Nuclear expression of YB‐1 in diffuse large B‐cell lymphoma: correlation with disease activity and patient outcome

The aim of this study is to investigate the correlations among Y‐box binding protein‐1 (YB‐1) and P‐glycoprotein(P‐gp) and their prognostic significance in diffuse large B‐cell lymphoma (DLBCL). The expression of YB‐1 and P‐gp was examined immunohistochemically on 68 patients with DLBCL who were treated from 2003 to 2005. Samples were paraffin‐embedded newly diagnosed DLBCL tissues taken from the surgical specimens before adjuvant chemotherapy. We determined the prognostic significance of YB‐1 and its relationship with P‐gp in patients with DLBCL. Of the 68 tumors examined, 42 (61.8%) were positive for YB‐1 expression in the nucleus. The nuclear expression of YB‐1 was significantly associated with clinical stages, bone marrow involvement, extra nodal involvement, and poor response to chemotherapy. No associations were observed between P‐gp and clinical features, in context of the poor response to chemotherapy. Nuclear expression of YB‐1 was correlated significantly with increased expression of P‐gp patients with a nuclear YB‐1 tumor had a poorer prognosis than did those with a cytoplasmic YB‐1 tumor in all of the DLBCL patients (P = 0.035). Thus, correlation of YB‐1 and P‐gp emerged as a possible biomarker for unfavorable prognosis in DLBCL. It may provide useful information for clinicians to determine the appropriate therapy for each type of DLBCL.