Expression and Phosphorylation of Eukaryotic Translation Initiation Factor 4E Binding Protein 1 in B-Cell Lymphomas and Reactive Lymphoid Tissues

Context.-Cap-mediated messenger RNA translation controlled by the eukaryotic initiation factor 4F (eIF-4F) complex plays a key role in human cancer. eIF-4F activity is controlled by a repressor binding protein (4E-BP1), which promotes translation when phosphorylated. Objective.-To examine the level of expression and phosphorylation of 4E-BP1 in various subtypes of B-cell lymphoma and reactive lymphoid tissues. Design.-Archival formalin-fixed, paraffin-embedded B-cell lymphoma samples and reactive lymphoid tissues were immunostained and examined for expression of 4E-BP1 and phosphorylated 4E-BP1. Expression of components of the eIF-4F complex and unphosphorylated and phosphorylated 4E-BP1 was confirmed using Western immunoblotting on lysates of frozen lymphoma samples and reactive tissues. Results.-Immunohistochemical analysis demonstrated weak to undetectable 4E-BP1 staining within benign, reactive germinal centers (N = 10). In contrast, 4E-BP1 was consistently expressed (moderate to strong staining) in 98% of various subtypes of mature B-cell lymphoma (N = 50). 4E-BP1 expression was also demonstrable in all 4 lymph nodes with in situ or partial involvement by follicular lymphoma and in all 12 cases of BCL2-negative lymphoma. The level of phosphorylation of 4E-BP1 in lymphomas, evaluated by immunohistochemistry, was heterogeneous. Conclusions.-The immunohistochemical expression pattern of 4E-BP1 exhibits regional and cellular specificity in reactive lymphoid tissues and may offer a diagnostic tool for distinguishing reactive follicles from neoplastic B-cell proliferations. (Arch Pathol Lab Med. 2011;135:365-371)