的关系及关键机制。此外，我们随后发现EGF/EGFR通路在肝癌组织中异常激活，且与HLA-ABC以及PD-L1蛋白表达紧密相关。因此，我们还探讨了EGF/EGFR通路对肝癌细胞HLA-ABC和PD-L1表达的影响及关键机制。本课题的研究成果主要包括：1.从体内外验证了Snail高表达对前列腺癌细胞HLA-ABC蛋白表达的抑制作用，并证实了该HLA-ABC表达抑制可降低CD8+T细胞肿瘤细胞杀伤活力；2.通过常见前列腺癌细胞系及145例临床组织样本证实了前列腺癌中Snail与HLA-ABC表达成负相关；3.机制研究发现Snail高表达可抑制HLA-I重链基因HLA-ABC的转录表达；NF-κB/p65可正调控HLA-ABC表达，而Snail高表达抑制p65表达但增加两者间的结合；PAK1可增加Snail蛋白泛素化及入核，促进其蛋白稳定和功能；4.EGF/EGFR通路在肝癌组织中与PD-L1的表达呈正相关而与HLA-ABC的表达呈负相关；5. EGF/EGFR激活可促进肝癌细胞的PD-L1表达而降低HLA-ABC的表达；6.p38MAPK和富含AU序列的PD-L13’UTR区介导的PD-L1mRNA稳定性增加对于EGF/EGFR诱导的PD-L1表达至关重要；7.p38MAPK-己糖激酶HK2信号轴引起的糖酵解增强介导EGF/EGFR引起的HLA-ABC表达降低。以上研究结果可为促进肿瘤免疫、提高肿瘤免疫治疗效果提供潜在分子靶点。