Expression and phosphorylation of translation regulatory protein 4E-binding protein (BP)-1 in low-risk diffuse large B cell lymphoma

Abstract

Protein translation initiation is controlled by eukaryotic initiation factor 4E (eIF-4E) binding protein 1 (4E-BP1). Phosphorylated 4E-BP1 dissociates from eIF-4E, allowing translation of transcripts mediating cell cycling, survival, and angiogenesis. The expression and phosphorylation of 4E-BP1, and influence on prognosis of diffuse large B cell lymphoma (DLBCL), is unknown. Because at least some patients with low-risk (International Prognostic Index score 0–2) DLBCL treated with standard anthracycline-based chemotherapy experience a short survival, we examined if 4E-BP1 expression and phosphorylation may provide additional prognostic information in 35 patients with low-risk DLBCL. We examined their initial diagnostic pathology specimens for 4E-BP1 expression and phosphorylation using immunohistochemistry, and we correlated these with clinical outcomes. While 4E-BP1 was uniformly expressed, there was wide distribution in its level of phosphorylation (biological activity). 4E-BP1 phosphorylation correlated strongly with overall survival (OS; P = 0.007) and progression-free survival (PFS; P = 0.02) and was the most significant independent variable for both OS and PFS on multivariable analysis. Our findings suggest that immunohistochemical evaluation of 4E-BP1 phosphorylation may help refine the prognostication of patients with low-risk DLBCL. Prospective studies in an independent cohort of patients are warranted.