Expression And Significance Of PIK3CA Gene In Different Pathological Changes Of The Vulvar Tissues

Expression and significance of PIK3CA gene in different pathological changes of the vulvar tissuesObjectivesVulvar squamous cell carcinoma(VSCC)approximately accounts for 80％～90ï¼…malignant female vulvar tumors. However, genetic study of it has been very limited for a long time and most of which is relevant report of mutation and expression of known single oncogene or suppressorgene. Up to now, there has been no report concerning VSCC-related gene colony. Phosphatidylinositol-3 kinase catalytic alpha(PIK3CA)is a recently-found oncogene encoding PIK3CA protein, namely PI3Kp110α. There is a close correlation between amplification and mutation of the oncogene and development and progression of many tumors, such as thyroid cancer, lung cancer, gastric carcinoma, pancrease carcinoma, hepatocellular carcinoma, endometrial carcinoma, cervical and ovarian cancer, etc. The study of PIK3CA gene in development and progression of vulvar carcinoma is still empty worldwide.We have detected significant amplification of chromosome 3q region where PIK3CA gene is located in VSCC tissues via Comparative Genomic Hybridization(CGH) technique in an early stage of our study. We plan to study and analyze semi-quantitatively expression of PIK3CA gene in pathological changes of the vulvar tissues via immunohistochemistry and image analysis in order to explore the role it plays in the development and progression of VSCC.Materials and MethodsImmunohistochemistrySample: 76 paraffin samples of pathological changes of vulvar tissues and normal vulvar tissues without radiotherapy, immumotherapy or chemotherapy, were collected from China Medical University, May 1997 to May 2005. VSCC 30 cases, Severe dysplasia and carcinoma in situ 16 cases, Mild and moderate dysplasia 20 cases. And additional normal vulvar skin tissue 10 cases for comparison.Reagent: Particular rabbit anti-human PIK3CA antibody purchased from Boshide biology Ltd. Corp. Streptavidin peroxidase(SP)reagent cases purchased from Zhongshanjinqiao Beijing Biology Ltd. Corp. Diaminobenzidine(DAB)purchased from FuzhouMaixin Biology Ltd. Corp. Self confected EDTA acid antigen repaired buffered liquid and 3ï¼…H₂O₂ liquid.Experimental Methods: The experiment was conducted by immunohistochemistry according to instructions of the reagent cases. The first antibody dilution concentration is 1∶75. This study used pre-existing positive sections as comparison samples, and used phosphate buffered saline(PBS)instead of the first antibody as negative comparison samples. Every sample is stained with Hematoxylin-eosin.Results Determination and Image Analysis: Result Determination: brown-yellow particles which distributed in the cytoplasm of vulvar epithelia of different pathological changes mean positive PIK3CA expression. Image Analysis: selected 6 complete and nonoverlapping fields of vision for each case, determined optical densities of immuno-reaction positive particles of PIK3CA and regarded the average value of the 6 optical densities as the ultimate value for each case.Statistical Analysis: To adopt Wilcoxon 2-Sample Test. A probability value＜0.05 was considered statistically significant.ResultsThe expression levels of PIK3CA in VSCC and severe dysplasia, carcinoma in situ were significantly higher than those in normal vulvar tissues and mild, moderate dysplasia(P＜0.01). There was no statistical significance between normal vulvar tissues and mild, moderate dysplasia as well as between VSCC and severe dysplasia, carcinoma in situ concerning PIK3CA expression(P＞0.05). In the VSCC group, the expression level of PIK3CA was associated with grade, clinical staging as well as lymph node metastasis status(P＜0.05).Conclusion1. Overexpression of PIK3CA is associated with development and progression of the VSCC.2. PIK3CA gene is expected to become an early diagnostic index of the VSCC.