IRF-4 and c-Rel expression in antiviral-resistant adult T-cell leukemia/lymphoma

Inhibition of c-Rel expression in myeloid and lymphoid cells with distearoyl -phosphatidylserine (DSPS) liposomal nanoparticles encapsulating therapeutic siRNA

c-Rel, a member of the nuclear factor kappa B (NF-κB) family, is preferentially expressed by immune cells and is known to regulate inflammation, autoimmune diseases and cancer. However, there is a lack of therapeutic intervention to specifically inhibit c-Rel in immune cells. Recent success with Pfizer and Moderna mRNA lipid-encapsulated vaccines as well as FDA approved medicines based on siRNA prompted us to test a lipid nanoparticle-based strategy to silence c-Rel in immune cells. Specifically, we encapsulated c-Rel-targeting siRNA into distearoyl-phosphatidylserine (DSPS)-containing nanoparticles. DSPS is a saturated phospholipid that serves as the "eat-me" signal for professional phagocytes such as macrophages and neutrophils of the immune system. We demonstrated here that incorporation of DSPS in liposome nanoparticles (LNP) improved their uptake by immune cells. LNP containing high concentrations of DSPS were highly effective to transfect not only macrophages and neutrophils, but also lymphocytes, with limited toxicity to cells. However, LNP containing low concentrations of DSPS were more effective to transfect myeloid cells than lymphoid cells. Importantly, DSPS-LNP loaded with a c-Rel siRNA were highly effective to inhibit c-Rel expression in several professional phagocytes tested, which lasted for several days. Taken together, our results suggest that DSPS-LNP armed with c-Rel siRNA could be exploited to target immune cells to limit the development of inflammatory diseases or cancer caused by c-Rel upregulation. In addition, this newly developed DSPS-LNP system may be further tested to encapsulate and deliver other small molecule drugs to immune cells, especially macrophages, neutrophils, and lymphocytes for the treatment of diseases.

Alvocidib inhibits IRF4 expression via super-enhancer suppression and adult T-cell leukemia/lymphoma cell growth

Adult T-cell leukemia/lymphoma (ATL) is an intractable hematological malignancy with extremely poor prognosis. Recent studies have revealed that super-enhancers (SE) play important roles in controlling tumor-specific gene expression and are potential therapeutic targets for neoplastic diseases including ATL. Cyclin-dependent protein kinase (CDK) 9 is a component of a complex comprising transcription factors (TFs) that bind the SE region. Alvocidib is a CDK9 inhibitor that exerts antitumor activity by inhibiting RNA polymerase (Pol) II phosphorylation and suppressing SE-mediated, tumor-specific gene expression. The present study demonstrated that alvocidib inhibited the proliferation of ATL cell lines and tumor cells from patients with ATL. RNA sequencing (RNA-Seq) and chromatin immunoprecipitation sequencing (ChIP-Seq) disclosed that SE regulated IRF4 in the ATL cell lines. Previous studies showed that IRF4 suppression inhibited ATL cell proliferation. Hence, IRF4 is a putative alvocidib target in ATL therapy. The present study revealed that SE-mediated IRF4 downregulation is a possible mechanism by which alvocidib inhibits ATL proliferation. Alvocidib also suppressed ATL in a mouse xenograft model. Hence, the present work demonstrated that alvocidib has therapeutic efficacy against ATL and partially elucidated its mode of action. It also showed that alvocidib is promising for the clinical treatment of ATL and perhaps other malignancies and neoplasms as well.

Genetic alterations and oxidative stress in T cell lymphomas

T cell lymphomas encompass a diverse group of Non-Hodgkin lymphomas with a wide spectrum of clinical, immunological and pathological manifestations. In the last two decades there has been a progress in our understanding of the cell of origin, genetic abnormalities and their impact on behaviour in T cell lymphomas. Genetic alterations are one of the critical drivers of the pathogenesis of T cell lymphoma. Disease progression has been correlated with multiple genetic abnormalities where malignant clones arise primarily out of the host immune surveillance arsenal. There are many cellular processes involved in disease development, and some of them are T cell signaling, differentiation, epigenetic modifications, and immune regulation. Modulation of these crucial pathways via genetic mutations and chromosomal abnormalities possessing either point or copy number mutations helps tumor cells to develop a niche favourable for their growth via metabolic alterations. Several metabolic pathways especially regulation of redox homeostasis is critical in pathogenesis of lymphoma. Disruption of redox potential and induction of oxidative stress renders malignant cells vulnerable to mitochondrial damage and triggers apoptotic pathways causing cell death. Targeting genetic abnormalities and oxidative stress along with current treatment regime have the potential for improved therapeutics and presents new combination approaches towards selective treatment of T cell lymphomas.

Lineage- and Stage-specific Oncogenicity of IRF4

Dysregulation of transcription factor genes represents a unique molecular etiology of hematological malignancies. A number of transcription factors that play a role in hematopoietic cell development, lymphocyte activation or their maintenance have been identified as oncogenes or tumor suppressors. Many of them exert oncogenic abilities in a context-dependent manner by governing the key transcriptional program unique to each cell type. IRF4, a member of the interferon regulatory factor (IRF) family, acts as an essential regulator of the immune system and is a prime example of a stage-specific oncogene. The expression and oncogenicity of IRF4 are restricted to mature lymphoid neoplasms, while IRF4 potentially serves as a tumor suppressor in other cellular contexts. This is in marked contrast to its immediate downstream target, MYC, which can cause cancers in a variety of tissues. In this review article, we provide an overview of the roles of IRF4 in the development of the normal immune system and lymphoid neoplasms and discuss the potential mechanisms of lineage- and stage-specific oncogenicity of IRF4.

Genetic profiling and biomarkers in peripheral T-cell lymphomas: current role in the diagnostic work-up

Peripheral T-cell lymphomas are a heterogeneous, and usually aggressive, group of mature T-cell neoplasms with overlapping clinical, morphologic and immunologic features. A large subset of these neoplasms remains unclassifiable with current diagnostic methods ("not otherwise specified"). Genetic profiling and other molecular tools have emerged as widely applied and transformative technologies for discerning the biology of lymphomas and other hematopoietic neoplasms. Although the application of these technologies to peripheral T-cell lymphomas has lagged behind B-cell lymphomas and other cancers, molecular profiling has provided novel prognostic and diagnostic markers as well as an opportunity to understand the biologic mechanisms involved in the pathogenesis of these neoplasms. Some biomarkers are more prevalent in specific T-cell lymphoma subsets and are being used currently in the diagnosis and/or risk stratification of patients with peripheral T-cell lymphomas. Other biomarkers, while promising, need to be validated in larger clinical studies. In this review, we present a summary of our current understanding of the molecular profiles of the major types of peripheral T-cell lymphoma. We particularly focus on the use of biomarkers, including those that can be detected by conventional immunohistochemical studies and those that contribute to the diagnosis, classification, or risk stratification of these neoplasms.

An international, multicenter, retrospective study on the positive impact of cutaneous involvement on the clinical outcome of adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a largely incurable disease. Cutaneous involvement is common and could be first symptom of the disease. We analyzed 169 patients with ATLL of whom 63 had cutaneous involvement. Cutaneous involvement was found in 48, 27, 17, and 60% of acute, lymphomatous, chronic and smoldering ATLL cases, respectively. Eight cases had primary cutaneous tumoral variant. Erythroderma (24%) and plaques (22%) were the most frequent skin lesions. The presence of cutaneous involvement was associated with better overall survival compared to non-cutaneous involvement (aHR 0.55 [95% CI: 0.37-0.82], p < 0.01; 1-year OS 53 vs. 27%, respectively, p = 0.012). Combination zidovudine and interferon-alpha (AZT-IFN) yielded high response rates (overall response, OR = 100%, n = 8; complete response 62.5%) compared to chemotherapy (OR = 33.3%, n = 12/36). In conclusion, cutaneous involvement was associated with better survival in Latin American patients with ATLL. AZT-IFN demonstrated encouraging responses in ATLL patients with cutaneous involvement.

Real-World Data on Adult T-Cell Leukemia/Lymphoma in Latin America: A Study From the Grupo de Estudio Latinoamericano de Linfoproliferativos

PURPOSE

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive disease caused by the human T-cell leukemia virus type 1. Real-world data of ATLL in Latin America are lacking.

PATIENTS AND METHODS

We analyzed patients with ATLL (acute, lymphomatous, chronic, and smoldering) encountered in 11 Latin American countries between 1995 and 2019. Treatment response was assessed according to the 2009 consensus report. Survival curves were estimated using the Kaplan-Meier method and log-rank test.

RESULTS

We identified 253 patients; 226 (lymphomatous: n = 122, acute: n = 73, chronic: n = 26, and smoldering: n = 5) had sufficient data for analysis (median age 57 years). Most patients with ATLL were from Peru (63%), Chile (17%), Argentina (8%), and Colombia (7%). Hypercalcemia was positively associated with acute type (57% v lymphomatous 27%, P = .014). The median survival times (months) were 4.3, 7.9, 21.1, and not reached for acute, lymphomatous, chronic, and smoldering forms, with 4-year survival rates of 8%, 22%, 40%, and 80%, respectively. First-line zidovudine (AZT)-interferon alfa (IFN) resulted in an overall response rate of 63% (complete response [CR] 24%) for acute. First-line chemotherapy yielded an overall response rate of 41% (CR 29%) for lymphomatous. CR rate was 42% for etoposide, cyclophosphamide, vincristine, doxorubicin, and prednisone versus 12% for cyclophosphamide, vincristine, doxorubicin, and prednisone-like regimen (P < .001). Progression-free survival at 1 year for acute type patients treated with AZT-IFN was 67%, whereas 2-year progression-free survival in lymphomatous type patients who achieved CR after chemotherapy was 77%.

CONCLUSION

This study confirms Latin American ATLL presents at a younger age and has a high incidence of lymphomatous type, low incidence of indolent subtypes, and worse survival rates as compared with Japanese patients. In aggressive ATLL, chemotherapy remains the preferred choice for lymphomatous favoring etoposide-based regimen (etoposide, cyclophosphamide, vincristine, doxorubicin, and prednisone), whereas AZT-IFN remains a good first-line option for acute subtype.

Oncogenic viruses and chemoresistance: What do we know?

Chemoresistance is often referred to as a major leading reason for cancer therapy failure, causing cancer relapse and further metastasis. As a result, an urgent need has been raised to reach a full comprehension of chemoresistance-associated molecular pathways, thereby designing new therapy methods. Many of metastatic tumor masses are found to be related with a viral cause. Although combined therapy is perceived as the model role therapy in such cases, chemoresistant features, which is more common in viral carcinogenesis, often get into way of this kind of therapy, minimizing the chance of survival. Some investigations indicate that the infecting virus dominates other leading factors, i.e., genetic alternations and tumor microenvironment, in development of cancer cell chemoresistance. Herein, we have gathered the available evidence on the mechanisms under which oncogenic viruses cause drug-resistance in chemotherapy.

Interferon regulatory factor 4 as a therapeutic target in adult T-cell leukemia lymphoma

Background

Adult T-cell leukemia lymphoma (ATLL) is a chemotherapy-resistant malignancy with a median survival of less than one year that will afflict between one hundred thousand and one million individuals worldwide who are currently infected with human T-cell leukemia virus type 1. Recurrent somatic mutations in host genes have exposed the T-cell receptor pathway through nuclear factor κB to interferon regulatory factor 4 (IRF4) as an essential driver for this malignancy. We sought to determine if IRF4 represents a therapeutic target for ATLL and to identify downstream effectors and biomarkers of IRF4 signaling in vivo.

Results

ATLL cell lines, particularly Tax viral oncoprotein-negative cell lines, that most closely resemble ATLL in humans, were sensitive to dose- and time-dependent inhibition by a next-generation class of IRF4 antisense oligonucleotides (ASOs) that employ constrained ethyl residues that mediate RNase H-dependent RNA degradation. ATLL cell lines were also sensitive to lenalidomide, which repressed IRF4 expression. Both ASOs and lenalidomide inhibited ATLL proliferation in vitro and in vivo. To identify biomarkers of IRF4-mediated CD4 + T-cell expansion in vivo, transcriptomic analysis identified several genes that encode key regulators of ATLL, including interleukin 2 receptor subunits α and β, KIT ligand, cytotoxic T-lymphocyte-associated protein 4, and thymocyte selection-associated high mobility group protein TOX 2.

Conclusions

These data support the pursuit of IRF4 as a therapeutic target in ATLL with the use of either ASOs or lenalidomide.

Antiretroviral Therapy in HTLV-1 Infection: An Updated Overview

The human T cell leukemic/lymphotropic virus type 1 (HTLV-1), discovered several years ago, is the causative agent for a rapid progressive haematological malignancy, adult T cell leukemia (ATL), for debilitating neurological diseases and for a number of inflammatory based diseases. Although the heterogeneous features of the diseases caused by HTLV-1, a common topic concerning related therapeutic treatments relies on the use of antiretrovirals. This review will compare the different approaches and opinions in this matter, giving a concise overview of preclinical as well as clinical studies covering all the aspects of antiretrovirals in HTLV-1 infection. Studies will be grouped on the basis of the class of antiretroviral, putting together both pre-clinical and clinical results and generally following a chronological order. Analysis of the existing literature highlights that a number of preclinical studies clearly demonstrate that different classes of antiretrovirals, already utilized as anti-HIV agents, are actually capable to efficiently contrast HTLV-1 infection. Nevertheless, the results of most of the clinical studies are generally discouraging on the same point. In conclusion, the design of new antiretrovirals more specifically focused on HTLV-1 targets, and/or the establishment of early treatments with antiretrovirals could hopefully change the perspectives of diseases caused by HTLV-1.

Molecular targeting of PD-1 signaling pathway as a novel therapeutic approach in HTLV-1 infection

HTLV-1, the first human oncogenic retrovirus, is a type C retrovirus that belongs to the Deltaretrovirus genus. The HTLV-1 genome has 8.5 kbp length, and consists of major genes such as gag, pol, pro, env, and pX region. This retrovirus is considered as one of the most deadly infectious agent for peripheral-blood mononuclear cells (PBMC). The infection of HTLV-1 can lead to dangerous complications, such as infective dermatitis (ID), uveitis, arthritis, lymphadenitis, arthropathies, Sjögren's Syndrome (SS), and particularly HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) or Adult T-Cell Leukemia Lymphoma (ATLL). At the moment, Zidovudine (AZT) plus IFN-α is the only treatment available for HTLV-1 infections. Based on scientific studies, alongside the therapeutic regimens, intrinsic mechanisms also play a determinant role in reducing the signs of disease. Programmed cell death-1 (PD-1) signaling pathway, one of the most important checkpoints, has recently received interest, such as the development of a novel generation of anti-tumors. In the present study, we discuss the role of PD-1 signaling pathway in HTLV-1 infection as well as its application as a novel approach for treatment of HTLV-1 infections.

The rapidly changing landscape in mature T-cell lymphoma (MTCL) biology and management

Historical advances in the care of patients with non-Hodgkin lymphoma (NHL) have been restricted largely to patients with B-cell lymphoma. The peripheral T-cell lymphomas (PTCLs), which are rare and heterogeneous in nature, have yet to experience the same degree of improvement in outcome over the past 20 to 30 years. It is estimated that there are approximately 80,000 and 14,000 cases, respectively, of NHL and Hodgkin lymphoma per year in the United States. As a subgroup of NHL, the PTCLs account for 6% to 10% of all cases of NHL, making them exceedingly rare. In addition, the World Health Organization 2017 classification describes 29 distinct subtypes of PTCL. This intrinsic diversity, coupled with its rarity, has stymied progress in the disease. In addition, most subtypes carry an inferior prognosis compared with their B-cell counterparts, an outcome largely attributed to the fact that most treatment paradigms for patients with PTCL have been derived from B-cell neoplasms, a radically different disease. In fact, the first drug ever approved for patients with PTCL was approved only a decade ago. The plethora of recent drug approvals in PTCL, coupled with a deeper understanding of the molecular pathogenesis of the disease, has stimulated the field to pursue new avenues of research that are now largely predicated on the development of novel, targeted small molecules, which include a host of epigenetic modifiers and biologics. There is an expectation these advances may begin to favorably challenge the chemotherapy paradigms that have been used in the T-cell malignancies.

Phosphorylated STAT3 expression predicts better prognosis in smoldering type of adult T-cell leukemia/lymphoma

Adult T‐cell leukemia/lymphoma (ATLL) is a mature T‐cell neoplasm, and is divided into 2 indolent (smoldering and chronic) and 2 aggressive (acute and lymphoma) clinical subtypes. Based on previous integrated molecular analyses suggesting the importance of the JAK‐STAT pathway in ATLL, we attempted to clarify the clinicopathological significance of this pathway. Clinical and morphological findings were reviewed in 116 cases with ATLL. The nuclear localizations of phosphorylated STAT3 (pSTAT3), pSTAT5, and pSTAT6 were analyzed by immunohistochemistry. Targeted sequencing was undertaken on the portion of STAT3 encoding the Src homology 2 domain. Expression of pSTAT3 was observed in 43% (50/116) of ATLL cases, whereas pSTAT5 and pSTAT6 were largely undetected. Cases with the lymphoma type showed significantly less frequent pSTAT3 expression (8/45, 18%) than those with the other subtypes (41/66, 62%; P < .001). STAT3 mutations were detected in 36% (10/28) and 19% (12/64) of cases with the smoldering and aggressive types of ATLL, respectively. The correlation between STAT3 mutation and pSTAT3 expression was not significant (P = .07). Both univariate and multivariate analysis revealed that pSTAT3 expression was significantly associated with better overall survival and progression‐free survival in the smoldering type of ATLL, whereas STAT3 mutation was not related to a line of clinical outcome. Collectively, our data show that only the lymphoma type showed a low prevalence of tumor cells positive for pSTAT3 expression, and raises the possibility that pSTAT3 expression is a novel biomarker to predict better prognosis in the smoldering type of ATLL.

The Unsolved Puzzle of c-Rel in B Cell Lymphoma

Aberrant constitutive activation of Rel/NF-κB transcription factors is a hallmark of numerous cancers. Of the five Rel family members, c-Rel has the strongest direct links to tumorigenesis. c-Rel is the only member that can malignantly transform lymphoid cells in vitro. Furthermore, c-Rel is implicated in human B cell lymphoma through the frequent occurrence of REL gene locus gains and amplifications. In normal physiology, high c-Rel expression predominates in the hematopoietic lineage and a diverse range of stimuli can trigger enhanced expression and activation of c-Rel. Both expression and activation of c-Rel are tightly regulated on multiple levels, indicating the necessity to keep its functions under control. In this review we meta-analyze and integrate studies reporting gene locus aberrations to provide an overview on the frequency of REL gains in human B cell lymphoma subtypes, namely follicular lymphoma, diffuse large B cell lymphoma, primary mediastinal B cell lymphoma, and classical Hodgkin lymphoma. We also summarize current knowledge on c-Rel expression and protein localization in these human B cell lymphomas and discuss the co-amplification of BCL11A with REL. In addition, we highlight and illustrate key pathways of c-Rel activation and regulation with a specific focus on B cell biology.

Molecular biology of human T cell leukemia virus

Human T cell leukemia virus type 1 (HTLV-1) is a horizontally transmitted virus infection of CD4+ lymphocytes which causes adult T cell leukemia-lymphoma (ATLL) and HTLV-associated myelopathy (HAM). The viral genome encodes two oncoproteins, transactivator protein (Tax) and helix basic zipper protein (HBZ), which are considered tumor initiator and maintenance factors, respectively. Tax is the primary inducer of clonal infected T cell expansion, and genetic instability. The immune response to Tax results in the selection of cells with little or no Tax expression, which have undergone genetic and epigenetic alterations that promote T cell activation, proliferation, and resistance to apoptosis. This selection of malignant cells occurs over several decades in 5% of infected individuals. Novel insights into the molecular details of each of these events has led to targeted therapies for ATLL.

Epidemiology, clinical features, and outcome of HTLV-1-related ATLL in an area of prevalence in the United States

Adult T-cell leukemia/lymphoma (ATLL) is a fatal disease caused by human T-cell leukemia virus type 1 (HTLV-1). We retrospectively analyzed 195 patients with ATLL (lymphomatous n = 96, acute n = 80, unfavorable chronic n = 7, chronic n = 5, smoldering n = 3, and unclassified n = 4) diagnosed between 1987 and 2016 (median age 52 years, 77% Afro-Caribbean). Hypercalcemia was associated with acute ATLL (65%, vs 23% lymphomatous) (P = .012). The median survival for patients treated with modern therapies between 2000 and 2016 was 4.1 months for acute, 10.2 months for lymphomatous, 72 months for chronic/smoldering, and not reached for unfavorable chronic type, with 4-year survival rates of 10%, 4%, 60%, and 83%, respectively. The overall response rate (ORR) after first-line multiagent chemotherapy was 78% (complete response [CR] 39%) for acute vs 67% (CR 33%) for lymphomatous ATLL. First-line zidovudine interferon-α (AZT-IFN) resulted in ORR of 56% (CR 23%) for acute (n = 43), 33% (CR 16.5%) for lymphomatous (n = 6), and 86% (CR 29%) for unfavorable chronic ATLL. The median progression-free survival (PFS) in patients with aggressive ATLL who achieved CR after AZT-IFN was 48 months vs 11 months after chemotherapy (P = .003). Allogeneic hematopoietic stem cell transplant (allo-HSCT) resulted in a PFS of 24 and 28 months in 2 patients with lymphomatous ATLL. Our results suggest high-dose AZT-IFN is a reasonable up-front option for patients with aggressive leukemic ATLL followed by chemotherapy switch in nonresponders, whereas chemotherapy should be used in lymphomatous type followed by allo-HSCT when feasible.

Revised Adult T-Cell Leukemia-Lymphoma International Consensus Meeting Report

PURPOSE

Adult T-cell leukemia-lymphoma (ATL) is a distinct mature T-cell malignancy caused by chronic infection with human T-lymphotropic virus type 1 with diverse clinical features and prognosis. ATL remains a challenging disease as a result of its diverse clinical features, multidrug resistance of malignant cells, frequent large tumor burden, hypercalcemia, and/or frequent opportunistic infection. In 2009, we published a consensus report to define prognostic factors, clinical subclassifications, treatment strategies, and response criteria. The 2009 consensus report has become the standard reference for clinical trials in ATL and a guide for clinical management. Since the last consensus there has been progress in the understanding of the molecular pathophysiology of ATL and risk-adapted treatment approaches.

METHODS

Reflecting these advances, ATL researchers and clinicians joined together at the 18th International Conference on Human Retrovirology-Human T-Lymphotropic Virus and Related Retroviruses-in Tokyo, Japan, March, 2017, to review evidence for current clinical practice and to update the consensus with a new focus on the subtype classification of cutaneous ATL, CNS lesions in aggressive ATL, management of elderly or transplantation-ineligible patients, and treatment strategies that incorporate up-front allogeneic hematopoietic stem-cell transplantation and novel agents.

RESULTS

As a result of lower-quality clinical evidence, a best practice approach was adopted and consensus statements agreed on by coauthors (> 90% agreement).

CONCLUSION

This expert consensus highlights the need for additional clinical trials to develop novel standard therapies for the treatment of ATL.

Decreased RORC expression and downstream signaling in HTLV-1-associated adult T-cell lymphoma/leukemia uncovers an antiproliferative IL17 link: A potential target for immunotherapy?

Retinoic acid‐related drugs have shown promising pre‐clinical activity in Adult T‐cell Leukemia/Lymphoma, but RORC signaling has not been explored. Therefore, we investigated transcriptome‐wide interactions of the RORC pathway in HTLV‐1 and ATL, using our own and publicly available gene expression data for ATL and other leukemias. Gene expression data from ATL patients were analyzed using WGCNA to determine gene modules and their correlation to clinical and molecular data. Both PBMCs and CD4⁺ T‐Cells exhibited decreased RORC expression in four different ATL cohorts. A small subset of RORC^hi ATL patients was identified with significantly lower pathognomonic CADM1 and HBZ levels but similar levels of other ATL markers (CD4/CD25/CCR4), hinting at a less aggressive ATL subtype. An age‐dependent decrease in RORC expression was found in HTLV‐1‐infected individuals, but not in healthy controls, suggesting an early molecular event predisposing to leukemogenesis. Genes upstream of RORC signaling were members of a proliferative gene module (containing proliferation markers PCNA/Ki67), whereas downstream members clustered in an anti‐proliferative gene module. IL17C transcripts showed the strongest negative correlation to PCNA in both ATL cohorts, which was replicated in two large cohorts of T‐ and B‐cell acute lymphoid leukemia (ALL). Finally, IL17C expression in purified CD4 + CCR4 + CD26‐CD7‐ “ATL‐like” cells from HTLV‐1‐infected individuals and ATL patients was negatively correlated with clonality, underscoring a possible antileukemic/antiproliferative role. In conclusion, decreased RORC expression and downstream signaling might represent an early event in ATL pathogenesis. An antiproliferative IL17C/PCNA link is shared between ATL, T‐ALL and B‐ALL, suggesting (immuno)therapeutic benefit of boosting RORC/IL17 signaling.

What's new?

Drugs that affect the retinoic acid pathway are of interest for the treatment of adult T‐cell leukemia (ATL). Here, investigation of the role of retinoic acid‐related orphan receptor C (RORC), a regulator of the proinflammatory Th17/IL‐17 axis, reveals a prevailing occurrence of low RORC expression among ATL patients. By comparison, fewer patients exhibited a RORC^hi phenotype, which was associated with reduced levels of pathognomonic biomarkers CADM1 and HbZ, indicating a protective role for elevated RORC. An antiproliferative link was identified between RORC and IL17C. The data suggest that strategies to increase RORC/IL17C signaling could be important to improving ATL outcomes.

Cytokine Networks Dysregulation during HTLV-1 Infection and Associated Diseases

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of a neural chronic inflammation, called HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and of a malignant lymphoproliferation, called the adult T-cell leukemia/lymphoma (ATLL). The mechanisms through which the HTLV-1 induces these diseases are still unclear, but they might rely on immune alterations. HAM/TSP is associated with an impaired production of pro-inflammatory cytokines and chemokines, such as IFN-γ, TNF-α, CXCL9, or CXCL10. ATLL is associated with high levels of IL-10 and TGF-β. These immunosuppressive cytokines could promote a protumoral micro-environment. Moreover, HTLV-1 infection impairs the IFN-I production and signaling, and favors the IL-2, IL-4, and IL-6 expression. This contributes both to immune escape and to infected cells proliferation. Here, we review the landscape of cytokine dysregulations induced by HTLV-1 infection and the role of these cytokines in the HTLV-1-associated diseases progression.

Constitutive activation and overexpression of NF-κB/c-Rel in conjunction with p50 contribute to aggressive tongue tumorigenesis

Tongue squamous cell carcinoma (TSCC) is a most aggressive head and neck cancer often associated with a poor survival rate. Yet, it always shows better prognosis in presence of HPV16 infection. NF-κB plays a pivotal role in carcinogenesis and chemo-radio resistance of cancer but its role in tongue cancer is not yet explored. In this study, a total of hundred tongue tissue biopsies comprising precancer, cancer and adjacent normal controls including two tongue cancer cell lines (HPV^+/−ve) were employed to examine expression and transactivation of NF-κB proteins, their silencing by siRNA and invasion assays to understand their contributions in tongue carcinogenesis. An exclusive prevalence (28%) of HR-HPV type 16 was observed mainly in well differentiated tumors (78.5%). Increased DNA binding activity and differential expression of NF-κB proteins was observed with p50 and c-Rel being the two major DNA binding partners forming the functional NF-κB complex that increased as a function of severity of lesions in both HPV^+/−ve tumors but selective participation of p65 in HPV16^+ve TSCCs induced well differentiation of tumors resulting in better prognosis. siRNA treatment against c-Rel or Fra-2 led to upregulation of p27 but strong inhibition of c-Rel, c-Jun, c-myc, HPVE6/E7 and Fra-2 which is exclusively overexpressed in HPV^−ve aggressive tumors. In conclusion, selective participation of c-Rel with p50 that in cross-talk with AP-1/Fra-2 induced poor differentiation and aggressive tumorigenesis mainly in HPV^−ve smokers while HPV infection induced expression of p65 and p27 leading to well differentiation and better prognosis preferably in non-smoking TSCC patients.

Targeting the HTLV-I-Regulated BATF3/IRF4 Transcriptional Network in Adult T Cell Leukemia/Lymphoma

Adult T cell leukemia/lymphoma (ATLL) is a frequently incurable disease associated with the human lymphotropic virus type I (HTLV-I). RNAi screening of ATLL lines revealed that their proliferation depends on BATF3 and IRF4, which cooperatively drive ATLL-specific gene expression. HBZ, the only HTLV-I encoded transcription factor that is expressed in all ATLL cases, binds to an ATLL-specific BATF3 super-enhancer and thereby regulates the expression of BATF3 and its downstream targets, including MYC. Inhibitors of bromodomain-and-extra-terminal-domain (BET) chromatin proteins collapsed the transcriptional network directed by HBZ and BATF3, and were consequently toxic for ATLL cell lines, patient samples, and xenografts. Our study demonstrates that the HTLV-I oncogenic retrovirus exploits a regulatory module that can be attacked therapeutically with BET inhibitors.

MicroRNA-3662 expression correlates with antiviral drug resistance in adult T-cell leukemia/lymphoma cells

Interferon regulatory factor (IRF) 4 and the proto-oncogene c-Rel cooperate in growth and antiviral drug resistance of adult T-cell leukemia/lymphoma (ATLL). To elucidate the target of IRF4 and c-Rel in ATLL, we determined the simultaneous binding sites of IRF4 and c-Rel using ChIP-seq technology. Nine genes were identified within 2 kb of binding sites, including MIR3662. Expression of miR-3662 was regulated by IRF4, and to a lesser extent by c-Rel. Cell proliferation was inhibited by knockdown of miR-3662 and expression of miR-3662 was correlated with antiviral drug resistance in ATLL cell lines. Thus, miR-3662 represents a target for therapies against ATLL.

An activating mutation of interferon regulatory factor 4 (IRF4) in adult T-cell leukemia

The human T-cell leukemia virus-1 (HTLV-1) oncoprotein Tax drives cell proliferation and resistance to apoptosis early in the pathogenesis of adult T-cell leukemia (ATL). Subsequently, probably as a result of specific immunoediting, Tax expression is down-regulated and functionally replaced by somatic driver mutations of the host genome. Both amplification and point mutations of interferon regulatory factor 4 (IRF4) have been previously detected in ATL., K59R is the most common single-nucleotide variation of IRF4 and is found exclusively in ATL. High-throughput whole-exome sequencing revealed recurrent activating genetic alterations in the T-cell receptor, CD28, and NF-κB pathways. We found that IRF4, which is transcriptionally activated downstream of these pathways, is frequently mutated in ATL. IRF4 RNA, protein, and IRF4 transcriptional targets are uniformly elevated in HTLV-1-transformed cells and ATL cell lines, and IRF4 was bound to genomic regulatory DNA of many of these transcriptional targets in HTLV-1-transformed cell lines. We further noted that the K59R IRF4 mutant is expressed at higher levels in the nucleus than WT IRF4 and is transcriptionally more active. Expression of both WT and the K59R mutant of IRF4 from a constitutive promoter in retrovirally transduced murine bone marrow cells increased the abundance of T lymphocytes but not myeloid cells or B lymphocytes in mice. IRF4 may represent a therapeutic target in ATL because ATL cells select for a mutant of IRF4 with higher nuclear expression and transcriptional activity, and overexpression of IRF4 induces the expansion of T lymphocytes in vivo.

Prognostic relevance of integrated genetic profiling in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is a heterogeneous group of peripheral T-cell malignancies characterized by human T-cell leukemia virus type-1 infection, whose genetic profile has recently been fully investigated. However, it is still poorly understood how these alterations affect clinical features and prognosis. We investigated the effects of genetic alterations commonly found in ATL on disease phenotypes and clinical outcomes, based on genotyping data obtained from 414 and 463 ATL patients using targeted-capture sequencing and single nucleotide polymorphism array karyotyping, respectively. Aggressive (acute/lymphoma) subtypes were associated with an increased burden of genetic and epigenetic alterations, higher frequencies of TP53 and IRF4 mutations, and many copy number alterations (CNAs), including PD-L1 amplifications and CDKN2A deletions, compared with indolent (chronic/smoldering) subtypes. By contrast, STAT3 mutations were more characteristic of indolent ATL. Higher numbers of somatic mutations and CNAs significantly correlated with worse survival. In a multivariate analysis incorporating both clinical factors and genetic alterations, the Japan Clinical Oncology Group prognostic index high-risk, older age, PRKCB mutations, and PD-L1 amplifications were independent poor prognostic factors in aggressive ATL. In indolent ATL, IRF4 mutations, PD-L1 amplifications, and CDKN2A deletions were significantly associated with shorter survival, although the chronic subtype with unfavorable clinical factors was only marginally significant. Thus, somatic alterations characterizing aggressive diseases predict worse prognosis in indolent ATL, among which PD-L1 amplifications are a strong genetic predictor in both aggressive and indolent ATL. ATL subtypes are further classified into molecularly distinct subsets with different prognosis. Genetic profiling might contribute to improved prognostication and management of ATL patients.

IL-10-mediated signals act as a switch for lymphoproliferation in Human T-cell leukemia virus type-1 infection by activating the STAT3 and IRF4 pathways

Human T-cell leukemia virus type-1 (HTLV-1) causes two distinct diseases, adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Since there are no disease-specific differences among HTLV-1 strains, the etiological mechanisms separating these respective lymphoproliferative and inflammatory diseases are not well understood. In this study, by using IL-2-dependent HTLV-1-infected T-cell lines (ILTs) established from patients with ATL and HAM/TSP, we demonstrate that the anti-inflammatory cytokine IL-10 and its downstream signals potentially act as a switch for proliferation in HTLV-1-infected cells. Among six ILTs used, ILTs derived from all three ATL patients grew much faster than those from three HAM/TSP patients. Although most of the ILTs tested produced IFN-γ and IL-6, the production of IL-10 was preferentially observed in the rapid-growing ILTs. Interestingly, treatment with exogenous IL-10 markedly enhanced proliferation of the slow-growing HAM/TSP-derived ILTs. The IL-10-mediated proliferation of these ILTs was associated with phosphorylation of STAT3 and induction of survivin and IRF4, all of which are characteristics of ATL cells. Knockdown of STAT3 reduced expression of IL-10, implying a positive-feedback regulation between STAT3 and IL-10. STAT3 knockdown also reduced survivin and IRF4 in the IL-10- producing or IL-10- treated ILTs. IRF4 knockdown further suppressed survivin expression and the cell growth in these ILTs. These findings indicate that the IL-10-mediated signals promote cell proliferation in HTLV-1-infected cells through the STAT3 and IRF4 pathways. Our results imply that, although HTLV-1 infection alone may not be sufficient for cell proliferation, IL-10 and its signaling pathways within the infected cell itself and/or its surrounding microenvironment may play a critical role in pushing HTLV-1-infected cells towards proliferation at the early stages of HTLV-1 leukemogenesis. This study provides useful information for understanding of disease mechanisms and disease-prophylactic strategies in HTLV-1 infection.

Inhibition of c-REL using siRNA increased apoptosis and decreased proliferation in pre-B ALL blasts: Therapeutic implications

The c-Rel transcription factor is a unique member of the NF-kB family that has a role in apoptosis, proliferation and cell survival. Overexpression of c-Rel is detected in many human B cell tumors, including B-cell leukemia and several cancers. The study aimed to investigate the effects of c-Rel siRNA on the proliferation and apoptosis of relapsed pre-B acute leukemia cells. The c-Rel siRNA was transfected into Leukemia cells using an Amaxa cell line Nucleofector kit L (Lonza). Quantitative real-time RT-PCR (qRT-PCR) and western blot were done to measure the expression levels of mRNA and protein, respectively. The flow cytometry was used to analyze the effect of c-Rel siRNA on the apoptosis and proliferation of Leukemia cells. Observed c-Rel expression in the 5 pre-B Acute lymphoblastic leukemia (ALL) patients were higher than the normal cells. The c-Rel siRNA transfection significantly blocked the expression of c-Rel mRNA in a time-dependent manner, leading to a strong growth inhibition and enhanced apoptosis (P<0.05). Our results demonstrated that c-Rel plays a fundamental role in the survival. Therefore, c-Rel can be considered as an attractive target for gene therapy in ALL patients. Also siRNA-mediated silencing of this gene may be a novel strategy in ALL treatment.

Genetic alterations in adult T-cell leukemia/lymphoma

Adult T‐cell leukemia/lymphoma (ATL) is a peripheral T‐cell neoplasm with a dismal prognosis. It is caused by human T‐cell leukemia virus type‐1 (HTLV‐1) retrovirus. A long latency period from HTLV‐1 infection to ATL onset suggests that not only HTLV‐1 proteins, such as Tax and HBZ, but also additional genetic and/or epigenetic events are required for ATL development. Although many studies have demonstrated the biological functions of viral genes, alterations of cellular genes associated with ATL have not been fully investigated. Recently, a large‐scale integrated genetic analysis revealed the entire landscape of somatic aberrations in ATL. This neoplasm is characterized by frequent gain‐of‐function alterations in components of the T‐cell receptor/NF‐κB signaling pathway, including activating mutations in the PLCG1,PRKCB,CARD11 and VAV1 genes, and CTLA4‐CD28 and ICOS‐CD28 fusions. Importantly, molecules associated with immune surveillance, such as HLA‐A/B,CD58 and FAS, are affected recurrently. Among them, one notable lesion occurs as frequent structural variations that truncate the PD‐L1 3′‐untranslated region, leading to its overexpression. Other genetic targets include transcription factors (IRF4,IKZF2, and GATA3) and chemokine receptors (CCR4,CCR7 and GPR183), which are functionally relevant in normal T cells. A substantial proportion of ATL cases show widespread accumulation of repressive epigenetic changes, such as trimethylation of histone H3 lysine 27 and DNA hypermethylation of CpG islands, which coordinately modulate multiple pathways, including Cys2‐His2 zinc finger genes involved in silencing retroelements. Here we review the current understanding of the genetic/epigenetic aberrations in ATL, focusing on their relevance in its molecular pathogenesis.

LMP1 signaling pathway activates IRF4 in latent EBV infection and a positive circuit between PI3K and Src is required

Interferon (IFN) regulatory factors (IRFs) have crucial roles in immune regulation and oncogenesis. We have recently shown that IRF4 is activated through c-Src-mediated tyrosine phosphorylation in virus-transformed cells. However, the intracellular signaling pathway triggering Src activation of IRF4 remains unknown. In this study, we provide evidence that Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) promotes IRF4 phosphorylation and markedly stimulates IRF4 transcriptional activity, and that Src mediates LMP1 activation of IRF4. As to more precise mechanism, we show that LMP1 physically interacts with c-Src, and the phosphatidylinositol 3 kinase (PI3K) subunit P85 mediates their interaction. Depletion of P85 by P85-specific short hairpin RNAs disrupts their interaction and diminishes IRF4 phosphorylation in EBV-transformed cells. Furthermore, we show that Src is upstream of PI3K for activation of both IRF4 and Akt. In turn, inhibition of PI3K kinase activity by the PI3K-speicfic inhibitor LY294002 impairs Src activity. Our results show that LMP1 signaling is responsible for IRF4 activation, and further characterize the IRF4 regulatory network that is a promising therapeutic target for specific hematological malignancies.

Human T-cell leukemia virus-associated malignancy

Human T-cell leukemia virus type 1 (HTLV-1) is a tumorigenic delta retrovirus and the causative infectious agent of a non-Hodgkin's peripheral T-cell malignancy called adult T-cell leukemia/lymphoma (ATL). ATL develops in approximately 5% of infected individuals after a significant clinical latency period of several decades. Clinical classifications of ATL include smoldering, chronic, lymphoma, and acute subtypes, with varying median survival ranges of a few months to several years. Depending on the ATL subtype and disease symptoms, treatment options include 'watchful waiting', chemotherapy, antiviral therapy, allogeneic hematopoietic stem cell transplantation (alloHSCT), and targeted therapies. Herein we review the characteristics and development of ATL, as well as current and future treatment options and perspectives.

Treatment of adult T-cell leukaemia/lymphoma: is the virus a target?

PURPOSE OF REVIEW

To discuss current understanding of the mechanisms of human T-lymphotropic virus type-1 (HTLV-1) tumorigenesis and current and potential treatment strategies for adult T-cell leukaemia/lymphoma (ATL), an aggressive malignant disease of CD4 cells caused by HTLV-1.

RECENT FINDINGS

Treatment of the aggressive subtypes of ATL remains inadequate, with little improvement in overall survival in the 30 years since HTLV-1 was discovered. Detailed analysis of the clonal expansion of HTLV-1 has provided new insight into pathogenesis. Most HTLV-1-infected cells, including ATL, express CCR4 which can be targeted. Reports of antitumour effects with allogeneic bone marrow transplantation provide a rationale for novel immunotherapy approaches. Progress has been made in the indolent subtypes of ATL with the use of 'antiviral' therapies.

SUMMARY

ATL has poor prognosis. There is a major, urgent, unmet clinical need to identify HTLV carriers who will develop ATL to develop biomarkers of transforming disease and disease progression and to provide novel treatment approaches within the context of clinical trials. Several strategies now include putative or actual antiviral therapy. Potentially, the risk of ATL would be reduced by eliminating some or all infected clones. HTLV-1 infection, and hence ATL, can be prevented by antenatal HTLV-1 screening.

c-Rel and its many roles in cancer: an old story with new twists

When the genes encoding NF-κB subunits were first isolated, their homology to the previously identified c-Rel proto-oncogene and its viral homologue v-Rel was clear. This provided the first indication that these transcription factors also had a role in cancer. Because of its homology to v-Rel, which transforms chicken B cells together with the important role c-Rel can have as a regulator of B- and T-cell proliferation, most attention has focussed on its role in B-cell lymphomas, where the REL gene is frequently amplified. However, a growing number of reports now indicate that c-Rel has important functions in many solid tumours, although studies in mice suggest it may not always function as an oncogene. Moreover, c-Rel is a critical regulator of fibrosis, which provides an environment for tumour development in many settings. Overall, c-Rel is emerging as a complex regulator of tumorigenesis, and there is still much to learn about its functions in human malignancies and the response to cancer therapies.

The Emerging Role of miRNAs in HTLV-1 Infection and ATLL Pathogenesis

Human T-cell leukemia virus (HTLV)-1 is a human retrovirus and the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a fatal malignancy of CD4/CD25+ T lymphocytes. In recent years, cellular as well as virus-encoded microRNA (miRNA) have been shown to deregulate signaling pathways to favor virus life cycle. HTLV-1 does not encode miRNA, but several studies have demonstrated that cellular miRNA expression is affected in infected cells. Distinct mechanisms such as transcriptional, epigenetic or interference with miRNA processing machinery have been involved. This article reviews the current knowledge of the role of cellular microRNAs in virus infection, replication, immune escape and pathogenesis of HTLV-1.

Regulation pattern of fish irf4 (the gene encoding IFN regulatory factor 4) by STAT6, c-Rel and IRF4

Interferon regulatory factor 4 (IRF4) plays pivotal roles in both innate and adaptive immune responses in mammals. In fish, there are two homologues of irf4, irf4a and irf4b. In this study, we examined the regulatory patterns of zebrafish irf4a and irf4b by STAT6 and c-Rel. Firstly, expression of irf4a and irf4b was monitored in several tissues at mRNA level. By infection with SVCV, irf4a and irf4b were upregulated in both kidney and spleen, and were immediately induced by treatment with poly I:C in ZF4 cells. Moreover, the activation of irf4a promoter was regulated by overexpression of stat6 and c-rel in a cooperation manner, which could be inhibited by mutation of the putative binding sites of STAT6 and c-Rel in irf4a promoter region. However, irf4b promoter was activated slightly only by STAT6 but not c-Rel. Furthermore, overexpression of irf4a inhibited the activation of its own promoter under induction of STAT6 and c-Rel, which was the result of that IRF4a bound to STAT6 and c-Rel directly. In addition, cellular location analysis showed that IRF4a was located only in nuclear region. These data indicate that fish irf4a can also be upregulated by STAT6 and c-Rel.

The oncogenic transcription factor IRF4 is regulated by a novel CD30/NF-κB positive feedback loop in peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTCLs) are generally aggressive non-Hodgkin lymphomas with poor overall survival rates following standard therapy. One-third of PTCLs express interferon regulatory factor-4 (IRF4), a tightly regulated transcription factor involved in lymphocyte growth and differentiation. IRF4 drives tumor growth in several lymphoid malignancies and has been proposed as a candidate therapeutic target. Because direct IRF4 inhibitors are not clinically available, we sought to characterize the mechanism by which IRF4 expression is regulated in PTCLs. We demonstrated that IRF4 is constitutively expressed in PTCL cells and drives Myc expression and proliferation. Using an inhibitor screen, we identified nuclear factor κB (NF-κB) as a candidate regulator of IRF4 expression and cell proliferation. We then demonstrated that the NF-κB subunits p52 and RelB were transcriptional activators of IRF4. Further analysis showed that activation of CD30 promotes p52 and RelB activity and subsequent IRF4 expression. Finally, we showed that IRF4 transcriptionally regulates CD30 expression. Taken together, these data demonstrate a novel positive feedback loop involving CD30, NF-κB, and IRF4; further evidence for this mechanism was demonstrated in human PTCL tissue samples. Accordingly, NF-κB inhibitors may represent a clinical means to disrupt this feedback loop in IRF4-positive PTCLs.

A critical role for IL-17RB signaling in HTLV-1 tax-induced NF-κB activation and T-cell transformation

Human T-cell leukemia virus type 1 (HTLV-1) infection is linked to the development of adult T-cell leukemia (ATL) and the neuroinflammatory disease HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 Tax protein functions as a potent viral oncogene that constitutively activates the NF-κB transcription factor to transform T cells; however, the underlying mechanisms remain obscure. Here, using next-generation RNA sequencing we identified the IL-25 receptor subunit IL-17RB as an aberrantly overexpressed gene in HTLV-1 immortalized T cells. Tax induced the expression of IL-17RB in an IκB kinase (IKK) and NF-κB-dependent manner. Remarkably, Tax activation of the canonical NF-κB pathway in T cells was critically dependent on IL-17RB expression. IL-17RB and IL-25 were required for HTLV-1-induced immortalization of primary T cells, and the constitutive NF-κB activation and survival of HTLV-1 transformed T cells. IL-9 was identified as an important downstream target gene of the IL-17RB pathway that drives the proliferation of HTLV-1 transformed cells. Furthermore, IL-17RB was overexpressed in leukemic cells from a subset of ATL patients and also regulated NF-κB activation in some, but not all, Tax-negative ATL cell lines. Together, our results support a model whereby Tax instigates an IL-17RB-NF-κB feed-forward autocrine loop that is obligatory for HTLV-1 leukemogenesis.

Gene expression profiling identifies IRF4-associated molecular signatures in hematological malignancies

The lymphocyte-specific transcription factor Interferon (IFN) Regulatory Factor 4 (IRF4) is implicated in certain types of lymphoid and myeloid malignancies. However, the molecular mechanisms underlying its interactions with these malignancies are largely unknown. In this study, we have first profiled molecular signatures associated with IRF4 expression in associated cancers, by analyzing existing gene expression profiling datasets. Our results show that IRF4 is overexpressed in melanoma, in addition to previously reported contexts including leukemia, myeloma, and lymphoma, and that IRF4 is associated with a unique gene expression pattern in each context. A pool of important genes involved in B-cell development, oncogenesis, cell cycle regulation, and cell death including BATF, LIMD1, CFLAR, PIM2, and CCND2 are common signatures associated with IRF4 in non-Hodgkin B cell lymphomas. We confirmed the correlation of IRF4 with LIMD1 and CFLAR in a panel of cell lines derived from lymphomas. Moreover, we profiled the IRF4 transcriptome in the context of EBV latent infection, and confirmed several genes including IFI27, IFI44, GBP1, and ARHGAP18, as well as CFLAR as novel targets for IRF4. These results provide valuable information for understanding the IRF4 regulatory network, and improve our knowledge of the unique roles of IRF4 in different hematological malignancies.

Interferon regulatory factor 4 is activated through c-Src-mediated tyrosine phosphorylation in virus-transformed cells

The importance of the oncogenic transcription factor interferon regulatory factor 4 (IRF4) in hematological malignancies has been increasingly recognized. We have previously identified the B cell integration cluster (BIC), the gene encoding miR-155, as the first microRNA (miRNA)-encoding gene transcriptionally targeted by IRF4 in virus-transformed cancer cells. Activation of IRFs is prerequisite for their functions. However, how IRF4 is activated in cancer is an open question. Our phosphoproteome profiling has identified several tyrosine phosphorylation sites on IRF4 in Epstein-Barr virus (EBV)-transformed cells. Further, we show here that c-Src dramatically stimulates IRF4 phosphorylation and activity and that Y61 and Y124 are two key sites responding to c-Src-mediated activation. Consistently, c-Src is constitutively expressed and active in EBV-transformed cells. However, c-Src is unlikely to be a direct kinase for IRF4. Furthermore, we have a polyclonal antibody specific to phospho-IRF4(Y121/124) developed in rabbit. We have further shown that inhibition of c-Src activity reduces p-IRF4(Y121/124) and significantly represses transcription of the IRF4 target BIC in EBV-transformed cells. Our results therefore, for the first time, demonstrate that IRF4 is phosphorylated and activated through a c-Src-mediated pathway in virus-transformed cells. These findings will improve our understanding of IRF4 in neoplasia and will provide profound insights into the interaction of oncogenic viruses with IRF4 in the development of hematological malignancies.

"Antivirals" in the treatment of adult T cell leukaemia- lymphoma (ATLL)

Adult T cell leukaemia / lymphoma (ATLL) is a mature (post thymic) T cell lymphoma caused by the human T-lymphotropic virus type 1 (HTLV-1) infection. Overall survival in the aggressive subtypes (Acute Leukaemia and Lymphomatous) remains poor in part due to chemotherapy resistance. To improve treatment outcome for de novo disease, better induction therapies are required and since the pathogenic agent is known it would seem sensible to target the virus. In a recent meta-analysis the use of zidovudine and interferon alpha (ZDV/IFN) has been associated with improved response rates and prolonged overall survival in leukemic subtypes of ATLL (both acute and Chronic) confirmed in a multivariate analysis. In a more recent UK study the overall response rate for patients with aggressive ATLL treated with chemotherapy alone was 49 % compared to 81 % with combined first line therapy (chemotherapy with concurrent or sequential ZDV/IFN). Combined first line therapy prolonged median OS in acute (p = 0.0081) and lymphomatous ATLL (p = 0.001).These data support the use of low dose ZDV/IFN with chemotherapy as first line treatment for patients with newly diagnosed aggressive ATLL. Although the mechanisms of action are incompletely understood, some possible explanations for their efficacy will be discussed.

Markedly additive antitumor activity with the combination of a selective survivin suppressant YM155 and alemtuzumab in adult T-cell leukemia

Adult T-cell leukemia (ATL) is an aggressive malignancy of CD4(+)CD25(+) lymphocytes caused by human T-cell lymphotropic virus type 1. Currently, there is no accepted curative therapy for ATL. In gene expression profiling, the antiapoptotic protein survivin (BIRC5) demonstrated a striking increase in ATL, and its expression was increased in patient ATL cells resistant to the anti-CD52 monoclonal antibody alemtuzumab (Campath-1H). In this study, we investigated the antitumor activity of a small-molecule survivin suppressant YM155 alone and in combination with alemtuzumab in a murine model of human ATL (MET-1). Both YM155 alone and its combination with alemtuzumab demonstrated therapeutic efficacy by lowering serum soluble IL-2Rα (sIL-2Rα) levels (P < .001) and prolonged the survival of tumor-bearing mice (P < .0001). Moreover, the combination of YM155 with alemtuzumab demonstrated markedly additive antitumor activity by significantly lowering serum sIL-2Rα levels and improving the survival of leukemia-bearing mice compared with monotherapy with either YM155 (P < .001) or alemtuzumab (P < .05). More significantly, all mice that received the combination therapy survived and were tumor free >6 months after treatment. Our data support a clinical trial of the combination of YM155 with alemtuzumab in ATL. This trial was registered at www.clinicaltrials.gov as #NCT00061048.

Simultaneous RNA quantification of human and retroviral genomes reveals intact interferon signaling in HTLV-1-infected CD4+ T cell lines

BACKGROUND

IFN-α contributes extensively to host immune response upon viral infection through antiviral, pro-apoptotic, antiproliferative and immunomodulatory activities. Although extensively documented in various types of human cancers and viral infections, controversy exists in the exact mechanism of action of IFN-α in human immunodeficiency virus type 1 (HIV-1) and human T-lymphotropic virus type 1 (HTLV-1) retroviral infections.

RESULTS

IFN-α displayed strong anti-HIV-1 effects in HIV-1/HTLV-1 co-infected MT-4 cells in vitro, demonstrated by the dose-dependent inhibition of the HIV-1-induced cytopathic effect (IC50 = 83.5 IU/ml, p < 0.0001) and p24 levels in cell-free supernatant (IC50 = 1.2 IU/ml, p < 0.0001). In contrast, IFN-α treatment did not affect cell viability or HTLV-1 viral mRNA levels in HTLV-1 mono-infected cell lines, based on flow cytometry and nCounter analysis, respectively. However, we were able to confirm the previously described post-transcriptional inhibition of HTLV-1 p19 secretion by IFN-α in cell lines (p = 0.0045), and extend this finding to primary Adult T cell Leukemia patient samples (p = 0.031). In addition, through microarray and nCounter analysis, we performed the first genome-wide simultaneous quantification of complete human and retroviral transciptomes, demonstrating significant transcriptional activation of interferon-stimulated genes without concomitant decrease of HTLV-1 mRNA levels.

CONCLUSIONS

Taken together, our results indicate that both the absence of in vitro antiproliferative and pro-apoptotic activity as well as the modest post-transcriptional antiviral activity of IFN-α against HTLV-1, were not due to a cell-intrinsic defect in IFN-α signalisation, but rather represents a retrovirus-specific phenomenon, considering the strong HIV-1 inhibition in co-infected cells.

Use of Zidovudine and Interferon Alfa With Chemotherapy Improves Survival in Both Acute and Lymphoma Subtypes of Adult T-Cell Leukemia/Lymphoma

Purpose

Adult T-cell leukemia/lymphoma (ATLL) is a mature (post-thymic) T-cell lymphoma associated with human T-lymphotropic virus type 1 infection. Survival in aggressive subtypes remains poor, and treatment resistance is frequent. Use of zidovudine (ZDV) and interferon alfa (IFN-α) has been associated with improved response rates in small studies and prolonged overall survival in leukemic ATLL subtypes in a recent meta-analysis.

Patients and Methods

We report the clinicopathologic characteristics, treatment, and outcome of 73 patients with aggressive ATLL (acute ATLL, 29; lymphoma ATLL, 44) diagnosed and treated in England between 1999 and 2009. The impact of ZDV/IFN-α on treatment response and survival was assessed.

Results

The overall response rate ranged from 49% with chemotherapy alone to 81% with combined first-line therapy (chemotherapy with concurrent/sequential ZDV/IFN-α). Median overall survival (OS) was 9 months: 7.5 months for acute ATLL and 10 months for lymphoma ATLL. Use of ZDV/IFN-α at any time prolonged survival in acute (P < .001) and lymphoma ATLL (P < .001) and was the sole factor associated with reduction in risk of death in aggressive ATLL (hazard ratio, 0.23; 95% CI, 0.09 to 0.60; P = .002). Combined first-line therapy prolonged median OS in acute (P = .0081) and lymphoma ATLL (P = .001) compared with chemotherapy alone.

Conclusion

These data support the use of low-dose ZDV/IFN-α with chemotherapy in first-line treatment of acute and lymphoma ATLL.

Newly emerging therapies targeting viral-related lymphomas

Gamma-(γ)-herpes virus lymphomas comprise a heterogenous group of B-cell and T-cell neoplasms most commonly associated with Epstein-Barr virus and rarely human herpes virus-8 infection. Adult T-cell leukemia/lymphoma (ATLL) is a unique disease entity caused by the human T-cell lymphotrophic virus, type 1 (HTLV-I), the only retrovirus known to cause cancer in humans. Viral lymphomas behave aggressively and disproportionally affect immunocompromised individuals and those living in underdeveloped regions. These diseases are often difficult to treat with conventional approaches. Despite recent advancements using cytotoxic, lymphoma-specific, and adoptive therapies, the long-term outcome of patients with γ-herpesvirus lymphomas occurring in severely immunocompromised patients and ATLL continues to be poor. Lytic-inducing therapies targeting NF-κB, and viral and tumor cell epigenetic mechanisms afford the advantage of exploiting the intrinsic presence of oncogenic viruses to eradicate infected tumor cells. In this review, viral-related lymphomas and newly emerging clinical approaches targeting viral latency are discussed.

An update on the management of peripheral T-cell lymphoma and emerging treatment options

Peripheral T-cell lymphomas (PTCLs) comprise a rare and heterogeneous subset of non-Hodgkin’s lymphomas (NHLs) that arise from post-thymic T-cells or natural killer (NK)-cells at nodal or extranodal sites. Worldwide, PTCLs represent approximately 12% of all NHLs and the 2008 World Health Organization (WHO) classification includes over 20 biologically and clinically distinct T/NK-cell neoplasms that differ significantly in presentation, pathology, and response to therapy. Because of the rarity and heterogeneity of these diseases, large clinical trials have not been conducted and optimal therapy is not well defined. Most subtypes are treated with similar combination chemotherapy regimens as used for aggressive B-cell NHL, but with poorer outcomes. New treatment combinations and novel agents are currently being explored for PTCLs and this review highlights a number of options that appear promising.

Oncogenic IRFs provide a survival advantage for Epstein-Barr virus- or human T-cell leukemia virus type 1-transformed cells through induction of BIC expression

miR-155, processed from the B-cell integration cluster (BIC), is one of the few well-studied microRNAs (miRNAs) and is involved in both innate immunity and tumorigenesis. BIC/miR-155 is induced by distinct signaling pathways, but little is known about the underlying mechanisms. We have identified two conserved potential interferon (IFN) regulatory factor (IRF)-binding/interferon-stimulated response element motifs in the Bic gene promoter. Two oncogenic IRFs, IRF4 and -7, in addition to some other members of the family, bind to and significantly transactivate the Bic promoter. Correspondingly, the endogenous levels of IRF4 and -7 are correlated with that of the BIC transcript in Epstein-Barr virus (EBV)-transformed cells. However, RNA interference studies have shown that depletion of IRF4, rather than of IRF7, dramatically decreases the endogenous level of BIC by up to 70% in EBV- or human T-cell leukemia virus type 1 (HTLV1)-transformed cell lines and results in apoptosis and reduction of proliferation rates that are restored by transient expression of miR-155. Moreover, the endogenous levels of the miR-155 target, SHIP1, are consistently elevated in EBV- and HTLV1-transformed cell lines stably expressing shIRF4. In contrast, transient expression of IRF4 decreases the SHIP1 level in EBV-negative B cells. Furthermore, the level of IRF4 mRNA is significantly correlated with that of BIC in adult T-cell lymphoma/leukemia (ATLL) tumors. These results show that IRF4 plays an important role in the regulation of BIC in the context of EBV and HTLV1 infection. Our findings have identified Bic as the first miRNA-encoding gene for IRFs and provide evidence for a novel molecular mechanism underlying the IRF/BIC pathway in viral oncogenesis.

How I treat adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive malignancy of mature activated T cells caused by human T-cell lymphotropic virus type I. ATL carries a bad prognosis because of intrinsic chemoresistance and severe immunosuppression. In acute ATL, Japanese trials demonstrated that although combinations of chemotherapy improved response rate, they failed to achieve a significant impact on survival. Patients with chronic and smoldering ATL have a better prognosis, but long-term survival is poor when these patients are managed with a watchful-waiting policy or with chemotherapy. Recently, a worldwide meta-analysis revealed that the combination of zidovudine and IFN-α is highly effective in the leukemic subtypes of ATL and should be considered as standard first-line therapy in that setting. This combination has changed the natural history of the disease through achievement of significantly improved long-term survival in patients with smoldering and chronic ATL as well as a subset of patients with acute ATL. ATL lymphoma patients still benefit from chemotherapy induction with concurrent or sequential antiretroviral therapy with zidovudine/IFN. To prevent relapse, clinical trials assessing consolidative targeted therapies such as arsenic/IFN combination or novel monoclonal antibodies are needed. Finally, allogeneic BM transplantation should be considered in suitable patients.