Tumor-intrinsic PD-L1 signals regulate cell growth, pathogenesis, and autophagy in ovarian cancer and melanoma

Curtis A. Clark, Harshita B. Gupta, Gangadhara Sareddy, Srilakshmi Pandeswara, Shunhua Lao, Bin Yuan, Justin M. Drerup, Alvaro Padron, José Conejo-Garcia, Kruthi Murthy, Yang Liu, Mary Jo Turk, Kathrin Thedieck, Vincent Hurez, Rong Li, Ratna Vadlamudi, Tyler J. Curiel

Research output: Contribution to journalArticlepeer-review

288 Scopus citations


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-L1lo cells), which express basal PD-L1. We observed that PD-L1lo cells proliferated more weakly than control cells in vitro. As expected, PD-L1lo 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-L1lo 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.

Original languageEnglish (US)
Pages (from-to)6964-6974
Number of pages11
JournalCancer Research
Issue number23
StatePublished - Dec 1 2016

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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