Cancer cells exploit the expression of the programmed death-1 (PD-1) ligand 1 (PD-L1) to subvert T-cell-mediated immunosurveillance1,2. The success of therapies that disrupt PD-L1-mediated tumour tolerance has highlighted the need to understand the molecular regulation of PD-L1 expression1. Here we identify the uncharacterized protein CMTM6 as a critical regulator of PD-L1 in a broad range of cancer cells, by using a genome-wide CRISPR–Cas9 screen. CMTM6 is a ubiquitously expressed protein that binds PD-L1 and maintains its cell surface expression. CMTM6 is not required for PD-L1 maturation but co-localizes with PD-L1 at the plasma membrane and in recycling endosomes, where it prevents PD-L1 from being targeted for lysosome-mediated degradation. Using a quantitative approach to profile the entire plasma membrane proteome, we find that CMTM6 displays specificity for PD-L1. Notably, CMTM6 depletion decreases PD-L1 without compromising cell surface expression of MHC class I. CMTM6 depletion, via the reduction of PD-L1, significantly alleviates the suppression of tumour-specific T cell activity in vitro and in vivo. These findings provide insights into the biology of PD-L1 regulation, identify a previously unrecognized master regulator of this critical immune checkpoint and highlight a potential therapeutic target to overcome immune evasion by tumour cells.

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M.L.B. is supported by a Cancer Research UK Fellowship, Addenbrooke’s Charitable Trust award and NIHR fellowship. M.A.D. is supported by a Senior Leukaemia Foundation Australia Fellowship and work in the Dawson laboratory is supported by the NHMRC (Grants 1085015, 1106444 and 1106447) Cancer Council Victoria and Leukaemia Foundation Australia. P.J.L. is supported by a Wellcome Trust PRF (101835/Z/13/Z) and work in the Lehner laboratory is supported by NHSBT, NIHR Cambridge BRC, a Wellcome Trust Strategic Award to CIMR, and the Addenbrooke’s Charitable Trust.

Author information


  1. Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia

    • Marian L. Burr
    • , Christina E. Sparbier
    • , Yih-Chih Chan
    • , Paul A. Beavis
    • , Enid Y. N. Lam
    • , Melissa A. Henderson
    • , Charles C. Bell
    • , Sabine Stolzenburg
    • , Omer Gilan
    • , Tahereh Noori
    • , Paul J. Neeson
    • , Phillip K. Darcy
    • , Sarah-Jane Dawson
    • , Ilia Voskoboinik
    • , Joseph A. Trapani
    •  & Mark A. Dawson
  2. Sir Peter MacCallum Department of Oncology, University of Melbourne, Victoria 3052, Australia

    • Marian L. Burr
    • , Paul A. Beavis
    • , Enid Y. N. Lam
    • , Melissa A. Henderson
    • , Charles C. Bell
    • , Omer Gilan
    • , Paul J. Neeson
    • , Phillip K. Darcy
    • , Sarah-Jane Dawson
    • , Ilia Voskoboinik
    • , Joseph A. Trapani
    •  & Mark A. Dawson
  3. Cambridge Institute for Medical Research, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK

    • Marian L. Burr
    • , James C. Williamson
    • , Stuart Bloor
    •  & Paul J. Lehner
  4. School of Cancer Medicine, La Trobe University, Melbourne, Victoria 3086, Australia

    • Katherine Woods
    • , Andreas Behren
    •  & Jonathan Cebon
  5. Olivia Newton-John Cancer Research Institute, Heidelberg, Victoria 3084, Australia

    • Katherine Woods
    • , Andreas Behren
    •  & Jonathan Cebon
  6. Department of Genetics, Stanford University, Stanford, California, USA

    • David W. Morgens
    •  & Michael C. Bassik
  7. Centre for Cancer Research, University of Melbourne, Melbourne, Australia

    • Sarah-Jane Dawson
    •  & Mark A. Dawson
  8. Department of Haematology, Peter MacCallum Cancer Centre, Melbourne, Australia

    • Mark A. Dawson


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M.L.B., P.J.L. and M.A.D. designed the research and interpreted data. M.A.D. and M.L.B. wrote the manuscript with assistance from P.J.L., Y-C.C. and E.Y.N.L. M.L.B., C.E.S., Y.-C.C., E.Y.N.L., C.C.B., S.S., and O.G. performed experiments and analysed data directly supervised by M.A.D. M.L.B. performed the CRISPR screen assisted by S.B. and J.C.W. performed the plasma membrane profiling supervised by P.J.L. K.W. and A.B. performed T cell assays supervised by J.C. P.A.B. and M.A.H. performed the mouse experiments. D.W.M. and M.C.B. designed and generated the CRISPR sgRNA library. P.J.N., P.K.D., S-J.D., I.V. and J.A.T. provided critical reagents and aided in manuscript preparation.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Marian L. Burr or Paul J. Lehner or Mark A. Dawson.

Reviewer Information Nature thanks S. Ogawa, A. Ribas and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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