| Backround The recently identified PTEN/MMAC1/TEP1 gene is the first tumor suppressor which has sequence homology with dual-specificity phosphatase. PTEN is a multifunctional protein endowed with a phosphatase activity capable of dephosphosphorylating both tyrosinephosphate, serine/threonine phosphate residues on proteins and phospholipids of the phosphatidy linositol pathway[1-3]. PTEN appears to be mutated at considerable frequency in several types of human tumors, including those from brain, breast, endometrium, and prostate[4-6]. PTEN play an important role in pathogenesis of tumor, tumor cell invasion and metastasis. In this experiment, we investigated the expression of PTEN in oesophagus carcinoma tissue, normal oesophageal epithelium tissue, three types of cell line-SHEE (an immortalized human fetal esophageal epithelial cell line induced by HPV 18 E6E7 AAV, the cell line has propagated continuously for more than 50 passages, the phenotype keeps the characteristics of primary epithelial cells), SHEEMT (a malignantly transformed immortalized esophageal epithelial cell line) and EC8712 (poor-differentiated esophageal squamous carcinoma cell line).Objective The research aims to detect expression of PTEN in esophageal squamous cell carcinomas with the SABC immunohistochemistry method to study the relationship between its expression with pathological grade of esophagus cancer, and three typesof cell line on different differentiation phase of esophageal squamous epithelial cell were examined the PTEN expression by means of cytometry and Western blot methods.Methods1. Immunohistochemistry The expression level of PTEN was detected with the SABC immunohistochemistry method in 56 cases of paraffin-embedded oesophageal squamous cell carcinoma tissues, with 32 samples paired with normal tissue. The relationship between the geneexpression and clinicopathological features was analyzed. Furthermore, three types of cell line, including SHEE, SHEEMT and EC8712 were cultivated and were also investigated by SABC immunohistochemistry method;2. Flow cytometry Three types of cell line were quantitatively examined by flow cytometry methods for the oncogene PTEN expression. Using goat anti-mouse IgG-FITC labeling and flow cytometry, we analyzed distributive image of PTEN content in cell of immortalized esophageal epithelium and esophageal carcinoma cell and compared its expression with WinMDI 2.9 software;3. Western blot Three types of cell line were cultured and were quantitatively examined by western blot methods for the oncogene PTEN expression. The OD of PTEN expression in cell of immortalized esophageal epithelium and esophageal carcinoma cell was analyzed and compared with Quantityone-4, 2, 3 software.Results1. Immunohistochemistry Positive staining was observed in the cytoplasma as well as in the nucleus. Normal esophageal squamousepithelial cell uniformly showed strong PTEN expression, while in cancer tissue, the positive expression was variable. Of the 56 carcinoma of esophagus cases, there 32 cases paired with normal squamous epithelium. No PTEN expression was detected in 3 out of 32 normal cases, 29 cases were positive for PTEN protein (90.63%). Of the 56 esophageal carcinoma cases, 27 lacked PTEN protein (48.22%). The positive rates of PTEN expression decreased progressively from nomal oesophageal epithelium (29/32) to oesophagus cancer (29/56), with significant difference (P<0.05). The expression level of grade I was higher than that of grade II, III(P<0.05), but the level of grade I was similar with grade II (P>0.05), the expression of PTEN in carcinoma had correlation with pathological stage (P<0.05). PTEN expression also show correlation with other factors as chorion invasion, but no correlation with lymphocytic infiltration; The immunohistochemistry result of cell lines showed the positive signals were found in cytoplasma and nucleus. The SHEE cell line expressed at higher level than SHEEMT cell line and...
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