靶向干细胞增强抗原加工和递呈治疗胶质母细胞瘤

The biological characteristics of glioma stem cells (GSCs) determine that they can evade the surveillance of the immune system in vivo, and the increase of the expression of specific antigens can help the immune system to kill the GSCs. Our results of early experiments showed that human leukocyte antigen (HLA) and antigen processing machinery (APM) components on the surface of GSCs are down-regulated or absent significantly. So we proposed a hypothesis that it will help to improve the recognition of T lymphocytes to cancer cells that the expression of multiple specific tumor antigens on the surface of GSCs will be increased by enhancing HLA and APM components, which is down-regulated or missing in epigenetic mode. In this study, the transferrin (Tf) receptor that is highly expressed on the surface of glioma cells, especially GSCs will be a target. We will prepare nanoparticles that were conjugated to the Tf and encapsulate histone deacetylase inhibitor SAHA. The mechanisms of immunogenic cell death (ICD) on GSCs will be investigated, and the biological effects of treating nude mice with orthotopic xenografts will be observed. It is the first time for treating GBM by the activation of HLA and APM components to increase the expression of a variety of tumor antigens at the same time, and exploring molecular mechanism of ICD by the chemotherapeutic drugs in GSCs. It provides new ideas for solving the problem of weak response of immunotherapy, such as PD-1 antibody or CAR-T therapy, to some patients in clinic.

胶质瘤干细胞（GSCs）生物学特性决定了其可以逃避体内免疫系统的监视，提高特异性抗原表达有利于免疫系统对GSCs的杀伤。我们的预实验结果发现GSCs表面人类白细胞抗原（HLA）和抗原加工机器（APM）组件明显下调或缺失。据此提出假说，提高表观遗传方式下调或缺失的HLA和APM组件，以此来提高GSCs表面多种特异性肿瘤抗原表达，有利于提高T淋巴细胞对癌细胞的识别。本研究以高表达于胶质瘤细胞尤其是GSCs表面的转铁蛋白（Tf）受体为靶向，构建偶联Tf包裹组氨酸去乙酰化酶抑制剂SAHA的纳米微粒，探讨其诱导GSCs发生免疫原性细胞死亡（ICD）的机制，以及治疗原位移植瘤裸鼠的生物学效应。本研究首次以提高HLA和APM组件同时提高多种肿瘤抗原表达方式治疗GBM，并探讨化疗药物诱导GSCs发生ICD的分子机制，为临床上解决部分患者对PD-1抗体或CAR-T等免疫疗法反应性较差的问题提供新的思路。

多形性胶质母细胞瘤（Glioblastoma multiforme, GBM）是常见的脑肿瘤，多数经传统治疗后会在短期内复发。研究者们认为胶质瘤干细胞（glioma stem cells，GSCs）是GBM复发的根源，该类细胞具有耐受放疗和化疗的特点。探讨GSCs发生免疫逃逸的机制有助于指导GBM临床免疫治疗。本研究发现，GSCs通过下调抗原递呈来降低T细胞对其的识别能力，从而逃避全身免疫系统的监视。GSCs通过自身的生物学特性保持抗原递呈分子主要组织相容性复合体I类分子（MHC-I）和抗原加工组分低表达。组蛋白去乙酰化酶抑制剂SAHA上调了GSCs的MHC-I和抗原加工组件成分，通过抑制干细胞固有的Wnt/β-catenin信号通路上调这些抗原加工和递呈分子，从而提高GSCs表面肿瘤特异抗原和肿瘤相关抗原的递呈，触发适应性免疫应答，激活细胞毒T淋巴细胞发挥抗肿瘤免疫反应。胶质瘤细胞来源的外泌体MHC-I同样具有递呈抗原的功能，在系统性免疫过程中发挥重要作用，上调外泌体MHC-I能够提高抗原递呈，激活系统性免疫，提高PD-L1单克隆抗体治疗的敏感性。偶联转铁蛋白受体的载药纳米微粒PAMAM-Tf/SAHA有抗肿瘤功效，通过诱导肿瘤细胞发生免疫原性细胞死亡发挥作用，提高机体免疫功能。本研究证实SAHA通过提高抗原加工和递呈有效地促进机体抗肿瘤免疫，靶向载药纳米微粒发挥更强的功能，为临床上免疫治疗提供新的思路。