1036 Microbiota-induced RORγt + regulatory T cells underlie sex differences in tumor control
Year: 2026
Type: conference-abstract
Abstract: Background Regulatory T cells (Tregs) are correlated with poor prognosis in multiple cancer types. Therapies targeting thymically derived Tregs (tTregs) have shown promise; however, they can lead to severe immune related adverse events. 1 RORγt+ peripherally induced Tregs (pTregs) are potently suppressive cells that differentiate from naïve CD4+ T cells and are specific to commensal microbes.2 Recent studies have shown the importance of pTregs in solid tumors, including pro-tumorigenic functions distinct from tTregs.3 4 We aim to target pTregs independently from tTregs to promote anti-tumor immunity while preserving systemic self-tolerance. We hypothesize that RORγt supports pTreg suppressive function to promote tumor growth at sites outside the colon.Methods Using a tamoxifen inducible RORγt knockout mouse model, Foxp3CreERT2Rorcfl/fl, we tracked tumor growth of subcutaneous MC38 tumors in wildtype and tamoxifen-treated mice (TregΔRorc). We used flow cytometry and single cell RNAseq to assess immune activation and exhaustion in the tumor and colon. Finally, to assess the role of the microbiome we performed mixed bedding experiments of male and female mice, tracked tumor growth, and performed 16S sequencing on stool.Results Deletion of RORγt in Tregs led to decreased tumor growth specifically in male mice with no signs of detrimental systemic inflammation. In male TregΔ Rorc mice, tumor infiltrating T cells showed increased activation and Th1/cytotoxic signatures and promoted greater tumor clearance rates in response to anti-PD1 immunotherapy. Additionally, Tregs from TregΔRorc mice were less suppressive as shown by reduced expression of IL-10, PD1, KLRG1, CD39, and CCR6; however, no adverse events were present. These data suggest the absence of functional microbiota-specific Tregs increases anti-tumor immunity and immunotherapy efficacy. Interestingly, this phenotype was unique to males, indicating a role for sex in our model. Strikingly, when microbiomes were normalized between males and females, TregΔRorc female mice mimicked males in tumor growth and immune infiltration, suggesting the male TregΔRorc microbiome is required for anti-tumor efficacy. 16S sequencing showed significant decreases in immunogenic bacteria genera, like Helicobacter, and increases in butyrate producing genera, like Faecalibaculum in TregΔRorc mice, potentially priming and promoting effector T cell function systemically.Conclusions We have shown that targeting pTregs can efficiently promote anti-tumor immunity and immunotherapy responses without leading to systemic inflammation. Additionally, our findings highlight an interplay between sex, microbiome composition, and anti-tumor immunity. Overall, these findings have the potential to identify novel pTreg or microbial targets that could enhance immunotherapy efficacy without detrimental toxicities that cause patients to cease treatment prematurely.References Tay C, Tanaka A, Sakaguchi S. Tumor-infiltrating regulatory T cells as targets of cancer immunotherapy. Cancer Cell 2023;41:450–465.Sefik E, Geva-Zatorsky N, Oh S, Konnikova L, Zemmour D, McGuire A.M, Burzyn D, Ortiz-Lopez A, Lobera M, Yang J, et al. Individual intestinal symbionts induce a distinct population of RORγ+ regulatory T cells. Science 2015;349:993–997.Blatner N.R, Mulcahy M.F, Dennis K.L, Scholtens D, Bentrem D.J, Phillips J.D, Ham S, Sandall B.P, Khan M.W, Mahvi, D.M, et al. Expression of RORγt marks a pathogenic regulatory T cell subset in human colon cancer. Sci Transl Med. 2012;4:164ra159.Hossain M.M, King P, Hackett J, Gerard H.C, Niwinski R, Wu L, Van Kaer L, Dyson G, Gibson H, Borowsky A.D, et al. Peripheral-derived regulatory T cells contribute to tumor-mediated immune suppression in a nonredundant manner. Proc Natl Acad Sci USA. 2024;121:e2404916121Ethics Approval All animal experiments were performed in the American Association for the Accreditation of Laboratory Animal Care-accredited specific-pathogen-free facilities in the Division of Laboratory Animal Resources at the University of Pittsburgh School of Medicine (UPSOM). All animal protocols were approved by the Institutional Animal Care and Use Committees of the University of Pittsburgh.
Institutions: University of Pittsburgh, UPMC Hillman Cancer Center
Language: English
Topic: T-cell and B-cell Immunology
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,490
OpenAlex ID: W7225181515