Clark Curtis A, Gupta Harshita B, Sareddy Gangadhara, Pandeswara Srilakshmi, Lao Shunhua, Yuan Bin, Drerup Justin M, Padron Alvaro, Conejo-Garcia José, Murthy Kruthi, Liu Yang, Turk Mary Jo, Thedieck Kathrin, Hurez Vincent, Li Rong, Vadlamudi Ratna, Curiel Tyler J
The Graduate School of Biomedical Sciences, University of Texas Health Science Center, San Antonio, Texas.
Department of Medicine, University of Texas Health Science Center, San Antonio, Texas.
Cancer Res. 2016 Dec 1;76(23):6964-6974. doi: 10.1158/0008-5472.CAN-16-0258. Epub 2016 Sep 26.
PD-L1 antibodies produce efficacious clinical responses in diverse human cancers, but the basis for their effects remains unclear, leaving a gap in the understanding of how to rationally leverage therapeutic activity. PD-L1 is widely expressed in tumor cells, but its contributions to tumor pathogenicity are incompletely understood. In this study, we evaluated the hypothesis that PD-L1 exerts tumor cell-intrinsic signals that are critical for pathogenesis. Using RNAi methodology, we attenuated PD-L1 in the murine ovarian cell line ID8agg and the melanoma cell line B16 (termed PD-L1 cells), which express basal PD-L1. We observed that PD-L1 cells proliferated more weakly than control cells in vitro As expected, PD-L1 cells formed tumors in immunocompetent mice relatively more slowly, but unexpectedly, they also formed tumors more slowly in immunodeficient NSG mice. RNA sequencing analysis identified a number of genes involved in autophagy and mTOR signaling that were affected by PD-L1 expression. In support of a functional role, PD-L1 attenuation augmented autophagy and blunted the ability of autophagy inhibitors to limit proliferation in vitro and in vivo in NSG mice. PD-L1 attenuation also reduced mTORC1 activity and augmented the antiproliferative effects of the mTORC1 inhibitor rapamycin. PD-L1 cells were also relatively deficient in metastasis to the lung, and we found that anti-PD-L1 administration could block tumor cell growth and metastasis in NSG mice. This therapeutic effect was observed with B16 cells but not ID8agg cells, illustrating tumor- or compartmental-specific effects in the therapeutic setting. Overall, our findings extend understanding of PD-L1 functions, illustrate nonimmune effects of anti-PD-L1 immunotherapy, and suggest broader uses for PD-L1 as a biomarker for assessing cancer therapeutic responses. Cancer Res; 76(23); 6964-74. ©2016 AACR.
程序性死亡配体1（PD-L1）抗体在多种人类癌症中产生了有效的临床反应，但其作用的基础仍不清楚，这使得在理解如何合理利用治疗活性方面存在差距。PD-L1在肿瘤细胞中广泛表达，但其对肿瘤致病性的贡献尚未完全明确。在本研究中，我们评估了这样一个假设，即PD-L1发挥对发病机制至关重要的肿瘤细胞内在信号。使用RNA干扰方法，我们在表达基础水平PD-L1的小鼠卵巢细胞系ID8agg和黑色素瘤细胞系B16（称为PD-L1细胞）中减弱了PD-L1的表达。我们观察到，PD-L1细胞在体外的增殖比对照细胞更弱。正如预期的那样，PD-L1细胞在免疫健全的小鼠中形成肿瘤的速度相对较慢，但出乎意料的是，它们在免疫缺陷的NSG小鼠中形成肿瘤的速度也较慢。RNA测序分析确定了一些参与自噬和mTOR信号传导的基因，这些基因受PD-L1表达的影响。为支持其功能作用，PD-L1表达减弱增强了自噬，并削弱了自噬抑制剂在体外和NSG小鼠体内限制增殖的能力。PD-L1表达减弱还降低了mTORC1活性，并增强了mTORC1抑制剂雷帕霉素的抗增殖作用。PD-L1细胞转移至肺部的能力也相对不足，并且我们发现给予抗PD-L1抗体可阻断NSG小鼠体内肿瘤细胞的生长和转移。在B16细胞中观察到了这种治疗效果，但在ID8agg细胞中未观察到，这说明了在治疗环境中存在肿瘤或区域特异性效应。总体而言，我们的发现扩展了对PD-L1功能的理解，阐明了抗PD-L1免疫疗法的非免疫效应，并提示PD-L1作为评估癌症治疗反应的生物标志物有更广泛的用途。癌症研究；76(23)；6964 - 6974。©2016美国癌症研究协会。
