HLA-E等位基因与卵巢癌易感性及免疫治疗的相关性研究

The overexpression of HLA-E, a nonclassical HLA class I molecule, has been reported in ovarian cancer. HLA-E expression by neoplastic cells might favor tumor cells escape from immunosurveillance through the interaction with inhibitory CD94/NKG2A receptor expressed by NK cells, however, the potential role of HLA-E presenting Hsp60sp to CD8+T cells has been poorly addressed. The results of our preliminary experiments suggested that the frequency of HLA-E*0103 allele in the patients with ovarian cancer exceeded which in healthy population. Moreover, the affinity and thermal stability of HLA-E*0103 in complex with Hsp60sp were greater than which of HLA-E*0101. Thus, we hypothesized that HLA-E*0103 was more helpful to favor ovarian cancer cells escape from immunosurveillance of NK cells, and the induced-HLA-E-restricted CD8+T cells might produce anti-tumor immune responses to this allele. This study will explore the relationship between HLA-E alleles and the susceptibility and immunotherapy in ovarian cancer from several aspects including molecules, cells, tissues and animals by means of lentiviral vectors, flow cytometry, immunohistochemistry and an animal model of transplanted tumor in mice. This study will provide a novel method of tumor immunotherapy for the patients with HLA-E*0103 allele.

HLA-E是一种非经典的HLA-I类分子，在卵巢癌中过表达。HLA-E分子在肿瘤细胞上的表达可能通过与NK细胞表面的CD94/NKG2A抑制性受体结合而逃逸免疫监视，然而HLA-E递呈肽段Hsp60sp激活CD8+T细胞的潜在功能尚不清楚。本项目的预实验结果提示HLA-E*0103等位基因在卵巢癌患者中的频率远大于健康人群，且其与Hsp60sp的亲合力和热稳定性均高于HLA-E*0101。为此，我们提出假说：HLA-E*0103更易使卵巢癌细胞逃逸NK细胞的监视，而诱导HLA-E限制性CD8+T细胞可以成为该等位基因特异性的抗肿瘤手段。本研究将采用慢病毒载体转染、流式技术、免疫组化和动物移植瘤等手段，从分子、细胞、组织以及动物水平等多方面探讨HLA-E等位基因与卵巢癌易感性及免疫治疗的关系。本研究将为HLA-E*0103等位基因特异性的肿瘤患者提供新的免疫治疗方案。

卵巢癌是女性妇科恶性肿瘤死亡率最高的疾病，其预后差，5年生存率只有30%。因此，深入研究卵巢癌的生物学特性及探索新的治疗方式对于提高卵巢癌患者的生存率至关重要。人类白细胞抗原（human leucocyte antigen, HLA）基因系统即人类主要组织相容性复合体（major histocompatibility complex, MHC），是由一组高度多态性基因组成的染色体区域。其编码产物参与抗原递呈、制约细胞间相互作用及诱导免疫应答，在许多疾病特别是自身免疫病、肿瘤和感染的防治中具有重要的研究价值。HLA-E属于非经典的MHC-I类分子，在肿瘤细胞表面的过量表达可能是肿瘤逃避免疫监视的一个新机制。. 本项目从HLA-E等位基因的角度探讨了HLA-E*0103与卵巢癌易感性的关系。结果显示HLA-E*0103在卵巢癌患者中的频率远远高于健康对照组，卵巢癌组织过表达HLA-E蛋白，且HLA-E*0103*0103纯合型的卵巢癌组织呈强阳性表达。进一步研究表明，HLA-E*0103等位基因使得HLA-E分子在细胞表面的表达增加，与保护性肽段B7sp的结合更稳定，从而抑制NK细胞对高表达HLA-E分子的肿瘤细胞的杀伤。本项目从一个全新的角度揭示了卵巢癌基因易感性及肿瘤免疫逃逸的机制。. 本项目还探讨了卵巢癌组织过表达HLA-E蛋白的原因及如何设计针对HLA-E分子的肿瘤免疫治疗途径。我们的研究显示，卵巢癌细胞高表达HLA-E蛋白与肿瘤微环境有关，其中一些可溶性的蛋白分子起了一定的作用，但具体机制还有待研究。另外，肿瘤微环境中存在针对HLA-E与Hsp60sp肽段的杀伤性CD8+ T细胞，而体外诱导的特异性识别HLA-E/Hsp60sp复合物的CD8+ T细胞也能直接杀伤卵巢癌细胞。因此，诱导或强化这群能特异性杀伤肿瘤细胞的CD8+ T细胞有望成为卵巢癌免疫治疗的手段。