Elucidate the mechanism of targeting MTR to enhance anti-tumor immunity in KRAS-driven lung cancer

KRAS-driven non-small cell lung cancer (NSCLC) patients are resistant to most therapies, including immune checkpoint blockade (ICB), resulting in poor clinical outcomes. Tumors use diverse strategies for immune evasion, complicating the efficacy of ICB therapies. Oncogene-driven immune evasion involves both intrinsic tumor alterations and extrinsic modulation of the tumor microenvironment (TME). Targeting cancer metabolism, particularly one-carbon metabolism that integrates the folate and methionine cycles, holds promise for enhancing immune responses and improving ICB efficacy. While anti-folates have been used in lung cancer treatment, resistance often limits their effectiveness, driving interest in targeting other key enzymes within one-carbon metabolism. Methionine synthase (MTR), which facilitates the conversion of 5-methyl-tetrahydrofolate to tetrahydrofolate and the regeneration of methionine, is a potential therapeutic target. However, its role in KRAS- driven NSCLC remains poorly understood. We identified MTR as a critical factor for KrasG12D/+;p53-/- (KP) lung cancer cell survival via an in vitro CRISPR screening with a metabolism-focused sgRNA library in a mouse KP lung tumor-derived cell line. Validation studies proved that MTR knockout impaired KP cell proliferation and colony formation, suppressed KP allograft tumor growth in syngeneic C57BL/6 mice, extended mouse survival in genetically engineered mouse models of KRAS-driven lung cancer, and increased tumor CD8 T cell infiltration. Moreover, depletion of both CD4 and CD8 T cells in C57BL/6 mice rescued the growth of MtrKO tumors. These findings highlight MTR’s tumor-promoting role and its link to immune-mediated tumor suppression, suggesting that MTR-mediated tumor metabolism facilitates immune evasion, and targeting MTR may be crucial for enhancing antitumor immunity and improving response to IBC in KRAS-driven NSCLC. To test this hypothesis, we will use KP allograft model and GEMMs to: 1) determine the role of T cell-mediated antitumor immunity in KP lung tumor reduction caused by MTR loss; 2) elucidate the mechanism by which MTR facilitates immune evasion in KP lung tumorigenesis; 3) determine if targeting MTR can enhance the ICB efficacy in treating KP lung cancer, and assess the therapeutic window for systemic MTR inhibition. We expect that these fundamental studies will shed light on the mechanisms by which MTR-mediated metabolic pathways influence antitumor immunity in KP lung tumorigenesis. These will also provide a rationale for combining MTR inhibition with ICB as a therapeutic strategy for KRAS-driven NSCLC. Additionally, this research will offer strong justification for motivating future development of targeted MTR inhibitors for clinical use. Project Number: 1R01CA308211-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Yanxiang Guo | Institution: RUTGERS BIOMEDICAL AND HEALTH SCIENCES, Newark, NJ | Award Amount: $516,808 | Activity Code: R01 | Study Section: Tumor Host Interactions Study Section[THI] View on NIH RePORTER: https://reporter.nih.gov/project-details/11271203