We respond to PQ3 with our data showing that tumor PD-L1 (CD274, B7-H1) is a major regulator of tumor inflammatory infiltrates. Our preliminary data show that melanoma PD-L1 regulates TIL through several previously unknown tumor-intrinsic and extrinsic mechanisms. We define novel effects of tumor intrinsic PD-L1 signaling on tumor proliferation, sensitivity to immune killing, in vivo growth independent of anti-tumor immunity, and regulation of mTOR signals. We identified intracellular PD-L1, including those whose surface expression is low or negative, and identified interactions with tumor PD-1. We hypothesize that melanoma intrinsic PD-L1-driven signals, particularly mTOR signals, alter tumor progression and treatment responses. The research team is comprised of tumor immunotherapy, tumor immunology and PD-L1 experts at UTHSCSA and Dartmouth. We focus on melanoma for scientific reasons and based on our expertise.
Aim 1 Define how tumor PD-L1 alters tumor immune infiltrates and immunotherapy responses. We use control versus PD-L1lo (shRNA) B16 in a novel model to study differential treatment outcomes by tumor PD-L1 status. We generated PD-L1KO B16 by CRISPR for highly detailed follow up mechanistic studies, and to assess if PD-L1 null status differentially affects treatment versus PD-L1lo. Effects will also be tested in transplanted BrafV600E mutated D4M melanoma (PD-L1+) engineered to be PD-L1lo and PD-L1KO, in mice with induced BrafV600E melanomas, and in syngeneic skin grafts of skin from Braf/Pten versus PD-L1KO Braf/Pten mice.
Aim 2 Test tumor PD-L1-driven mTOR signal effects on TIL and immunotherapy responses. We will test PD-L1 KO, PD-1 KO and double KO melanoma cells for mTOR signals, TIL and treatment effects. Cells will be engineered for defects in mTORC1/2 for mechanistic studies, complemented with mTOR inhibitor treatments. We will use engineered tumors that express cytoplasm-only versus cell surface-only PD-L1, to define novel, intracellular PD-L1 signals. Constructs with mutations in known PD-1 signal sites will be engineered into these tumors for a complete understanding of PD-L1/PD-1 interactions.
Aim 3 Define cell-intrinsic PD-L1 effects in human melanoma. We use well-defined human melanoma lines that are basal PD-L1+ and/or PD-1+ and/or BrafV600E mutated. We will use human vectors to knock down or knock out PD-L1, PD-1 and mTORC1/2 genes. In vitro assessments of effects on proliferation, responses to mTOR inhibitors, ?PD-L1 and ?PD-1 will be assessed. In vivo effects in NSG mice will be assessed. Primary human melanoma lines will be studied to complement data from long-term lines.

Public Health Relevance

Factors regulating tumor immune cell infiltrates that drive tumor progression and alter response to immunotherapy are largely unknown. In response to PQ3, we identified tumor intrinsic PD-L1 (B7-H1, CD274) as a major regulator of these infiltrates with profound effects on tumor progression, and response to immunotherapy. We focus on melanoma, but as many tumors express PD-L1, which is also a target for successful immunotherapies, our studies have very broad potential applications and could lead to field- changing insights and paradigms.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Special Emphasis Panel (ZCA1)
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Mccarthy, Susan A
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University of Texas Health Science Center
Internal Medicine/Medicine
Schools of Medicine
San Antonio
United States
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Molodtsov, Aleksey; Turk, Mary Jo (2018) Tissue Resident CD8 Memory T Cell Responses in Cancer and Autoimmunity. Front Immunol 9:2810