Jun-Nosuke Uchihara

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Retraction: The following article has been retracted through agreement between the first author and several coauthors, the journal Editor‐in‐Chief, Peter Lichter, and John Wiley & Sons, Ltd.: Tomita M, Kawakami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.

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)

NIK-333 inhibits growth of human T-cell leukemia virus type I-infected T-cell lines and adult T-cell leukemia cells in association with blockade of nuclear factor-κB signal pathway

Adult T-cell leukemia (ATL) is caused by human T-cell leukemia virus type I (HTLV-I) and remains incurable. NIK-333, a novel synthetic retinoid, prevents the recurrence of human hepatoma after surgical resection of primary tumors. We explored the effects of NIK-333 on HTLV-I-infected T-cell lines and ATL cells. NIK-333 inhibited cell proliferation, induced G1 arrest, and resulted in massive apoptosis in all tested HTLV-I-infected T-cell lines and ATL cells, whereas little effect was observed on normal peripheral blood mononuclear cells. NIK-333 treatment decreases the levels of cyclin D1, cyclin D2, cIAP2, and XIAP proteins. Further analysis showed that NIK-333 inactivated nuclear factor-κB in HTLV-I-infected T-cell lines. In animal studies, treatment with NIK-333 (100 mg/kg given orally every other day) produced partial inhibition of growth of tumors of a HTLV-I-infected T-cell line transplanted s.c. in severe combined immunodeficient mice. Our results indicate that NIK-333 is a potentially useful therapeutic agent for patients with ATL. [Mol Cancer Ther 2006;5(3):704–12]

Anti-adult T-cell leukemia/lymphoma effects of indole-3-carbinol

BackgroundAdult T-cell leukemia/lymphoma (ATLL) is a malignancy derived from T cells infected with human T-cell leukemia virus type 1 (HTLV-1), and it is known to be resistant to standard anticancer therapies. Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables such as cabbage, broccoli and Brussels sprout, is a promising chemopreventive agent as it is reported to possess antimutagenic, antitumorigenic and antiestrogenic properties in experimental studies. The aim of this study was to determine the potential anti-ATLL effects of I3C both in vitro and in vivo.ResultsIn the in vitro study, I3C inhibited cell viability of HTLV-1-infected T-cell lines and ATLL cells in a dose-dependent manner. Importantly, I3C did not exert any inhibitory effect on uninfected T-cell lines and normal peripheral blood mononuclear cells. I3C prevented the G1/S transition by reducing the expression of cyclin D1, cyclin D2, Cdk4 and Cdk6, and induced apoptosis by reducing the expression of XIAP, survivin and Bcl-2, and by upregulating the expression of Bak. The induced apoptosis was associated with activation of caspase-3, -8 and -9, and poly(ADP-ribose) polymerase cleavage. I3C also suppressed IκBα phosphorylation and JunD expression, resulting in inactivation of NF-κB and AP-1. Inoculation of HTLV-1-infected T cells in mice with severe combined immunodeficiency resulted in tumor growth. The latter was inhibited by treatment with I3C (50 mg/kg/day orally), but not the vehicle control.ConclusionOur preclinical data suggest that I3C could be potentially a useful chemotherapeutic agent for patients with ATLL.

Transactivation of CCL20 gene by Epstein-Barr virus latent membrane protein 1.

CCL20 is expected to play a crucial role in the initiation of immune responses and tumour growth. However, expression of CCL20 in Epstein–Barr virus (EBV)‐associated diseases has not been studied. We examined the contribution of EBV infection and EBV‐encoded latent membrane protein (LMP)‐1 to CCL20 expression. EBV infection and LMP‐1 induced CCL20 mRNA expression in the EBV‐negative Burkitt lymphoma (BL) cell lines and the embryonic kidney cell line. Histone deacetylase inhibitor‐stimulated endogenous LMP‐1 also induced CCL20 expression in an EBV‐positive BL cell line. Analysis of the CCL20 promoter showed that it was activated by LMP‐1 C‐terminal activation region (CTAR)‐1 and CTAR‐2. Co‐expression of IκBα, IκBβ, IκB kinase (IKK)α, IKKβ, IKKγ, nuclear factor (NF)‐κB‐inducing kinase and tumour necrosis factor receptor‐associated factor 2 dominant‐negative constructs with LMP‐1 inhibited the activation of the CCL20 promoter by LMP‐1, suggesting that LMP‐1 induces CCL20 via NF‐κB signalling. The requirement for the NF‐κB‐binding site in the CCL20 promoter in LMP‐1 responsiveness was established. Our results indicate that activation of the NF‐κB pathway by LMP‐1 is required for the activation of CCL20 expression.

Anti-adult T-cell leukemia effects of a novel synthetic retinoid, Am80 (Tamibarotene)

Clinical trials for treatment of adult T‐cell leukemia (ATL) caused by human T‐cell leukemia virus type I (HTLV‐I) using all‐trans‐retinoic acid (ATRA) have shown satisfactory therapeutic responses, although efficacies were limited. Recently, many synthetic retinoids have been developed and among them, a novel synthetic retinoid, Am80 (Tamibarotene) is an RARα‐ and RARβ‐specific retinoid expected to overcome ATRA resistance. The present study examined the inhibitory effects of Am80 on HTLV‐I‐infected T‐cell lines and ATL cells. Am80 had negligible growth inhibition of peripheral blood mononuclear cells but marked growth inhibition of both HTLV‐I‐infected T‐cell lines and ATL cells. Am80 arrested cells in the G1 phase of the cell cycle and induced apoptosis in HTLV‐I‐infected T‐cell lines. It inhibited also the phosphorylation of IκBα and NF‐κB‐DNA binding, in conjunction with reduction of expression of proteins involved in the G1/S cell cycle transition and apoptosis. Am80 also inhibited the expression of JunD, resulting in suppression of AP‐1‐DNA binding. Furthermore, severe combined immunodeficient mice with tumors induced by subcutaneous inoculation of HTLV‐I‐infected T cells, responded to Am80 treatment with partial regression of tumors and no side‐effects. These findings demonstrate that Am80 is a potential inhibitor of NF‐κB and AP‐1, and is a potentially useful therapeutic agent against ATL. (Cancer Sci 2008; 99: 2286–2294)

Retracted: Transactivation of CCL20 gene by Epstein–Barr virus latent membrane protein 1

CCL20 is expected to play a crucial role in the initiation of immune responses and tumour growth. However, expression of CCL20 in Epstein–Barr virus (EBV)‐associated diseases has not been studied. We examined the contribution of EBV infection and EBV‐encoded latent membrane protein (LMP)‐1 to CCL20 expression. EBV infection and LMP‐1 induced CCL20 mRNA expression in the EBV‐negative Burkitt lymphoma (BL) cell lines and the embryonic kidney cell line. Histone deacetylase inhibitor‐stimulated endogenous LMP‐1 also induced CCL20 expression in an EBV‐positive BL cell line. Analysis of the CCL20 promoter showed that it was activated by LMP‐1 C‐terminal activation region (CTAR)‐1 and CTAR‐2. Co‐expression of IκBα, IκBβ, IκB kinase (IKK)α, IKKβ, IKKγ, nuclear factor (NF)‐κB‐inducing kinase and tumour necrosis factor receptor‐associated factor 2 dominant‐negative constructs with LMP‐1 inhibited the activation of the CCL20 promoter by LMP‐1, suggesting that LMP‐1 induces CCL20 via NF‐κB signalling. The requirement for the NF‐κB‐binding site in the CCL20 promoter in LMP‐1 responsiveness was established. Our results indicate that activation of the NF‐κB pathway by LMP‐1 is required for the activation of CCL20 expression.