Expression of Y box-binding protein-1 correlates with DNA topoisomerase IIalpha and proliferating cell nuclear antigen expression in lung cancer.

Y box-binding protein-1 (YB-1), a member of the DNA binding protein family, interacts with inverted CCAAT boxes (Y-boxes). Y-boxes are located on the promoter of numerous genes, such as DNA topoisomerase IIalpha (Topo IIalpha), proliferating cell nuclear antigen (PCNA) and multidrug resistance 1 (MDR1). In this study, we used immunohistochemical (IHC) staining to detect YB-1 expression in 59 lung cancer tissues and to evaluate whether YB-1 expression was associated with the expression of YB-1 target genes such as Topo IIalpha, PCNA and MDR1 in human lung carcinoma. Twenty-eight out of 59 cases (47.5%) were stained positive for YB-1 in the cytoplasm, while 30 out of 59 cases (50.8%) were positive for PCNA in the nuclei. Topo IIalpha-positive cells were detected in 16 out of 59 cases (27.1%). Eight out of 59 cases (13.6%) had greater than 5% P-gp positive cells expression. There was a significant correlation between the YB-1 and Topo IIalpha expression in small cell lung cancer (SCLC) (p=0.0242). YB-1 expression also correlated with PCNA expression in non-small cell lung cancer (NSCLC) (p=0.0001). Higher levels of YB-1 expression were associated with T3-4 and Stage III-IV tumors in adenocarcinomas (p=0.0072; p=0.0168). In contrast, no relationship was found between YB-1 expression and P-gp expression. Our study suggests that YB-1 expression correlates with Topo IIalpha and PCNA expression in lung cancer.