Contribution of microRNAs in understanding the pancreatic tumor microenvironment involving cancer associated stellate and fibroblast cells.

Understanding of molecular events associated with tumor microenvironment in pancreatic cancer (PC) is an active area of research especially because of the rich desmoplasia seen in human PC. Desmoplasia is contributed by several cell types including cancer-associated fibroblast (CAF) and stellate cells (PSCs), which are believed to play critical roles in conferring aggressiveness to PC. The aberrant expression of microRNAs (miRNAs) in PSCs and CAF cells appears to play a pivotal role in the development and progression of PC. In this study, expression analysis of miR-21/miR-221 in conditioned media derived from PSCs/CAF cells, and from PSCs/CAF cells showed up-regulation of both miRNAs compared to MIAPaCa-2 PC cells. In addition, miR-21 expression in stellate cells derived from normal pancreas was substantially lower when compared to PSCs or CAF cells. COLO-357 PC cells cultured in the presence of conditioned media derived from PSC/CAF cells led to a significant increase in clonogenicity and pancreatosphere formation. Furthermore, inhibition of miR-21 with antisense oligonucleotide (ASO) transfection resulted in decreased migration/invasive capacity of PSCs. Similarly, the effect of ASO-miR-221 transfection in CAF cells reduced the expression of NF-κB and K-Ras (target of miR-221) along with inhibition of migration/invasion. Moreover, miRNA expression profiling of PSCs, MIAPaCa-2, and COLO-357 cells, and further validation by real-time PCR, showed several differentially expressed miRNAs, among which four was significantly up-regulated. Collectively, these results suggest a crosstalk between PSCs/CAF cells and PC cells, resulting in the up-regulation of miR-21/miR-221 expression which in part may confer aggressiveness to PC. We conclude that targeting these miRNAs could be useful for developing precision medicine for the prevention of tumor progression and/or for the treatment of PC