Introduction
Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths, with a five-year survival rate under 10% [1]. Its lethality stems from its aggressive progression and strong chemotherapy resistance, both closely linked to epithelial-mesenchymal transition (EMT). EMT enables epithelial cells to gain migratory mesenchymal traits and is regulated by transcription factors such as SNAIL, SLUG, ZEB1/2, and TWIST [2]. Among these, SNAIL plays a major role in metastasis [3], while ZEB1 is associated with poor prognosis [4]. EMT is tightly modulated by networks including ELAVL1, which encodes the RNA-binding protein HuR. HuR stabilizes mRNAs by binding AU-rich elements (AREs) in their 3′ untranslated regions (3′UTRs), promoting their expression [5].
Aims & Methods
This study aimed to identify post-transcriptional interactions between ELAVL1 and EMT-related genes and assess their prognostic value in PDAC. mRNA was extracted from cancerous and adjacent normal tissues (n=65), converted to cDNA, and analyzed by RT-PCR. BxPC-3, MiaPaCa-2, and Su.86.86 cell lines were cultured under standard conditions. Immunoprecipitation was performed on 1–2×10⁷ cells using a mouse monoclonal anti-HuR antibody, with IgG as control. qRT-PCR assessed mRNA enrichment. Binding sites were annotated using CISBP-RNA, considering only RNAdirect-confirmed 3′UTR motifs. Target 3′UTR sequences were retrieved from GENCODE V47. Statistical analysis was performed using GraphPad Prism, applying the Wilcoxon signed-rank test, Kruskal-Wallis test with Dunn’s correction, and Spearman correlation. Data were presented as median ± interquartile range, with p<0.05 considered significant.
Results
Expression levels of EMT-related genes and ELAVL1 varied according to survival outcomes. In short-term survivors (1–12 months), SNAIL and SLUG were significantly upregulated (2.19- and 1.92-fold), while ZEB2 was downregulated (0.65-fold). Medium-term survivors (13–35 months) showed reduced ZEB1 (0.53), SNAIL (0.30), SLUG (0.35), and TWIST (0.68). Long-term survivors (36–125 months) had the lowest levels of ZEB1 (0.24), ZEB2 (0.50), SLUG (0.24), TWIST (0.35), and ELAVL1 (0.72). ELAVL1 showed strong positive correlations with ZEB1, SNAIL, and SLUG (r = 0.74–0.76), whereas overall survival was weakly negatively correlated with the expression of ZEB1, SNAIL, SLUG, and TWIST (r = -0.25 to -0.32). Although ZEB1, SNAIL, and TWIST did not show significant survival differences individually, low SLUG predicted better early survival (36 vs. 15 months, p = 0.0278). ELAVL1 expression was stratified as high and low. High ELAVL1 corresponded to a 71.65-fold increase in ZEB1, whereas high ZEB1 reduced ELAVL1 by 96.1%. High ELAVL1 also led to a 312.35-fold increase in SNAIL, while low ELAVL1 still supported elevated SNAIL expression (8.45-fold). High SNAIL expression reduced ELAVL1 by 90%, though simultaneous high expression of both resulted in a 3.71-fold ELAVL1 increase. High SLUG reduced ELAVL1 by 93%, whereas low SLUG led to a 198.11-fold increase. Binding site analysis revealed ELAVL1 targets within 3′UTRs: 34 in ZEB1, 1 in SNAIL, and 9 in SLUG.
Conclusion
ELAVL1 (HuR) likely plays a central role in regulating EMT in PDAC through stabilization of key transcription factor mRNAs. High levels of ELAVL1, SNAIL, SLUG, and ZEB1 were associated with worse outcomes, particularly in short-term survivors. Conversely, low expression of SLUG was linked to improved survival. The strong correlations and validated binding sites suggest ELAVL1 as a promising prognostic biomarker and potential therapeutic target in PDAC.
References
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