AP1-dependent galectin-1 expression delineates classical hodgkin and anaplastic large cell lymphomas from other lymphoid malignancies with shared molecular features.

PURPOSE Galectin-1 (Gal1) is an immunomodulatory glycan-binding protein regulated by an AP1-dependent enhancer in Hodgkin Reed-Sternberg cells. We recently found that Reed-Sternberg cell Gal1 promotes the immunosuppressive T-helper 2/T-regulatory cell-skewed microenvironment in classical Hodgkin lymphoma (cHL). We sought to investigate whether the coordinate expression of activated AP1 pathway components and Gal1 serves as a diagnostic signature of cHL. In addition, because there are common signaling and survival pathways in cHL and additional non-Hodgkin lymphomas, we also evaluated whether the AP1/Gal1 signature is shared by other molecularly or morphologically related lymphomas. EXPERIMENTAL DESIGN We evaluated 225 cases of primary cHL and non-Hodgkin lymphoma for evidence of a functional AP1/Gal1 signature by immunohistochemical techniques. RESULTS Gal1 is selectively expressed by malignant Reed-Sternberg cells in >90% of primary cHLs, and Gal1 expression is concordant with the activated AP1 component, c-Jun. In contrast, diffuse large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and another Hodgkin-related entity, nodular lymphocyte-predominant Hodgkin lymphoma, do not express Gal1. However, anaplastic large cell lymphoma (ALCL), consistently expresses both Gal1 and its transcriptional regulator, c-Jun. The presence of activated c-Jun, indicative of functional AP1 activity, was confirmed by phospho-c-Jun immunostaining in cHL and ALCL. CONCLUSIONS These findings establish a functional AP1 signature that includes Gal1 expression in cHL and ALCL and suggests a common mechanism for tumor immunotolerance in these diseases. In addition, the combination of Gal1 and c-Jun serve as diagnostic biomarkers that delineate cHL and ALCL from other lymphomas with shared morphologic and/or molecular features.