Prognostic significance of pre B cell leukemia transcription factor 2 (PBX2) expression in non-small cell lung carcinoma

Previous studies on the mammary carcinoma cell line have shown that the pre B cell leukemia transcription factor 1 (PBX1) was a transcription factor for valosin-containing protein (VCP), which is involved in invasion and metastasis of cancers. The roles of PBX1 and PBX2, a highly homologous transcription factor to PBX1, for expression of VCP were examined in the cell lines from non-small cell lung cancer (NSCLC). The effects of PBX1 and PBX2 on VCP expression were examined with siRNA in A549 and PC14 NSCLC cell lines. Expression levels of PBX2 and VCP were immunohistochemically examined and compared with each other in 206 NSCLC cases. Subsequently, significance of PBX expression in clinical behavior of NSCLC patients was evaluated. Expression levels of VCP mRNA significantly decreased when PBX2 but not PBX1 expression was knocked down in NSCLC cell lines. Immunohistochemically, staining intensity of PBX2 was correlated with that of VCP in clinical samples. Then correlation of PBX2 expression and clinical behavior of NSCLC patients was evaluated. Univariate analysis revealed high expression levels of PBX2 and VCP to be poor prognosticators for overall and disease-free survival. Multivariate analysis revealed that high expression of VCP but not PBX2 to be an independent prognostic factor. PBX2 is a transcription factor for VCP in NSCLC. Because high levels of PBX2 expression correlated with prognosis of NSCLC, PBX2 could be a target molecule for treatment of NSCLC. (Cancer Sci 2009; 100: 1198–1209)