Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 22 1 2023 02 20 62 71 Mohammad Khakpoor-Koosheh Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Hosein Rostamian Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Elham Masoumi Department of Immunology, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran Leila Jafarzadeh Department of Laboratory Sciences, Sirjan School of Medical Sciences, Sirjan, Iran Keyvan Fallah-Mehrjardi Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Mohammad Javad Tavassolifar Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Farshid Noorbakhsh Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Hamid Reza Mirzaei Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran jamshid Hadjati Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Nima Rezaei Department of Medical Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran AND Research Center for Immunodeficiencies, Children's Medical Center Hospital, Tehran University of Medical Sciences, Tehran, Iran 2021 12 17 2022 10 24 High production of lactic acid is a common feature of various tumors. Lactic acid is an immunosuppressive molecule with crucial roles in tumor cells' immune escape, which could largely be attributed to its negative effects on the T cells present in the tumor microenvironment (TME). Strategies that decrease the glycolysis rate of tumor cells could enhance immunosurveillance and limit tumor growth. Pyruvate kinase M2 (PKM2) is a key enzyme in the glycolysis pathway, and it plays a vital role in lactic acid buildup in the TME. MicroRNA (miR)-124 has been shown to be able to decrease tumor cell lactic acid synthesis indirectly by reducing PKM2 levels. In this study, we first overexpressed miR-124 in the tumor cells and evaluated its effects on the PKM2 expression and lactic acid production of the tumor cells using quantitative real-time polymerase chain reaction (qRT-PCR) and spectrophotometry, respectively. Then, we cocultured miR-124–treated tumor cells with T cells to investigate the effects of miR-124 overexpression on T cell proliferation, cytokine production, and apoptosis. Our results demonstrated that miR-124 overexpression could significantly reduce the amount of lactic acid produced by tumor cells by manipulating their glucose metabolism, which led to the augmented proliferation and IFN-γ production of T cells. Moreover, it rescued T cells from lactic acid-induced apoptosis. Our data suggest that lactic acid is a hindering factor for T-cell–based immunotherapies; however, manipulating tumor cells' metabolism via miR-124 could be a promising way to improve antitumor responses of T cells. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/3419 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/3419/1910