Expression and clinicopathological significance of Mel-18 and Bmi-1 mRNA in gastric carcinoma

The expression of Mel-18 and Bmi-1 in a series of 71 gastric cancer tissues and paired normal mucosal tissues distant from the tumorous lesion was assayed by quantitative real time RT-PCR. The correlation between Mel-18 and Bmi-1 mRNA expression, and between Mel-18 or Bmi-1 mRNA level and clinicopathological characteristics were analyzed.Expression of Mel-18 and Bmi-1 genes was variably detected, but overexpression of Bmi-1 mRNA and decreased expression of Mel-18 mRNA were the most frequent alteration. In addition, the expression of Bmi-1 and Mel-18 mRNA inversely correlates in gastric tumors. Moreover, a significant positive correlation between Bmi-1 overexpression and tumor size, depth of invasion, or lymph node metastasis, and a significant negative correlation between Mel-18 low-expression with lymph node metastasis or the clinical stage were observed.Our data suggest that Mel-18 and Bmi-1 may play crucial but opposite roles in gastric cancer. Decreased Mel-18 and increased Bmi-1 mRNA expression was associated with the carcinogenesis and progression of gastric cancer. It is possible to list Bmi-1 and Mel-18 as biomarkers for predicting the prognosis of gastric cancer.The Polycomb group (PcG) genes were first identified in Drosophila as a class of regulators responsible for maintaining homeotic gene expression throughout cell division [1], PcG genes are conserved from Drosophila to mammals, and the expression levels of mammalian PcG genes differ between different tissues and cell types [2], PcG genes act as epigenetic silencers during embryo morphogenesis with a central role in the nervous system, heart, and skeleton development [3-7].In addition, PcG members have been involved in the regulation of such adult processes as the cell cycle, X-inactivation, and hematopoiesis [8-14]. PcG expression is deregulated in some types of human cancer [15].Moreover, several PcG genes may regulate the self-renewal of specific stem cell types, suggesting a link between the maint