Twenty-four hour later, cells were detached using an enzyme-free dissociation solution (Sigma-Aldrich, Saint-Louis, MO, USA)

Twenty-four hour later, cells were detached using an enzyme-free dissociation solution (Sigma-Aldrich, Saint-Louis, MO, USA). expression and secretion of the potent pro-lymphangiogenic factor vascular endothelial growth factor C in pancreatic cancer cells through an NF-B-independent mechanism. By usingin vitroandin vivoapproaches, we reveal that re-expression of miR-206 in PDAC cells is sufficient to inhibit tumor blood and lymphatic vessel formation, thus leading to a significant delay of tumor growth and progression. Taken together, our study sheds light onto the role of miR-206 as a pleiotropic modulator of different hallmarks of cancer, and as such raising the intriguing possibility that miR-206 may be an Dicer1 attractive candidate for miRNA-based anticancer therapies. == Introduction == Pancreatic ductal adenocarcinoma (PDAC) comprises > 90% of pancreatic cancers and is one of the most deadly cancer diseases in the western world despite its comparably low incidence. 1, 2Clinical outcome is poor with only 5% of cases surviving up to 5 years after diagnosis. 1, 3PDAC arises from precursor ductal lesions termed pancreatic intraepithelial neoplasia, tends to rapidly invade in surrounding tissues, and to metastasize to other organs, primarily the liver, while it is highly resistant to chemo- and radiation therapy. 2Hence, it is of utmost importance to fully elucidate the underlying molecular mechanisms of PDAC in order to develop novel therapeutic strategies. One of the earliest somatic mutations in PDAC occurs in codon 12 of theKRASoncogene. This results in a constitutively active KRAS protein (mostly KRASG12D) and is found in > 90% of cases. The mutation is thought of as a key event in pancreatic intraepithelial neoplasia formation. 2, 4However, additional high-frequency genetic alterations are required to attain an invasive carcinoma phenotype. These include inactivation of tumor suppressor genesp16INK4a/ARF(> 95%), p53(5075%), SMAD4(55%) andBRCA2(510%). 2, 5Activated KRAS in combination with Ink4a/Arf deficiency orPTENdeletion are sufficient to trigger the activation of signaling circuits including the NF-B pathway and the subsequent constitutive production of pro-inflammatory cytokines associated with vascular or immunological responses in the tumor microenvironment. 6Indeed, it has been demonstrated that NF-B signaling is constitutively activated in the majority of primary tumor specimens and human pancreatic cancer cell lines. 7NF-B has been shown to promote growth and tumorigenesis, inhibit apoptosis, as well as to foster angiogenesis, invasion, metastasis and chemoresistance in PDAC. 6, 8, 9, 10 MicroRNAs DG172 dihydrochloride (miRNAs) are endogenous small (~22 nucleotides long) non-coding RNAs that mostly negatively regulate gene expression by base pairing within the 3-untranslated region of target messenger RNAs (mRNA). 11miRNAs have been well-described as regulators of many biological processes, including cancer development. Recent reports have revealed frequent alterations in miRNA expression levels also in PDAC specimens. Elevated miR-21 levels have been reported in high-grade pancreatic intraepithelial neoplasia lesions, 12whereas high expression of miR-135b was suggested as a PDAC biomarker. 13Here, we identify miR-206 to be significantly downregulated in tumors of PDAC patients. We reveal that miR-206 is a novel negative regulator of NF-B signaling and, thereby, miR-206 functions as a tumor suppressor by inhibiting tumor growth, cancer cell invasiveness and release of an NF-B-dependent circuit of pro-angiogenic cytokines and growth factors. DG172 dihydrochloride We further demonstrate that DG172 dihydrochloride miR-206 emerges a vascular DG172 dihydrochloride regulatory role by leading to both vascular and lymphatic regression in PDAC tumors. Mechanistically, we propose that miR-206 exerts its tumor suppressive function through combinatorial targeting of the oncogenesKRASandANXA2, which, however , may have distinct roles with KRAS affecting tumor vascularization, whereas ANXA2 mainly effecting invasiveness through extracellular matrix (ECM) degradation. == Results == == miR-206 is downregulated in PDAC == In a previous study, we conducted a genome-wide miRNA screen, which revealed 13 miRNA families as coherent modulators of NF-B signaling. 14Here, in order to identify clinically relevant miRNA-NF-B interactions in PDAC, we analyzed a publicly available miRNA expression profiling data set (GEO databaseGSE32688) for differential expression of miRNAs in seven non-malignant versus 25 early stage PDAC tissues. 15Sixty-five miRNAs were found to be significantly deregulated (P <0. 01) in PDAC specimens compared with healthy tissues (Figure 1a). Interestingly, miR-206, a strong negative regulator of NF-B transcriptional activity, 14was significantly downregulated in tumors (Figures 1a and b). miR-206 downregulation in PDAC cells was further confirmed.