The relationship between loss expression of DPC4/Smad4 gene and carcinogenesis of pancreatobiliary carcinoma

Objective: To clarify the relationship between loss of DPCA gene expression and pathogenesis of pancreato- biliary carcinoma. Methods: 75 slides of normal duct (20), hyperplasia (15), dysplasia (15), invasive carcinoma (25) from patients with pancreatic diseases including pancreatic carcinoma (25 patients), chronic pancreatitis (6), pancreas injury (2) and 71 slides of common bile duct (CBD) carcinoma (38), gallbladder carcinoma (18), hilar bile duct (HBD) carcinoma (15) from patients with primary biliary tract carcinoma were analyzed for the expression of DPC4 protein by im- munohistochemical staining. Results: All specimens from 20 cases of normal duct and 15 cases of hyperplasia showed marked expres- sion of DPC4 protein. The frequency of loss expres- sion of the DPC4 gene was 33 % in dysplasia, and 48% in invasive carcinoma. There was a significant statistical difference between byperplasia and dyspla- sia (P<0.01) and in dysplasia vs invasive carcinoma (P<0.05). The frequency of loss expression of the DPC4 gene was 47.3% in CBD carcinoma, 11% in gallbladder carcinoma, and 13% in HBD carcinoma. The frequency of loss expression of the DPCA gene was significantly different in CBD carcinoma vs gall- bladder carcinoma and HBD carcinoma (P<0.01). Conclusions: Inactivation of the DPC4 gene occurs late in the neoplastic progression of pancreatic carci- noma. The frequency of DPC4 gene alternation was different in various locations of biliary tract carcino- ma. In CBD carcinoma, this frequency is similar to that in pancreatic carcinoma, indicating their similar molecular alternations.

Frequency of Loss Exprssion of DPC4 Protein in Various Locations of Biliary Tract Carcinoma

Objective To clarify the relationship between loss of expression of DPC4 proteins and pathogenesis of biliary tract carcinoma. Methods 71 primary biliary tract carcinomas (BTCa), including 38 common bile duct (CBD) carcinomas, 18 gallbladder carcinomas, and 15 hilar bile ducts (HBD) carcinomas were examined by immunohistochemical staining. In addition, the CBD carcinomas were divided into two groups, a tumor group with metastasis (M+ group, 27 cases) and a tumor group without metastasis (M- group, 11 cases). Results The frequency of loss expression of DPC4 protein was 32.8% in BTCa, 47.3 % in CBD carcinoma ,11% in gallbladder carcinoma and 13% in HBD carcinoma. A comparison of the frequency of loss expression of DPC4 showed significantly statistical difference in the CBD carcinoma versus gallbladder carcinoma and HBD carcinoma (P < 0.01). The frequency of loss expression of DPC4 was 48.1 % in the M* group and 45.4% in the M" group. There was no significantly statistical difference between them (P>0.05). Conclusion There is a close relationship between the pathogenesis of BTCa and inactivation of DPC4 with different frequencies of DPC4 gene alteration in various locations of the biliary tract, but inactivation of DPC4 is not related with tumor metastasis in BTCa.

Effect of deleted pancreatic cancer locus 4 gene transfection on biological behaviors of human colorectal carcinoma cells

AIM: To investigate the effect of deleted pancreatic cancer locus 4 (DPC4) gene transfection on biological behaviors of human colorectal carcinoma cells and the role of DPC4 gene in colorectal carcinogenesis. METHODS: PcDNA3.1-DPC4 plasmid was re-constructed by gene-recombination technology. SW620 cells, a human colorectal carcinoma cell line, were transfected with PcDNA3.1-DPC4 plasmid using lipofectamine transfecting technique. Transfected cells were selected with G418. Expression of Smad4 protein was detected in cells transfected with DPC4 gene by immunohistochemistry and Western blot. Biological characterristics of transfected cells were evaluated by population-doubling time and cloning efficiency. Alterations of percentage of S phage cells (S%) and apoptosis rate were determined by flow-cytometry. RESULTS: PcDNA3.1-DPC4 plasmid was constructed successfully. SW620 cells transfected with PcDNA3.1-DPC4 plasmid (DPC4+-SW620 cells) showed a strong intracellular expression of Smad4 protein, and the positive signal was localized in cytoplasm and nuclei, mainly in cytoplasm, where the expressions of Smad4 protein in SW620 cells transfected with PcDNA3.1 plasmid (PcDNA3.1-SW620 cells) and non-transfected SW620 cells (SW620 cells) were weaker than those in DPC4+-SW620 cells. The population-doubling time in DPC4+-SW620 cells (116 h) was significantly longer than that in SW620 cells (31 h) and PcDNA3.1-Sw620 cells (29 h) (P<0.01). The cloning efficiencies of DPC4+-SW620 cells (12%) were markedly lower than those of SW620 cells (69%) and PcDNA3.1-Sw620 cells (67%) (P<0.01). Compared with SW620 cells and PcDNA3.1-Sw620 cells, the Go-G1% of DPC4+-SW620 cells was obviously higher and the S% was markedly lower (P<0.05). Apoptosis rate of DPC4+-SW620 cells was significantly higher than that of SW620 cells and PcDNA3.1-SW620 cells. CONCLUSION: PcDNA3.1-DPC4 plasmid can be successfully re-constructed and stably transfected into human SW620cells, thereby the cells can steadily express Smad4. DPC4 protein may regulate proliferation of colorectal carcinoma cells by inhibiting cell growth and inducing cell apoptosis.