PTPN2对三阴性乳腺癌患者anti-PD-1/PD-L1反应疗效的影响及机制研究

Triple negative breast cancer (TNBC) is the most lethal subtype of breast cancer. Currently, TNBC treatment lacks a clinically-approved standard protocol and is primarily treated with traditional chemotherapy and surgery. The advent of immune checkpoint inhibitor (ICI) immunotherapy (i.e., anti-CTLA-4 and anti-PD-1/PD-L1) has dramatically extended the survival time in metastatic melanoma and non small cell lung cancer patients over the past 5 years which has shed some light on TNBC treatment. Although TNBC is the most immunogenic subtype of breast cancer, the objective response rate of ICI in TNBC is only 15%. Therefore, methods that improve the objective response rate to ICI in TNBC remains an urgent area of investigation. IFN-γ and IFN-γ regulated genes are associated with immunotherapy responsiveness in cancer patients and in mouse models. PTPN2 (a non-receptor type tyrosine-specific phosphatase) negatively regulates the IFN-γ signaling pathway. Therefore, this project will investigate whether PTPN2 down-regulation improves the response rate and efficacy to ICI in TNBC. Our hypothesis is that PTPN2 down-regulation in TNBC will: 1) promote expression of IFN-γ regulated genes and anti-tumor immunity associated genes, 2) potentiate the anti-tumor immunity microenvironment, and 3) improve the response rate and efficacy to ICI. We will test the hypothesis from both a mechanistic aspect and a treatment outcome aspect. Our results will provide a potential and novel strategy that inhibits TNBC growth and extends the survival time in TNBC patients.

三阴性乳腺癌(TNBC)目前没有标准的治疗方案。Anti-CTLA-4或anti-PD-1/PD-L1(Immune Checkpoint Inhibitors, ICI) 在控制恶性黑色素瘤和非小细胞肺癌的生长、维持疾病稳定及延长患者生存时间上取得了令人瞩目的效果，给TNBC的治疗带来了希望。ICI免疫治疗在TNBC患者中的反应率仅为15%左右。因此，如何提高TNBC患者对ICI反应率是亟待解决的问题。本项目主要探究降低肿瘤中的PTPN2是否可提高TNBC患者对ICI的反应率，增强其疗效。我们的假设为降低TNBC中的PTPN2，可促进IFN- γ介导的信号分子及抗肿瘤免疫基因的表达，从而改变肿瘤的免疫微环境，提高TNBC患者对ICI的反应率和疗效。我们将从作用机理和反应疗效2个方面对假设进行论证。我们的研究结果将会为抑制TNBC生长、延长TNBC患者的生存时间提供一种潜在有效的治疗方法。

三阴性乳腺癌（TNBC）因雌激素受体、孕激素受体和HER2的表达均为阴性，导致其对内分泌治疗和靶向治疗反应甚微。而且，TNBC患者对免疫检查点抑制剂的临床获益率相对较低。因此，提高TNBC患者对免疫检查点抑制剂的疗效是一个亟待解决的问题。.本项目以PTPN2为靶标，主要探究其对TNBC免疫微环境和对免疫检查点抑制剂疗效的影响。研究采用loss-of-function和gain-of-function策略，通过体外细胞实验和体内动物实验，探究PTPN2对TNBC免疫微环境的影响和机制。体外细胞实验结果显示，敲低TNBC细胞中PTPN2的表达，显著提高肿瘤细胞的增殖、迁移和侵袭能力。但是，将敲低/敲除PTPN2的TNBC细胞注射到遗传背景相同的小鼠体内后，PTPN2敲低/敲除组的肿瘤生长显著慢于对照组。这些结果暗示肿瘤细胞的PTPN2敲低/敲除，改变了肿瘤免疫微环境，从而抑制PTPN2敲低/敲除组TNBC肿瘤细胞在体内的生长。进一步研究发现，PTPN2敲低组的TNBC肿瘤组织中，CD8+T细胞占比显著升高，FOXP3+ Treg细胞占比显著降低。PTPN2敲除组的TNBC肿瘤组织中，CD4+T和CD8+T细胞占比显著升高，FOXP3+ Treg细胞占比显著降低。相关机制研究发现，敲低TNBC细胞中PTPN2的表达，促进了IFN-γ介导的STAT1/STAT3的活化，增强了抗原呈递分子MHC-I/MHC-II的表达和PD-1配体PD-L1的表达，以及T细胞招募分子CXCL9/CXCL10/CXCL11的表达。而TNBC细胞中外源性过表达PTPN2的实验显示了和上述相反的结果。同时，通过趋化因子芯片筛选CCN4可能是由PTPN2介导的增强肿瘤免疫反应的潜在因子。.我们的研究结果为以PTPN2为靶标，和免疫检查点抑制剂的联合应用作为治疗TNBC的有效方法提供了理论支持。