Multitarget microRNA sponge for pancreatic ductal adenocarcinoma: Simultaneous targeting of miR-21, miR-155, and miR-18a.

Pancreatic ductal adenocarcinoma remains one of the most lethal malignancies with only an 11% 5-year survival rate. Oncogenic microRNAs (miRNA), particularly miR-21, miR-155, and miR-18a, drive tumor progression by silencing tumor suppressors and promoting chemoresistance. Single-target miRNA inhibition has shown limited clinical efficacy because of complex network redundancy and compensatory pathway activation, necessitating multitarget therapeutic approaches. We designed and validated a trispecific miRNA sponge construct containing high-affinity target sites for all 3 oncomiRs, demonstrated in silico through miRNAsong analysis with an approximately 11-kcal/mol thermodynamic specificity gap relative to off-targets. The sponge was functionally tested in the human pancreatic ductal adenocarcinoma cell lines PANC-1 and AsPC-1 using comprehensive assays including dual-luciferase reporter, quantitative reverse transcription polymerase chain reaction, flow cytometry-based apoptosis analysis, scratch-wound migration, and gemcitabine chemosensitization studies. In AsPC-1 cells, the trispecific sponge achieved 99.0%-99.9% silencing of target miRNAs and 349-fold reporter reduction, inducing a 6.1-fold increase in apoptosis and approximately 44% reduction in wound closure at 72 hours compared with nontargeting controls. PANC-1 cells showed moderate but significant responses with 65%-98% miRNA silencing, a 2.2-fold increase in apoptosis, and approximately 51% reduction in wound closure at 72 hours under identical assay conditions. Mechanistically, simultaneous miRNA inhibition synergistically reactivated tumor suppressor genes PDCD4, ESR1, and NOTCH2 (6.3-7.7-fold upregulation) and sensitized chemoresistant cells to gemcitabine by 1.5- to 1.8-fold. Across the evaluated functional endpoints, the trispecific sponge conferred approximately 1.2- to 95-fold changes relative to the nontargeting control and, in many instances, elicited equal or greater effects than single-target constructs, consistent with a broader network-level impact rather than uniform superiority in every assay. This platform represents a promising strategy for pancreatic ductal adenocarcinoma therapy warranting preclinical development and clinical translation. SIGNIFICANCE STATEMENT: Pancreatic cancer chemoresistance drives poor survival. The trispecific microRNA sponge simultaneously targets miR-21, miR-155, and miR-18a, synergistically reactivating tumor suppressors and enhancing gemcitabine efficacy more than single-target approaches. This multitarget microRNA strategy represents a novel therapeutic platform for overcoming chemoresistance in pancreatic cancer.