Background: circRNA has been established to play a pivotal role in tumorigenesis development in a variety of cancers; nevertheless, the biological functions and molecular mechanisms of hypoxia-induced exosomal circRNAs in pancreatic cancer remain largely unknown. Methods: Differentially expressed circRNAs in exosomes between hypoxic exosomes and normoxic exosomes in PC cells were verified by RNA sequencing. The expression of circPDK1 in PC tumors and PC patients was evaluated by qRT-PCR and ISH, and the biological functions of circPDK1 in PC were verified through a series of in vitro and in vivo experiments. Using Western blotting, Co-IP, RNA pull-down, ChIP, RIP, dual-luciferase assays, and rescue experiments, the underlying mechanism of circPDK1 was verified. Results: CircPDK1 was highly abundant in PC tumor tissues and serum exosomes and was associated with poor survival. Exosomal circPDK1 significantly promoted PC cell proliferation, migration, and glycolysis both in vitro and in vivo. Mechanistically, circPDK1 could be activated by HIF1A at the transcriptional level and sponges miR-628-3p to activate the BPTF/c-myc axis. In addition, circPDK1 serves as a scaffold that enhances the interaction between UBE2O and BIN1, inducing the UBE2O-mediated degradation of BIN1. Conclusions: We found that circPDK1 was activated by HIF1A at the transcriptional level by modulating the miR-628-3p/BPTF axis and degrading BIN1. Exosomal circPDK1 is a promising biomarker for PC diagnosis and prognosis and represents a potential therapeutic target for PC.

The members of the miR-17-92 cluster are upregulated in various cancers and function as a cluster of oncogenic miRNA. Our study characterized a new function of miR-17-5p, a member of the miR-17-92 cluster, in regulating cell proliferation in pancreatic cancer. Our results indicate that miR-17-5p was up-regulated in pancreatic adenocarcinoma and directly targeted the retinoblastoma-like protein 2 (RBL2), a tumor suppressor belonging to the Rb family. High levels of miR-17-5p and low levels of RBL2 were associated with poor prognosis. RBL2 interacted with the transcription factor E2F4 and bound to the promoter regions of the E2F target genes. Disruption of the RBL2/E2F4 complex by miR-17-5p overexpression shifted the activity of E2F from gene repressing to gene activating, which induced cell cycle entry and proliferation. These results suggest that miR-17-5p promoted proliferation in pancreatic ductal adenocarcinoma cells (PDAC), and altered cell cycle profiles in vivo and in vitro, by disrupting the RBL2/E2F4-associated gene repressing complexes via direct targeting of RBL2. The new regulatory network, involving miR-17-5p and RBL2, emerges as a new target of PDAC treatment.

Ten-eleven translocation 1 (TET1) is a dioxygenase that converts 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) to induce DNA demethylation. TET1 has been reported to be absent in cancers, and to influence various oncogenes and anti-oncogenes. However the function of TET1 in pancreatic tumor remains poorly understood. In this study, we investigated the role of TET1 in the progression of pancreatic tumor and its mechanism of tumor suppression. Quantitative real-time PCR (qRT-PCR), immunohistochemical (IHC) staining and dot blot were performed to detect the TET1 and 5-hmC expression in pancreatic tumor tissues and its adjacent non-tumor tissues. The clinical parameters significance of pancreatic tumor tissues was determined statistically. TET1 over-expression and knock-out cell lines were built and confirmed in vitro. Cell proliferation assay, wound-healing assays, transwell migration assay and nude mice model of orthotopic pancreatic cancer implantation were performed to assess the function of TET1 in pancreatic tumor. Western blot, qRT-PCR, immunofluorescence (IF), bisulfate sequencing (BSP), Chromatin immunoprecipitation (ChIP) were used to uncover the mechanism. TET1 levels and 5-hmC content were downregulated in pancreatic tumor tissues and cell lines, and pancreatic tumor patients with low TET1 levels had a shorter overall survival than patients with high levels of TET1. TET1 suppressed pancreatic tumor proliferation and metastasis in vivo and in vitro. TET1 bound to the secreted frizzled-related protein 2 (SFRP2) promoter and catalyzed demethylation to activate transcription of SFRP2, inhibiting both the canonical and non-canonical Wnt signaling pathways, and ultimately obstructing epithelial-mesenchymal transition (EMT) in pancreatic tumors. We found TET1 plays as a suppressor in pancreatic tumor progression via obstructing Wnt signaling pathways.

In this study, we investigated the role of tumor-associated macrophages (TAMs) in the progression of pancreatic ductal adenocarcinoma (PDAC). PDAC patients with higher levels of CD68+ TAMs exhibited shorter overall survival. In Transwell assays, PDAC cells incubated with TAMs or conditioned media from TAM cells (TAM-CM) showed higher migration and invasion rates than controls. PET/CT scan analysis of orthotopic PDAC model mice revealed greater primary tumor growth and liver metastasis in the TAM-CM treatment group than the controls. H&E staining of liver tissues showed significantly higher numbers of metastatic nodules in the TAM-CM treatment group. Heat inactivation of TAM-CM significantly reduced Transwell migration by PDAC cells, suggesting the involvement of one or more secreted proteins in PDAC progression. Transcriptome sequencing analysis of PDAC cells treated with TAM-CM revealed significant enrichment of transforming growth factor-β (TGF-β) signaling pathway genes. Western blot and qRT-PCR analysis showed that TAM-CM enhanced PDAC migration cells by inducing epithelial-to-mesenchymal transition through the TGF-β-Smad2/3/4-Snail signaling axis. The pro-tumorigenic effects of TAMs or TAM-CM were abolished by TGF-β signaling pathway inhibitors and neutralizing TGF-β antibody. These results demonstrate that TAMs promote PDAC progression through the TGF-β signaling pathway.

Liver ischemia/reperfusion (I/R) injury is a complex and common clinical disease with limited therapeutic options. The aim of our study was to discover the candidate target genes in liver I/R injury and to further elucidate the potential regulatory mechanisms, especially the ones involving transcription factors and miRNAs. The analysis of mouse data set GSE10657 from Gene Expression Omnibus database (GEO) revealed 203 differentially expressed genes (DEGs) including 19 transcription factors (TFs). Functional and pathway enrichment analyses were conducted to explore their biological functions. We further obtained the targets of TFs and miRNAs, to form our TF-mRNA/TF-miRNA-mRNA co-regulatory network. In our network, we found that the important subunits of activator protein 1 (AP-1) including JUN, FOS and ATF3, were hub genes in liver I/R injury. AP-1 target genes were activated in our mouse models. AP-1 could transcriptionally activate phosphatase and tensin homolog (PTEN) while AP-1-dependent miRNAs countered this effect. In conclusion, this study suggested that AP-1, together with AP-1-dependent miRNAs formed a co-regulatory network enabling AP-1 target genes to be tightly controlled, which will complete the mechanism of liver ischemia/reperfusion injury and provide direction for finding potential therapeutic targets.

As one of the major treatment obstacles in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL), relapse of Ph+ALL may result from the pe