Abstract B094: Inhibition of HuR in Cancer Cells Enhances T Cell Activation and Sensitizes Tumors to Immunotherapy

Abstract Despite the promising potential of cancer immunotherapy, most cancers are clinically poor immune-responsive, or immune “cold”. Effective T cell activation remains challenging, particularly within immune-suppressive tumor microenvironments. The RNA-binding protein HuR is ubiquitously overexpressed in various cancers, playing a crucial role in tumor initiation and progression. Our previous research highlights HuR as a potential target in cancer treatment, as its inhibition has been shown to reduce metastasis, invasion, and drug resistance, while also increase the sensitivity of cancer cells to chemotherapy. Moreover, HuR inhibition has been associated with enhanced response to immune checkpoint blockade in cancer immunotherapy. Our recent findings demonstrated that blocking HuR cytoplasmic translocation downregulates PD-L1 expression, thereby disrupting immune checkpoints between cancer cells and T cells. In current study, we found that HuR inhibition promoted T cell activation and T cell mediated tumor cell killing using a co-culture system. Cancer cell lines with and without HuR-knockout (KO) were co-cultured with human peripheral blood mononuclear cells (hPBMCs) in the present with T cell activators. Compared to parental cancer cells, HuR KO cells significantly enhanced T cell activation, as indicated by increased secretion of cytokines, such as IFN-γ and IL-6, and a higher portion of CD25+ T cells. Similarly, treatment with the small molecule HuR inhibitor KH-39 also potentiated T cell mediated tumor cell killing in the co-culture system. Furthermore, combining KH-39 and an anti-PD-1 antibody produced a synergistic effect in several syngeneic animal models, significantly prolonging overall survival compared to single-agent treatments. Mechanistically, we established a correlation between HuR and CD147 expression across various cancer types, including breast and prostate cancer, using GEPIA2.0. Our study demonstrates that HuR directly binds to CD147 mRNA, regulating its expression in SUM159 and PC3 cancer cells. Knockdown of CD147 via siRNA in these cell lines significantly reduced cellular proliferation and clonogenic growth. Treatment with the HuR inhibitor KH-39 markedly decreased CD147 levels and its downstream target, P-AKT, in both cell lines. Furthermore, in the T cell mediated killing assays using human PBMCs, KH-39 treatment consistently enhanced cancer cell death in SUM159 and PC3 cells. In vivo, the combination of KH-39 with an anti-PD-1 antibody in the EMT-6 murine tumor model significantly inhibited tumor growth and improved survival outcomes, outperforming either treatment alone. These findings suggest that HuR inhibition in cancer cells indirectly promotes T cell activation, positioning HuR as a promising target for improving immune responses in cancer immunotherapy. Citation Format: Sunghae Kim, Qi Zhang, Ryan P. Sherrier, Jeffrey Aubé, Xiaoqing Wu, Liang Xu. Inhibition of HuR in Cancer Cells Enhances T Cell Activation and Sensitizes Tumors to Immunotherapy [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B094.