Suppression of protein quality control system by TRIM30a sensitises tumour cells to NK cell-mediated immune surveillance.

Tumorigenesis entails circumventing cell-intrinsic regulatory mechanisms while avoiding extrinsic immune surveillance and other host defence systems. Nevertheless, how tumour cells' ability to eliminate misfolded proteins affects immune surveillance remains poorly understood. In this study, we find that overexpression of murine tripartite motif-containing protein 30a (TRIM30a) sensitises tumour cells to natural killer (NK) cells-mediated cytolysis. TRIM30a has no effect on tumour cell proliferation or apoptosis in vitro. However, TRIM30a-overexpressing tumour cells grow substantially slower than control tumour cells in immune-competent mice but not in NK-depleted mice. Mechanistically, TRIM30a overexpression impedes the clearance of misfolded protein and increases the production of reactive oxygen species induced by proteotoxic stress, implying that TRIM30a impairs protein quality control (PQC) systems in tumour cells. Furthermore, TRIM30a reduces expression of genes encoding proteasome subunits and antioxidant proteins. Our study demonstrates that TRIM30a is a potential tumour suppressor and immune modulator that promotes tumour cytolysis by NK cells, and suggests that an enhanced PQC and antioxidant capacity is an integral part of the immune escape mechanism during tumorigenesis.