CD155 on Tumor Cells Drives Resistance to Immunotherapy by Inducing the Degradation of the Activating Receptor CD226 in CD8 + T Cells.

The activating receptor CD226 is expressed on lymphocytes, monocytes, and platelets and promotes anti-tumor immunity in pre-clinical models. Here, we examined the role of CD226 in the function of tumor-infiltrating lymphocytes (TILs) and resistance to immunotherapy. In murine tumors, a large proportion of CD8 ⁺ TILs had decreased surface expression of CD226 and exhibited features of dysfunction, whereas CD226 ^hi TILs were highly functional. This correlation was seen also in TILs isolated from HNSCC patients. Mutation of CD226 at tyrosine 319 (Y319) led to increased CD226 surface expression, enhanced anti-tumor immunity and improved efficacy of immune checkpoint blockade (ICB). Mechanistically, tumor-derived CD155, the ligand for CD226, initiated phosphorylation of Y319 by Src kinases, thereby enabling ubiquitination of CD226 by CBL-B, internalization, and proteasomal degradation. In pre-treatment samples from melanoma patients, CD226 ⁺ CD8 ⁺ T cells correlated with improved progression-free survival following ICB. Our findings argue for the development of therapies aimed at maintaining the expression of CD226.
Competing Interests: Declaration of Interests M.J.S. has research agreements with Bristol Myers Squibb (BMS) and Tizona Therapeutics and is on the Scientific Advisory Board of Tizona Therapeutics and Compass Therapeutics. T.B. has research agreements with BMS. B.G.M.H. is a consultant advisor to BMS, Merck Sharp and Dohme, Roche, AstraZenca, Pfizer, Eisai, and Takeda and has research agreements with Amgen. G.V.L. is a consultant advisor to Aduro, Amgen, Mass-Array, BMS, Merck MSD, Novartis, Roche, OncoSec Medical, Sandoz, and Pierre Fabre. A.M. is a consultant advisor for BMS, Merck MSD, Novartis, Roche, and Pierre Fabre. W.C.D. declares a scientific research agreement with BMS, consulting agreements with Omeros Corp. and Cascadia Drug Development Group, and receipt of speaker’s honoraria from Amgen. A.V. has research agreements with BMS. R.A.S. has received fees for professional services from Novartis Pharma AG, MSD Sharp & Dohme (Australia), NeraCare, AMGEN Inc., BMS, Novartis Pharmaceuticals Australia Pty. Limited, Myriad Genetics GmbH, GlaxoSmithKline Australia. L.F. reported grants from the Swiss National Science Foundation, Swiss Cancer League, Hookipa Pharma, Krebsliga Schweiz, and Novartis Foundation as well as an advisory role for Novartis and BMS. S.E.N. has a research agreement with Servier. M.B., M.J.S., and T.B. have registered a patent for the use of CD226 in cancer immunotherapies (Australian Provisional Patent Application No. 2019900621).
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