Kazuiku Ohshiro

Fucoidan extracted from Cladosiphon okamuranus Tokida induces apoptosis of human T-cell leukemia virus type 1-infected T-cell lines and primary adult T-cell leukemia cells.

Abstract: Adult T-cell leukemia (ATL) is caused by human T-cell leukemia virus type 1 (HTLV-1) and remains incurable. The highest endemic area of HTLV-1 carriers in Japan is located in Okinawa, and novel treatments are urgently needed in this area. We extracted fucoidan, a sulfated polysaccharide, from the brown seaweed Cladosiphon okamuranus Tokida cultivated in Okinawa, Japan and examined its tumor-suppression activity against ATL. Fucoidan significantly inhibited the growth of peripheral blood mononuclear cells of ATL patients and HTLV-1-infected T-cell lines but not that of normal peripheral blood mononuclear cells. Fucoidan induced apoptosis of HTLV-1-infected T-cell lines mediated through downregulation of cellular inhibitor of apoptosis protein-2 and survivin and G1 phase accumulation through the downregulation of cyclin D2, c-myc, and hyperphosphorylated form of the retinoblastoma tumor suppressor protein. Further analysis showed that fucoidan inactivated NF-κB and activator protein-1 and inhibited NF-κB-inducible chemokine, C-C chemokine ligand 5 (regulated on activation, normal T expressed and secreted) production, and homotypic cell-cell adhesion of HTLV-1-infected T-cell lines. In vivo use of fucoidan resulted in partial inhibition of growth of tumors of an HTLV-1-infected T-cell line transplanted subcutaneously in severe combined immune deficient mice. Our results indicate that fucoidan is a potentially useful therapeutic agent for patients with ATL.

Retracted: Curcumin (diferuloylmethane) inhibits constitutive active NF-κB, leading to suppression of cell growth of human T-cell leukemia virus type I-infected T-cell lines and primary adult T-cell leukemia cells

Retraction: The following article has been retracted through agreement between the first author and several coauthors, the journal Editor‐in‐Chief, Peter Lichter, and John Wiley & Sons, Ltd.: Tomita M, Kawakami H, Uchihara JN, Okudaira T, Masuda M, Takasu N, Matsuda T, Ohta T, Tanaka Y, Ohshiro K, Mori N. (2006). Curcumin (diferuloylmethane) inhibits constitutive activeNF‐kappaB, leading to suppression of cell growth of human T‐cell leukemia virus type I‐infected T‐cell lines and primary adult T‐cell leukemia cells. Int J Cancer; 118 (February (3)): 765‐772, published online on 16 AUG 2005 in Wiley Online Library (www.onlinelibrary.wiley.com). After an investigation the retraction has been agreed due to inappropriate duplication of images and overlap with other published work

Antiadult T‐cell leukemia effects of brown algae fucoxanthin and its deacetylated product, fucoxanthinol

Adult T‐cell leukemia (ATL) is a fatal malignancy of T lymphocytes caused by human T‐cell leukemia virus type 1 (HTLV‐1) infection and remains incurable. Carotenoids are a family of natural pigments and have several biological functions. Among carotenoids, fucoxanthin is known to have antitumorigenic activity, but the precise mechanism of action is not elucidated. We evaluated the anti‐ATL effects of fucoxanthin and its metabolite, fucoxanthinol. Both carotenoids inhibited cell viability of HTLV‐1‐infected T‐cell lines and ATL cells, and fucoxanthinol was approximately twice more potent than fucoxanthin. In contrast, other carotenoids, β‐carotene and astaxanthin, had mild inhibitory effects on HTLV‐1‐infected T‐cell lines. Importantly, uninfected cell lines and normal peripheral blood mononuclear cells were resistant to fucoxanthin and fucoxanthinol. Both carotenoids induced cell cycle arrest during G1 phase by reducing the expression of cyclin D1, cyclin D2, CDK4 and CDK6, and inducing the expression of GADD45α, and induced apoptosis by reducing the expression of Bcl‐2, XIAP, cIAP2 and survivin. The induced apoptosis was associated with activation of caspase‐3, ‐8 and ‐9. Fucoxanthin and fucoxanthinol also suppressed IκBα phosphorylation and JunD expression, resulting in inactivation of nuclear factor‐κB and activator protein‐1. Mice with severe combined immunodeficiency harboring tumors induced by inoculation of HTLV‐1‐infected T cells responded to treatment with fucoxanthinol with suppression of tumor growth, showed extensive tissue distribution of fucoxanthinol, and the presence of therapeutically effective serum concentrations of fucoxanthinol. Our preclinical data suggest that fucoxanthin and fucoxanthinol could be potentially useful therapeutic agents for patients with ATL.

Inhibition of constitutively active Jak-Stat pathway suppresses cell growth of human T-cell leukemia virus type 1-infected T-cell lines and primary adult T-cell leukemia cells

BackgroundHuman T-cell leukemia virus type 1 (HTLV-1), the etiologic agent for adult T-cell leukemia (ATL), induces cytokine-independent proliferation of T-cells, associated with the acquisition of constitutive activation of Janus kinases (Jak) and signal transducers and activators of transcription (Stat) proteins. Our purposes in this study were to determine whether activation of Jak-Stat pathway is responsible for the proliferation and survival of ATL cells, and to explore mechanisms by which inhibition of Jak-Stat pathway kills ATL cells.ResultsConstitutive activation of Stat3 and Stat5 was observed in HTLV-1-infected T-cell lines and primary ATL cells, but not in HTLV-1-negative T-cell lines. Using AG490, a Jak-specific inhibitor, we demonstrated that the activation of Stat3 and Stat5 was mediated by the constitutive phosphorylation of Jak proteins. AG490 inhibited the growth of HTLV-1-infected T-cell lines and primary ATL cells by inducing G1 cell-cycle arrest mediated by altering the expression of cyclin D2, Cdk4, p53, p21, Pim-1 and c-Myc, and by apoptosis mediated by the reduced expression of c-IAP2, XIAP, survivin and Bcl-2. Importantly, AG490 did not inhibit the growth of normal peripheral blood mononuclear cells.ConclusionOur results indicate that activation of Jak-Stat pathway is responsible for the proliferation and survival of ATL cells. Inhibition of this pathway may provide a new approach for the treatment of ATL.

Activation of hypoxia-inducible factor 1 in human T-cell leukaemia virus type 1-infected cell lines and primary adult T-cell leukaemia cells.

HTLV-1 (human T-cell leukaemia virus type 1) is the causative agent for ATL (adult T-cell leukaemia). HTLV-1 Tax can activate the PI3K (phosphoinositide 3-kinase)/Akt signalling pathway, which is responsible for survival of HTLV-1-infected T-cells. HIFs (hypoxia-inducible factors) are transcriptional regulators that play a central role in the response to hypoxia. Overexpression of HIF-1alpha in many cancers is associated with a poor response to treatment and increased patient mortality. Our objectives in the present study were to investigate whether HIF-1 was activated in HTLV-1-infected T-cells and to elucidate the molecular mechanisms of HIF-1 activation by focusing on the PI3K/Akt signalling pathway. We detected a potent pathway that activated HIF-1 in the HTLV-1-infected T-cells under a normal oxygen concentration. Enhanced HIF-1alpha protein expression and HIF-1 DNA-binding activity were exhibited in HTLV-1-infected T-cell lines. Knockdown of HIF-1alpha by siRNA (small interfering RNA) suppressed the growth and VEGF (vascular endothelial growth factor) expression of the HTLV-1-infected T-cell line. HIF-1 protein accumulation and transcriptional activity were enhanced by Tax, which was inhibited by dominant-negative Akt. Importantly, mutant forms of Tax that are defective in activation of the PI3K/Akt pathway failed to induce HIF-1 transcriptional activity. The PI3K inhibitor LY294002 suppressed HIF-1alpha protein expression, HIF-1 DNA-binding and HIF-1 transcriptional activity in HTLV-1-infected T-cell lines. In primary ATL cells, HIF-1alpha protein levels were strongly correlated with levels of phosphorylated Akt. The results of the present study suggest that PI3K/Akt activation induced by Tax leads to activation of HIF-1. As HIF-1 plays a major role in tumour progression, it may represent a molecular target for the development of novel ATL therapeutics.

Curcumin targets Akt cell survival signaling pathway in HTLV-I-infected T-cell lines

The Akt signaling pathway is important for survival and growth of cancer cells. In the present paper we show that the Akt signaling pathway is constitutively activated in human T‐cell leukemia virus type I (HTLV‐I)‐infected T‐cell lines and in primary adult T‐cell leukemia (ATL) cells. Curcumin, a natural compound present in turmeric, has been studied vigorously as a potent chemopreventive agent for cancer therapy because of its inhibitory effect on proliferation and induction of apoptosis in several tumor cell lines. We investigated the effect of curcumin on Akt activity in HTLV‐I‐infected T‐cell lines and primary ATL cells. Phosphorylated PDK1 is an activator of Akt by phosphorylating Akt. Curcumin reduced phosphorylation of PDK1 and inhibited constitutive activation of Akt. Curcumin activated glycogen synthase kinase (GSK)‐3β, a downstream target of Akt kinase, by inhibiting phosphorylation of this protein. Curcumin reduced the expression of cell cycle regulators, cyclin D1 and c‐Myc proteins, which are both degraded by activated GSK‐3β. Our results suggest that activation of the Akt signaling pathway plays an important role in ATL cell survival, and that curcumin may have anti‐ATL properties mediated, at least in part, by inhibiting Akt activity. We propose that Akt‐targeting agents could be useful for the treatment of ATL. In this regard, curcumin is a potentially promising compound for the treatment of ATL. (Cancer Sci 2006; 97: 322 – 327)

Resistance to Apo2 Ligand (Apo2L)/Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)-Mediated Apoptosis and Constitutive Expression of Apo2L/TRAIL in Human T-Cell Leukemia Virus Type 1-Infected T-Cell Lines

ABSTRACT Adult T-cell leukemia (ATL), a CD4+-T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1), is difficult to cure, and novel treatments are urgently needed. Apo2 ligand (Apo2L; also tumor necrosis factor-related apoptosis-inducing ligand [TRAIL]) has been implicated in antitumor therapy. We found that HTLV-1-infected T-cell lines and primary ATL cells were more resistant to Apo2L-induced apoptosis than uninfected cells. Interestingly, HTLV-1-infected T-cell lines and primary ATL cells constitutively expressed Apo2L mRNA. Inducible expression of the viral oncoprotein Tax in a T-cell line up-regulated Apo2L mRNA. Analysis of the Apo2L promoter revealed that this gene is activated by Tax via the activation of NF-κB. The sensitivity to Apo2L was not correlated with expression levels of Apo2L receptors, intracellular regulators of apoptosis (FLICE-inhibitory protein and active Akt). NF-κB plays a crucial role in the pathogenesis and survival of ATL cells. The resistance to Apo2L-induced apoptosis was reversed by N-acetyl-l-leucinyl-l-leucinyl-l-norleucinal (LLnL), an NF-κB inhibitor. LLnL significantly induced the Apo2L receptors DR4 and DR5. Our results suggest that the constitutive activation of NF-κB is essential for Apo2L gene induction and protection against Apo2L-induced apoptosis and that suppression of NF-κB may be a useful adjunct in clinical use of Apo2L against ATL.

A modified version of galectin-9 suppresses cell growth and induces apoptosis of human T-cell leukemia virus type I-infected T-cell lines.

Retraction: The following article has been retracted through agreement between the first author and several coauthors, the journal Editor‐in‐Chief, Peter Lichter, and John Wiley & Sons, Ltd.: Okudaira T, Hirashima M, Ishikawa C, Makishi S, Tomita M, Matsuda T, Kawakami H, Taira N, Ohshiro K, Masuda M, Takasu N, Mori N. (2007). A modified version of galectin‐9 suppresses cell growth and induces apoptosis of human T‐cell leukemia virus type I‐infected T‐cell lines. Int J Cancer; 120 (May (10)): 2251‐2261, published online on 2 FEB 2007 in Wiley Online Library (www.onlinelibrary.wiley.com). After an investigation the retraction has been agreed due to inappropriate duplication of images and overlap with other published work.

Inhibition of heat shock protein-90 modulates multiple functions required for survival of human T-cell leukemia virus type I-infected T-cell lines and adult T-cell leukemia cells.

Retraction: The following article has been retracted through agreement between the first author and several coauthors, the journal Editor‐in‐Chief, Peter Lichter, and John Wiley & Sons, Ltd.: Kawakami H, Tomita M, Okudaira T, Ishikawa C, Matsuda T, Tanaka Y, Nakazato T, Taira N, Ohshiro K, Mori N. (2007). Inhibition of heat shock protein‐90 modulates multiple functions required for survival of human T‐cell leukemia virus type I‐infected T‐cell lines and adult T‐cell leukemia cells. Int J Cancer; 120 (April (8)): 1811‐1820, published online on 17 JAN 2007 in Wiley Online Library (www.onlinelibrary.wiley.com). After an investigation the retraction has been agreed due to inappropriate duplication of images and overlap with other published work.

Bisphosphonate incadronate inhibits growth of human T-cell leukaemia virus type I-infected T-cell lines and primary adult T-cell leukaemia cells by interfering with the mevalonate pathway

Anti‐resorptive bisphosphonates are used for the treatment of hypercalcaemia and bone complications associated with malignancies and osteoporosis, but also have been shown to have anti‐tumour effects in various cancers. Adult T‐cell leukaemia (ATL) is a fatal T‐cell malignancy caused by infection with human T‐cell leukaemia virus type I (HTLV‐I), and remains incurable. ATL is associated with osteolytic bone lesions and hypercalcaemia, both of which are major factors in the morbidity of ATL. Thus, the search for anti‐ATL agents that have both anti‐tumour and anti‐resorptive activity is warranted. The bisphosphonate agent, incadronate, prevented cell growth of HTLV‐I‐infected T‐cell lines and primary ATL cells, but not of non‐infected T‐cell lines or normal peripheral blood mononuclear cells. Incadronate induced S‐phase cell cycle arrest and apoptosis in HTLV‐I‐infected T‐cell lines, and treatment of these cells with substrates of the mevalonate pathway blocked the incadronate‐mediated growth suppression. Incadronate also prevented the prenylation of Rap1A protein. These results demonstrated that incadronate‐induced growth suppression occurs by interfering with the mevalonate pathway. Importantly, treatment with incadronate reduced tumour formation from an HTLV‐I‐infected T‐cell line when these cells were inoculated subcutaneously into severe combined immunodeficient mice. These findings suggest that incadronate could be potentially useful for the treatment of ATL.