[Show abstract][Hide abstract] ABSTRACT: Management strategies of chronic phase chronic myelogenous leukemia (CML) have been revolutionized due to the discovery of a selective tyrosine kinase inhibitor, imatinib (Gleevec, STI571), which is substantially improving median survival. However, emergence of imatinib-resistance has put up a serious problem that requires novel treatment methods. Catechins, polyphenolic compounds in green tea, are gathering much attention due to their potential antitumor effects. So far (-)-epigallocatechin-3-gallate (EGCG), the most abundant component of catechin, has been shown to cause typical apoptosis in several tumor cell lines in most cases through activation of caspases. In this study, we showed that EGCG predominantly caused necrosis-like cell death via a caspase-independent mechanism in CML cells, K562 and C2F8, whereas imatinib induced the typical apoptotic cell death. Moreover, this caspase-independent cell death partially mediated the release of apoptosis-inducing factor, AIF, and serine protease, HtrA2/Omi, from the mitochondria to cytosol. In addition, EGCG enhanced the imatinib-induced cell death (P < 0.01) resulting in additive cell death in K562 cells and EGCG alone, effectively reduced the viability of imatinib-resistant K562 cells (P < 0.01). Catechin is a possible candidate for an antitumor agent that causes cell death in CML cells via a caspase-independent mechanism.
Cancer Science 02/2009; 100(2):349-56. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: C/EBPbeta plays a pivotal role in activation of human immunodeficiency virus type 1 (HIV-1) in monocytes/macrophages. However, mechanisms for functional regulation of C/EBPbeta remain uncharacterized. Previous studies indicated that NF-kappaB activation by tumor necrosis factor (TNF) receptor family, which activates TNF receptor associated factor (TRAF), induces HIV-1 expression. We found that TRAF signals activate HIV-1 LTR with mutations of NF-kappaB sites in promonocytic cell line U937, suggesting existence of an alternative HIV-1 activating pathway. In this study, we have characterized the signal transduction pathway of TRAF other than that leading to NF-kappaB, using U937 cell line, and its subline, U1, which is chronically infected by HIV-1. We show that signals downstream of TRAF2 and TRAF5 activate p38 MAPK, which directly phosphorylates C/EBPbeta, and that activation of p38 MAPK potently activates C/EBPbeta-mediated induction of HIV-1 gene expression. We also show TRAF2 and TRAF5 are expressed in monocytes/macrophages of spleen samples from HIV-1 infected patients. Identification of TRAF-p38 MAPK-CEBPbeta pathway provides a new target for controlling reactivation of latent HIV-1 in monocytes/macrophages.
Microbes and Infection 06/2007; 9(6):721-8. · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Overexpression of CD30 is the hallmark of Hodgkin and Reed-Sternberg (H-RS) cells and drives constitutive nuclear factor-kappaB activation that is the molecular basis for the pathophysiology of Hodgkin's lymphoma. Transcription of the CD30 gene is controlled by the core promoter that is driven by Sp-1 and the microsatellite sequences (MSs) that represses core promoter activity. To understand the mechanism(s) of CD30 overexpression in H-RS cells, we structurally and functionally characterized the CD30 MSs. Although the CD30 MS of H-RS cell lines was polymorphic, it was not truncated compared with that of control cells. A strong core promoter activity and constitutive Sp-1 binding were revealed in all cell lines examined irrespective of the levels of CD30 expression. In transient reporter gene assays, all MS clones derived from H-RS cell lines repressed the core promoter activity in unrelated cell lines, but not in the H-RS cell lines. An AP-1-binding site was found in the MS at nucleotide position of -377 to -371, the presence of which was found to relieve repression of the core promoter in H-RS cell lines but not in other tumor cell lines. H-RS cell lines showed constitutive and strong AP-1-binding activity, but other cell lines did not. The AP-1 complex contained JunB, whose overexpression activated reporter constructs driven by the CD30 promoter including the MSs, and was dependent on the AP-1 site. JunB expression was detected in H-RS cells in vitro and in vivo, but not in reactive cells or tumor cells of non-Hodgkin's lymphoma of diffuse large B-cell type. Transduction of JunB small interfering RNAs suppressed CD30 promoter activity in L428 cells but not in control cells. Taken together, overexpression and binding of JunB to the AP-1 site appear to relieve the repression of the core promoter by the CD30 MS in H-RS cells, which provide one basis for the constitutive overexpression of CD30 in Hodgkin's lymphoma.
American Journal Of Pathology 09/2003; 163(2):633-41. · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We previously reported that ligand-independent signaling by highly expressed CD30 in Hodgkin-Reed-Sternberg (H-RS) cells is responsible for constitutive activation of NF-kappa B. In the present study, we characterize the intracellular localization of tumor necrosis factor (TNF) receptor associated factor (TRAF) proteins in H-RS cells. Confocal immunofluorescence microscopy of cell lines derived from H-RS cells and HEK293 transformants highly expressing CD30 revealed aggregation of TRAF2 and TRAF5 in the cytoplasm as well as clustering near the cell membrane. In contrast, TRAF proteins were diffusely distributed in the cytoplasm in cell lines unrelated to Hodgkin's disease (HD) and control HEK293 cells. Furthermore, the same intracellular distribution of TRAF proteins was demonstrated in H-RS cells of lymph nodes of HD, but not in lymphoma cells in lymph nodes of non-Hodgkin's lymphoma. Dominant-negative TRAF2 and TRAF5 suppressed cytoplasmic aggregation along with constitutive NF-kappa B activation in H-RS cell lines. Confocal immunofluorescence microscopy also revealed co-localization of IKK alpha, NIK, and I kappa B alpha with aggregated TRAF proteins in H-RS cell lines. These results suggest involvement of TRAF protein aggregation in the signaling process of highly expressed CD30 and suggest they function as scaffolding proteins. Thus, cytoplasmic aggregation of TRAF proteins appears to reflect constitutive CD30 signaling which is characteristic of H-RS cells.
American Journal Of Pathology 06/2002; 160(5):1647-54. · 4.60 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: We earlier identified a variant of CD30 (CD30v) that retains only the cytoplasmic region of the authentic CD30. This variant is expressed in alveolar macrophages. CD30v can activate the nuclear factor-κB (NF-κB) as CD30, and its overexpression in HL-60 induced a differentiated phenotype. To better understand the physiological and pathological functions of CD30v, expression of this variant was examined using a multiple approach to examine 238 samples of human malignant myeloid and lymphoid neoplasms. Screening by reverse transcriptase-polymerase chain reaction (RT-PCR) revealed expression of CD30v transcripts in 52 of 72, 7 of 11, 63 of 90, and 7 of 30 samples of acute myeloid leukemia (AML), myeloid blast crisis of myeloproliferative disorders (MBC), and lymphoproliferative disorders (LPDs) of B- and T-cell origin, respectively. CD30v expression was high in monocyte-oriented AMLs (FAB M4 and M5), B-cell chronic lymphocytic leukemia (B-CLL), and multiple myeloma (MM). Using the specific antibody HCD30C2, prepared using a peptide corresponding to the nine amino acids of the amino-terminal CD30v, expression of CD30v protein was detected in 10 of 25 and 2 of 10 AML and ALL samples, respectively. In AMLs, immunocytochemical detection of CD30v revealed the presence of loose clusters of CD30v-expressing cells dispersed amid a population of CD30v-negative blasts. Finally, the parallel expression of CD30v mRNA and protein, as evidenced by Northern and Western blotting, was confirmed in selected cases of AMLs and LPDs. A significant correlation was found between expressions of CD30v and CD30 ligand transcripts in AML and LPD (P = 0.02, odds ratio = 3.2). The association of CD30v with signal-transducing proteins, tumor necrosis factor receptor-associated factor (TRAF) 2, and TRAF5 was demonstrated by coimmunoprecipitation analysis, as was demonstrated for authentic CD30 protein. Expression of transcripts for TRAF1, TRAF2, TRAF3, and TRAF5, as demonstrated by RT-PCR, was noted in leukemic blasts that express CD30v. Collectively, frequent expression of CD30v along with TRAF proteins in human neoplastic cells of myeloid and lymphoid origin provide supportive evidence for biological and possible pathological functions of this protein in the growth and differentiation of a variety of myeloid and lymphoid cells.
American Journal Of Pathology 12/1999; · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Signals emanated from CD30 can activate the nuclear factor κB (NFκB). 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 NFκB activating capacity, TRAF2 and TRAF5. TRAF5 is the newest member of the TRAF family that binds to lymphotoxin β
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 two-hybrid 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 NFκB activation.
Simultaneous expression of these TRAF domains further suppressed the NFκB 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 NFκB activation by CD30 signaling.
Journal of Biological Chemistry 01/1997; 272(4):2042-2045. · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CD30 is a member of the tumor necrosis factor receptor superfamily, which is expressed on some activated lymphocytes, virus-infected cells and transformed lymphocytes. To facilitate our understanding of biological functions and functional domains, we isolated rat cDNA clones encoding the rat homolog of human CD30 from a cDNA library of a rat T-cell line, TARL-2. The nucleotide sequence of the cDNA showed 73% homology with that of human CD30. The deduced rat CD30 protein consisted of 493 amino acids with an M(r) of 59 160 and contained a single transmembrane domain. It lacked the second repeat of the cysteine-rich motif in the extracellular domain found in human CD30. The amino acid sequence showed 51.8 and 61.2% identity with the cysteine-rich and the cytoplasmic domains, respectively. In the cytoplasmic domain, however, the amino acid sequence was highly conserved in about 100 residues near the C-terminus showing 77.7% identity, whereas the rest of the cytoplasmic domain showed 45.2% identity. This conservation suggests the functional importance of this region. Comparison with the recently reported mouse CD30 revealed 83.7% conservation of the amino acid sequence and a common structure of the extracellular domain which lacks the second cysteine-rich motif. Northern blots revealed a 3.4-kb mRNA in the PHA-activated spleen cells and human T-cell leukemia virus type 1 (HTLV-1)-infected rat T-cell lines, whereas smaller transcripts of 2.3 kb were found in the lung. A rabbit polyclonal antibody raised against GST-fusion protein of the cytoplasmic domain detected bands with an apparent M(r) of 80 kDa and 100- 110 kDa expressed in TARL-2 and spleen cells. Transient overexpression of rat CD30 in TARL-2 cells activated HIV LTR in a NF-kappa B site-dependent manner, indicating that CD30 signals activate NF-kappa B. The chromosomal location of the gene was identified by fluorescence in situ hybridisation at 5q36.2, and appeared to correspond to human 1p36, where human CD30 has been mapped. The identification and characterization of the rat counterpart of human CD30 will facilitate studies of the biological function of this molecule.