miR-136-5p Preferentially Suppresses Cancer Stem-like Cells in Pancreatic Cancer

In pancreatic cancer, cancer stem-like cells (CSCs) contribute to tumor initiation, reduced drug sensitivity, and recurrence. Limited strategies are currently available to target this cell population. Here we used a proteasome-low CSC enrichment system to identify microRNAs that negatively regulate CSC-like properties. From PANC-1 cells expressing a ZsGreen-ODC degron reporter, a proteasome-low population was isolated through sequential fluorescence-activated cell sorting of ZsGreen-positive cells. Molecular and functional analyses confirmed the CSC-like phenotype of this cell population. Integrated in silico analysis was used to select 31 microRNAs predicted to target CSC-related molecules, which were then evaluated by in vitro viability-based screening to identify candidates that selectively suppressed the viability of CSC-like cells, relative to non-CSCs. Moreover, comprehensive miRNA expression profiling revealed that miR-136-5p was downregulated in the CSC-like population and was therefore selected for further analysis. Mechanistically, miR-136-5p directly targets the 3' untranslated region of DCLK1 and reduces its expression, with a greater reduction in the short isoform. Finally, in a CSC-derived xenograft mouse model, systemic delivery of miR-136-5p using super carbonate apatite nanoparticles significantly suppressed tumor growth. Taken together, these findings suggest that miR-136-5p restoration may provide a therapeutic approach for targeting CSC-driven tumor growth in pancreatic cancer.