Abstract

Significance The success rate of therapeutic trials that target tumor antigens is quite limited. We demonstrate for the first time to our knowledge that lung cancer cells that have undergone epithelial-to-mesenchymal transition lose immunoproteasome expression, resulting in markedly reduced antigen presentation. Reduced expression of the immunoproteasome was associated with and can predict poor outcome in non-small cell lung carcinoma (NSCLC) patients. Induction of the immunoproteasome with IFNγ or 5-aza-2′-deoxycytidine (5-aza-dC) treatment can overcome this immune escape mechanism of mesenchymal cells by restoring functional HLA class I-bound peptides. These findings have substantial relevance for development of effective strategies to target tumor cells with inherent resistance to T cell-mediated immunotherapy.