PTEN methylation is associated with advanced stage and microsatellite instability in endometrial carcinoma

Down-regulation of PTEN expression due to loss of promoter activity in human hepatocellular carcinoma cell lines

AIM: To investigate the regulation of phosphatase and tensin homolog deleted on chromosome ten (PTEN) gene expression in human hepatocellular carcinoma (HCC) cell lines.

METHODS: The mRNA and protein levels of PTEN were detected by Northern blot and Western blot in HCC cell lines, respectively. Plasmids containing different fragments of PTEN promoter with Luciferase reporter were constructed and transiently transfected into HCC cell lines to study the promoter activity. DNA analysis and RT-PCR were performed to detect the mutation of PTEN promoter and PTEN cDNA.

RESULTS: Either protein or mRNA levels of PTEN in L02 cells (as a control) were significantly higher than that in HCC cell lines. The profile of PTEN promoter activity in 8 cell lines was closely correlated with levels of PTEN mRNA and PTEN protein. Furthermore, the sequence analysis of 8 cells lines showed no mutation in the region of PTEN promoter and PTEN cDNA.

CONCLUSION: PTEN expression is down-regulated in HCC cell lines probably due to loss of activity of PTEN promoter.

Growth, invasion, metastasis, differentiation, angiogenesis and apoptosis of gastric cancer regulated by expression of PTEN encoding products

AIM: To investigate expression of PTEN in gastric cancer and to explore its roles in tumorigenesis and progression of gastric cancer.

METHODS: Formalin-fixed and paraffin-embedded tissues of adjacent non-tumor mucosa and primary foci from 113 cases of gastric cancers were studied for the expression of PTEN and Caspase-3 and microvessel density (MVD) by streptavidin-peroxidase (S-P) immunohistochemistry with antibodies against PTEN, Caspase-3, and CD34. The relationship between PTEN and Caspase 3 expression and clinicopathological parameters of tumors was compared.

RESULTS: Primary gastric cancer cells expressed PTEN less frequently than adjacent epithelial cells of primary foci (54.9% vs 89.4%; P = 0.000, χ² = 33.474). PTEN expression was significantly associated with invasive depth (P = 0.003, rs = 0.274), metastasis (P = 0.036, rs = 0.197), growth pattern (P=0.008, rs = 0.282), Lauren’s classification (P = 0.000, rs = 0.345), and histological classification (P = 0.005, rs = 0.262) of tumors, but not with tumor size (P = 0.639, rs = 0.045), Borrmann’s classification (P = 0.544, rs = 0.070) or TNM staging (P = 0.172, rs = 0.129). PTEN expression was negatively correlated with MDV in primary gastric cancer (P = 0.020, F = 5.558). Primary gastric cancer cells showed less frequent immunoreactivity to Caspase-3 than adjacent epithelial cells of primary foci (32.7% vs 50.4%; P = 0.007, χ² = 7.286). Caspase-3 expression was dependent of PTEN expression in primary gastric cancer cells (P = 0.000, χ² = 15.266).

CONCLUSION: Down-regulated expression of PTEN plays an important role in tumorigenesis, progression, growth, differentiation and angiogenesis of gastric cancer. Low expression of PTEN can decrease expression of Caspase-3 to disorder apoptosis of tumor cells, which might explain the molecular mechanisms of PTEN contributions to tumorigenesis and progression of gastric cancer.