Expression and clinicopathological significance of Mel-18 mRNA in colorectal cancer.

Mel-18 is a member of the polycomb group (PcG) of proteins, which are chromatin regulatory factors that play an important role in oncogenesis. This study was designed to investigate the clinical and prognostic significance of Mel-18 in colorectal cancer (CRC) patients. For this purpose, expression of Mel-18 mRNA was evaluated in 82 primary CRC and paired noncancerous mucosa samples by qRT-PCR and Western blotting. We found that overall Mel-18 mRNA expression in the CRC tissue was significantly lower than in the noncancerous mucosal tissue (p = 0.007, Wilcoxon matched-pairs signed-ranks test). Mel-18 was conversely correlated with the pathological classifications (p = 0.003 for T, p < 0.001 for N, and p = 0.015 for M classifications, respectively) and clinical AJCC stage (p < 0.001). Furthermore, CRC patients with a higher level of Mel-18 showed prolonged disease-free survivals (DFS) (p < 0.001). In multivariate analysis, the diminished Mel-18 expression may be a risk factor for the patients' 3-year DFS (HR = 1.895; 95 % CI 1.032, 3.477; p = 0.039). It was therefore concluded that the lower Mel-18 expression might contribute to the CRC development/progression.