Expression Of Mcm2 And Its Significance In Gastric Cancer

PURPOSE Minichromosome maintenance proteins(MCMs) are members of the prereplicative complex that is essential for eukaryotic DNA replication. They are only present within the nucleus throughout the cell cycle, but rapidly downregulated in differentiated cells. Recent studies have demonstrated MCMs are novel proliferation markers for tumor. The aim of this study is to determine the pattern and frequency of Mcm2 (a member of the family of MCMs) expression in gastric normal mucosa and cancer, and to assess the relationship between Mcm2 expression and clinicopathological characteristics of gastric cancer . In this study, the expression of Mcm2 is also compared with the expression of Ki-67 , another kind of markers for cell proliferation, to determine which is a better marker for gastric cancer.METHODS We examined the immunohistochemical staining of Mcm2 in gastric normal mucosa(n=23) and cancer(n=69), and quantified Mcm2 expression by calculating a labeling index(LI). And then, the pattern and LI of Mcm2 expression in normal mucosa and cancer were compared, and an analysis of the association between Mcm2 expression and traditional clinicopathological characteristics of gastric cancer was also carried out. The expression of Mcm2 was also compared with Ki-67. RESULTS Mcm2 expression in normal gastric mucosa is confined to the basalthird to second of gastric crypts but no expression in surface gastriccytes. The median of Mcm2 LI is 18%(5%~37%)in normal gastric mucosa. In gastric cancer, Mcm2 expression is seen throughout epithelium, including in surface gastriccytes. The median of Mcm2 LI in gastric cancer are 66% (4l%~90%) . The differences between normal mucosa and cancer are of statistical significance (P<0.00l=. There is no statistical significance between the LI of Mcm2 and some clinicopathological characteristics such as age, sex, dimension, histopathology, AJCCS stage, lymph node metastases and distant metastases. A significant association is also demonstrated between Mcm2 LI and the grade of gastric caner . Compared with the staining of Ki-67, Mcm2 stained a percentage of nuclei highest than Ki-67, and it is a better marker related to the grade of gastric cancer. CONCLUSION These data support the evidence that Mcm2 may serve as a reliable proliferation marker in gastric tissue and according to the pattern and LI of Mcm2 expression, it is feasible to discriminate between normal tissue and cancer. It implys that Mcm2 has potential to be a better diagonostic marker for gastric cancer than other markers such as Ki-67 . In addition, as Mcm2 LI is related to the grade of gastric cancer , it can predict the degree of differentiation in gastric cancer, which help to predict the clinical prognosis.