Cancer-associated fibroblasts (CAF) are a major constituent of the pancreatic cancer microenvironment and that the meaning is as intended. Pancreatic cancer cells can induce normal fibroblasts to convert into CAF and, reciprocally, CAF promote tumor invasions and proliferations. The mechanism of the conversion from normal fibroblasts (NF) to CAF remains unclear. MicroRNA are short non-coding RNA involved in the post-transcription gene regulation, which have been defined as an imperative controller in tumor invasions, proliferations and colony formations. Microvesicles (MV) have been proved to be an important mediator of intercellular communication and can selectively transport secreted microRNA from a donor cell into a recipient cell. In this study, we isolated primary pancreatic fibroblasts from wild type C57 mice and co-cultured them with pancreatic cancer cell lines, BxPC-3 and SW1990, and observed the conversion from NF to CAF, or at least CAF-like cells. This phenomenon could also be replicated in primary fibroblasts treated with MV separated from a cancer cell media. We identified that miR-155 was upregulated in PaC-derived MV and we confirmed that normal fibroblasts could convert into CAF after MV containing miR-155 had been taken up. TP53INP1 is a target of miR-155 in fibroblasts and a downregulation of TP53INP1 protein levels could contribute to the fibroblasts’ activation. These results indicated that pancreatic cancer cells might reprogram normal adjacent fibroblasts into CAF by means of secreted MV containing miR-155. Targeting the circulating microRNA might be a potential therapy for malignant tumors.

Insulin-like growth factor 1 receptor (IGF1R) is a transmembrane receptor that is activated by insulin-like growth factor 1 (IGF-1) and by a related hormone called IGF-2. It belongs to the large class of tyrosine kinase receptors and plays an important role in colorectal cancer etiology and progression. In this study, we used bioinformatic analyses to search for miRNAs that potentially target IGF1R. We identified specific target sites for miR-143 and miR-145 (miR-143/145) in the 3′-untranslated region (3′-UTR) of the IGF1R gene. These miRNAs are members of a cluster of miRNAs that have been reported to exhibit tumor suppressor activity. Consistent with the bioinformatic analyses, we identified an inverse correlation between miR-143/145 levels and IGF1R protein levels in colorectal cancer tissues. By overexpressing miR-143/145 in Caco2, HT29 and SW480 colorectal cancer cells, we experimentally validated that miR-143/145 directly recognizes the 3′-UTR of the IGF1R transcript and regulates IGF1R expression. Furthermore, the biological consequences of the targeting of IGF1R by miR-143/145 were examined by cell proliferation assays in vitro. We demonstrated that the repression of IGF1R by miR-143/145 suppressed the proliferation of Caco2 cells. Taken together, our findings provide evidence for a role of the miR-143/145 cluster as a tumor suppressor in colorectal cancer through the inhibition of IGF1R translation.

Taken together, the present study provides the first evidence that miR-148a plays a significant role in the suppression of pancreatic tumorigenesis via the inhibition of ErbB3 translation.