Expression And Significance Of Matrix Metalloproteinase-7 In Ameloblastoma

IntroductionAmeloblastomas(ABs)is a benign pleomorphic tumor arising from odontogenic epithelium.The biological behaviour of ABs is characterized by a local invasion and a high risk of recurrence.ABs is the most frequently encountered odontogenic tumor,the frequency of which is 59.3%in China.Although ABs is benign tumor,it can infiltrate trabecula of bone.If it occurs in mandible ascending branch and maxillary molar region, it can directly extend to fossa orbitalis,maxillary antrum or basalis,and threat human life.Extracellular matrix(ECM)is the main barrier in invasion and metastasizs of tumor cells.Tumorous invasion and metastasis begin with the degradation of ECM resulting from various proteolytic enzyme,such as matrix metalloproteinases(MMPs). Matrix metalloproteinase-7(MMP-7),the smallest member of MMPs,is also defined as matrilysin.Its expression is closely associated with malignant tumours' occurrence and patients' prognosis.The function and regulation mechanism of MMP-7 and its expression in tumor remain to be unclear.The present study aims to detect the expression of MMP-7 mRNA and MMP-7 protein in human ABs by Immunohistochemistry(IHC),Westem Blot,RT-PCR,and to discuss the association between MMP-7 and the biological behaviour of human ABs, and evaluate the important role of MMP-7 in tumor occurrence and development.Materials and methods1.IHC:A total paraffin blocks were collected from College of Stomatology and the First Affiliated Hospital of China Medical University between 2001 and 2007.The expression and distribution of MMP-7 proteins are detected by immunohistochemical technique in 100 cases of ABs(8 ABs carcinoma),27 cases of normal oral mucosas (NOM,bucco-mucosa,gum),26 cases of keratocystic odontogenic tumors(KCOTs). Classification is done according to the depth of the color and the proportion of the masculine cell.2.Western Blot and RT-PCR analysis:The freeze specimens detected were collected from the Pathology Department of College of Stomatology,China Medical University between 2004 and 2006.The expressions of MMP-7 proteins are detected by Western Blot in 18 cases of ABs,2 cases of NOM.The expressions of MMP-7 mRNA are detected by TR-PCR in 21 cases of ABs,3 cases of NOM.Results1.IHC:The immunohistochemical staining showed that MMP-7 obviously expressed in human primary ABs,recurrent ABs,ABs carcinoma,and KCOTs.KCOTs had the highest positive rate(96.15%),followed by recurrent ABs(91.43%),primary ABs(87.72%).MMP-7 also expressed in NOMs and the positive rate of which was 70.37%.Using Fisher exact probabilities in 2×2 table x~2 test,we found that there were significant differences between KCOTs and NOMs(P=0.024),benign ABs NOMs (P=0.029),recurrent ABs and NOMs(P=0.045),ABs and NOMs(P=0.029).But there was no significant difference between NOMs and primary ABs(P=0.069),NOMs and ABs carcinoma(P=0.648),KCOTs and ABs(P=0.457),including primary ABs (P=0.425),recurrent ABs(P=0.629)and ABs carcinoma(P=0.421).MMP-7 was detected in the plasma of peripheral columnar or cuboidal cells and central polyhedral cells of odontogenic epithelium,most of which were moderately and weakly positive. The expressions of MMP-7 had heterogenicity.Strong positivity was found in well differentiated keratinocytes,while negativity or weakly positivity in primary embryonic cells.The expressions of MMP-7 in the plasm of phlogotic cells,vascular endothelial cells and fibrocytes were also positive.In normal mucosas,MMP-7 was detected in surface layer and the superficial layer of stratum spinosum.In ABs carcinoma,the expressions of MMP-7 were moderately positive or weakly positive.2.Western Blot and RT-PCR analysis:Western Blot analysis showed the expression of MMP-7 obviously increased in all 18 ABs.But almost no expression was detected in 3 normal mucosas.There were significant differences between ABs and NOMs(t=2.245,P=0.038).RT-PCR results showed that MMP-7 espressed in 7 of 15 ABs(33.33%)were positive,and no expression of MMP-7 was found in 3 NOMs. There were significant differences between ABs and NOMs(t=3.030,P=0.007).3.Statistical analysis:There was no relation between the expression of MMP-7 mRNA and MMP-7 protein(r=0.333,P=0.290).Conclusions1.The protein and mRNA levels of MMP-7 in ABs were higner than those in NOM.2.MMP-7 might involve in the occurrence and development of ABs.The ability of invasion and the risk of recurrence of ABs were correlated with the high expression of MMP-7.