No abstract

Overexpression of CD30 and constitutive NF-kappaB activation characterizes tumor cells of Hodgkin's disease (HD), Hodgkin and Reed-Sternberg (H-RS) cells. We report that in H-RS cells overexpression of CD30 leads to self-aggregation, recruitment of TRAF2 and TRAF5, and NF-kappaB activation, independent of CD30 ligand. CD30 and TRAF proteins co-localized in H-RS cell lines and in lymph nodes of HD. An adenovirus-vector carrying a decoy CD30 lacking the cytoplasmic region or a dominant negative IkappaBalpha mutant blocks NF-kappaB activation, down regulates IL-13 expression and induces apoptosis. Thus, in H-RS cells, ligand-independent activation of CD30 signaling drives NF-kappaB activation and this leads to constitutive cytokine expression, which provides a molecular basis for HD. Inhibition of NF-kappaB activation by adenovirus vector-mediated gene transfer may provide a novel strategy of cell- and target molecule-specific therapy for patients with HD.

Signals emanated from CD30 can activate the nuclear factor B (NFB). The two conserved subdomains, D1 and D2, in the C-terminal cytoplasmic region of CD30 were tested for interaction with two tumor necrosis factor receptor-associated factor (TRAF) proteins with NFB activating capacity, TRAF2 and TRAF5. TRAF5 is the newest member of the TRAF family that binds to lymphotoxin ␤ receptor and CD40. TRAF5, as well as TRAF2, interacted with the D2 subdomain of CD30 in vitro and in vivo. Deletion analysis by the yeast twohybrid system revealed that the C-terminal 22 and 30 amino acid residues are dispensable for interaction of TRAF5 and TRAF2 with CD30, respectively. Substitution of alanine for threonine at 463 abolished the interaction with TRAF2. Overexpression of the TRAF domain of TRAF2 or TRAF5 showed a dominant negative effect on CD30-mediated NFB activation. Simultaneous expression of these TRAF domains further suppressed the NFB activation, suggesting an interplay of these TRAF proteins. Expression of TRAF2 and TRAF5 mRNA was demonstrated in T-and B-cell lines that express CD30. Taken together, our results indicate that TRAF2 and TRAF5 directly interact with CD30 and are involved in NFB activation by CD30 signaling.CD30 is a member of TNF 1 receptor superfamily that comprises a group of cysteine-rich receptor proteins such as CD27, CD40, and Fas antigen (1-4). Biochemical studies of CD30 as well as functional studies of the ligand for CD30 (CD30L) provided strong evidence to support regulatory roles for CD30 in lymphocytes (5-7). CD30L induces various biological effects on human CD30-positive cell lines such as activation, proliferation, differentiation, and cell death, depending on cell type, stage of differentiation, transformation status, and the presence of other stimuli (7). Recently, it was reported that CD30-deficient mice showed impaired negative selection in the thymus (8) and that CD30 is involved in signaling TCR-mediated cell death of T-cell hybridoma (9). As for signal transduction of CD30, Ellis et al. reported the induction of Ca 2ϩ influx by cross-linking CD30 on Jurkat cells (10), and signals mediated by CD30 were seen to regulate gene expression through activation of NFB (11,12).Because the cytoplasmic tail of receptors of the TNF receptor family does not have intrinsic catalytic activity such as kinase activity, it was considered that molecules that associate with these receptors mediate signal transduction. Putative signal transducing proteins that associate with TNF receptor type II were cloned and named TNF receptor-associated factor (TRAF) 1 and 2 (13). Subsequently, TRAF3 or CRAF1 (CD40 bp, CAP1, LAP1) was identified as the CD40 signal transducing molecule reviewed in Ref. 18). We have recently cloned TRAF5 that associates with lymphotoxin ␤ receptor and CD40 and mediates NFB activating signals (19,20).We have found that an approximately 100-amino acid sequence of the C-terminal region of the CD30 cytoplasmic region was highly conserved among human, rat, and mouse CD30 protein, and in thi...

High expression of CD30 and JunB is characteristic of tumor cells in anaplastic large cell lymphoma (ALCL) and Hodgkin lymphoma (HL). Possible interactions of CD30 and JunB were examined in this study. We found that the CD30 promoter in tumor cells of both nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK)-positive and NPM-ALK-negative ALCL and HL is regulated by a constitutively active CD30-extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK). Phosphorylation of ERK1/2 MAPK was confirmed in nuclei of tumor cells in both ALCL and HL. CD30-ERK1/2 MAPK signals induce JunB expression, which maintains high activity of the CD30 promoter. JunB induction seems to be largely independent of nuclear factor KB in ALCL and HL. These results show a common mechanism of CD30 overexpression in ALCL and HL, although the outcome of CD30 signaling differs between NPM-ALK-positive ALCL and NPM-ALK-negative ALCL, cutaneous ALCL, and HL as we recently reported. (Cancer Res 2005; 65(17): 7628-34)