[Cauda equina relapse after autologous stem cell transplantation in a patient with primary plasma cell leukemia].

We report a rare case showing involvement with the cauda equina after autologous peripheral blood stem cell transplantation for primary plasma cell leukemia (PCL). A 55-year-old man was diagnosed with PCL(IgA-k type, stage III)in November of 2006. He was treated with VAD chemotherapy consisting of vincristine, doxorubicin, and dexamethasone. After achieving hematological remission, he received tandem high-dose melphalan supported by autologous peripheral blood stem cell transplantation. Five months after his second transplant, he complained of lumbago and bilateral leg pain. M-protein and Bence-Jones protein were not detected in serum or urine. An axial magnetic resonance imaging study revealed enlargement of the cauda equina nerve roots on T-1 weighted image. A sagittal T-1 weighted gadolinium-enhanced imaging study showed hyperintensities along the cauda equina. Leptomeningeal enhancement was also seen below the level of Th6. A cytological examination of the cerebrospinal fluid (CSF) with May-Giemsa stain showed atypical plasma cells. Immunoelectrophoresis of the CSF revealed monoclonal IgA-k type protein. A diagnosis of central nervous system (CNS)relapse was made. The patient died of pneumonia two months after relapse. It should be kept in mind that CNS relapse can occur during hematological remission in patients with multiple myeloma including PCL.

Overexpression of caveolin-1 in adult T-cell leukemia.

Caveolin-1 is implicated in the regulation of signal pathways. Adult T-cell leukemia (ATL) is a T-cell malignancy causatively associated with human T-cell leukemia virus type 1 (HTLV-1). To determine the role of caveolin-1 in leukemogenesis, we examined caveolin-1 expression levels in HTLV-1-infected T-cell lines and ATL cells. These cells expressed high levels of caveolin-1 compared with uninfected T-cell lines and normal peripheral blood mononuclear cells (PBMCs). Caveolin-1-positive ATL cells were detected in ATL lymph nodes and skin lesions, and caveolin-1 was also detected in the plasma of patients with ATL. Infection of a human T-cell line, an epithelial cell line, and normal PBMCs with HTLV-1 induced caveolin-1 expression. The viral protein Tax transcriptionally activated caveolin-1 gene through nuclear factor-kappaB and cAMP response element binding protein signal pathways. HTLV-1-infected T-cell lines, and ATL cells are known to be resistant to transforming growth factor beta (TGF-beta)-induced growth inhibition. Caveolin-1 was colocalized with TGF-beta type I receptor in HTLV-1-infected T-cell lines and suppressed TGF-beta signaling. Caveolin-1 knockdown in an HTLV-1-infected T-cell line exhibited susceptibility to TGF-beta. Thus, we describe a new function for Tax, repression of TGF-beta signaling through caveolin-1 expression, which may play a critical role in ATL leukemogenesis.

Aberrant expression of the transcription factor Twist in adult T-cell leukemia.

Adult T-cell leukemia (ATL) is a T-cell malignancy etiologically associated with human T-cell leukemia virus type 1 (HTLV-1). Twist, a highly conserved basic helix-loop-helix transcription factor, is a newly identified oncogene. However, there are no reports on Twist expression in ATL. To define the role of Twist in leukemogenesis of ATL, we examined its expression in T-cell lines and PBMC. HTLV-1-infected T-cell lines and ATL cells expressed high levels of Twist compared with uninfected T-cell lines and normal PBMC. Immunohistochemistry showed immunostaining for Twist in ATL cells in ATL lymph nodes and skin lesions. Infection of normal PBMC with HTLV-1 induced Twist expression. Induction of the viral protein Tax in a human T-cell line led to upregulation of Twist. Tax-induced Twist expression involved the NF-kappaB and CREB signaling pathways. Twist augmented Tax-mediated HTLV-1 LTR and NF-kappaB activation. Short interfering RNA against Twist inhibited cell growth of HTLV-1-infected T-cell lines and downregulation of Twist expression in an HTLV-1-infected T-cell line inhibited the expression of Akt1, interleukin-2 receptor alpha chain, and Tax as well as the known target genes of Twist, YB-1 and Akt2. In conclusion, the results suggest that Tax-induced induction of Twist contributes to leukemogenesis of ATL.

Treatment-related Burkitt's lymphoma: literature review and case report of successful treatment with rituximab monotherapy.

The development of Burkitt's lymphoma (BL) is uncommon in elderly people. Most treatment-related hematological malignancies are of a myeloid lineage. Only a few cases with BL secondary to cancer treatment have been described. We report a rare case of an elderly patient with radiotherapy-related BL. A 71-year-old Japanese man, who had a past history of oropharyngeal cancer treated with local irradiation 15 years ago, presented with a left mandibular mass in December 2004. A partial mandibulectomy disclosed pathological features consistent with BL. Although the patient was initially treated with intensive chemotherapy, the development of complications precluded further anticancer drug treatment. Rituximab was administered once weekly for 5 consecutive weeks, with resolution of the mandibular mass. He remained in remission without further lymphoma treatment for more than 3 years after diagnosis. Rituximab monotherapy should be considered as a therapeutic option for elderly patients with BL.

[HIV- and HHV-8-negative primary effusion lymphoma-like lymphoma presenting with lymphomatous effusions complicated by cardiac tamponade-a case report].

We report a rare case of human immunodeficiency virus (HIV)- and human herpes virus-8 (HHV-8)-negative primary effusion lymphoma (PEL)-like lymphoma presenting with lymphomatous effusions complicated by cardiac tamponade. A 68-year-old woman was hospitalized with generalized weakness in June 2006. Echocardiogram revealed the presence of pericardial effusion and she had the signs of cardiac tamponade. Urgent pericardial drainage relieved her symptoms. Chest computed tomography showed bilateral pleural effusions along with pericardial effusion. Cytologic findings of both effusions were suggestive of malignancies, including malignant lymphoma. Immunocytochemical studies with a panel of antibodies, including CD20 and CD79a, could not provide a definite diagnosis. Flow cytometric analysis of pleural effusion revealed that tumor cells were positive for CD10 and CD19, but negative for CD20, CD23, surface immunoglobulin, and T-cell associated antigens. Clonal rearrangement of the immunoglobulin heavy chain gene was detected by Southern blot analysis. Polymerase chain reaction proved to be negative for HHV-8. The serology test for HIV was negative. After a diagnosis of HHV-8-negative PEL-like lymphoma, she was treated with CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine and prednisolone). However, she died of progressive lymphoma 7 months after the diagnosis. PEL-like lymphomas are of B-cell origin. In some cases of PEL-like lymphoma, tumor cells may be negative for representative markers of B-cell phenotype such as CD20 and CD79a.

Intensive chemotherapy for a patient with primary cutaneous diffuse large B-cell lymphoma with Burkitt-like morphology.

We report a rare case of primary cutaneous diffuse large B-cell lymphoma (DLBCL) with Burkitt-like morphology. A 54-year-old man presented with multiple subcutaneous tumors. Pathological examination showed morphological features resembling Burkitt or Burkitt-like lymphoma (BL/BLL) with high MIB-1 positivity. Cytogenetic studies revealed no 8q24/c-myc translocation. After the diagnosis of Burkitt-like DLBCL, the patient was treated with CODOX-M chemotherapy (cyclophosphamide, doxorubicin, vincristine, cytarabine and methotrexate), which led to durable remission. The present case suggests that short-term, high-intensity chemotherapy used for BL/BLL may be appropriate for primary cutaneous Burkitt-like DLBCL, as well as systemic lymphoma with Burkitt-like morphology.

Overexpression of Aurora A by loss of CHFR gene expression increases the growth and survival of HTLV-1-infected T cells through enhanced NF-kappaB activity.

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent for adult T-cell leukemia (ATL). Aurora A, a mitotic checkpoint protein, is overexpressed in human cancer cells. The cell cycle-dependent turnover of Aurora A is regulated by E3 ubiquitin ligases such as checkpoint with fork head-associated and ring finger (CHFR). Here, we found overexpression of Aurora A protein in HTLV-1-infected T-cell lines and primary ATL cells. The expression of CHFR mRNA was reduced in these cells by abnormal methylation of CHFR promoter region. Knockdown of Aurora A using small interfering RNA suppressed the growth of HTLV-1-infected T-cell line. Transfection of Aurora A expression plasmid enhanced Tax-induced nuclear factor-kappaB (NF-kappaB) reporter activity. Transfection of CHFR expression plasmid into an HTLV-1-infected T-cell line reduced cell growth, Aurora A protein level and constitutive NF-kappaB reporter activity. Aurora kinase inhibitor suppressed the growth and survival of HTLV-1-infected T-cell lines and primary ATL cells. It also reduced constitutive NF-kappaB activity in an HTLV-1-infected T-cell line by reducing IkappaB kinase beta phosphorylation and the expression of antiapoptotic protein survivin. Our results suggested that loss of CHFR expression resulted to accumulation of Aurora A, which increased NF-kappaB activity. These findings highlight the critical role of Aurora A in HTLV-1-infected T cells, making this molecule a potentially suitable target for future therapies for ATL.

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

BACKGROUND: Adult 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. RESULTS: In 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 IkappaBalpha phosphorylation and JunD expression, resulting in inactivation of NF-kappaB 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. CONCLUSION: Our preclinical data suggest that I3C could be potentially a useful chemotherapeutic agent for patients with ATLL.

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 RARalpha- and RARbeta-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 IkappaBalpha and NF-kappaB-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-kappaB and AP-1, and is a potentially useful therapeutic agent against ATL.

Anti-adult 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, beta-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 G(1) phase by reducing the expression of cyclin D1, cyclin D2, CDK4 and CDK6, and inducing the expression of GADD45alpha, 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 IkappaBalpha phosphorylation and JunD expression, resulting in inactivation of nuclear factor-kappaB 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.

[Primary diffuse large B-cell lymphoma of the uterine cervix--a case report].

Primary malignant lymphoma of the female genital tract is an extremely rare clinical entity. We report a case of primary non-Hodgkin lymphoma of the uterine cervix. A 68-year-old woman presented with abnormal genital bleeding in May 2002. A coloposcopic examination revealed a mass in the uterine cervix. Magnetic resonance imaging showed a bulky cervical tumor(7.5 x 8 cm)invading the right parametrium and adjacent levator ani muscle. Involvement of pelvic lymph nodes was also observed. The uterine lesion exhibited homogenous hypointensity on T1 weight image and isointense to hyperintense on T2-weight image. No other lesions were detected by the whole-body computed tomography, gallium scintigraphy, and bone marrow examination. Although cytology of the smear from the uterine cervix was nondiagnostic, the histologic examination of the punch biopsy material showed a diffuse proliferation of atypical lymphoid cells. Immunophenotypic studies revealed tumor cells were positive for CD19, CD20, CD30, and k-chain. A diagnosis of diffuse large B-cell lymphoma of the uterine cervix, clinical stage IIE was made. The patient was treated with 6 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone(CHOP)chemotherapy followed by the involved field irradiation. She remains alive and free of disease more than 5 years after the diagnosis.

A modified version of galectin-9 induces cell cycle arrest and apoptosis of Burkitt and Hodgkin lymphoma cells.

The identification of galectin-9 as a ligand for T-cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3), expressed on T-helper type-1 (Th1) cells, has established the Tim-3-galectin-9 pathway as a regulator of Th1 immunity. Whereas there is compelling evidence for the effects of galectin-9 on T-cell fate, limited information is available on the impact of galectin-9 on B lymphocytes. We found that protease-resistant galectin-9, hG9NC(null), but not galectin-1 or -8, prevented cell growth of malignant B cells, such as Burkitt lymphoma (BL) and Hodgkin lymphoma (HL). beta-galactoside binding was essential for galectin-9-induced cell growth suppression. hG9NC(null) induced cell cycle arrest by reducing the expression of cyclin D1, D2, B1, Cdk4, Cdc25C and c-Myc, and apoptosis by reducing the expression of XIAP, c-IAP2 and survivin. Most of the genes that encode these proteins are regulated by nuclear factor-kappaB (NF-kappaB), and constitutive activation of NF-kappaBeta is a common characteristic of both types of malignancies. hG9NC(null) inhibited IkappaBalpha phosphorylation, resulting in suppression of NF-kappaB. AP-1 has also been implicated in the control of cell survival. hG9NC(null) inhibited the expression of JunD, resulting in the suppression of AP-1. Our results suggest that hG9NC(null) is a potentially suitable agent for the management of BL and HL.

Mechanisms of Legionella pneumophila-induced interleukin-8 expression in human lung epithelial cells.

BACKGROUND: Legionella pneumophila is a facultative intracellular bacterium, capable of replicating within the phagosomes of macrophages and monocytes, but little is known about its interaction with human lung epithelial cells. We investigated the effect of L. pneumophila on the expression of interleukin-8 (IL-8) in human A549 alveolar and NCI-H292 tracheal epithelial cell lines. RESULTS: Infection of L. pneumophila strain, but not heat-killed strain, resulted in upregulation of IL-8. IL-8 mRNA expression was induced immediately after the infection and its signal became gradually stronger until 24 h after infection. On the other hand, IL-8 expression in A549 cells infected with L. pneumophila lacking a functional type IV secretion system was transient. The IL-8 expression was slightly induced at 16 h and increased at 24 h after infection with flagellin-deficient Legionella. Activation of the IL-8 promoter by L. pneumophila infection occurred through the action of nuclear factor-kappaB (NF-kappaB). Transfection of dominant negative mutants of NF-kappaB-inducing kinase, IkappaB kinase and IkappaB inhibited L. pneumophila-mediated activation of IL-8 promoter. Treatment with hsp90 inhibitor suppressed L. pneumophila-induced IL-8 mRNA due to deactivation of NF-kappaB. CONCLUSION: Collectively, these results suggest that L. pneumophila induces activation of NF-kappaB through an intracellular signaling pathway that involves NF-kappaB-inducing kinase and IkappaB kinase, leading to IL-8 gene transcription, and that hsp90 acts as a crucial regulator in L. pneumophila-induced IL-8 expression, presumably contributing to immune response in L. pneumophila. The presence of flagellin and a type IV secretion system are critical for Legionella to induce IL-8 expression in lung epithelial cells.

Helicobacter pylori induces CCL20 expression.

CCL20 attracts immature dendritic cells and memory T cells and plays a role on mucosal surfaces in inflammation. However, whether Helicobacter pylori infection induces CCL20 in human gastric epithelial cells remains to be determined. The aim of this study was to analyze the molecular mechanism of H. pylori-induced CCL20 expression. Expression of CCL20 mRNA was assessed by reverse transcription-PCR. Five normal and five H. pylori-infected gastric tissue samples were stained immunohistochemically for CCL20. A luciferase assay was used to monitor activation of the CCL20 gene promoter, and an electrophoretic mobility shift assay was used to explore the binding of transcription factors to this promoter. The CCL20 expression in epithelial cells of H. pylori-positive tissues was higher than that in H. pylori-negative tissues. H. pylori induced CCL20 expression in gastric epithelial cell lines, and the induction was dependent on an intact cag pathogenicity island. Activation of the CCL20 promoter by H. pylori occurred through the action of NF-kappaB. Transfection of IkappaB kinase and NF-kappaB-inducing kinase dominant negative mutants inhibited H. pylori-mediated activation of CCL20. Treatment with an inhibitor of Hsp90 suppressed H. pylori-induced CCL20 mRNA due to deactivation of NF-kappaB. Collectively, these results suggest that H. pylori activates NF-kappaB through an intracellular signaling pathway that involves IkappaB kinase and NF-kappaB-inducing kinase, leading to CCL20 gene transcription, and that Hsp90 is a crucial regulator of H. pylori-induced CCL20 expression, presumably contributing to the immune response in H. pylori.

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.

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

ATL is a fatal malignancy of T lymphocytes caused by HTLV-I infection and remains incurable. Galectins are a family of animal lectins that function both extracellularly (by interacting with cell surface and extracellular matrix glycoproteins and glycolipids) and intracellularly (by interacting with cytoplasmic and nuclear proteins) to modulate signaling pathways. We found that protease-resistant galectin-9 by modification of its linker peptide, hG9NC(null), prevented cell growth of HTLV-I-infected T-cell lines and primary ATL cells. The suppression of cell growth was inhibited by lactose, but not by sucrose, indicating that beta-galactoside binding is essential for hG9NC(null)-induced cell growth suppression. hG9NC(null) induced cell cycle arrest by reducing the expression of cyclin D1, cyclin D2, cyclin B1, Cdk1, Cdk4, Cdk6, Cdc25C and c-Myc, and apoptosis by reducing the expression of XIAP, c-IAP2 and survivin. Most of these genes are regulated by NF-kappaB, which plays a critical role in oncogenesis by HTLV-I. hG9NC(null) suppressed IkappaBalpha phosphorylation, resulting in suppression of NF-kappaB. Most importantly, treatment with hG9NC(null) (6.7 mg/kg injected intraperitoneally every day) reduced tumor formation from an HTLV-I-infected T-cell line when these cells were inoculated subcutaneously into SCID mice. Our results suggest that hG9NC(null) could be a suitable agent for the management of ATL.

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.

The molecular chaperone Hsp90 is involved in the stabilization and conformational maturation of many signaling proteins that are deregulated in cancers. The geldanamycin derivative 17-AAG is currently tested in clinical trials and known to inhibit the function of Hsp90 and promote the proteasomal degradation of its misfolded client proteins. ATL is a fatal malignancy of T lymphocytes caused by HTLV-I infection and remains incurable. Since Hsp90 is overexpressed in HTLV-I-infected T-cell lines and primary ATL cells, we analyzed the effects of 17-AAG on cell survival, apoptosis and expression of signal transduction proteins. HTLV-I-infected T-cell lines and primary ATL cells were significantly more sensitive to 17-AAG in cell survival assays than normal PBMCs. 17-AAG induced the inhibition of cell cycle and apoptosis. These effects could be mediated by inactivation of NF-kappaB, AP-1 and PI3K/Akt pathways, as well as reduction of expression of proteins involved in the G1-S cell cycle transition and apoptosis. Proteasome inhibition interfered with 17-AAG-mediated signaling proteins depletion. Collectively, our results indicate that 17-AAG suppresses ATL cell survival through, at least in part, destabilization of several client proteins and suggest that 17-AAG is a potentially useful chemotherapeutic agent for ATL.

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.