Clinical and oncologic implications in epigenetic down-regulation of CD26/dipeptidyl peptidase IV in adult T-cell leukemia cells

Quantification of T cell clonality in human T cell leukaemia virus type-1 carriers can detect the development of adult T cell leukaemia early

Adult T cell leukaemia/lymphoma (ATL) arises from clonally expanded T cells that are infected with human T cell leukaemia virus type-1 (HTLV-1). Here, we show that ATL can be detected early in HTLV-1-carriers through quantification of T-cell receptor (TCR)Vβ subunit diversity on T-cells infected with HTLV-1 (CD3+ CCR4+ CD26- T-cells) using an 'oligoclonality index' (OCI-flow). We established a reference range for OCI-flow by analysing peripheral blood mononuclear cells (PBMCs) from HTLV-1-carriers who had not developed ATL in a median of 10.5 years follow up (n = 38) and patients with ATL (n = 30). In the third cohort of HTLV-1-carriers with no history or clinical evidence of ATL (n = 106), 19% of high proviral load (PVL, ≥4 copies of HTLV-1/100 PBMCs) carriers had an OCI-flow in the ATL range, >0.770. Carriers with an OCI-flow >0.770 (n = 14) had higher lymphocyte counts and PVLs and were more likely to have a family history of ATL than carriers with OCI-flow ≤0.770. ATL subsequently developed in two of these 14 carriers but no carriers with OCI-flow ≤0.770 (p = 0.03, cumulative follow-up 129 person-years). This method can be used to identify a subset of high-PVL HTLV-1-carriers at increased risk of developing ATL who may benefit from intervention therapy, prior to the detection of disease.

Targeting epigenetic regulators in the treatment of T-cell lymphoma

Introduction: T-cell lymphomas represent a broad group of malignant T-cell neoplasms with marked molecular, clinical, and biologic heterogeneity. Survival rates after conventional chemotherapy regimens are poor for most subtypes and new therapies are needed. Rapidly expanding knowledge in the field of epigenomics and the development of an increasing number of epigenetic-modifying agents have created new opportunities for epigenetic therapies for patients with this complex group of diseases.Areas covered: The present review summarizes current knowledge on epigenetic alterations in T-cell lymphomas, availability, and mechanisms of action of epigenetic-modifying agents, results of clinical trials of epigenetic therapies in T-cell lymphomas, status of FDA approval, and biomarker approaches to guide therapy. Promising future directions are discussed.Expert opinion: Mutations in epigenetic-modifying genes are among the most common genetic alterations in T-cell lymphomas, highlighting the potential for epigenetic therapies to improve management of this group of diseases. Single-agent efficacy is well documented, leading to FDA approval for several indications, but overall response rates and durability of responses remain modest. Critical next steps for the field include optimizing combination therapies that incorporate epigenetic-modifying agents and developing predictive biomarkers that help guide patient and drug selection.

More than just an enzyme: Dipeptidyl peptidase-4 (DPP-4) and its association with diabetic kidney remodelling

PURPOSE OF THE REVIEW

This review article discusses recent advances in the mechanism of dipeptidyl peptidase-4 (DPP-4) actions in renal diseases, especially diabetic kidney fibrosis, and summarizes anti-fibrotic functions of various DPP-4 inhibitors in diabetic nephropathy (DN).

RECENT FINDINGS

DN is a common complication of diabetes and is a leading cause of the end-stage renal disease (ESRD). DPP-4 is a member of serine proteases, and more than 30 substrates have been identified that act via several biochemical messengers in a variety of tissues including kidney. Intriguingly, DPP-4 actions on the diabetic kidney is a complex mechanism, and a variety of pathways are involved including increasing GLP-1/SDF-1, disrupting AGE-RAGE pathways, and integrin-β- and TGF-β-Smad-mediated signalling pathways that finally lead to endothelial to mesenchymal transition. Interestingly, an array of DPP-4 inhibitors is well recognized as oral drugs to treat type 2 diabetic (T2D) patients, which promote better glycemic control. Furthermore, recent experimental and preclinical data reveal that DPP-4 inhibitors may also exhibit protective effects in renal disease progression including anti-fibrotic effects in the diabetic kidney by attenuating above signalling cascade(s), either singly or as a combinatorial effect. In this review, we discussed the anti-fibrotic effects of DPP-4 inhibitors based on recent reports along with the possible mechanism of actions and future perspectives to underscore the beneficial effects of DPP-4 inhibitors in DN.

SUMMARY

With recent experimental, preclinical, and clinical evidence, we summarized DPP-4 activities and its mechanism of actions in diabetic kidney diseases. A knowledge gap of DPP-4 inhibition in controlling renal fibrosis in DN has also been postulated in this review for future research perspectives.

Switching and loss of cellular cytokine producing capacity characterize in vivo viral infection and malignant transformation in human T- lymphotropic virus type 1 infection

Adult T-cell leukaemia/lymphoma (ATL) arises from chronic non-malignant human T lymphotropic virus type-1 (HTLV-1) infection which is characterized by high plasma pro-inflammatory cytokines whereas ATL is characterized by high plasma anti-inflammatory (IL-10) concentrations. The poor prognosis of ATL is partly ascribed to disease-associated immune suppression. ATL cells have a CD4+CCR4+CD26-CD7- immunophenotype but infected cells with this immunophenotype (‘ATL-like’ cells) are also present in non-malignant HTLV-1 infection. We hypothesized that ‘ATL-like’ and ATL cells have distinct cytokine producing capacity and a switch in the cytokines produced occurs during leukemogenesis. Seventeen asymptomatic carriers (ACs), 28 patients with HTLV-1-associated myelopathy (HAM) and 28 with ATL were studied. Plasma IL-10 concentration and the absolute frequency of IL-10-producing CD4+ T cells were significantly higher in patients with ATL compared to AC. IL-10-producing ATL cells were significantly more frequent than ‘ATL-like’ cells. The cytokine-producing cells were only a small fraction of ATL cells. Clonality analysis revealed that even in patients with ATL the ATL cells were composed not only of a single dominant clone (putative ATL cells) but also tens of non-dominant infected clones (‘ATL-like’ cells). The frequency of cytokine-producing cells showed a strong inverse correlation with the relative abundance of the largest clone in ATL cells suggesting that the putative ATL cells were cytokine non-producing and that the ‘ATL-like’ cells were the primary cytokine producers. These findings were confirmed by RNAseq with cytokine mRNA expression in ATL cells in patients with ATL (confirmed to be composed of both putative ATL and ‘ATL-like’ cells by TCR analysis) significantly lower compared to ‘ATL-like’ cells in patients with non-malignant HTLV-1 infection (confirmed to be composed of hundreds of non-dominant clones by TCR analysis). A significant inverse correlation between the relative abundance of the largest clone and cytokine mRNA expression was also confirmed. Finally, ‘ATL-like’ cells produced less pro- and more anti-inflammatory cytokines than non ‘ATL-like’ CD4+ cells (which are predominantly HTLV uninfected). In summary, HTLV-1 infection of CD4+ T cells is associated with a change in cytokine producing capacity and dominant malignant clonal growth is associated with loss of cytokine producing capacity. Non-dominant clones with ‘ATL-like’ cells contribute to plasma cytokine profile in patients with non-malignant HTLV-1 infection and are also present in patient with ATL.

Human T-cell lymphotropic virus type-1 (HTLV-1) infection of CD4+ T cells is associated with a change in their cytokine producing capacity and is responsible for the different plasma cytokine profiles in patients with adult T-cell leukaemia/Lymphoma (ATL) and non-malignant HTLV-1 infection. Dominant malignant clonal growth of the infected CD4+ T cells is associated with loss of cytokine producing capacity. ACs, patients with HAM and patients with ATL have a common cytokine cluster with positive correlations between pro- (TNFα and IL-6) and anti- (IL-10) inflammatory cytokines. Plasma IL-10 was higher in the HAM and ATL states compared to AC whilst there was no difference in pro-inflammatory cytokines. Patients with HAM have raised plasma concentrations of IFNγ, IL-10 and IL-17 suggesting a complex interaction between these cytokine in HAM which was not seen in ATL. Aggressive ATL is associated with raised plasma concentrations of pro- and anti-inflammatory cytokines compared to indolent ATL. This cytokine profile did not precede or predict aggressive ATL. The ‘ATL-like’ infected cells in ACs and in patients with HAM have lower pro- and higher anti-inflammatory cytokine secretion than non- ‘ATL-like’ cells which are predominantly HTLV-1 uninfected. Putative ATL cells have little or no cytokine producing capacity. ‘ATL-like’ infected cells from non-dominant infected clones were present not only in patients with non-malignant HTLV-1 infection but also ATL. ‘ATL-like’ cells have cytokine producing capacity and contribute to plasma cytokine profile in patients with non-malignant HTLV-1 infection and possibly also in ATL.

Adult T-cell leukemia: molecular basis for clonal expansion and transformation of HTLV-1-infected T cells

Adult T-cell leukemia (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) that develops through a multistep carcinogenesis process involving 5 or more genetic events. We provide a comprehensive overview of recently uncovered information on the molecular basis of leukemogenesis in ATL. Broadly, the landscape of genetic abnormalities in ATL that include alterations highly enriched in genes for T-cell receptor-NF-κB signaling such as PLCG1, PRKCB, and CARD11 and gain-of function mutations in CCR4 and CCR7 Conversely, the epigenetic landscape of ATL can be summarized as polycomb repressive complex 2 hyperactivation with genome-wide H3K27 me3 accumulation as the basis of the unique transcriptome of ATL cells. Expression of H3K27 methyltransferase enhancer of zeste 2 was shown to be induced by HTLV-1 Tax and NF-κB. Furthermore, provirus integration site analysis with high-throughput sequencing enabled the analysis of clonal composition and cell number of each clone in vivo, whereas multicolor flow cytometric analysis with CD7 and cell adhesion molecule 1 enabled the identification of HTLV-1-infected CD4+ T cells in vivo. Sorted immortalized but untransformed cells displayed epigenetic changes closely overlapping those observed in terminally transformed ATL cells, suggesting that epigenetic abnormalities are likely earlier events in leukemogenesis. These new findings broaden the scope of conceptualization of the molecular mechanisms of leukemogenesis, dissecting them into immortalization and clonal progression. These recent findings also open a new direction of drug development for ATL prevention and treatment because epigenetic marks can be reprogrammed. Mechanisms underlying initial immortalization and progressive accumulation of these abnormalities remain to be elucidated.

Risk stratification of adult T-cell leukemia/lymphoma using immunophenotyping

Adult T‐cell leukemia/lymphoma (ATL), a human T‐lymphotropic virus type 1 (HTLV‐1)‐associated disease, has a highly variable clinical course and four subtypes with therapeutic and prognostic implications. However, there are overlapping features between ATL subtypes and between ATL and nonmalignant (non‐ATL) HTLV‐1 infection complicating diagnosis and prognostication. To further refine the diagnosis and prognosis of ATL, we characterized the immunophenotype of HTLV‐1‐infected cells in ATL and non‐ATL. A retrospective study of peripheral blood samples from 10 HTLV‐1‐uninfected subjects (UI), 54 HTLV‐1‐infected patients with non‐ATL, and 22 with ATL was performed using flow cytometry. All patients with ATL had CD4⁺ CCR4⁺ CD26⁻ immunophenotype and the frequency of CD4⁺ CCR4⁺ CD26⁻ T cells correlated highly significantly with the proviral load in non‐ATL suggesting CD4⁺ CCR4⁺ CD26⁻ as a marker of HTLV‐1‐infected cells. Further immunophenotyping of CD4⁺ CCR4⁺  CD26⁻ cells revealed that 95% patients with ATL had a CD7⁻ (≤30% CD7⁺ cells), whereas 95% HTLV+ non‐ATL had CD7⁺ (>30% CD7⁺ cells) immunophenotype. All patients with aggressive ATL had a CCR7⁺ (≥30%), whereas 92% with indolent ATL and 100% non‐ATL had a CCR7⁻ (<30%) immunophenotype. Patients with nonprogressing indolent ATL were CD127⁺ but those with progressive lymphocytosis requiring systemic therapy had a CD127⁻ (≤30%) immunophenotype. In summary, HTLV‐1‐infected cells have a CD4⁺ CCR4⁺ CD26⁻ immunophenotype. Within this population, CD7⁻ phenotype suggests a diagnosis of ATL, CCR7⁺ phenotype identifies aggressive ATL, while CCR7⁻CD127⁻ phenotype identifies progressive indolent ATL.

Blood flow cytometry in Sézary syndrome: new insights on prognostic relevance and immunophenotypic changes during follow-up

OBJECTIVES

Sézary syndrome (SS) is characterized by erythroderma, generalized lymphadenopathy, and the presence of circulating atypical lymphocytes, which are difficult to identify by morphologic data.

METHODS

We revised our series of 107 patients in an attempt to better define the phenotypic aberrancies in blood at diagnosis and the immunophenotypic stability over time detected by flow cytometry. Polymerase chain reaction assay was also used to study CD26/dipeptidyl peptidase IV (DPPIV) gene methylation.

RESULTS

The most common aberrancies were represented by the lack of CD26 (96/107) or CD38 (101/107) expression and the presence of a "dim" CD3, CD4, or CD2 population. There was a high variability in CD7 expression. In total, 31% of the patients had phenotypical heterogeneity in CD26 and CD7 expression at diagnosis. The phenotype was stable over time in 73 of 95 patients with available follow-up data, while 22 of 95 patients developed changes in CD26, CD7, or CD2 expression. CD4+CD26- SS showed hypermethylation of the CpG islands for the promoter region of CD26/DPPIV. Multivariate analysis showed that CD26 expression is a favorable prognostic factor (hazard ratio, 2.94; P = .045).

CONCLUSIONS

We confirm the relevance of CD26 negativity in SS diagnosis and monitoring. Nevertheless, the presence of rare CD26+ cases suggests that a multiparameter flow cytometry approach should be used. Changes in methylation profile could account for phenotypical heterogeneity.

Comparison of the dipeptidyl peptidase-4 gene methylation levels between severely obese subjects with and without the metabolic syndrome

BACKGROUND

The dipeptidyl peptidase-4 (DPP4) enzyme is a novel adipokine potentially involved in the development of the metabolic syndrome (MetS). Previous observations demonstrated higher visceral adipose tissue (VAT) DPP4 gene expression in non-diabetic severely obese men with (MetS+) vs. without (MetS-) MetS. DPP4 mRNA abundance in VAT correlated also with CpG site methylation levels (%Meth) localized within and near its exon 2 (CpG94 to CpG102) in non-diabetic severely obese women, regardless of their MetS status. The actual study tested whether DPP4 %Meth levels in VAT are different between MetS- and MetS+ non-diabetic severely obese subjects, whether variable metabolic and plasma lipid profiles are observed between DPP4 %Meth quartiles, and whether correlation exists in DPP4 %Meth levels between VAT and white blood cells (WBCs).

METHODS

DNA was extracted from the VAT of 26 men (MetS-: n=12, MetS+: n=14) and 79 women (MetS-: n=60; MetS+: n=19), as well as from WBCs in a sub-sample of 17 women (MetS-: n=9; MetS+: n=8). The %Meth levels of CpG94 to CpG102 were assessed by pyrosequencing of sodium bisulfite-treated DNA. ANOVA analyses were used to compare the %Meth of CpGs between MetS- and MetS+ groups, and to compare the metabolic phenotype and plasma lipid levels between methylation quartiles. Pearson correlation coefficient analyses were computed to test the relationship between VAT and WBCs CpG94-102 %Meth levels.

RESULTS

No difference was observed in CpG94-102 %Meth levels between MetS- and MetS+ subjects in VAT (P=0.67), but individuals categorized into CpG94-102 %Meth quartiles had variable plasma total-cholesterol concentrations (P=0.04). The %Meth levels of four CpGs in VAT were significantly correlated with those observed in WBCs (r=0.55-0.59, P≤0.03).

CONCLUSIONS

This study demonstrated that %Meth of CpGs localized within and near the exon 2 of the DPP4 gene in VAT are not associated with MetS status. The actual study also revealed an association between the %Meth of this locus with plasma total-cholesterol in severe obesity, which suggests a link between the DPP4 gene and plasma lipid levels.

Adult T-cell leukemia: a review of epidemiological evidence

Adult T-cell leukemia (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type I (HTLV-1) infection and often occurs in HTLV-1-endemic areas, such as southwestern Japan, the Caribbean islands, Central and South America, Intertropical Africa, and Middle East. To date, many epidemiological studies have been conducted to investigate the incidence of ATL among general population or HTLV-1 carriers and to identify a variety of laboratory, molecular, and host-specific markers to be possible predictive factors for developing ATL because HTLV-1 infection alone is not sufficient to develop ATL. This literature review focuses on the epidemiology of ATL and the risk factors for the development of ATL from HTLV-1 carriers, while keeping information on the epidemiology of HTLV-1 to a minimum. The main lines of epidemiological evidence are: (1) ATL occurs mostly in adults, at least 20-30 years after the HTLV-1 infection, (2) age at onset differs across geographic areas: the average age in the Central and South America (around 40 years old) is younger than that in Japan (around 60 years old), (3) ATL occurs in those infected in childhood, but seldom occurs in those infected in adulthood, (4) male carriers have about a three- to fivefold higher risk of developing ATL than female, (5) the estimated lifetime risk of developing ATL in HTLV-1 carriers is 6-7% for men and 2-3% for women in Japan, (6) a low anti-Tax reactivity, a high soluble interleukin-2 receptor level, a high anti-HTLV-1 titer, and high levels of circulating abnormal lymphocytes and white blood cell count are accepted risk factors for the development of ATL, and (7) a higher proviral load (more than 4 copies/100 peripheral blood mononuclear cells) is an independent risk factor for progression of ATL. Nevertheless, the current epidemiological evidence is insufficient to fully understand the oncogenesis of ATL. Further well-designed epidemiological studies are needed.

Heterogeneity in clonal nature in the smoldering subtype of adult T-cell leukemia: continuity from carrier status to smoldering ATL

To better understand indeterminate HTLV-1 carriers and smoldering (SM) subtype of adult T-cell leukemia (ATL), HTLV-1 proviral integrated status, proviral load (PVL) and ATL-related biomarkers were examined in 57 smoldering cases, including unusual carriers with a percentage of ATL-like cells. We found that according to Southern blot hybridization analytic features, 28 patients with SM ATL could be divided into 3 groups consisting of 16 (57.4%) patients with a monoclonal band, 6 (21.4%) with oligoclonal bands and the remaining 6 with smears. Although no clinical differences were observed among the 3 SM subtypes, HTLV-1-infected CD4 T-cell counts increased in order of poly-, oligo- and monoclonal subtypes. This trend began in the carrier stage and also was observed in PVL, CD25 and CCR4, indicating that a clone consisting of leukemic phenotypic cells was continuously growing. Moreover, the antigen modulation rates of CD26 and CD7 and the increasing rate of CD25 and CCR4 cells were closely correlated to growing clonal size, indicating that these markers had the possibility to predict a monoclonal band. In particular, CD26 or the ratio of CD26/CD25 had a validity differential for leukemic nature and predictive detection of clonal band. Conclusively, the present study shows that smoldering ATL is heterogeneous in the leukemogenic process, and the behavior of CD26 plays a central role in the evolution from early occult to overt smoldering ATL.

5-Aza-2'-deoxycytidine induced growth inhibition of leukemia cells through modulating endogenous cholesterol biosynthesis

5-Aza-2'-deoxycytidine (5-Aza-CdR), a nucleoside analog that can inhibit DNA cytosine methylation, possesses potent antitumorigenic activities for myeloid disorders. Although 5-Aza-CdR is known to be incorporated into DNA and inhibit DNA (cytosine-5)-methyltransferases, the precise mechanisms underlying the drug's antineoplastic activity remain unclear. Here we utilized a mass spectrometry-based quantitative proteomic method to analyze the 5-Aza-CdR-induced perturbation of protein expression in Jurkat-T cells at the global proteome scale. Among the ≈ 2780 quantified proteins, 188 exhibited significant alteration in expression levels upon a 24-hr treatment with 5 μm 5-Aza-CdR. In particular, we found that drug treatment led to substantially reduced expression of farnesyl diphosphate synthase (FDPS) and farnesyl diphosphate farnesyltransferase (FDFT1), two important enzymes involved in de novo cholesterol synthesis. Consistent with this finding, 5-Aza-CdR treatment of leukemia (Jurkat-T, K562 and HL60) and melanoma (WM-266-4) cells led to a marked decrease in cellular cholesterol content and pronounced growth inhibition, which could be rescued by externally added cholesterol. Exposure of these cells to 5-Aza-CdR also led to epigenetic reactivation of dipeptidyl peptidase 4 (DPP4) gene. Additionally, suppression of DPP4 expression with siRNA induced elevated protein levels of FDPS and FDFT1, and increased cholesterol biosynthesis in WM-266-4 cells. Together, the results from the present study revealed, for the first time, that 5-Aza-CdR exerts its cytotoxic effects in leukemia and melanoma cells through epigenetic reactivation of DPP4 gene and the resultant inhibition of cholesterol biosynthesis in these cells.

The dietary flavonoid apigenin enhances the activities of the anti-metastatic protein CD26 on human colon carcinoma cells

There is accumulating evidence that secondary plant metabolites such as flavonoids may have anti-cancer properties, and yet the molecular pathways that lead to alterations in cancer cell behaviour remain unclear. We investigated the possible actions of apigenin, a flavone present in leafy vegetables like parsley, on the levels of CD26 in carcinoma cells. CD26 is a multifunctional cell-surface protein that through its associated dipeptidyl peptidase (DPPIV) and ecto-adenosine deaminase (eADA) enzyme activities is able to suppress pathways involved in tumour metastasis. CD26 is down-regulated in various cancers including colorectal carcinoma. Apigenin substantially up-regulated cell-surface CD26 on HT-29 and HRT-18 human colorectal cancer cells. Levels of CD26 protein, along with its associated DPPIV enzyme activity, capacity to bind eADA, and ability to link cells to fibronectin, were increased with a maximum after 24-48 h. Elevation of CD26 occurred at concentrations that were at least 10-fold less than those shown to affect cell growth, and 100-fold below those that could affect cell viability. Furthermore, the CD26 effect was enhanced when apigenin was paired with chemotherapeutic agents utilized in the treatment of advanced colorectal cancer including irinotecan, 5-fluorouracil and oxaliplatin. For irinotecan, apigenin caused a 4-fold increase in the potency of the drug. These results demonstrate that apigenin can increase the cellular levels of CD26 and its multiple functions, and may oppose the predicted effect of decreased DPPIV and eADA activities on carcinoma cells, which is to facilitate tumour growth and metastasis.

DPP4 gene DNA methylation in the omentum is associated with its gene expression and plasma lipid profile in severe obesity

Severely obese subjects with the metabolic syndrome (MS) have higher dipeptidyl peptidase-4 (DPP4) expression in their visceral adipose tissue (VAT) compared to obese individuals without MS. We tested the hypothesis that methylation level of CpG sites in the DPP4 promoter CpG island in VAT was genotype-dependent and associated with DPP4 mRNA abundance and MS-related phenotypes. The VAT DNA was extracted in 92 severely obese premenopausal women undergoing biliopancreatic derivation for the treatment of obesity. Women were nondiabetic and none of them used medication to treat MS features. Cytosine methylation rates (%) of 102 CpG sites in the DPP4 CpG island were assessed by pyrosequencing of sodium bisulfite-treated DNA. Methylation rates were >10% for CpG sites 94-102. Their mean methylation rate (%Meth(94-102)) was different between genotypes for DPP4 polymorphisms rs13015258 (P = 0.001), rs17848915 (P = 0.0004), and c.1926 G>A (P = 0.001). The %Meth(94-102) correlated negatively with DPP4 mRNA abundance (r = -0.25, P < 0.05) and positively with plasma high-density lipoprotein (HDL) cholesterol concentrations (r = 0.22, P < 0.05), whereas DPP4 mRNA abundance correlated positively with plasma total-/HDL-cholesterol ratio (r = 0.25; P < 0.05). In the VAT of nondiabetic severely obese women, genotype-dependent methylation levels of specific CpG sites in the DPP4 promoter CpG island were associated with DPP4 gene expression and variability in the plasma lipid profile. Higher DPP4 gene expression in VAT and its relationship with the plasma lipid profile may be explained by actually unknown DPP4 biological effect or, to another extent, may also be a marker of VAT inflammation known to be associated with metabolic disturbances.

Minimal residual disease detection by flow cytometry in adult T-cell leukemia/lymphoma

Little information exists regarding the detection of minimal residual disease (MRD) in adult T-cell leukemia/lymphoma (ATLL). We evaluated 75 peripheral blood samples from 17 ATLL cases using flow cytometry (FC); 50 of the samples were concurrently evaluated by polymerase chain reaction (PCR) for clonal T-cell receptor gamma chain (TRG) gene rearrangement and the presence of human T-cell lymphotropic virus-1 proviral sequences. Residual ATLL cells were identified using a multiparametric approach to identify aberrant T-cell immunophenotypes. Malignant T cells were CD4+, CD3 dim+, CD26-, CD25 bright, CD7+, and CD27+, with occasional dim expression of CD2 or CD5. FC exhibited a high sensitivity, detecting as few as 0.29% ATLL cells/WBC (4.9 cells/microL) in the peripheral blood. PCR for TRG gene rearrangement was slightly more sensitive, and FC and PCR complemented each other in detecting MRD. In 2 patients, there was complete remission; 4 patients had disease refractory to therapy, and 3 died; 11 others had persistent disease with variable numbers of ATLL cells in the peripheral blood. Higher levels of ATLL cells appeared to correlate with disease severity. FC detection of aberrant T cells permits sensitive and quantitative monitoring of MRD in ATLL.

Suppression of neuroblastoma growth by dipeptidyl peptidase IV: relevance of chemokine regulation and caspase activation

Imbalanced protease expression and activities may contribute to the development of cancers, including neuroblastoma (NB). NB is a fatal childhood cancer of the sympathetic nervous system that frequently overexpresses mitogenic peptides, chemokines and their receptors. Dipeptidyl peptidase IV (DPPIV), a cell surface serine protease, inactivates or degrades some of these bioactive peptides and chemokines, thereby regulating cell proliferation and survival. Our studies show that DPPIV is expressed in normal neural crest-derived structures, including superior cervical and dorsal root ganglion cells, sciatic nerve, and in adrenal glands, but its expression is greatly decreased or lost in cells derived from NB, their malignant counterpart. Restoration of DPPIV expression in NB cells led to their differentiation in association with increased expression of the neural marker MAP2 and decreased expression of chemokines, including stromal-derived factor 1 (SDF1) and its receptor CXCR4. Furthermore, DPPIV promoted apoptosis, and inhibited SDF1-mediated in vitro cell migration and angiogenic potential. These changes were accompanied by caspase activation and decreased levels of phospho-Akt and MMP9 activity, which are downstream effectors of SDF1-CXCR4 signaling. Importantly, DPPIV suppressed the tumorigenic potential of NB cells in a xenotransplantation mouse model. These data support a potential role for DPPIV in inhibiting NB growth and progression.

Leukaemogenic mechanism of human T-cell leukaemia virus type I

Adult T-cell leukaemia (ATL) is a neoplastic disease derived from CD4(+) T-lymphocytes and etiologically associated with human T-cell leukaemia virus type I (HTLV-I). In addition to structural genes, HTLV-I encodes regulatory and accessory genes in the pX region. Among them, Tax is thought to play a central role in leukaemogenesis through its potent transforming activity. However, since Tax is a major target of the host immune system, its expression is often lost in ATL cells, indicating Tax is dispensable in the last phase of leukaemogenesis. The HTLV-I bZIP factor (HBZ), encoded on the HTLV-I minus strand, was recently shown to be expressed in all ATL cells, and to support growth of human T-cell lines. These findings suggest that HBZ is critical to ATL onset. In addition to viral factors and genetic and epigenetic changes in cellular genes, the host immune status and genetic background also function in leukaemogenesis.

Human T-cell leukemia virus type I induces adult T-cell leukemia: from clinical aspects to molecular mechanisms

BACKGROUND

Human T-cell leukemia virus type I (HTLV-I) is a causative virus of adult T-cell leukemia (ATL), HTLV-I-associated myelopathy/tropical spastic paraparesis, and HTLV-I-associated uveitis. ATL is a neoplastic disease of CD4-positive T lymphocytes that is characterized by pleomorphic tumor cells with hypersegmented nuclei, termed "flower cells." The mechanisms of leukemogenesis have not been fully clarified.

METHODS

The authors reviewed the virological, clinical, and immunological features of HTLV-I and ATL and summarized recent findings on the oncogenic mechanisms of ATL and therapeutic advances.

RESULTS

Multiple factors, such as viral genes, genetic and epigenetic alterations, and the host immune system, may be implicated in the leukemogenesis of ATL. Among them, viral genes, tax, and HBZ have been thought to play important roles. The prognosis of aggressive-type ATL remains poor, regardless of intensive chemotherapy. Effectiveness of allogeneic stem cell transplantation for ATL has been recently reported.

CONCLUSIONS

Although the precise mechanism of leukemogenesis of ATL remains unclear, recent progress provides important clues in oncogenesis by HTLV-I. Future research should focus on the composition of novel therapeutic strategies, including prevention, based on the evidence in the leukemogenic mechanisms.

[HTLV-I and leukemogenesis]

Human T-cell leukemia virus type I (HTLV-I) is a causative virus of adult T-cell leukemia (ATL). ATL is a highly aggressive neoplastic disease of CD4 positive T lymphocyte, which is featured by the pleomorphic tumor cells with hypersegmented nuclei, called " flower cell". HTLV-I increases its copy number by clonal proliferation of the host cells, not by replication of the virus. Therefore, HTLV-I eventually induces ATL. Tax, encoded by HTLV-I pX region, has been recognized as a protein that plays a central role of the transformation of HTLV-I-infected cells by its pleiotropic actions. However, fresh ATL cells frequently lose Tax protein expression by several mechanisms. Recently, HBZ was identified in the complementary strand of HTLV-I and it is suggested that HBZ is a critical gene in leukemogenesis. Furthermore, there is a long latency period before onset of ATL, indicating the multistep mechanisms of leukemogenesis. Therefore, it is suggested that multiple factors, such as viral proteins, genetic and epigenetic changes of host genome, and immune status of the hosts, could be implicated in leukemogenesis of ATL.