Beyond Transcription: Studying Human Antigen R (HuR/ELAVL1) and Its Role in Post-Transcriptionally Regulating the Pancreatic Cancer-Driver, Yes-Associated Protein 1 (YAP1)
Abstract
Oncology research has evolved beyond the fundamental study of the ‘central dogma’ of genetic information transfer. Instead, cancer is recognized as a diverse, heterogeneous, and plastic phenomenon which adds to the clinical obstacles of identifying early detection and treatment strategies. Tumors rely not only on cell-autonomous mechanisms, but also on signals of the tumor microenvironment and molecular mechanisms that get induced upon treatment. Pancreatic ductal adenocarcinoma (PDAC) is the predominant and most lethal histological subtype of pancreatic cancer, with a 5-year survival rate of only 10%. These dismal outcomes are largely due to a lack of prevention, detection, and therapeutic strategies. Characterization of the high-frequency mutations in PDAC has provided little change to clinical practice; underscoring the critical need to identify novel biomarkers to stratify patients for available treatment options. Recent advances in next-generation sequencing linking genomic, histological, and transcriptome-wide molecular subtypes should provide opportunities to address this issue. These studies emphasize the need for a better understanding of the mechanisms that drive the molecular switches responsible for the intra- and inter- heterogeneity found in PDAC samples. Here, I evaluate a non-genomic mechanism of gene dysregulation, described as post-transcriptional control, via the RNA-binding protein (RBP), Human Antigen R (HuR). First, I outline critical improvements to methods of studying RBPs and their interactions with mRNA cargo. Then, I apply these techniques to identify a novel mRNA target, the established pro-oncogenic molecule, Yes-associated protein 1 (YAP1). Like HuR, YAP1 is an important regulator of gene expression responding to context-dependent cell-intrinsic and extrinsic cues. The role of YAP1 contributing towards PDAC tumorigenesis has been studied in tumor onset, development, metastasis, and therapeutic resistance. Moreover, molecular subtyping studies demonstrate that YAP1 overexpression and activity are strongly correlated with the more aggressive classifiers of PDAC (e.g., basal-like/squamous). In this study, we demonstrate that YAP1 mRNA is a direct target of the HuR protein. Suppression of HuR via genetic (e.g. siRNA and CRISPR-Cas9 knockout) and pharmacological inhibition significantly silence YAP1 mRNA and protein expression. Consequentially, YAP1 transcriptional targets are also significantly decreased as demonstrated through RNA-Seq analysis and independent real-time PCR (qPCR). Related to this work, we explored utilizing our understanding of HuR biology to put forth a biomarker signature. HuR has been heavily cited for its role in driving tumorigenesis through the regulation of important pro-survival genes; however, a reliable biomarker for HuR activation has yet to be established. In this study, I used distance-weighted discrimination to develop a HuR inhibition signature (HIS) reflective of genes most significantly impacted by HuR knockdown. This signature strongly correlates with YAP1 mRNA expression and is a more robust prognostic marker for both overall- and disease-free survival in patient samples. Ongoing work will validate this signature in independent patient cohorts and will investigate the nature of this relationship in patient-derived and genetic engineered mouse models (GEMMs), with the goal of defining this mechanism throughout the pancreatic tumor progression model.
Subject Area
Molecular biology|Oncology|Cellular biology
Recommended Citation
Brown, Samantha Zimmer, "Beyond Transcription: Studying Human Antigen R (HuR/ELAVL1) and Its Role in Post-Transcriptionally Regulating the Pancreatic Cancer-Driver, Yes-Associated Protein 1 (YAP1)" (2021). ProQuest ETD Collection - Thomas Jefferson University. AAI28322267.
https://jdc.jefferson.edu/dissertations/AAI28322267
