Abstract 2160: MCT4 blockade reverses lactate-mediated immunosuppression in LKB1-deficient NSCLC
Authors: Qian Yu , Guijarro Irene , Galan-Cobo Ana , Dang Minghao , Poteete Alissa , Zhang Fahao , Wang Qi , Wang Jing , Parra Edwin , Skoulidis Ferdinandos , Wistuba Ignacio , Verma Svena , Merghoub Taha , Wang Linghua , Wolchok Jedd , Reuben Alexandre , Heymach John 
Published: June 2022

Abstract
Genomic alterations that result in loss of function of the tumor suppressor serine/threonine kinase STK11/LKB1 occur in 20-30% of lung adenocarcinomas. We previously observed that STK11/LKB1 mutations are genomic drivers of primary resistance in lung adenocarcinoma. Moreover, LKB1-mutant NSCLCs exhibit higher hypoxia and glycolysis rates, resulting in enhanced production and secretion of lactate. Accordingly, we hypothesize that high production of lactate of LKB1 mutant tumor may contribute to its immunologically cold phenotype and that blockade of the lactate pathway may potentiate the efficacy of immune checkpoint blockade (ICB) therapies. We characterized the immune landscape of LKB1 mutant clinical samples and performed scRNAseq analysis in KRAS mutant (K) and KRAS mutant LKB1 knockout (KL) syngeneic murine models. To evaluate inhibition of lactate metabolism as a therapeutic strategy, we knocked out the lactate transporter SLC16A3/MCT4 and characterized the impact on the tumor microenvironment (TME), and response to ICB. Clinical analysis of LKB1 mutant NSCLC patients from the MD Anderson’s ICON and PROSPECT cohorts suggested that LKB1 mutant tumors showed reduced immune cell infiltration, restricted T cell function, and enhanced M2-like macrophages phenotypes. Moreover, in preclinical models, LKB1 mutant tumors showed enhanced glycolysis and upregulation of MCT4 expression in a variety of human and murine cell lines. Deletion of MCT4 dramatically reduced glycolysis, energy production, and cell proliferation. By scRNAseq, we identified distinct immune subclusters modulated by LKB1 mutation. Hypofunctional T cells and M2-like macrophages were abundant in LKB1 mutant tumors, while these populations were significantly reduced in KL tumors with MCT4 KO. The conditioned medium from KL cells impaired T cell activation and decreased T cell killing, IFNγ production and glycolysis rate. Moreover, conditioned medium from KL cells induced M2-associated genes expression, as well as CD206+ expression in both peritoneal macrophages and Raw264.7 cells. These effects were at least in part MCT-dependent, as medium from MCT4 KO cells induced the opposite effects on T cells and macrophages, and the effects could be reversed by introducing exogenous lactate, suggesting that blockade of lactate transport reactivated T cells and reversed M2 polarization. Importantly, MCT4 KO in LKB1-mutant tumors sensitized tumors to anti-PD1 immunotherapy in syngeneic murine tumors and promoted long-term anti-tumor immunity. Collectively, our data indicate that LKB1 mutant tumors enhanced lactate secretion into the TME and this results in decreased T cell cytotoxic potential as well as higher pro-tumor M2 polarization, leading to resistance to immunotherapy. These data suggest that therapeutic inhibition of MCT4 is a promising strategy to overcome immunotherapy resistance in NSCLC patients harboring LKB1 mutant tumors.
Citation Format: Yu Qian, Irene Guijarro, Ana Galan-Cobo, Minghao Dang, Alissa Poteete, Fahao Zhang, Qi Wang, Jing Wang, Edwin Parra, Ferdinandos Skoulidis, Ignacio Wistuba, Svena Verma, Taha Merghoub, Linghua Wang, Jedd Wolchok, Alexandre Reuben, John Heymach. MCT4 blockade reverses lactate-mediated immunosuppression in LKB1-deficient NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2160.