Therapeutic potential of T cell responses against tumor initiating cell-associated antigens in CRC

结直肠癌（CRC）患者的生存取决于转移灶的建立。它们起源于一小部分长期肿瘤起始细胞（LTTIC）。T细胞在肿瘤病变中的浸润程度是结直肠癌的主要预后参数，提示基于T细胞的肿瘤免疫监测具有临床意义。我们证明了T细胞在原位的富集和效应功能仅限于肿瘤抗原特异性T细胞群。肿瘤特异性调节性T细胞（tumor specific regulatory T cells, Treg）可以抑制抗原特异性效应T细胞的激活和功能，从而可能在基于T细胞的免疫监视和控制CRC进展过程中发挥关键作用。我们假设有效的免疫监测和改善的CRC预后是基于T细胞对LT-TIC上表达的肿瘤抗原（TA）的反应。在第一个资助期内，我们建立了一个完整的基于蛋白质组的技术，通过该技术，我们确定了原发性和转移性CRC上的T细胞靶抗原的新实体，这些抗原在转移级联中存在差异表达，其中一些在LT-TIC上选择性表达。在结直肠癌患者中，针对这些抗原的T细胞应答比针对“典型”TAs的T细胞应答要丰富得多。我们进一步建立了一种方法来确定CRC患者自发Treg反应的特异性，并通过这种方法表征肿瘤特异性Treg的主要靶抗原及其对TA反应性记忆T细胞的功能影响。在第二个资助期，我们将研究一种假设，即与CTL特异性治疗典型CRC相关TAs相比，用LT-TIC特异性CTL克隆治疗体内异种移植的TIC球体会降低转移潜力和致瘤性。此外，我们将扩展已获得的关于LT tic相关CRC抗原的信息，以研究原发性和转移性CRC中高T细胞浸润与LT- tic特异性T细胞数量增加和预后改善相关的假设。

Survival of colorectal carcinoma (CRC) patients is determined by the establishment of metastases. These arise from a small subpopulation of long term tumor-initiating cells (LTTIC). The extent of T cell infiltrates in tumor lesions represents the major prognostic parameter in CRC suggesting clinical relevance of T cell based tumor immune surveillance. We demonstrated that T cell enrichment and effector function in situ is restricted to the population of tumor antigen specific T cells. Activation and function of antigen specific effector T cells can be inhibited by tumor specific regulatory T cells (Treg) which thus may play a critical role during T cell based immune surveillance and control of CRC progression. We hypothesize that efficient immune surveillance and improved CRC prognosis is based on T cell responses against tumor antigens (TA) expressed on LT-TIC. During the first funding period we established a whole proteome-based technology by which we identified new entities of T cell target antigens on primary and metastatic CRC that are differentially expressed throughout the metastatic cascade, some of them being selectively expressed on LT-TIC. T cell responses against these antigens were much more abundant in CRC patients than T cell responses against “canonical” TAs. We further established a method to determine the specificities of spontaneous Treg responses in CRC patients and by this characterized major target antigens of tumor-specific Treg and their functional impact on TA reactive memory T cells. Throughout the second funding period we will investigate the hypothesis that treatment of xenotransplanted TIC spheroids in vivo with LT-TIC specific CTL clones in contrast to CTL specific for canonical CRC associated TAs will result in reduced metastatic potential and tumorigenicity. In addition, we will expand the gained information on LT TIC-associated CRC antigens to investigate the hypothesis that high T cell infiltrates in primary and metastatic CRC are associated with increased numbers of LT-TIC specific T cells and improved prognosis.