MicroRNA-21 in Pancreatic Ductal Adenocarcinoma Tumor-Associated Fibroblasts Promotes Metastasis

Abstract

IntroductionPancreatic ductal adenocarcinoma (PDAC) is projected to rise to the second leading cause of U.S. cancer-related deaths by 2020. Novel therapeutic targets are desperately needed. MicroRNAs (miRs) are small noncoding RNAs that function by suppressing gene expression and are dysregulated in cancer. miR-21 is overexpressed in PDAC tumor cells (TC) and is associated with decreased survival, chemoresistance and invasion. Dysregulation of miR regulatory networks in PDAC tumor-associated fibroblasts (TAFs) have not been previously described. In this study, we show that miR-21 expression in TAFs promotes TC invasion.MethodsIn-situ hybridization for miR-21 was performed on the 153 PDAC patient UCLA tissue microarray and 23 patient-matched lymph node metastases. Stromal and TC histoscores were correlated with clinicopathologic parameters by univariate and multivariate Cox regression. miR-21 positive cells were further characterized by immunofluorescence for mesenchymal/epithelial markers. For in vitro studies, TAFs were isolated from freshly resected human PDAC tumors by the outgrowth method. miR-21 was overexpressed/inhibited in fibroblasts and then co-cultured with GFP-MiaPaCa TCs to assess TC invasion in modified Boyden chambers.ResultsmiR-21 was upregulated in TAFs of 78% of tumors, and high miR-21 significantly correlated with decreased overall survival (P = 0.04). Stromal miR-21 expression was also significantly associated with lymph node invasion (P = 0.004), suggesting that it is driving TC spread. Co-immunofluorescence revealed that miR-21 colocalized with peritumoral fibroblasts expressing α-smooth muscle actin. Moreover, expression of miR-21 in primary TAFs correlated with miR-21 in TAFs from patient-matched LN metastases; evidence that PDAC tumor cells induce TAFs to express miR-21. miR-21 expression in TAFs and TCs promotes invasion of TCs and is inhibited with anti-miR-21.ConclusionsmiR-21 expression in PDAC TAFs is associated with decreased overall survival and promotes TC invasion. Anti-miR-21 may represent a novel therapeutic strategy for dual targeting of both tumor and stroma in PDAC.

Cell‐to‐cell communication: microRNAs as hormones

“…They confirmed transfer of miR‐21 from primary CAFs to ovarian cancer cells by co‐culturing CAFs transfected with labeled miR‐21 with ovarian cancer cells (Au Yeung et al ., 2016). In addition, miR‐21 was frequently upregulated in CAFs from both human pancreatic ductal adenocarcinoma samples and primary cell cultures, and higher expression of miR‐21 was significantly correlated with decreased overall survival in pancreatic ductal adenocarcinoma patients (Donahue et al ., 2014; Kadera et al ., 2013). In esophageal squamous cell carcinoma, miR‐21 expression in tumor tissues was found to be primarily localized in the stroma adjacent to the cancer cells (Nouraee et al ., 2013).…”

Expression and clinicopathological significance of microRNA-21 and programmed cell death 4 in malignant melanoma

“…5,17 Overexpression of miR-21 is associated with the progression, metastasis and poor prognosis of many types of tumours via its regulation of the phosphatase and tensin homologue (PTEN), the tissue inhibitor of metalloproteinase 3 and PDCD4 genes. [6][7][8] A study of 127 primary melanoma tissues demonstrated that levels of miR-21 were significantly increased compared with benign naevi. 18 Increased expression of miR-21 was also demonstrated in 86 primary cutaneous melanomas and expression levels were correlated with Breslow thickness and advanced clinical stage.…”

MicroRNAs in the Communication between Cancer Associated Fibroblasts (CAF) and Cancer Cells

“…[15] In addition, miR-21 was frequently upregulated in CAFs in various entities. [16,17] Moreover, expression of this miR in stellate cells derived from normal pancreas was substantially lower when compared to PSCs or CAF cells. [4] Specific upregulation of miR-409-3p and miR-409-5p was found in prostate cancer stromal tissue specimens [18], whereas miR-15 and miR-16 were downregulated in fibroblasts surrounding prostate tumors [19].…”

“…These genome-wide screenings provided potentially deregulated miRNAs in CAFs from different entities (upregulated: miR-221-5p, miR-31-3p, miR-221-3p; and reduced: miR-205, miR-200b, miR-200c, miR-141, miR-101, miR-342-3p, let-7g, miR-26b). (Table 1) Prognostic impact of altered miR expression in CAFs in clinical cohorts has been observed for patients with breast cancer (miR-26b) [11], gastric cancer (miR-106b [22], miR-143 [23], miR-145 [24], miR-200b [14]), esophageal carcinoma (miR-21 [16], miR-27a/b [25]) and pancreatic adenocarcinoma (miR-21 [16]). Furthermore, miR-21 expression in CAFs was elevated in colorectal cancer specimens compared to fibroblasts in colonic polyps [26] and it was associated with decreased overall survival in pancreatic cancer patients who received 5-FU, but not gemcitabine.…”