Expression Of β-catenin, MMP-7 And FasL In Colorectal Carcinoma And Their Interacting Relationship

The carcinogenesis in normal organism is a complicate process during which multiple factors, multiple genes and multiple phases get involved. The cell's malignant epitype is determined by the corresponding oncoproteins. Cells in advanced organism are highly differentiated. Different cells have different functions, but all cells hold the same genome. They behave differentially because of different gene expression. Gene expression is regulated by multiple signaling transduct pathways(STP). Each STP determines certain gene expression and protein synthesization, and eventually cell's function. Some oncogenes / tumor suppression genes related ontoproteins/ tumor suppression proteins are key factors in certain STPs. The activation of oncogenes or inactivations of tumor suppression genes may lead to abnormal turn on / off of STPs, which may be followed by a series of cascade amplification reaction, and end up with protein alteration in quantity and quality. From this aspect, we can say that it is the abnormal STPs alteration and sequential abnormal protein synthesization which induce the carcinogenesis.β-catenin is the core factor in Wnt STP. The Wnt STP is silent in mature body, while the abnormal β-catenin expression can activate Wnt STP and trigger various carcinogenesis. This helps us to understand the onset of colorectal carcinoma. Normally, the β-catenin protein expresses mainly in cell membrane, only a little in cytoplasm and none in nuclear. Pathologically, β-catenin re-activates Wnt STP as soon as it enters nuclei, there it combines with TCF/LEF(T cell factor/lymphoid enhancer factor) to formβ-catenin-TCF/LEF transcription complex which promotes following target gene's transcript.MMP-7 is one of the target genes of β-catenin-TCF/LEF transcription complex.Before, we thought that MMP-7 destroy some components of ECM(extracellular matrix) and play an important role in the process of tumor's infiltration and metastasis only. Recently, we find out that MMP-7 expresses highly in inflamed tissue and colorectal adenoma.In addition,not only it could decompound many substrates but it also activates Wnt STP on side way and actually promotes onset and progress of colorectal carcinoma.FasL is one of the substrates of MMP-7. It belongs to TNF family and is the natural ligand of Fas. FasL expresses highly in adenoma and carcinoma too. It can combine with the Fas + epithelium cells and Fas + T cell, and induces their apoptosis. At the same time, the interaction between FasL and MMP-7 disorders the immuno-microenviroment more, and finally makes tumor's immuno-escape possible, colorectal carcinoma is one of the common digestive malignant tumours. Due to the change of diet and living style, the incidence of this disease has been increasing significantly in our country. As other tumors, the mechanism of colorectal carcinogenesis is not clear. In this study, we tested the expression of P-catenin mRNA and P-catenin, MMP-7,FasL protein in different colorectal lesions, and analysed their interacting relationship, we tried to provide theoretic support for early diagnosis and therapy of colorectal carcinoma. Materials and methods:(1)A11 104 tissue specimens used in this study were resected surgically or endoscopically in Henan provincial People's Hospital and Henan provincial tumor Hospital from Jan.2003 to Jun.2004. The specimens were stored at -70°C and taken out till needed. The samples including 44 adenocarcinomas, 38 adenomas, 10 non-tumorous polyps and 12 normal colorectal mucosae were fixed in 4% polyoxymethylene(including 0.1%DEPC) and embedded in paraffin. (2)The expression oflB-catenin mRNA was detected by in situ hybridization and P-catenin, MMP-7 and FasL protein were detected by the standard streotavidion-peroxidase(S-P) immunohistochemistry technique.(3) The data was analysed by statistical software package SPSS 10.0 . A single-tailed a=0.05 was considered as statistical significance. Results:(l)The positive rates of P-catenin mRNA in adenocarcinomas, adenomas, non-tumorous polyps and normal colorectal mucosae are 66.7%,60.0%,71.0% and 70.5% respectively. P-catenin mRNA exist in all specimens and there is no differences among these four groups ( P>0.05 ) .But the positive degrees in adenocarcinomae and adenomas are significantly higher than it in non-tumorous polyps and normal colorectal mucosae (PO.01), and the positive degree in adenocarcinomae is significantly higher than adenomas (PO.01). (2)The membranous expression ofp-catenin protein exists in most of normal colorectal mucosae, non-tumorous polyps and adenomas, only a few of them absent membranous expression. The absent rate is 8.3%, 10.0% and 13.4% respectively and there are no statistic differences (P>0.05) . The absent membranous expression ofp-catenin protein appeares in major adenocarcinomas and the absent rate is 72.7%,which is significantly higher than another three groups(PO.Ol). The absent membranous expression of p-catenin protein has no correlation with sex, age, site, lymph node metastasis and Duke's stage of colorectal carcinoma (P>0.05). There is a tendency that poorly differentiated colorectal carcinomas have a correspondingly less membranous expression of p-catenin protein (PO.05) .(3) The heterotopical expression rates of P-catenin protein in normal colorectal mucosae group and non-tumorous polyps group are 25.0% and 30.0% respectively and there is no statistical differences (P>0.05). The heterotopical expression rates in adenomas group and adenocarcinomas group are 81.6% and 90.9% respectively, which are significantly higher than another groups(PO.Ol), but there is no statistical difference between them (P>0.05) .The heterotopical expression of P-catenin protein has no significant correlation with sex, age, differentiation, site, lymph node metastasis and Duke's stage of colorectal carcinoma (P>0.05) .(4) The positive rates of cytoplasmic expression of p-catenin in normal colorectal mucosae group and non-tumorous polyps group are 25.0% and 30.0% respectively and there is no statistical differences (P>0.05) .The cytoplastic expression in adenomas group and adenocarcinomas group are 81.6% and 90.9% respectively, thereis no statistical difference (P>0.05), but they are significantly higher than another two groups(P <0.01). Also the positive degree in adenocarcinomae is significantly higher than adenomas(P<0.05).(5) All the positive rates of nuclear expression of (3-catenin protein in normal colorectal mucosae group and non-tumorous polyps group is 0 ,while in adenomas group and adenocarcinomas group are29.5% and 68.1% respectively, which are significantly higher than another two groups(P<0.01). Both positive rate and positive degree of adenocarcinomas group are significantly higher than adenomas group(P<0.01).(6) )The positive rates of MMP-7 protein expression in normal colorectal mucosae group and non-tumorous polyps group are 8.3% and 10.0% respectively and there is no statistical differences (P>0.05) , while in adenomas group and adenocarcinomas group are 52.6% and 70.4% respectively and there is no statistic difference, but they are significantly higher than another two groups(PO.Ol). The positive degree in adenocarcinomae is significantly higher than adenomas(P<0.05).The MMP-7 protein expression had no correlation with sex, age and site of colorectal carcinoma (P>0.05), but there is a tendency that the poorly differentiated colorectal carcinomas have more membranous expression of MMP-7 protein(P<0.05). The MMP-7 protein expressions in the C stage of Duke's group with lymph metastasis group are higher than the A, B stage of Duke's group without lymph metastasis group respectively (PO.05).(7) The positive rates of FasL protein expression in adenocarcinomas, adenomas, non-tumorous polyps and normal colorectal mucosae are 0> 10.0%> 34.2% and 63.6% respectively, the positive rates are significantly higher in adenocarcinoma group than adenomas group, non-tumorous polyps group and normal colorectal mucosae group(P<0.01, PO.05). There is also a tendency that the poorly differentiated colorectal carcinomas have more membranous expression of FasL protein. The positive rates in low differentiated group is higher than it in moderate and high differentiated group(P<0.05),and the C stage of Duke's group with lymph metastasis group are higher than the A, B stage of Duke's group without lymph metastasis group respectively (PO.05).(8)There are 5 positive correlations among the abnormal expressions ofp-catenin mRNA , P-catenin protein , MMP-7 protein and FasL protein.? the high expression of P-catenin mRNA with the heterotopical expression of P-catenin protein;? the positive rates ofp-catenin protein in cytoplasm with its positive rates in nuclei;@the heterotopical expression of P-catenin protein with the positive rates of MMP-7 protein expression;@the positive rates of MMP-7 protein expression with the rate ofp-catenin protein's absent membranous expression;? the positive rates of MMP-7 protein expression with the positive rates of FasL protein expression.(all above correlationships PO.01). conclusions:(l)the uprising ofp-catenin gene expression is at transcriptional level and it may be one of the causes which lead to high expression of P-catenin protein. Thep-catenin protein is highly expressed even in adenomas, then it accumulates in cytoplasm and enters the nuclei step by step and make carcinogenesis ultimately. At the same time, its normal membranous expression lost gradually, which diminishes the P-catenin-depended inter-celluar adhesive function and then cancer cells fall off more easily.It can be said that the high expression of P-catenin gene and protein play an important role in the arising and development of colorectal cancer. (2)MMP-7 protein expressed highly in adenomas , which suggested it is an early event during the conversion of colorectal adenoma—? carcinoma. (3)the heterotopical expression of p-catenin protein is positively correlated with the positive rates of MMP-7 protein expression. Not only mmp-7 is a target gene of the Wnt signaling transduct pathway but also could it activate Wnt STP on side road, It composed a positive feedback of P-catenin—MMP-7—p-catenin. (4)FasL protein also expresses highly in adenomas and much higher in colorectal carcinoma, which suggested it is an early event during the conversion of colorectal adenoma—> carcinoma, too.(5)The positive rates of MMP-7 protein and FasL protein expression are positively correlated. Their collective high expressions cooperate with each other during the carcinogenesis of colorectal carcinoma.(6)The abnormal expressions of P-catenin mRNA and P-catenin, MMP-7 and FasL protein are all early events and they interact with each other during the carcinogenesis in colorectal carcinoma. Detection of above factors may be great helpful in thediagnosis, prevention and therapy of colorectal carcinoma.