Elucidating roles of TRPS1 in regulating antitumor immunity

Overcoming regulatory T cell (Treg) mediated immunosuppression in tumors remains a critical, yet elusive goal for cancer therapy. In prior work, we identified a novel role for the developmental transcription factor TRPS1 (transcriptional repressor GATA binding 1) in promoting Treg function within human and murine tumors. There is currently no known function of TRPS1 within cells of the hematopoietic lineage. Thus, we seek to investigate the fundamental molecular mechanisms by which TRPS1 regulates Treg phenotype, function, and/or lineage stability using an innovative suite of new genetic tools and multi-omic assays. In preliminary studies, we found enforced TRPS1 expression in primary human Tregs was sufficient to induce a tumor-infiltrating Treg proteomic phenotype associated with upregulation of BATF and BLIMP-1; two known master regulators of Treg lineage stability and functional stability in cancer, respectively. TRPS1 expression promoted expression of immunosuppressive cytokines IL-10 and TGF-â and prevented IL-12 induced production of IFNã (i.e. Treg “fragility”). Using a novel Treg-conditional TRPS1 knockout animal (Foxp3CreTrps1flox/flox), we found mice with TRPS1-deficient Tregs exhibited reduced tumor growth kinetics and phenotypic evidence of TI-Treg lineage instability. Given these findings, our central hypothesis is that TRPS1 promotes Treg stability in tumors and is required for TI-Treg suppression of antitumor immunity and ICB response. Therefore, in Aim 1 of this project we will further elucidate the molecular mechanisms by which TRPS1 promotes TI-Treg stability, testing the hypothesis that upregulation of BATF and/or BLIMP-1 is critical for downstream effects of TRPS1. For this we will express TRPS1 variants lacking key protein domains (GATA domain, Ikaros domain, etc.) in the presence or absence of intact BATF or PRDM1 (BLIMP-1) loci in human Tregs to assess effects on the Treg cell state (RNA-seq, ATAC-seq, flow cytometry), TRPS1 genomic binding behavior, (ChIP-seq), TRPS1 protein binding partners (coIP-LC/MS), and Treg function (intracellular cytokine staining). In Aim 2, we will determine how TRPS1+ Tregs regulate antitumor immunity and immunotherapy response in vivo. Employing our novel Treg-conditional TRPS1 knockout strain we will quantify tumor growth, anti-PD-1 response, and tumor immune composition via 50-parameter spectral flow cytometry. Using a new TRPS1 fluorescent reporter strain (Trps1CreFoxp3Thy1.1/LSL-DTR/GFP), we will isolate TRPS1+ versus TRPS1- Tregs for multi-omic profiling and ex vivo functional assays. This strain will also provide a unique opportunity to definitively test whether selective depletion of TRPS1+ Tregs is sufficient to uncouple antitumor immune effects from peripheral inflammatory pathologies associated with systemic Treg dysfunction. The use of vertebrate animals is required in this study to enable manipulation of TRPS1+ Tregs in immunocompetent tumor-bearing animals, as no sufficient animal-free system exists to sufficiently conduct the proposed experiments. In summary, these studies will define the molecular mechanisms underlying TRPS1 as a novel targetable vulnerability of TI-Tregs. Our findings will open new avenues to understand the role of TRPS1 in immunity and will inform development of a new class of Treg inhibitors targeting the TRPS1 axis with potential for broad applicability across the oncology landscape. Project Number: 1R01CA311117-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Casey Ager | Institution: MAYO CLINIC ARIZONA, SCOTTSDALE, AZ | Award Amount: $657,698 | Activity Code: R01 | Study Section: Basic Cancer Immunobiology Study Section[BCIB] View on NIH RePORTER: https://reporter.nih.gov/project-details/11337416