Abstract 2885: RASSF1A133Sresulting from the prevalent SNP rs2073498 is associated with Treg defects

Abstract Rs2073498 is a prevalent (~10% population) single nucleotide polymorphism (SNP) that leads to A133S missense mutation in tumor suppressor and Hippo Signaling Pathway scaffold protein RASSF1A. Recent reports have illustrated the crucial involvement of Hippo pathway proteins in lymphocyte recruitment, differentiation, and function. Using a BL/6 mouse model engineered with alanine-to-serine point mutation, we showed that RASSF1A133S is associated with systematic defects in regulatory T cells (Tregs). When blood was phenotyped through a 17-color spectral flow cytometry panel, both RASSF1A133S/WT and RASSF1A133S/A133S carriers had a smaller circulatory CD25+FoxP3+ Treg pool than WT controls. Magnetically sorted splenic T cells were also stimulated with PMA/Ionomycin ex vivo, and fewer Tregs from A133S carriers were expressing anti-inflammatory cytokine IL-10. Preliminary results further demonstrated that RASSF1A133S/WT has fewer intratumor FoxP3+ Tregs in subcutaneously injected MC38 colon adenocarcinoma tumor models. In contrast, A133S did not have any significant effects on thymic T cell maturation states, splenic T cell naïve/memory phenotypes, or Treg survival fitness measured by Fas/FasL and BCL-2 expression. Ex vivo stimulation also demonstrated that A133S carriers retain similar IL-2 sensitivity and phospho-STAT5 response when compared to the controls, although RASSF1 downstream kinases MST1/2 have been reported to amplify IL-2-STAT5 signaling in Tregs (Shi et al., 2018). These results collectively suggest that RASSF1A133S may leads to Treg imbalance and predispose rs2073498 carriers to Treg mediated autoimmune risks. Citation Format: Haonan Xu, Keaton Jones, Cameron Lang, Simone Lanfredini, Sophie Hughes, Eric O'Neill. RASSF1A133Sresulting from the prevalent SNP rs2073498 is associated with Treg defects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2885.