Autophagy Blockage Up-Regulates HLA-Class-I Molecule Expression in Lung Cancer and Enhances Anti-PD-L1 Immunotherapy Efficacy.

Simple Summary: The restoration of HLA-class-I expression in lung cancer cells may reverse immune evasion, enhance cytotoxic T-cell activity, and improve immune checkpoint inhibitors' therapeutic efficacy. In the current study, we provide experimental evidence that autophagy blockage either at the late stage (chloroquine and bafilomycin) or early stage of the autophagic process (ULK1 inhibitors and MAP1LC3A silencing) can up-regulate the expression of HLA-class-I molecules in the A549 and H1299 NSCLC cell lines and their CD133+ stem cells. This upregulation enhances the cytotoxic activity of activated CD8+ T-cells, in particular after pre-incubation with anti-PD-L1 monoclonal antibodies. The restoration of HLA-class-I-mediated antigen presentation with autophagy blockers in lung cancer is a promising avenue that urgently requires further exploration in clinical trials. Background/Objectives: Immune checkpoint inhibitors have an established role in non-small cell lung cancer (NSCLC) therapy. The loss of HLA-class-I expression allows cancer cell evasion from immune surveillance, disease progression, and failure of immunotherapy. The restoration of HLA-class-I expression may prove to be a game-changer in current immunotherapy strategies. Autophagic activity has been recently postulated to repress HLA-class-I expression in cancer cells. Methods: NSCLC cell lines (A549 and H1299) underwent late-stage (chloroquine and bafilomycin) and early-stage autophagy blockage (ULK1 inhibitors and MAP1LC3A silencing). The HLA-class-I expression was assessed with flow cytometry, a Western blot, and RT-PCR. NSCLC tissues were examined for MAP1LC3A and HLA-class-I expression using double immunohistochemistry. CD8+ T-cell cytotoxicity was examined in cancer cells pre-incubated with chloroquine and anti-PD-L1 monoclonal antibodies (Moabs); Results: A striking increase in HLA-class-I expression following incubation with chloroquine, bafilomycin, and IFNγ was noted in A549 and H1299 cancer cells, respectively. This effect was further confirmed in CD133+ cancer stem cells. HLA-class-I, β2-microglobulin, and TAP1 mRNA levels remained stable. Prolonged exposure to chloroquine further enhanced HLA-class-I expression. Similar results were noted following exposure to a ULK1 and a PIKfyve inhibitor. Permanent silencing of the MAP1LC3A gene resulted in enhanced HLA-class-I expression. In immunohistochemistry experiments, double LC3A+/HLA-class-I expression was seldom. Pre-incubation of H1299 cancer cells with chloroquine and anti-PD-L1 MoAbs increased the mean % of apoptotic/necrotic cells from 2.5% to 18.4%; Conclusions: Autophagy blockers acting either at late or early stages of the autophagic process may restore HLA-class-I-mediated antigen presentation, eventually leading to enhanced immunotherapy efficacy. [ABSTRACT FROM AUTHOR]