Potential involvement of heat shock proteins in pancreaticduodenal homeobox-1-mediated effects on the genesis of gastric cancer: A 2D gel-based proteomic study

AIM To identify functional proteins involved in pancreaticduodenal homeobox-1(PDX1)-mediated effects on gastric carcinogenesis.METHODS A PDX1-overexpressed model was established by transfecting gastric cancer cell line SGC7901 with pcDNA3.1(+)-PDX1 vector(SGC-PDX1). Transfection with empty pcDNA3.1 vector(SGC-pcDNA) served as control. Comparative protein profiles of the two groups were analyzed by two-dimensional electrophoresis basedproteomics(2 DE gel-based proteomics). The differential proteins identified by 2 DE were further validated by qRTPCR and immunoblotting. Finally, co-immunoprecipitation was used to determine any direct interactions between PDX1 and the differential proteins.RESULTS2 DE gel proteomics identified seven differential proteins in SGC-PDX1 when compared with those in SGC-pcDNA. These included four heat shock proteins(HSPs; HSP70 p1 B, HSP70 p8, HSP60, HSP27) and three other proteins(ER60, laminin receptor 1, similar to epsilon isoform of 14-3-3 protein). Immunoblotting validated the expression of the HSPs(HSP70, HSP60, HSP27). Furthermore, their expressions were lowered to 80%, 20% and 24%, respectively, in SGC-PDX1, while PDX1 exhibited a 9-fold increase, compared to SGC-pcDNA. However, qRT-PCR analysis revealed that mRNA levels of the HSP s were increased in SGC-PDX1, suggesting that the expression of the HSP s was post-translationally regulated by the PDX1 protein. Finally, co-immunoprecipitation failed to identify any direct interaction between PDX1 and HSP70 proteins.CONCLUSION This study demonstrates the potential involvement of HSPs in PDX1-mediated effects on the genesis of gastric cancer.

Roux-en-Y gastric bypass promotes expression of PDX-1 and regeneration of β-cells in Goto-Kakizaki rats

AIM:To study the effects of Roux-en-Y gastric bypass(RYGB) on the expression of pancreatic duodenal homeobox-1(PDX-1) and pancreatic β-cell regeneration/neogenesis,and their possible mechanisms in diabetics.METHODS:Three groups of randomly selected nonobese diabetic Goto-Kakizaki(GK) rats were subjected to RYGB,sham-RYGB and sham-operation(sham-op) surgery,respectively.The rats were euthanized at postoperative 1,2,4 and 12 wk.Their pancreases were resected and analyzed using reverse transcription polymerase chain reaction to detect the mRNA of PDX-1.Anti-PDX-1 immunohistochemical(IHC) staining and Western blotting were used to detect the protein of PDX-1.Double IHC staining of anti-Brdu and-insulin was performed to detect regenerated β-cells.The index of double Brdu and insulin positive cells was calculated.RESULTS:In comparison with sham-RYGB and sham-op groups,a significant increase in the expressions of PDX-1 mRNA in RYGB group was observed at all experimental time points(1 wk:0.378 ± 0.013 vs 0.120 ± 0.010,0.100 ± 0.010,F = 727.717,P < 0.001;2 wk:0.318 ± 0.013 vs 0.110 ± 0.010,0.143 ± 0.015,F = 301.509,P < 0.001;4 wk:0.172 ± 0.011 vs 0.107 ± 0.012,0.090 ± 0.010,F = 64.297,P < 0.001;12 wk:0.140 ± 0.007 vs 0.120 ± 0.010,0.097 ± 0.015,F = 16.392,P < 0.001);PDX-1 protein in RYGB group was also increased significantly(1 wk:0.61 ± 0.01 vs 0.21 ± 0.01,0.15 ± 0.01,F = 3031.127,P < 0.001;2 wk:0.55 ± 0.00 vs 0.15 ± 0.01,0.17 ± 0.01,F = 3426.455,P < 0.001;4 wk:0.39 ± 0.01 vs 0.18 ± 0.01,0.22 ± 0.01,F = 882.909,P < 0.001;12 wk:0.41 ± 0.01 vs 0.20 ± 0.01,0.18 ± 0.01,F = 515.833,P < 0.001).PDX-1 mRNA and PDX-1 protein production showed no statistical significance between the two sham groups.Many PDX-1 positive cells could be found in the pancreatic islets of the rats in RYGB group at all time points.In addition,the percentage of Brdu-insulin double staining positive cells was higher in RYGB group than in the other two groups(1 wk:0.22 ± 0.13 vs 0.03 ± 0.06,0.03 ± 0.06,P < 0.05;2 wk:0.28 ± 0.08 vs 0.00 ± 0.00,0.03 ± 0.06,P < 0.05;4 wk:0.24 ± 0.11 vs 0.07 ± 0.06,0.00 ± 0.00,P < 0.001;12 wk:0.20 ± 0.07 vs 0.03 ± 0.06,0.00 ± 0.00,P < 0.05).CONCLUSION:RYGB can increase the expression of pancreatic PDX-1 and induce the regeneration of β-cells in GK rats.The associated regeneration of islet cells may be a possible mechanism that how RYGB could improve type 2 diabetes mellitus.

Transcription factor PDX-1 in human colorectal adenocarcinoma:A potential tumor marker?

AIM: To examine the expression of pancreatic duodenal homeobox-1 (PDX-1) transcription factor in human colorectal cancer. METHODS: RT-PCR, Western blotting, and immuno-histochemistry were performed to determine the expression pattern of transcription factor PDX-1 in primary colorectal tumor, hepatic metastasis, and benign colon tissue from a single patient. RESULTS: The highest PDX-1 transcription levels were detected in the metastasis material. Lower levels of PDX-1 were found to be present in the primary tumor, while normal colon tissue failed to express detectable levels of PDX-1. Western blot data revealed a PDX-1 expression pattern identical to that of mRNA expression. Immunohistochemistry confirmed high metastasis PDX-1 expression, lower levels in the primary tumor, and the presence of only traces of PDX-1 in normal colon tissue. CONCLUSION: These data argue for further evaluation of PDX-1 as a biomarker for colorectal cancer.

Zinc finger E-box-binding homeobox 1 mediates aerobic glycolysis via suppression of sirtuin 3 in pancreatic cancer

AIM TO uncover the roles of tumor-promoting gene ZEB1 in aerobic glycolysis regulation and shed light on the underlying molecular mechanism.METHODS Endogenous zinc finger E-box binding homeobox-1 （ZEB1） was silenced using a and the impact of ZEB1 and lentivirus-mediated method, methyI-CpG binding domain protein 1 （MBD1） on aerobic glycolysis was measured using seahorse cellular flux analyzers, reactive oxygen species quantification, and mitochondrial membrane potential measurement. The interaction between ZEB1 and MBD1 was assessed by co-immunoprecipitation and immunofluorescence assays. The impact of ZEB1 and MBD1 interaction on sirtuin 3 （SIRT3） expression was confirmed by quantitative polymerase chain reaction, western blotting, and dual-luciferase and chromatinimmunoprecipitation assays.RESULTS ZEB1 was a positive regulator of aerobic glycolysis in pancreatic cancer. ZEB1 transcriptionally silenced expression of SIRT3, a mitochondrial-localized tumor suppressor, through interaction with MBD1.CONCLUSION ZEB1 silenced SIRT3 expression via interaction with MBD1 to promote aerobic glycolysis in pancreatic cancer.

PDX-1 Expression in Pancreatic Ductal Cells after Partial Pancreatectomy in Adult Rats

To investigate the protein and mRNA expression of pancreas/duodenal homeobox-1 (PDX-1), a transcription factor as a marker for pancreatic stem cells, in pancreatic ductal cells of rats after partial (90 %) pancreatectomy and evaluated the significance of the PDX-1 expression. Western blot and Reverse transcriptase-polymerase chain reaction (RT-PCR) were used to detect the expression of PDX-1 protein and mRNA respectively. PDX-1 protein was only faintly detected in pancreatic ductal cells on the day 1 after partial pancreatectomy. On the day 2 and 3 after operation in operation group, a 2—3 fold increased PDX-1 protein was observed, corresponding to the characteristic 42—kD protein in Western blot. There was significant difference between operation group and sham-operation group (P<0.05). PDX-1 protein expression on the day 5 and 7 after operation had already been no difference from control group (P>0.05). RT-PCR revealed the PDX-1 mRNA expression showed no significant difference between operation group at various time points and sham-operation group (P>0.05). These results indicate that there was overexpression of PDX-1 in the cells of pancreatic epithelium during the regeneration of remnant pancreas after partial pancreatectomy in adult rats, suggesting the pancreatic stem cells in pancreatic ductal epithelial cells are involved in the regeneration of remnant pancreas and the expression of PDX-1 in ductal cells was regulated posttranscription.

Down-regulation of pancreatic transcription factors and incretin receptors in type 2 diabetes

Type 2 diabetes is one of the most prevalent and serious metabolic diseases.Under diabetic conditions,chronic hyperglycemia and subsequent induction of oxidative stress deteriorate pancreaticβ-cell function,which leads to the aggravation of type 2 diabetes.Although such phenomena are well known as glucose toxicity,its molecular mechanism remains unclear.In this review article,we describe the possible molecular mechanism forβ-cell dysfunction found in type 2 diabetes,focusing on(1)oxidative stress,(2)pancreatic transcription factors(PDX-1 and MafA)and(3)incretin receptors(GLP-1 and GIP receptors).Under such conditions,nuclear expression levels of PDX-1 and MafA are decreased,which leads to suppression of insulin biosynthesis and secretion.In addition,expression levels of GLP-1 and GIP receptors are decreased,which likely contributes to the impaired incretin effects found in diabetes.Taken together,it is likely that downregulation of pancreatic transcription factors(PDX-1and MafA)and down-regulation of incretin receptors(GLP-1 and GIP receptors)explain,at least in part,the molecular mechanism forβ-cell dysfunction found in type 2 diabetes.

Pancreatic and duodenal homeobox-1 in pancreatic ductal adenocarcinoma and diabetes mellitus

Diabetes mellitus and pancreatic ductal adenocarcinoma are two common diseases worldwidely which are both derived from different components of pancreas.The pancreatic and duodenal homeobox-1(PDX1)is an essential transcription factor for the early development of pancreas that is required for the differentiation of all pancreatic cell lineages.Current evidence suggests an important role of PDX1 in both the origin and progression of pancreatic diseases.In this review,we discussed recent studies of PDX1 in diabetes mellitus and pancreatic cancer,and the therapeutic strategies derived from this transcription factor.

Effects of supraphysiologic concentration glucose on pancreatic duodenal homeobox-1 expression and insulin secretion in rats

The islet transcription factor pancreatic duodenal homeobox-1 （PDX-1, also known as insulin promoter factor-1 or IPF-1） is an orphan homeodomain protein that plays an important role in the development, proliferation, differentiation and maturation of pancreatic cells. It is initially detected in the part of the dorsal and ventral primitive gut epithelium that later develops into the pancreas in embryonic period. In adults, its expression is found predominantly in the differentiated islet beta-cells. A recent study shows that PDX-1 is a major islet transcription factor which activates insulin gene transcription.1 Glucose-induced insulin biosynthesis is concerned with some motifs in insulin gene promoter, and PDX-1 activates insulin gene transcription and biosynthesis through binding to these motifs. Targeted inactivation of PDX-1 gene in the mice as well as its mutation in humans2 results in agenesis of the pancreas.