Overexpression of B cell–activating factor of TNF family (BAFF) is associated with Helicobacter pylori–independent growth of gastric diffuse large B-cell lymphoma with histologic evidence of MALT lymphoma

Abstract

We have recently demonstrated that nuclear expression of BCL10 predicts Helicobacter pylori (HP) independence of early-stage gastric diffuse large B-cell lymphoma (DLBCL) with histologic evidence of mucosa-associated lymphoid tissue (MALT). In this study, we examined the role of B cell-activating factor of TNF family (BAFF) in mediating BCL10 nuclear translocation and HP independence of gastric DLBCL (MALT). We used immunohistochemistry and immunoblotting to measure the expression of BAFF, pAKT, BCL3, BCL10, and NF-kappaB. Transactivity of NF-kappaB was measured by electromobility shift assay. In lymphoma samples from 26 patients with gastric DLBCL (MALT), we detected aberrant expression of BAFF in 7 of 10 (70%) HP-independent and in 3 of 16 (18.8%) HP-dependent cases (P = .015). BAFF overexpression was associated with pAKT expression (P = .032), and nuclear expression of BCL3 (P = .014), BCL10 (P = .015), and NF-kappaB (P = .004). In B-cell lymphoma Pfeiffer cells, BAFF activated NF-kappaB and AKT; the activated NF-kappaB up-regulated BCL10, and the activated AKT caused formation of BCL10/BCL3 complexes that translocated to the nucleus. Inhibition of AKT by LY294002 (a PI3K inhibitor) blocked BCL10 nuclear translocation, NF-kappaB transactivity, and BAFF expression. Our results indicate that autocrine BAFF signal transduction pathways may contribute to HP-independent growth of gastric DLBCL (MALT).