Exosomal NNMT from peritoneum lavage fluid promotes peritoneal metastasis in gastric cancer.

Peritoneal metastasis (PM) is the major cause of recurrence in patients with gastric cancer (GC) and is associated with poor prognosis. The oncogenic role of Nicotinamide N-methyltransferase (NNMT) in GC has been reported, but the role of secreted NNMT that is transported by exosomes remains unknown. In this study, exosomes were isolated from GC patients with or without PM and from GC cell line, including GC-114, GC-026, MKN45, and SNU-16 cells. The contents of NNMT were significantly enhanced in exosomes isolated from GC patients with PM compared with those from GC patients without PM. Furthermore, the levels of NNMT were significantly enhanced in exosomes from GC cell lines relative to those from normal human gastric epithelial cell line GES-1 cells. These data indicate that NNMT may be involved in intercellular communication for peritoneal dissemination. Moreover, colocalization of GC-derived exosomal NNMT was found in human peritoneal mesothelial cell line HMrSV5 cells. Additionally, relative to GES-1 exosomes, SNU-16 exosomes significantly activated TGF-ß/smad2 signaling in HMrSV5 cells. However, when NNMT was silenced, the activation of TGF-ß/smad2 by SNU-16 exosomes was abolished in HMrSV5 cells. We propose that NNMT-containing exosomes derived from GC cells could promote peritoneal metastasis via TGF-ß/smad2 signaling.

MEX3A knockdown inhibits the development of pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDA) is one of the most serious causes of death in the world due to its high mortality and inefficacy treatments. MEX3A was first identified in nematodes and was associated with tumor formation and may promote cell proliferation and tumor metastasis. So far, nothing is known about the relationship between MEX3A and PDA. METHODS: In this study, the expression level of MEX3A in PDA tissues was measured by immunohistochemistry. The qRT-PCR and western blot were used to identify the constructed MEX3A knockdown cell lines, which was further used to construct mouse xenotransplantation models. Cell proliferation, colony formation, cell apoptosis and migration were detected by MTT, colony formation, flow cytometry and Transwell. RESULTS: This study showed that MEX3A expression is significantly upregulated in PDA and associated with tumor grade. Loss-of-function studies showed that downregulation of MEX3A could inhibit cell growth in vitro and in vivo. Moreover, it was demonstrated that knockdown of MEX3A in PDA cells promotes apoptosis by regulating apoptosis-related factors, and inhibits migration through influencing EMT. At the same time, the regulation of PDA progression by MEX3A involves changes in downstream signaling pathways including Akt, p-Akt, PIK3CA, CDK6 and MAPK9. CONCLUSIONS: We proposed that MEX3A is associated with the prognosis and progression of PDA,which can be used as a potential therapeutic target.

[Induced differentiation of bone marrow stem cells in transplanted rat liver].

OBJECTIVE: To investigate the differentiation of bone marrow stem cells in transplanted livers and its impact on the long-term survival of rats with orthotopic liver transplantation. METHODS: Twenty-four female recipient rats with orthotopic liver transplantation were randomized into blank-control group, D-hanks solution group, bone marrow stem cells group with postoperative infusion of stem cells, and the pathological changes of the liver grafts and survival time of the rats were observed. The differentiation of the bone marrow stem cells were assessed 60 days after transplantation using in situ hybridization histochemistry for Sry gene and alpha-fetoprotein (AFP) immunohistochemistry. RESULTS: In rats with postoperative infusion of bone marrow stem cells through the portal vein, the median long-term graft survival time exceeded 180 days, significantly longer than that in the other two groups (P<0.05), and no obvious evidence of acute rejection was observed with positive Sry expression and AFP expression. CONCLUSION: Infusion of bone marrow stem cells through the portal vein following liver transplantation may alleviate acute graft rejection and promote long-term liver graft survival and AFP expression.

[Human bone marrow multipotent adult progenitor cells differentiate into hepatocyte-like cells with hepatocyte growth factor plus fibroblast growth factor-4 in vitro].

OBJECTIVE: To investigate the possibility of the human bone marrow multipotent adult progenitor cells (hMAPCs) to differentiate into hepatocytes with hepatocyte growth factor (HGF)/ fibroblast growth factor-4 (FGF-4) in vitro. METHODS: (1) Obtaining the hMAPCs. Bone marrow was obtained from volunteers and then centrifuged through density gradient centrifugation methods. The collected mononuclear cells were cultured through adheret culture to get mesenchymal stem cells (MSCs). The hMAPCs were obtained through collecting and isolating the MSCs by magnetic activated cell sorting (MACS) through depletion selection by use of CD45 and GlyA microbeads. (2) Differentiation of the hMAPCs with HGF+FGF-4. Group A: HGF (20 ng/ml) + FGF-4 (10 ng/ml) induced hMAPCs; group B (positive control group): L-02 human hepatocytes(cell lines); and group C (negative control group): the undifferentiated hMAPCs. (3) The expressions of albumin (Alb), alpha fetoprotein (AFP), cytokeratin-18 (CK-18), and cytokeratin-19 (CK-19) were detected with immunocytochemistry to identify the characteristics of the differentiated cells at different times and the ratio of the positive cells was determined. (4) ALB, AFP, CK-18, and CK-19 expressions of the differentiated cells were detected by RT-PCR assay to investigate the mRNA transcriptions of characteristic hepatic proteins. (5) Alb expressions of the differentiated cells at different times were detected by Western blot on the 21st and 35th days. RESULTS: (1) The results of immunocytochemistry. The staining of Alb, CK18 were essentially positive in group A. As an early marker of immature hepatocytes, AFP staining was positive on the 7th day but negative in later differentiating periods in group A. (2) The results of RT-PCR. On the 7th day, the differentiated hMAPCs expressed AFP mRNA but were negative in later differentiating periods. On the contrary, the mRNA of Alb and CK-18 were positive at all times. (3) The results of Western blot assay. Alb protein was positive on the 21st day and 35th day. CONCLUSIONS: Under some definite inducing conditions hMAPCs can differentiate into hepatocyte-like cells. They may serve as a potential cell source for liver engineering.

Protein kinase C-dependent activation of P44/42 mitogen-activated protein kinase and heat shock protein 70 in signal transduction during hepatocyte ischemic preconditioning.

AIM: To investigate the significance of protein kinase C(PKC), P44/42 mitogen-activated protein kinase (MAPKs) and heat shock protein (HSP)70 signal transduction during hepatocyte ischemic preconditioning. METHODS: In this study we used an in vitro ischemic preconditioning (IP) model for hepatocytes and an in vivo model for rat liver to investigate the significance of protein kinase C (PKC), P44/42 mitogen-activated protein kinase (P44/42 MAPKs) and heat shock protein 70 (HSP70) signal transduction in IP. Through a normal liver cell hypoxic preconditioning (HP) model in which cultured normal liver cells were subjected to 3 cycles of 5 min of incubation under hypoxic conditions followed by 5 min of reoxygenation and subsequently exposed to hypoxia and reoxygenation for 6 h and 9 h respectively. PKC inhibitor, activator and MEK inhibitor were utilized to analyze the phosphorylation of PKC, the expression of P44/42 MAPKs and HSP70. Viability and cellular ultrastructure were also observed. By using rat liver as an in vivo model of liver preconditioning (3 cycles of 10-min occlusion and 10-min reperfusion), in vivo phosphorylation of PKC and P44/42MAPKs, HSP70 expression were further analyzed. AST/ALT concentration, cellular structure and ultrastructure were also observed. All the data were statistically analyzed. RESULTS: Similar results were obtained in both in vivo and in vitro IP models. Compared with the control without IP (or HP), the phosphorylation of PKC and P44/42 MAPKs and the expression of HSP70 were obviously increased in IP (or HP) treated model in which cytoprotection could be found. The effects of preconditioning were mimicked by stimulating PKC with 4beta phorobol-12-myristate13-acetate (PMA). Conversely, inhibiting PKC with chelerythrine abolished the protection given by preconditioning. PD98059, inhibitor of MEK (the upstream kinase of P44/42MAPKs), also reverted the cytoprotection exerted by preconditioning. CONCLUSION: The results demonstrate that preconditioning induces a rapid activation of P44/42MAPKs and PKC activation plays a pivotal role in the activation of P44/42 MAPKs pathway that participates in the preservation of liver cells. HSP expression is regulated by signals in PKC dependent P44/42 MAPKs pathway.

[PKC-dependent activation of P44/42 MAPKs and HSP70 in signal transduction pathways during hepatocyte ischemic preconditioning].

OBJECTIVE: To investigate the significance of PKC, P44/42 MAPKs and HSP70 signal transduction in IP. METHODS: Through an in vivo rat liver IP model, PKC inhibitor, activator and MEK inhibitor were utilized to analyze the phosphorylation of PKC and P44/42 MAPKs. HSP expression, AST/ALT concentration, cellular structure and ultrastructure were also observed. All the data were statistically analyzed. RESULTS: Compared with the control without IP, the phosphorylation of PKC was significantly increased in IP treated models and PKC activated group (P < 0.01) and P44/42 MAPKs and the expression of HSP were also obviously increased. In contrast, opposite changes were found in PKC or MEK inhibited groups, the phosphorylation PKC was decreased in PKC inhibited group (P < 0.01). CONCLUSION: The model has shown that PKC activation plays a pivotal role in the activation of P44/42 MAPKs pathway that participates in the preservation of liver cells. At the same time, HSP expression is regulated by signals in P44/42 MAPKs pathway.

[Protecting effects of p44/42 MAPK signal transduction pathway on hepatocytes in ischemic preconditioning].

OBJECTIVE: To investigate the significance of PKC and p44/42 mitogen-activated protein kinase (MAPK) signal transduction in ischemic preconditioning (IP). METHODS: Through liver cell IP models, PKC inhibitor and MEK inhibitor were utilized to analyze the phosphorylation level of p44/42 MAPK and cell viability was also observed. Rat liver IP models were established which were treated with various drugs. Then the phosphorylation level of p44/42 MAPK in vivo and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) concentrations were detected. And cellular structures were observed under light microscopy. RESULTS: Similar results were obtained in vivo and in vitro IP models. Compared with the ischemia reperfusion (IR) group in vivo, the phosphorylation level of p44/42 MAPK was obviously increased in IP treated rats (q = 27.217, P < 0.01), and the cellular structure injured slightly. The concentrations of serum ALT and AST in IP group were significantly lower than those in IR group (281.0 U/L +/-35.6 U/L vs 762.8 U/L +/-130.5 U/L and 407.7 U/L +/-73.7 U/L vs 820.9 U/L +/-111.3 U/L, P < 0.01). However, opposite changes were found in PKC and MEK inhibited groups, when compared to IP group. The phosphorylation level of p44/42 MAPK was obviously decreased, the liver tissues injured evidently, and the concentrations of serum ALT and AST (645.61 U/L +/-90.4 U/L, 678.6 U/L +/-136.5U/L and 466.2 U/L +/-82.8 U/L, 732.9 U/L +/-91.1 U/L, respectively) were significantly greater than those in IP group. CONCLUSION: These results suggest that p44/42 MAPK pathway plays a vital role in the protection of hepatocytes in ischemic preconditioning.