Impact of HuR inhibition by the small molecule MS-444 on colorectal cancer cell tumorigenesis

Abstract

Colorectal cancer (CRC) is the third most common cancer and a leading cause of cancer-related mortality. Observed during CRC tumorigenesis is loss of post-transcriptional regulation of tumor-promoting genes such as COX-2, TNFα and VEGF. Overexpression of the RNA-binding protein HuR (ELAVL1) occurs during colon tumorigenesis and is abnormally present within the cytoplasm, where it post-transcriptionally regulates genes through its interaction with 3′UTR AU-rich elements (AREs). Here, we examine the therapeutic potential of targeting HuR using MS-444, a small molecule HuR inhibitor. Treatment of CRC cells with MS-444 resulted in growth inhibition and increased apoptotic gene expression, while similar treatment doses in non-transformed intestinal cells had no appreciable effects. Mechanistically, MS-444 disrupted HuR cytoplasmic trafficking and released ARE-mRNAs for localization to P-bodies, but did not affect total HuR expression levels. This resulted in MS-444-mediated inhibition of COX-2 and other ARE-mRNA expression levels. Importantly, MS-444 was well tolerated and inhibited xenograft CRC tumor growth through enhanced apoptosis and decreased angiogenesis upon intraperitoneal administration. In vivo treatment of MS-444 inhibited HuR cytoplasmic localization and decreased COX-2 expression in tumors. These findings provide evidence that therapeutic strategies to target HuR in CRC warrant further investigation in an effort to move this approach to the clinic.

Posttranscriptional Regulation of PARG mRNA by HuR Facilitates DNA Repair and Resistance to PARP Inhibitors

“…HuR function was perturbed using a small molecule inhibitor MS-444 that prevents HuR dimerization, a step critical for its stress- induced translocation to the cytoplasm (40, 41). Immunoblotting (Supp.…”

“…We believe that inhibition of the HuR/PARG axis enhances PARP-trapping on chromatin, and can be translated to improve PARPi efficacy in all PDAs, regardless of DNA repair status. In fact, we inhibited PARG expression using MS-444, a previously characterized tool for HuR inhibition (32, 41, 51). We consequently observed increased PARPi efficacy both in vitro and in vivo , independent of the cell line used (Fig 3C, 5A).…”

CRISPR Knockout of the HuR Gene Causes a Xenograft Lethal Phenotype

“…Currently, the best-characterized small molecule inhibitor of HuR is the chrysanthone-like compound MS-444 that inhibits HuR homodimerization and its cytoplasmic translocation (30,48). There have been promising pre-clinical studies that show MS-444 has potent affects in CRC mouse models (30) and other studies have demonstrated that MS-444 sensitizes PDA cells to oxaliplatin and 5-fluorouracil in relevant tumor microenvironment conditions, but issues with stability and bioavailability of MS-444 may hinder first human applications (17). Recently, there have been success in identifying other small molecules that disrupt the HuR-mRNA interactions, leading to impaired HuR function and premature decay of mRNAs that encode proteins related to tumor processes (37).…”

“…Parental HCT116 and HuR knockout clones 1 and 2 (2 × 10 6 cells) used between passages 14 – 23 were resuspended in PBS containing 50% Matrigel (Corning) and injected into the dorsal subcutaneous tissue. Tumor growth was assayed as described (28,30). …”

A Requirement for Mena, an Actin Regulator, in Local mRNA Translation in Developing Neurons

“…Given the extreme dosage sensitivity of Dyrk1a and its implication in numerous neurodevelopmental disorders, our finding that Dyrk1a protein levels are regulated in a Mena-dependent manner in axons raises the intriguing possibility that dysregulation of the Mena-RNP complex may contribute to such disorders. Additional mRNAs that are associated with Mena, like the validated targets β-catenin and elavl1 (HuR) are also implicated in multiple developmental processes and pathophysiological conditions (Alami et al, 2014; Blanco et al, 2016; Holland et al, 2013; Krumm et al, 2014; Li et al, 2017; Lu et al, 2014; O’Roak et al, 2012; Wang et al, 2016). Therefore, the Mena-RNP complex may represent a target for the development of novel therapeutic strategies for multiple disease pathologies.…”