Regulation of mRNA expression in drug-sensitive and drug-resistant gastric carcinoma cells is independent of YB-1 expression.

Y-Box protein 1 (YB-1) is a multifunctional cellular protein expressed in a range of mammalian cells, including human cancer cells. It is involved in the regulation of various genes including cancer-associated genes, but the full range of target genes and regulatory mechanisms have not been fully elucidated. To identify global mRNA expression patterns that are potentially regulated by YB-1, a previously established and well-characterized cell model derived from drug-sensitive (EPG85-257P/tetR/YB-1) and multidrug-resistant (EPG85-257RDB/tetR/YB-1) gastric carcinoma cells in which the expression of YB-1 can be inhibited by tetracycline-dependent activation of the RNA interference (RNAi) pathway, was analyzed by microarray technology. By this approach, various potentially regulated genes encoding members of important cellular pathways such as the Jak/STAT, VEGF and the MAP-kinase signaling pathways were identified. Independent validation of these findings by quantitative real-time reverse transcriptase polymerase chain reaction and Western blot did not confirm these regulatory effects. In conclusion, the findings suggest that YB-1 is not directly involved in the regulation of mRNA expression in drug-sensitive or drug-resistant gastric carcinoma cells.