免疫检查点抑制剂PD-1抗体改善黑色素瘤预后，但有效率低。癌基因及细胞因子诱导的PD-L1表达上调加重免疫抑制，是耐药机制之一。我们前期研究发现MDM2在31%的黑色素瘤中高表达，且与PD-1抗体疗效负相关。我们还发现MDM2可上调PD-L1表达并抑制T细胞功能，并且MDM2调节PD-L1泛素化水平但不影响其转录。MDM2影响PD-1抗体疗效的具体机制目前尚不明确。我们提出假设：MDM2作为E3泛素连接酶，通过泛素化调控黑色素瘤细胞PD-L1蛋白稳定性，上调PD-L1表达，从而影响PD-1抗体的疗效。本项目拟通过免疫共沉淀、融合蛋白沉降、高通量质谱等技术探索MDM2调控PD-L1表达的具体分子机制；分析MDM2表达改变对肿瘤微环境中T细胞功能的影响；在动物模型中验证抑制MDM2对PD-1抗体疗效的影响。本研究旨在揭示MDM2调控免疫治疗的新机制，为提高PD-1抗体疗效提供新靶点。

The immune checkpoint inhibitor anti-PD-1 antibody improves the prognosis of melanoma, but the efficiency is low. The up-regulation of PD-L1 expression induced by oncogenes and cytokines exacerbates immunosuppression and is one of the resistance mechanisms. Our previous study found that MDM2 is highly expressed in 31% of melanomas and is inversely related to the efficacy of anti-PD-1 antibody. We also found that MDM2 can upregulate PD-L1 expression and inhibit T cell function. MDM2 regulates PD-L1 ubiquitination levels but does not affect its transcription. The detailed mechanism by which MDM2 affects the efficacy of anti-PD-1 antibodies is currently unclear. We propose that: MDM2, as an E3 ubiquitin ligase, regulates the stability of PD-L1 protein in melanoma cells through ubiquitination and up-regulates the expression of PD-L1, thereby affecting the efficacy of anti-PD-1 antibodies. This project intends to explore the specific molecular mechanism of MDM2 regulation of PD-L1 expression through immunoprecipitation, fusion protein sedimentation, high-throughput mass spectrometry, and other technologies; to analyze the effect of MDM2 expression on T cell function in the tumor microenvironment and to verify the effect of MDM2 inhibition on the efficacy of anti-PD-1 therapy in animal models . This study aims to reveal the new mechanism of MDM2 regulating immunotherapy and provide a new target for improving the efficacy of anti-PD-1 antibody.