A Pilot Study of Exploring miRNA–Protein Interaction Networks in Pancreatic Ductal Adenocarcinoma Patients: Implications for Diagnosis and Prognosis

<b>Background:</b> Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies for which there are few effective biomarkers for diagnosis, prognosis, and treatment monitoring. Given the paucity of data in the literature, this study aimed to evaluate the biomarker potential of selected miRNAs (miR-222-3p, miR-3154, miR-3945, miR-4534, and miR-4742) and their protein targets in the context of PDAC. <b>Methods:</b> The expression levels of miRNA candidates were quantified by real-time quantitative PCR in lymphocyte samples from 46 PDAC patients and 50 healthy controls. In silico analyses were performed to identify potential target genes and proteins. ELISA was used to measure protein expression in both groups. Statistical analyses included ROC curve analysis, linear regression, and correlation analyses. In addition, correlations between miRNA/protein expression and clinicopathologic characteristics, including survival, were investigated. <b>Results:</b> miR-222-3p and miR-3154 were significantly downregulated in PDAC patients compared to controls (<i>p</i> < 0.001). Among the dual miRNA combinations, miR-222-3p and miR-4534 showed the highest discriminatory power (AUC = 0.629, <i>p</i> = 0.022). The miR-222-3p expression was significantly increased in patients with a history of alcohol consumption (<i>p</i> = 0.02). Significant correlations were observed between miR-3154 expression and T-stage (<i>p</i> = 0.01) and between perineural invasion and miR-222-3p levels (<i>p</i> = 0.02). Survival analysis showed that high miR-3945 expression was significantly associated with shorter overall survival (<i>p</i> = 0.001). Elevated levels of ESR1, HCFC1, and EPC1 were significantly associated with lymphatic invasion (<i>p</i> < 0.05), while high KCNA1 expression correlated with shorter survival (<i>p</i> = 0.006), indicating its potential as a negative prognostic biomarker. Linear regression analysis revealed a significant positive correlation between miR-3945 and KCNA1 expression (β = 0.259, <i>p</i> = 0.038), indicating a possible regulatory interaction. A borderline correlation was also found between miR-4742 and EPC1 expression (<i>p</i> = 0.055). <b>Conclusions:</b> This study identifies several miRNAs and associated proteins with diagnostic and prognostic significance in PDAC. The results emphasize the clinical relevance of integrating multi-layered analyses of miRNA-protein interactions. The observed associations highlight the role of these molecular markers in tumor progression and patient survival and offer promising opportunities for future research and clinical application in precision oncology.