Inflammatory signaling drives SQSTM1-dependent suppression of interferon-γ-induced MHC class I
An immune-inflamed tumor microenvironment features interferon-{gamma} (IFN-{gamma}) and inflammatory cytokines, yet how cancer cells integrate these opposing signals to regulate immunogenicity remains poorly understood. Here, we investigated the effect of interleukin-1{beta} (IL-1{beta}) on IFN-{gamma}-induced major histocompatibility complex class I (MHC-I) expression in non-small cell lung cancer (NSCLC) cells. IL-1{beta} suppressed IFN-{gamma}-induced surface MHC-I expression despite preserved or enhanced expression of antigen presentation-related genes, indicating post-transcriptional regulation. This effect emerged 12-24 h after stimulation and accompanied accelerated MHC-I turnover without altering total protein abundance. RNA sequencing identified selective induction of autophagy-related genes under combined IFN-{gamma} and IL-1{beta} stimulation. Immunofluorescence and biochemical analyses demonstrated MHC-I redistribution to autophagosome-lysosome compartments. Mechanistically, the selective autophagy receptor SQSTM1 associated with MHC-I and was required for its surface downregulation, whereas NBR1 depletion and autophagy or lysosomal inhibition failed to restore MHC-I expression, indicating a nonredundant role for SQSTM1. These findings identify post-translational MHC-I trafficking as an underappreciated regulatory layer linking inflammatory signaling to the canonical IFN-{gamma}-MHC-I axis and reveal an SQSTM1-dependent mechanism controlling MHC-I surface availability in immune-inflamed tumors.