The Primary Study Of Expression Of COX-2 And Its Mechanisms In Oral Squamous Cell Carcinoma

Background:In recent years, the research of cyclooxygenase-2 (COX-2) has been a hot topic in molecular oncology. COX-2, an important enzyme that catalyzes the synthesis of prostaglandins in inflammation and tumor, is overexpressed in a variety of malignant lesions. Increased levels of COX-2 may contribute to carcinogenesis by modulating xenobiotic metabolism, apoptosis, immune surveillance, invasion, metastasis and angiogenesis. And the invasion, metastasis and angiogenesis are important mechanisms of the tumorigenesis and progression in oral squamous cell carcinoma (OSCC). Molecular biology of tumors revealed that matrix metalloproteinase-9 (MMP-9), with proteolytic activity, may destroy the tissue boundaries through the degradation of basement membrane (BM) and extracellular matrix (ECM) proteins of oral mucosa epithelia and in consequence to invasion and metastasis. So it is considered to be one of markers which can accurately reflect the invasiveness and metastasis activity of tumors. Microvessel density (MVD) is the direct reflection of the number of tumor neovasculari-zation and can evaluate tumor angiogenesis properly. At present, little is known about study on the expression of COX-2 as well as its relationship with invasion, metastasis and tumor angiogenesis in OSCC. Objective:The aim of this present study is to investigate the expression of COX-2 MMP-9 and CD34, which determines MVD, in OSCC, to assess their correlations with the clinicopathologic features, and to evaluate the roles of COX-2 in tumorigenesis andprogression of OSCC by analyzing their relation with each other, so as to provide a potential new way and theory basis for early diagnosis, therapy and prognosis assessment of OSCC.Materials and methods:The analysis was performed retrospectively on 76 OSCC samples, 19 dysplastic oral mucosa (DOM) tissue samples and 12 normal oral mucosa tissue samples which were fixed in 4% paraformaldehyde phosphate-buffered saline and embedded in paraffin. No patients had received preoperative chemotherapy, radiation therapy or other biological therapy. PV-9000 two-step immunohistochemical method was used to detect the expression of COX-2. MMP-9 and CD34 in all samples, and MVD stained by CD34 was evaluated. Statistical analysis was performed with SPSS 10.0 software, using Pearson Chi-square test, Fisher's exact test, One-Way ANOVA, Independent-Samples T test and Spearman Correlation test. Statistically significant level was considered as "alpha equals 0.05". Results:1. COX-2 was localized in the cytoplasm and cell membrane in dysplastic and malignant epithelium rather than normal epithelium, and the staining pattern was predominantly brown and yellow granular; MMP-9 mainly was expressed in the pattern of brown and yellow granular in the cytoplasm of tumor cells, and rarely in tumor stromal cells; CD34 was expressed positively in the endothelial cells, showed as irregular ring or vessel bud of rose color.2. The COX-2 positive immunostaining rates was significantly higher in OSCC (81.6%) than that in NOM(8.3%, P<0.05) and in DOM(47.4%, P<0.05); In highly, moderately and poorly differentiation OSCC groups, the positive rates of COX-2 expression were 66.7%, 88.5% and 95.0% respectively, and a statistical significance for COX-2 was observed between the highly and moderately as well as poorly differentiation OSCC groups(P<0.05), but not between the moderately and poorly differentiation OSCC groups(P=:0.172); The results showed no significant difference between the groups divided by sex, age and lesion location(P>0.05), but was related with neck lymphnode metastasis, tumor size, local invasion and TNM stage (P<0.05).3. The MMP-9 positive immunostaining rates was significantly higher in OSCC (77.6%) than that in NOM(16.7%, P<0.01) and in DOM(42.1%, P<0.01); In highly,moderately and poorly differentiation OSCC groups, the positive rates of MMP-9 expression were 63.3%, 80.8% and 95.0% respectively, and a statistical significance for MMP-9 was observed between the poorly and moderately as well as highly differentiation OSCC groups(P<0.05), but not between the highly and moderately differentiation OSCC groups^^ 0.086); The results showed no significant difference between the groups divided by sex, age and lesion location(P>0.05), but was related with neck lymphnode metastasis, tumor size, local invasion and TNM stage (f<0.05).4. The MVD was significantly higher in OSCC (34.36ll4.99) than that in NOM(12.92 + 5.37, P < 0.01) and in DOM(25.32 + 7.90, P < 0.01); In highly, moderately and poorly differentiation OSCC groups, the MVD were 24.17 + 10.06, 32.70+10.34 and 51.80+10.18 respectively, and a statistical significance for MVD was observed among every OSCC groups (P<0.01); The results showed no significant difference between the groups divided by sex, age and lesion location^ > 0.05), but was related with neck lymphnode metastasis, tumor size, local invasion and TNM stage (P< 0.01).5. The expression of COX-2 had a positive correlation with that of MMP-9 (r= 0.641, F<0.01), and their expression had positive correlation with MVD respectively(r =0.509, F<0.01; r=0.527, /><0.01).Conclusion:The over expression of COX-2, MMP-9 and higher MVD in OSCC are remarkably related to neck lymphnode metastasis, tumor size, local invasion , TNM stage and histological grade; the over expression of COX-2 is one of early events in the course of OSCC development, COX-2 may promote the development of OSCC by improving the invasive and metastatic capacity of tumor cells and enhancing tumor angiogenesis activity, and COX-2 can be looked as a target for the prevention and treatment of OSCC.