Abstract 5959: Therapeutic targeting of HuR using a specific small-molecule inhibitor in triple negative breast cancer

Abstract Human Antigen R (HuR/ELAVL1) is an RNA-binding protein that interacts with U/AU-rich elements in target mRNAs, and its aberrant cytoplasmic accumulation have been observed in multiple cancers. HuR modulates the expression of key oncogenic and survival-related transcripts, thereby driving tumor progression, metastasis, and therapeutic resistance. Given this central role, HuR represents a compelling molecular target for cancer therapy. The present study specifically evaluates the potential of CMLD2, a highly selective small-molecule inhibitor of HuR, in the context of Triple-Negative Breast Cancer (TNBC). Comparative assessments were conducted using CMLD2 and DHTS across in silico and in vitro models. Immunohistochemical analysis of 71 TNBC samples revealed HuR overexpression in 66% of cases, along with elevated expression of HuR downstream target MMP9 (56%). Furthermore, in silico analysis established significant association between HuR overexpression and poor patient survival (p = 0.028). Functional assays in TNBC cell lines MDA-MB-231 and MDA-MB-468 demonstrated that both inhibitors suppressed proliferation, invasion, and clonogenicity; however, CMLD2 exhibited markedly higher specificity and consistency in inhibiting HuR function. Mechanistically, CMLD2 treatment downregulated HuR and its downstream effectors MMP9 and β-catenin, while reversing epithelial-mesenchymal transition (EMT) marker expression (E-cadherin, N-cadherin and Vimentin). Immunofluorescence and cell fractionation confirmed effective cytoplasmic HuR inhibition. Moreover, CMLD2 distinctly suppressed aerobic glycolysis, evidenced by reduced extracellular acidification and downregulation of key glycolytic mediators—PFKP, LDHA, and MCT4—validated at both transcript and protein levels. HuR silencing by siRNA supported the role of HuR in glycolytic regulation and TNBC progression. In vivo, CMLD2 significantly impaired tumor-forming ability in female BALB/c mice. Together, these findings underscore the therapeutic promise of CMLD2 as a specific and potent HuR inhibitor, providing strong experimental rationale for its further development as a targeted intervention in Triple-Negative Breast Cancer. Citation Format: Arundhathi Dev J R, Ajay Gogia, Sandeep R. Mathur, Ashutosh Mishra, Chandra Prakash Prasad. Therapeutic targeting of HuR using a specific small-molecule inhibitor in triple negative breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5959.