| Objective:Laterally spreading tumors (LSTs) are considered as a special subtype of superficial colorectal tumor, which stem from colon mucosa. They have different characteristics compared with protruded-type colorectal adenomas (PAs). The malignant potential of LSTs are higher than PAs, so they are given greater attention. However, the majority of studies on LSTs have focused on endoscopic diagnosis and therapy. Only a few reports concerned about the special growth patterns and high-cancer potential of LSTs. Our study aims to find out the special clinicopathologic and histopathological features of LSTs by comparing the age, gender, tumor size, location, tumor histoligy and grade of intraepithelial neoplasia of LSTs'and PAs'patients. At the same time, we detect the protein and mRNA expression of Wnt-1 and P-catenin in LSTs and PAs tissue, to examine activation of the Wnt/β-catenin pathway and its potential regulatory mechanisms in LSTs.Method:Twenty-three LSTs and twenty-four PAs were collected, and their clinicopathologic and histopathological features were compared in patient'age, gender, tumor size, location, tumor histoligy and grade of intraepithelial neoplasia. Reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) were used to detect the mRNA and protein expressions of Wnt-1 and P-catenin in LSTs and PAs tissue. SPSS1 statistic software was used to analyze the correlation of their abnormal expressions to laterally spreading tumor and protruded-type colorectal adenomas.Results:1,Clinicopathologic and histopathological features of patients:No significant difference was found in age, gender, tumor histology and grade of intraepithelial neoplasia between LSTs and PAs (P>0.05). The mean size of LSTs was significantly larger than that of PAs (30.9±16.2mm vs 16.2±6.2mm, P<0.001). There were significantly different in the location between LSTs and PAs (P<0.001). LSTs mainly located in rectum (47.8%) and right hemicolon (43.5%), whereas PAs mainly located in left hemicolon (62.5%), secondly in rectum (25%).2,IHC:Immunohistochemistry ofβ-catenin in normal mucosa was mainly expressed in cell membrane, cytoplasm only shown little expression, whileβ-catenin in LSTs and PAs were both observed the ectopic expression of cytoplasm and nucleus. The ectopic expression ofβ-catenin were significantly higher in LSTs than in PAs (P=0.006). Moreover, weak nucleus expression ofβ-catenin was found in 26.1% LSTs, but only in 4.2% PAs (P=0.035). Wnt-1 in LSTs and PAs were both found positive expression in cytoplasm, and the former were significantly higher than the latter (P=0.006). While in normal mucosa, Wnt-1 were expressed on absence, or only a small amount of expression. There was a positive correlation between the high expression of Wnt-1 and the ectopic expression ofβ-catenin in LSTs (rs=0.579, P<0.01).3,RT-PCR:The expression ofβ-catenin mRNA in LSTs (0.57±0.05) was slightly higher than that in PAs (0.51±0.09) and in normal mucosa (0.49±0.04), but it was no significant difference (P>0.05). The expression of Wnt-1 mRNA in LSTs was significantly higher than that in PAs (0.41±0.11 vs 0.23±0.04, P=0.017), while its expression was few in normal mucosa (0.05±0.02).Conclusions:1,LSTs are located more frequently in right hemicolon and are larger than PAs.2,We discovered increased expression of Wnt-1 and ectopic expression of P-catenin in LSTs tissue. Furthmore, there is a positive correlation between them. Our findings suggesting that activation of the Wnt/β-catenin pathway is more prevalent in LSTs than in PAs, which may be associated with its high malignant potential, and suggesting that Wnt-1 may be an upstream regulatory factor of ectopic expression ofβ-catenin. 3,The expression level of protein and mRNA ofβ-catenin was not parallel, which suggesting that the activation of the Wnt/β-catenin pathway may be not byβ-catenin abnormal increase in the level of transcription, but by the ectopic expression ofβ-catenin protein.
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