HuR’s role in pancreatic cancer metastasis

Abstract public domain (NIH RePORTER)

PROJECT SUMMARY Pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic cancer pathologic subtype, has a 5- year survival rate of only 13%, largely due to its metastatic propensity. Most patients present with metastatic disease, rendering them ineligible for curative intent surgery. Among those that undergo a successful resection, 78% will have metastatic recurrence within 2-years. Despite significant efforts to identify metastasis-specific driver mutations, few targetable pathways have been identified, underscoring the need to explore alternative mechanisms, such as post-transcriptional regulation. Human antigen R (HuR, ELAVL1) is an RNA-binding protein implicated in post-transcriptional regulation of stress-adaptive networks. We propose HuR is essential for PDAC cells to overcome challenges associated with the metastatic cascade. Under stress conditions, HuR stabilizes and enhances translation of mRNAs required for cellular adaptation. Preliminary data from our lab reveal that HuR knockout (KO) in PDAC cells via CRISPR-Cas9 reduces liver metastatic burden in our orthotopic murine metastatic model, highlighting HuR activity as a potential therapeutic vulnerability in metastasis. My central hypothesis is that HuR is a key regulator of PDAC metastasis by selectively stabilizing pro-metastasis mRNA targets. In Aim 1, I will investigate the functional role of HuR in supporting PDAC metastasis. I hypothesize that HuR is most critical for metastasis during the outgrowth phase in the secondary site, when PDAC cells must adapt to unique secondary site microenvironments. To test this, I will rescue HuR activity at distinct stages of metastasis in our HuR KO murine model and monitor metastatic burden. Additionally, I will assess HuR expression levels and activity in matched primary and metastatic tumors from human PDAC patients to determine whether metastatic lesions have a greater reliance on HuR. In Aim 2, I will identify HuR-bound mRNAs that mediate metastatic adaptation. I hypothesize that HuR modulates distinct mRNA targets and pathways depending on site-specific stress conditions. To test this, I will perform RNA immunoprecipitation sequencing (RIP-seq) on primary, liver, and lung metastatic PDAC tumors to comprehensively map HuR mRNA binding targets specific to metastasis biology. These targets will be prioritized using PDAC patient RNA-seq datasets and clinical data from the Brenden-Colson Center for Pancreatic Care (BCCPC) at Oregon Health and Science University (OHSU). I will validate identified HuR-bound mRNA PDAC metastatic drivers as bona fide HuR targets through various molecular techniques, such as independent RIP-qPCR, western blot analysis, and actinomycin D decay assays. Lastly, I will assess the functional relevance of top targets using target site blockers (TSBs) to disrupt HuR–mRNA target interactions and measure the effects on metastasis. Importantly, integrating preclinical and clinical data will enhance the translational impact of these findings. Completion of this proposal will elucidate a novel mechanism by which PDAC cells utilize HuR to successfully metastasize, identifying specific HuR-dependent pathways as potential therapeutic vulnerabilities in PDAC.

Public health relevance public domain (NIH RePORTER)

PROJECT NARRATIVE Metastatic disease is a major cause of pancreatic cancer morbidity and mortality, yet the mechanisms underlying progression are not well defined. The proposed research, herein, will interrogate the functional role of an RNA binding protein, HuR (ELAVL1), in pancreatic cancer metastasis, by post-transcriptional modification of mRNAs important for cellular adaptation to stress. Completion of this training proposal's aims will elucidate a novel mechanism by which pancreatic cancer cells utilize HuR to successfully metastasize, identifying specific HuR- dependent pathways as potential therapeutic vulnerabilities in pancreatic ductal adenocarcinoma (PDAC).