From patient tissue correlates to molecular mechanisms of cancer immune evasion: the emerging role of CD58 and PD-L1 co-regulation via CMTM6.

Immune evasion is a hallmark of cancer, yet the underlying mechanisms are often unknown in many patients. Using single-cell transcriptomics analysis, we previously identified the co-stimulator CD58 as part of a cancer cell-intrinsic immune checkpoint resistance signature in patient melanoma tissue. We subsequently validated CD58 loss as a driver of immune evasion using a patient-derived co-culture model of cancer and cytotoxic tumor-infiltrating lymphocytes in a pooled single-cell perturbation experiment, where we additionally observed concurrent upregulation of PD-L1 protein expression in melanoma cells with CD58 loss. In our most recent study, we uncovered the mechanisms of immune evasion mediated by CD58 loss, including impaired T cell activation and infiltration within tumors, as well as inhibitory signaling by PD-L1 via a shared regulator, CMTM6. Thus, cancer cell-intrinsic reduction of CD58 represents a multi-faceted determinant of immune evasion. Furthermore, its reciprocal interaction with PD-L1 via CMTM6 provides critical insights into how co-inhibitory and co-stimulatory immune cues are regulated.