AIMTo investigate whether microRNA (miR)-34a mediates oxaliplatin (OXA) resistance of colorectal cancer (CRC) cells by inhibiting macroautophagy via the transforming growth factor (TGF)-β/Smad4 pathway.METHODSmiR-34a expression levels were detected in CRC tissues and CRC cell lines by quantitative real-time polymerase chain reaction. Computational search, functional luciferase assay and western blotting were used to demonstrate the downstream target of miR-34a in CRC cells. Cell viability was measured with Cell Counting Kit-8. Apoptosis and macroautophagy of CRC cells were analyzed by flow cytometry and transmission electron microscopy, and expression of beclin I and LC3-II was detected by western blotting.RESULTSExpression of miR-34a was significantly reduced while expression of TGF-β and Smad4 was increased in CRC patients treated with OXA-based chemotherapy. OXA treatment also resulted in decreased miR-34a levels and increased TGF-β and Smad4 levels in both parental cells and the OXA-resistant CRC cells. Activation of macroautophagy contributed to OXA resistance in CRC cells. Expression levels of Smad4 and miR-34a in CRC patients had a significant inverse correlation and overexpressing miR-34a inhibited macroautophagy activation by directly targeting Smad4 through the TGF-β/Smad4 pathway. OXA-induced downregulation of miR-34a and increased drug resistance by activating macroautophagy in CRC cells.CONCLUSIONmiR-34a mediates OXA resistance of CRC by inhibiting macroautophagy via the TGF-β/Smad4 pathway.

BackgroundExtrahepatic Cholangiocarcinoma (EHCC) is one of the uncommon malignancies in the digestive system which is characterized by a poor prognosis. Aberrations of miRNAs have been shown involved in the progression of this disease. In this study, we evaluated the expression and effects of miR-34a on EHCC.MethodsmiR-34a expression levels were detected in EHCC tissues, adjacent non-tumor tissues, normal bile duct (NBD) specimens of patients and cholangiocarcinoma (CC) cell lines by quantitative real-time polymerase chain reaction (qRT-PCR). Relationships between miR-34a with clinical characteristics of EHCC patients were further analyzed. Computational search, functional luciferase assay and western blot were further used to demonstrate the downstream target of miR-34a in CC cells. Immunohistochemistry was carried on to identify the downstream target gene of miR-34a in EHCC patients. Cell morphology, invasion and migration assays were further applied to confirm the anti-carcinogenic effects of miR-34a through the downstream target.ResultsmiR-34a expression was significantly decreased in human EHCC tissues and CC cell lines when compared with the adjacent non-tumor tissues and normal bile duct tissues. miR-34a was found correlated with the migration and invasion in EHCC patients. Smad4 was over-expressed in most of the EHCC patients and was further demonstrated as one of the downstream targets of miR-34a, which was involved in the progression of EHCC. Moreover, activation of miR-34a suppressed invasion and migration through TGF-beta/Smad4 signaling pathway by epithelial-mesenchymal transition (EMT) in vitro.ConclusionsTaken together, our results suggest that miR-34a inhibits invasion and migration by targeting Smad4 to suppress EMT through TGF- beta/Smad signaling pathway in human EHCC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1359-x) contains supplementary material, which is available to authorized users.

Bone marrow-derived mesenchymal stem cells (BM-MSCs) have been shown to attenuate ischemia reperfusion (IR) injury in the heart, brain and kidney. However, their exact roles in the liver remain to be defined. Our objective was to investigate the potential effects of BM-MSCs on a hepatic IR rat model during the first 24 h after reperfusion, a crucial period for hepatic IR damage formation. A rat model of normothermic partial hepatic ischemia was obtained by vascular clamping for 60 min. BM-MSCs were transplanted via portal vein injection. Injury severity, oxidative stress response and apoptosis of liver cells were assessed at 2, 6, 12 and 24 h after reperfusion and cell transplantation was evaluated. At 12 and 24 h after reperfusion, rats transplanted with BM-MSCs had significantly lower serum levels of alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST), fewer damaged liver tissues, higher superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and lower malondialdehyde (MDA) levels compared to rats in the sham transplantation group. At 24 h after reperfusion, IR rats transplanted with BM-MSCs had significantly fewer apoptotic hepatocytes, higher levels of B-cell lymphoma 2 (Bcl-2) protein, and lower levels of Bcl-2-associated X (Bax) and caspase-3 (Casp3) proteins compared to sham transplantation rats. In conclusion, BM-MSCs transplanted via the portal vein partially prevent hepatic IR injury by suppressing oxidative stress and inhibiting apoptosis during the first 24 h after reperfusion.

HSP effectively induces autophagy following exposure to H2O2 via the p38MAPK/mTOR pathway, which leads to enhanced MSC survival and improved MSC repair following HIRI in rats.

Current studies tend to consider N-myc downstream regulated gene 1 (NDRG1) as a tumor suppressor gene, inhibiting cell proliferation and invasion. NDRG1 expression in cancer cells is generally low, but the molecular mechanism is unclear. Aberrant methylation of CpG islands (CGIs) in gene promoter was able to inactivate tumor suppressor genes and activate oncogenes, disordering cell proliferation and apoptosis, playing a promotion role in tumor occurrence and progression. The present study was performed to investigate the effect of epigenetic modification of NDRG1 on prostate cancer (PCa) cells. The protein expression in human specimens was measured by immunohistochemical staining. The expression level of NDRG1 was changed by plasmid vectors in PCa cells. These cells were used to study proliferation and invasiveness. NDRG1 expression in normal prostate cells was higher than that in PCa cells. Downregulation of NDRG1 expression enhanced cell proliferation and invasiveness. In contrast, its upregulation could reduce cell proliferation and invasiveness. In PCa cells, the methylation rate of CGIs in the promoter region of NDRG1 was higher than that in normal prostate cells. 5-Aza-CdR, a methylation inhibitor, was able to effectively reverse the aberrant methylation of NDRG1, enhancing its expression, inhibiting cell growth. NDRG1 can inhibit the cell proliferation and invasion of PCa, but its expression level is low. The aberrant methylation of NDRG1 promoter is an important mechanism for gene silencing, playing an important role in tumor occurrence and progression. Therefore, reversing the aberrant methylation of NDRG1 may be used for PCa treatment.