CMTM6 maintains the expression of PD-L1 and regulates anti-tumour immunity

Article on the regulation of PD-L1

Go to the profile of Rebecca Ratty
Aug 25, 2017
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Nature(2017)  doi:10.1038/nature23643

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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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Go to the profile of Rebecca Ratty

Rebecca Ratty

Senior Publishing Manager, Springer Nature