Expression Of MDM2 Protein And RB Protein In Laryngeal Squamous Cell Carcinoma And Their Relationship

Objective : Laryngocarcinoma is in high morbidity of head and neck malignancies. It accounts for 13.9% of head and neck tumours and represents 2.1% of all malignancies. 96%-98% of the laryngeal malignant tumor is squamous cell carcinoma. The morbidity of the laryngocarcinoma progressed obviously in recent years. The causes of laryngeal squamous cell carcinoma have not yet fully understood. People think it has a relationship with gender, smoking, air pollution, leukoplakia of larynx and other factors. But more and more people related it to the changes of the gene expression nowadays.MDM2 is an evolutionarily conserved gene. It first be found in the BALB/C cells which are in spontaneous transformation when gene amplification was performed. Rb is the first tumor suppressor gene of the human being which was found in retinoblastoma cell and be cloned. In the cell growth regulation, the dephosphorylation form of the Rb protein can maintain the activation of the cells in G0 or G1 phase, suppress and control cell growth and proliferation, while the phosphorylation form released from this control and make the cells to enter to the DNA synthesis and mitotic phase. SV40LT Ag and other cancer genes play an important role in DNA replication and transformation of the virus. Because their combination with the Rb protein, people interested in the homology of the eukaryotic cells in which tumor suppressor protein can make a combination with the oncoprotein. MDM2 protein, similar to SV40LT Ag, can inhibit the transcription and regulatory function of Rb. But the relationship between MDM2 and Rb is unclear at present.Major study in this experiment is the expression of MDM2 protein and Rb protein in laryngeal squamous cell carcinoma. By observing the expression of MDM2 protein and Rb protein in laryngeal squamous cell carcinoma, precancerous lesions, vocal cord polyps, peritumoral normal laryngeal mucosa tissues, we investigate its specificity and relationship with the occurrence and development of the laryngeal squamous cell carcinoma as well as to find a reference index for the early diagnosis of laryngeal cancer ,pathological and clinical staging evaluation .This will provide molecular biology reference for the clinical treatment planning.Methods: 70 cases were choosed from 2008-2009 ENT of The Second Affiliated Hospital of Hebei Medical University with complete clinical data and be confirmed by pathological examination including 40 cases of laryngeal squamous cell carcinoma ,10 cases of peritumoral normal tissue group(from the edge of the tumor > 1.5cm),10 cases of vocal cord polyp group and 10 cases of precancerous lesion group(10 cases of adult laryngeal papilloma ). All the 40 laryngeal squamous cell carcinoma patients were male, aged from 54-71, have a mean age of 62.57. They all had no preoperative radiotherapy and chemotherapy and were pathologically confirmed as laryngeal squamous cell carcinoma. According to the International Anti - Cancer Coalition (UICC) 2002 standard which was separated by its clinical features,5 cases of stageⅠ,7 cases of stageⅡ, 16 cases of stageⅢ, 12 cases of stageⅣwere included. According to the degree graded by tumor differentiation,18 cases of well differentiated laryngeal squamous cell carcinoma, 12 cases of moderately differentiated laryngeal squamous cell carcinoma, 10 cases of poorly differentiated laryngeal squamous cell carcinoma were included. Each specimen was put into the 10% formalin fixative immediately after its surgical remove, conventional paraffin-embedding, serial sections by 5μm thick, deparaffinaged by xylene in convention, dehydrated by alcohol in gradient, endogenous peroxidase removed ,antigen repaired by microwave, MDM2 and RB immunohistochemical staining detected by SP method, DAB stain, hematoxylin stain, dehydrated, transparented ,mounted by gum.Statistical analysis: All experimental datas were analyzed using statistical software SPSS17.0, compared by X 2 test. Spearman rank correlation analysis was used to find the correlation between MDM2 protein and Rb protein, P <0.05 is statistically significant.Results: The positive expression of MDM2 protein in the peritumoral normal tissue, vocal cord polyps, laryngeal precancerous lesions and laryngeal squamous cell carcinoma have significant difference, an upgrade trend was showed.The positive expression of Rb protein in peritumoral normal tissue, vocal cord polyps, laryngeal precancerous lesions and laryngeal squamous cell carcinoma have significant difference, a degrade trend was showed.The positive expression of MDM2 protein in well differentiated,moderately differentiated laryngeal cancer,poorly differentiated laryngeal squamous cell carcinoma has significant difference,showed an upgrade trend.The positive expression of Rb protein in well differentiated laryngeal squamous cell carcinoma,moderately differentiated laryngeal squamous cell carcinoma,poorly differentiated laryngeal squamous cell carcinoma has significant difference,showed a degrade trend.The positive expression of MDM2 protein in theⅠ,Ⅱ,Ⅲ,Ⅳstage of laryngeal squamous cell carcinoma has significant difference, showed an upgrade trend.The positive expression of Rb protein in theⅠ,Ⅱ,Ⅲ,Ⅳstage of laryngeal squamous cell carcinoma has significant difference, showed a degrade trend.The over expression of MDM2 protein and the inactivation of Rb protein is closely related to the development of laryngeal cancer, showing negative correlation.Conclusion: The positive expression of MDM2 protein in peritumoral normal tissue,vocal cord polyps,laryngeal precancerous lesions and laryngeal squamous cell carcinoma was increased while the positive expression of Rb protein in peritumoral normal tissue,vocal cord polyps,laryngeal precancerous lesions and laryngeal squamous cell carcinoma was decreased. This two have a negative correlation in the expression of the laryngeal squamous cell carcinoma .So a combination of both can be used as indicators for early diagnosis of laryngeal carcinoma.The positive expression of MDM2 protein in laryngeal squamous cell carcinoma in well differentiated laryngeal squamous cell carcinoma, moderately differentiated laryngeal squamous cell carcinoma, poorly differentiated laryngeal squamous cell carcinoma which are graded by pathology and in all theⅠ,Ⅱ,Ⅲ,Ⅳstages which are graded by clinical features are increased by order while the positive expression of Rb protein in laryngeal squamous cell carcinoma in well differentiated laryngeal squamous cell carcinoma, moderately differentiated laryngeal squamous cell carcinoma, poorly differentiated laryngeal squamous cell carcinoma and in all theⅠ,Ⅱ,Ⅲ,Ⅳstages are decreased by order. The detection of the MDM2 and Rb protein expression in the laryngeal squamous cell carcinoma can be used as a reference index for the assessment of the pathological grade and the clinical stage as well as to provide molecular biology reference for the clinical treatment planning.