Xu Aizhang, Bhanumathy Kalpana Kalyanasundaram, Wu Jie, Ye Zhenmin, Freywald Andrew, Leary Scot C, Li Rongxiu, Xiang Jim
State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, China ; School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
Cancer Research Cluster, Saskatchewan Cancer Agency, Saskatoon, SK Canada ; Departments of Oncology, University of Saskatchewan, HSB Room 4D30.1, 107 Wiggins Road, Saskatoon, SK S7N 5E5 Canada.
Cell Biosci. 2016 May 6;6:30. doi: 10.1186/s13578-016-0098-2. eCollection 2016.
Lymphopenia promotes naïve T-cell homeostatic proliferation and adoptive effector T-cell survival and memory formation. IL-7 plays a critical role in homeostatic proliferation, survival and memory formation of naïve T-cells in lymphopenia, and its underlying molecular mechanism has also been well studied. However, the mechanism for adoptively transferred effector T-cell survival and memory formation is not fully understood. Here, we transferred in vitro-activated transgenic OT-I CD8(+) effector T-cells into irradiation (600 rads)-induced lymphopenic C57BL/6, IL-7 knockout (KO) and IL-15 KO mice, and investigated the survival and memory formation of transferred T-cells in lymphopenia.
We demonstrate that transferred T-cells prolong their survival and enhance their memory in lymphopenic mice, in a manner that depends on IL-15 signaling, but not IL-7. We determine that in vitro stimulation of naïve or effector T-cells with IL-7 and IL-15 reduces IL-7Rα, and increases and/or maintains IL-15Rβ expression, respectively. Consistent with these findings, the expression of IL-7Rα and IL-15Rβ is down- and up-regulated, respectively, in vivo on transferred T-cells in an early phase post T-cell transfer in lymphopenia. We further show that in vitro IL-15 restimulation-induced memory T-cells (compared to IL-2 restimulation-induced effector T-cells) and in vivo transferred T-cells in irradiated IL-15-sufficient C57BL/6 mice (compared to IL-15-deficient IL-15 KO mice) have increased mitochondrial content, but less NADH and lower mitochondrial potential (ΔΨm), and demonstrate greater phosphorylation of signal transducers and activators of transcription-5 (STAT5) and Unc-51-like kinase-1 (ULK1), and higher expression of B-cell leukemia/lymphoma-2 (Bcl2) and memory-, autophagy- and mitochondrial biogenesis-related molecules.
Irradiation-induced lymphopenia promotes effector T-cell survival via IL-15 signaling the STAT5/Bcl2 pathway, enhances T-cell memory formation via IL-15 activation of the forkhead-box family of transcription factor (FOXO)/eomesodermin (Eomes) memory and ULK1/autophagy-related gene-7 (ATG7) autophagy pathways, and via IL-15 activation of the mitochondrial remodeling. Our data thus identify some important targets to consider when designing potent adoptive T-cell immunotherapies of cancer.
淋巴细胞减少促进初始T细胞的稳态增殖以及过继性效应T细胞的存活和记忆形成。白细胞介素-7（IL-7）在淋巴细胞减少时初始T细胞的稳态增殖、存活和记忆形成中起关键作用，其潜在分子机制也已得到充分研究。然而，过继性转移的效应T细胞存活和记忆形成的机制尚未完全阐明。在此，我们将体外激活的转基因OT-I CD8(+)效应T细胞转入经600拉德照射诱导淋巴细胞减少的C57BL/6小鼠、IL-7基因敲除（KO）小鼠和IL-15基因敲除小鼠体内，并研究淋巴细胞减少状态下转移T细胞的存活和记忆形成情况。
我们证明，转移的T细胞在淋巴细胞减少的小鼠中延长了其存活时间并增强了其记忆能力，其方式依赖于IL-15信号通路，而非IL-7。我们确定，用IL-7和IL-15体外刺激初始或效应T细胞分别会降低IL-7Rα表达，并增加和/或维持IL-15Rβ表达。与这些发现一致，在淋巴细胞减少状态下T细胞转移后的早期阶段，体内转移T细胞上的IL-7Rα和IL-15Rβ表达分别下调和上调。我们进一步表明，体外IL-15再刺激诱导的记忆T细胞（与IL-2再刺激诱导的效应T细胞相比）以及经照射的IL-15充足的C57BL/6小鼠体内转移的T细胞（与IL-15缺陷的IL-15基因敲除小鼠相比）线粒体含量增加，但烟酰胺腺嘌呤二核苷酸（NADH）减少且线粒体膜电位（ΔΨm）降低，并表现出信号转导和转录激活因子5（STAT5）和Unc-51样激酶1（ULK1）的磷酸化增强，以及B细胞淋巴瘤-2（Bcl2）和记忆、自噬及线粒体生物发生相关分子的表达上调。
照射诱导的淋巴细胞减少通过IL-15信号传导的STAT5/Bcl2途径促进效应T细胞存活，通过IL-15激活叉头框转录因子家族（FOXO）/胚外中胚层决定因子（Eomes）记忆和ULK1/自噬相关基因7（ATG7）自噬途径增强T细胞记忆形成，并通过IL-15激活线粒体重塑。因此，我们的数据确定了在设计有效的癌症过继性T细胞免疫疗法时需要考虑的一些重要靶点。
