We also found that gastric tumor tissues expressed significantly higher Bmi-1, and Bmi-1 overHM781-36B expression correlated with lymph node metastasis, or clinical stage, which was accordance with the results Evofosfamide cell line in in vitro study that knockdown

of Bmi-1 expression was accompanied by decreased transformed phenotype and migration ability in gastric cancer cell lines [33]. In these studies Bmi-1 was detected at protein level by IHC method. Here we detected Bmi-1 at mRNA level by QRT-PCR method and found that Bmi-1 is overexpressed in gastric tumors and Bmi-1 overexpression correlates with tumor size, depth of invasion (T classification), or lymph node metastasis (N classification), which confirms previous observation of Bmi-1 at protein level. It suggests that Bmi-1 may play a crucial role and act as an oncogene in gastric cancer, and associated with the carcinogenesis, progression, and metastasis of gastric cancer. Mel-18 was originally cloned from B16 mouse melanoma cells [62]. Mel-18 may bind to the nucleotide sequence 5′-GACTNGACT-3′, which is present in the promoter region of certain genes. One of the unique target genes of Mel-18 is c-Myc transcriptionally repressed

by Mel-18. In mature OSI 906 resting B cells, Mel-18 negatively regulates B cell receptor-induced proliferation through the down-regulation of the c-Myc/cdc25 cascade [63, 64]. Our previous studies suggest that Mel-18 is a physiologic regulator of Bmi-1 expression and transcriptionally down-regulates Bmi-1 expression during senescence in human fibroblasts and acts as a tumor suppressor in breast cancer [38, 43]. Our previous data also showed an inverse correlation between Bmi-1 and Mel-18 expression at protein level in breast cancer and gastric cancer [33, 38]. However, there was no correlation between Mel-18 expression at protein level and clinicopathological Ibrutinib purchase factors in in vivo study, which was

not accordance with the results in in vitro study that Mel-18 overexpression was accompanied by decreased transformed phenotype and migration ability in gastric cancer cell lines[33]. One of the reasons may due to the reliability of IHC method depends on the specific of antibody. Mel-18 antibody is rabbit polyclonal and it’s specific is not so good as Bmi-1 antibody which is mouse monoclonal. So we suspect the results of Mel-18 expression in tumor tissues at protein level detected by IHC may be not too reliable. To clarify this problem and further explore the role of Mel-18 in gastric cancer, we detected it’s expression at mRNA level by QRT-PCR in the present study. We found that most gastric tumor tissues (64.79%) expressed decreased mRNA levels of Mel-18, and there was a strong negative correlation between Bmi-1 and Mel-18 expression at mRNA level. The results confirm the expression of Mel-18 and its’ relationship with Bmi-1 at protein level in our previous study.