A New Strategy for Adult T-Cell Leukemia Treatment Targeting Glycogen Synthase Kinase-3β

OBJECTIVES

The role of glycogen synthase kinase (GSK)-3β in adult T-cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1) is paradoxical and enigmatic. Here, we investigated the role of GSK-3β and its potential as a therapeutic target for ATL.

METHODS

Cell proliferation/survival, cell cycle, apoptosis, and reactive oxygen species (ROS) generation were examined using the WST-8 assay, flow cytometry, and Hoechst 33342 staining, respectively. Expression of GSK-3β and cell cycle/death-related proteins, and survival signals was analyzed using RT-PCR, immunofluorescence staining, and immunoblotting.

RESULTS

HTLV-1-infected T-cell lines showed nuclear accumulation of GSK-3β. GSK-3β knockdown and its inhibition with 9-ING-41 and LY2090314 suppressed cell proliferation/survival. 9-ING-41 induced G2/M arrest by enhancing the expression of γH2AX, p53, p21, and p27, and suppressing the expression of CDK1, cyclin A/B, and c-Myc. It induced caspase-mediated apoptosis by decreasing the expression of Bcl-xL, Mcl-1, XIAP, c-IAP1/2, and survivin, and increasing the expression of Bak and Bax. 9-ING-41 also induced ferroptosis and necroptosis, promoted JNK phosphorylation, and suppressed IKKγ and JunB expression. It inhibited the phosphorylation of IκBα, Akt, and STAT3/5, induced ROS production, and reduced glycolysis-derived lactate levels.

CONCLUSION

GSK-3β functions as an oncogene in ATL and could be a potential therapeutic target.

The Oncoprotein Fra-2 Drives the Activation of Human Endogenous Retrovirus Env Expression in Adult T-Cell Leukemia/Lymphoma (ATLL) Patients

Human endogenous retroviruses (HERVs) are retroviral sequences integrated into 8% of the human genome resulting from ancient exogenous retroviral infections. Unlike endogenous retroviruses of other mammalian species, HERVs are mostly replication and retro-transposition defective, and their transcription is strictly regulated by epigenetic mechanisms in normal cells. A significant addition to the growing body of research reveals that HERVs' aberrant activation is often associated with offsetting diseases like autoimmunity, neurodegenerative diseases, cancers, and chemoresistance. Adult T-cell leukemia/lymphoma (ATLL) is a very aggressive and chemoresistant leukemia caused by the human T-cell leukemia virus type 1 (HTLV-1). The prognosis of ATLL remains poor despite several new agents being approved in the last few years. In the present study, we compare the expression of HERV genes in CD8+-depleted PBMCs from HTLV-1 asymptomatic carriers and patients with acute ATLL. Herein, we show that HERVs are highly upregulated in acute ATLL. Our results further demonstrate that the oncoprotein Fra-2 binds the LTR region and activates the transcription of several HERV families, including HERV-H and HERV-K families. This raises the exciting possibility that upregulated HERV expression could be a key factor in ATLL development and the observed chemoresistance, potentially leading to new therapeutic strategies and significantly impacting the field of oncology and virology.

Pivotal role of dihydroorotate dehydrogenase as a therapeutic target in adult T-cell leukemia

OBJECTIVES

We aimed to determine the role of dihydroorotate dehydrogenase (DHODH) in pathogenesis of adult T-cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1) and the effects of its inhibition on the de novo pyrimidine biosynthesis pathway.

METHODS

Cell proliferation, viability, cycle, and apoptosis were analyzed using WST-8 assays, flow cytometry, and Hoechst 33342 staining. To elucidate the molecular mechanisms involved in the anti-ATL effects of DHODH knockdown and inhibition, RT-PCR and immunoblotting were conducted.

RESULTS

HTLV-1-infected T-cell lines aberrantly expressed DHODH. Viral infection and the oncoprotein, Tax, enhanced DHODH expression, while knockdown of DHODH decreased HTLV-1-infected T-cell growth. In addition, BAY2402234, a DHODH inhibitor, exerted an anti-proliferative effect, which was reversed by uridine supplementation. BAY2402234 induced DNA damage and S phase arrest by downregulating c-Myc, CDK2, and cyclin A and upregulating p53 and cyclin E. It also induced caspase-mediated apoptosis by the upregulation of pro-apoptotic and downregulation of anti-apoptotic proteins. Furthermore, BAY2402234 induced caspase-independent ferroptosis and necroptosis. It decreased phosphorylation of IKK, IκBα, PTEN, Akt, and its downstream targets, suggesting that inhibition of NF-κB and Akt signaling is involved in its anti-ATL action.

CONCLUSION

These findings highlight DHODH as a potential therapeutic target for treating ATL.

The tyrosine kinase KDR is essential for the survival of HTLV-1-infected T cells by stabilizing the Tax oncoprotein

Human T-cell leukemia virus type 1 (HTLV-1) infection is linked to the development of adult T-cell leukemia/lymphoma (ATLL) and the neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 Tax oncoprotein regulates viral gene expression and persistently activates NF-κB to maintain the viability of HTLV-1-infected T cells. Here, we utilize a kinome-wide shRNA screen to identify the tyrosine kinase KDR as an essential survival factor of HTLV-1-transformed cells. Inhibition of KDR specifically induces apoptosis of Tax expressing HTLV-1-transformed cell lines and CD4 + T cells from HAM/TSP patients. Furthermore, inhibition of KDR triggers the autophagic degradation of Tax resulting in impaired NF-κB activation and diminished viral transmission in co-culture assays. Tax induces the expression of KDR, forms a complex with KDR, and is phosphorylated by KDR. These findings suggest that Tax stability is dependent on KDR activity which could be exploited as a strategy to target Tax in HTLV-1-associated diseases.

Increased H19/miR-675 Expression in Adult T-Cell Leukemia Is Associated with a Unique Notch Signature Pathway

The Notch pathway is a key cancer driver and is important in tumor progression. Early research suggested that Notch activity was highly dependent on the expression of the intracellular cleaved domain of Notch-1 (NICD). However, recent insights into Notch signaling reveal the presence of Notch pathway signatures, which may vary depending on different cancer types and tumor microenvironments. Herein, we perform a comprehensive investigation of the Notch signaling pathway in adult T-cell leukemia (ATL) primary patient samples. Using gene arrays, we demonstrate that the Notch pathway is constitutively activated in ATL patient samples. Furthermore, the activation of Notch in ATL cells remains elevated irrespective of the presence of activating mutations in Notch itself or its repressor, FBXW7, and that ATL cells are dependent upon Notch-1 expression for proliferation and survival. We demonstrate that ATL cells exhibit the expression of pivotal Notch-related genes, including notch-1, hes1, c-myc, H19, and hes4, thereby defining a critical Notch signature associated with ATL disease. Finally, we demonstrate that lncRNA H19 is highly expressed in ATL patient samples and ATL cells and contributes to Notch signaling activation. Collectively, our results shed further light on the Notch pathway in ATL leukemia and reveal new therapeutic approaches to inhibit Notch activation in ATL cells.

Gene expression profiling of p53 and c-myc in HTLV-1 positive blood donors in Congo

OBJECTIVES

The HTLV-1 infection persists for life, remaining as asymptomatic viral reservoirs in most patients, ensuring the chain of transmission, but around 4% develop adult T-cell leukemia/lymphoma (ATLL). HTLV-1 is an oncogenic retrovirus that transforms CD4+ T lymphocytes and deregulates the lymphoproliferative pathways that contribute to the development of ATLL. To achieve cell transformation, most oncogenic retroviruses use proto-oncogene capture transduction, with proviral integration disrupting the expression of tumor suppressors or proto-oncogenes.

THE AIM

We conducted this study on the prevalence of HTLV-1 infection in blood donors to expand the HTLV-1 database, assess the risk of transmission via blood products, as well as evaluate the risk of persistent infection or development of neoplastic diseases in HTLV-1 carriers.

MATERIALS AND METHODS

This is a cross-sectional study of blood donors of all categories. For this study, 265 blood donors were recruited at the Centre National de Transfusion Sanguine in Brazzaville. After testing for HTLV-1 antibodies by ELISA, proviral DNA was extracted from all ELISA-positive samples for detection by nested PCR, followed by RT qPCR using specific primers p53 and c-myc for gene expression.

RESULTS

20/265 were positive for anti-HTLV-1 antibody, 5 donors were positive for proviral DNA. The prevalence of HTLV-1 was 1.8%. All HTLV-1-positive donors were male (1.8%), with a positive correlation (p = 0.05); the 1.1% of positive donors were regular, with the majority aged between 31 and 45 years (1.5%), and concubine donors were the most frequent (1.1%). All samples showed normal expression of the p53 and c-myc genes.

CONCLUSION

The prevalence, though low, remains a serious problem. No abnormal p53 orc-mycgene expression was detected in HTLV-1-positive donors, which could mean that none of the T lymphocytes in these donors had been transformed by HTLV-1.

Unlocking adult T-cell leukemia/lymphoma's epigenetic secrets: delving into the mechanism and impact of EZH1/2 inhibition

Epigenetic modifications, particularly through methylation of DNA packaging histones, play a pivotal role in controlling gene expression. Aberrant patterns of histone methylation have been associated with the development and progression of hematological malignancies. Unraveling the impact of aberrant histone marks on gene expression and leukemogenesis has spurred a concerted effort to develop clinically effective epigenetic therapies. In malignancies associated with the accumulation of histone H3 lysine trimethylation (H3K27me3), one such intervention involves preventing the deposition of this repressive histone mark by inhibiting the histone-modifying enzymes EZH1 and EZH2. While inhibition of EZH1/2 has demonstrated efficacy in both preclinical studies and clinical trials in various cancers, studies delineating the dynamic effect of EZH1/2 inhibition on H3K27me3 and disease relapse in clinical samples are lacking. In a recent publication, Yamagishi et al. explore how responses of a patient with adult T-cell leukemia/lymphoma to valemetostat, an EZH1/2 inhibitor, are associated with changes in H3K27me3, chromatin accessibility and gene expression, and how these changes can be circumvented in relapsed disease.

Whole-genome CRISPR screening identifies molecular mechanisms of PD-L1 expression in adult T-cell leukemia/lymphoma

ABSTRACT

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive T-cell malignancy with a poor prognosis and limited treatment options. Programmed cell death ligand 1(PD-L1) is recognized to be involved in the pathobiology of ATLL. However, what molecules control PD-L1 expression and whether genetic or pharmacological intervention might modify PD-L1 expression in ATLL cells are still unknown. To comprehend the regulatory mechanisms of PD-L1 expression in ATLL cells, we performed unbiased genome-wide clustered regularly interspaced short palindromic repeat (CRISPR) screening in this work. In ATLL cells, we discovered that the neddylation-associated genes NEDD8, NAE1, UBA3, and CUL3 negatively regulated PD-L1 expression, whereas STAT3 positively did so. We verified, in line with the genetic results, that treatment with the JAK1/2 inhibitor ruxolitinib or the neddylation pathway inhibitor pevonedistat resulted in a decrease in PD-L1 expression in ATLL cells or an increase in it, respectively. It is significant that these results held true regardless of whether ATLL cells had the PD-L1 3' structural variant, a known genetic anomaly that promotes PD-L1 overexpression in certain patients with primary ATLL. Pevonedistat alone showed cytotoxicity for ATLL cells, but compared with each single modality, pevonedistat improved the cytotoxic effects of the anti-PD-L1 monoclonal antibody avelumab and chimeric antigen receptor (CAR) T cells targeting PD-L1 in vitro. As a result, our work provided insight into a portion of the complex regulatory mechanisms governing PD-L1 expression in ATLL cells and demonstrated the in vitro preliminary preclinical efficacy of PD-L1-directed immunotherapies by using pevonedistat to upregulate PD-L1 in ATLL cells.

Vulnerability to APOBEC3G linked to the pathogenicity of deltaretroviruses

Human retroviruses are derived from simian ones through cross-species transmission. These retroviruses are associated with little pathogenicity in their natural hosts, but in humans, HIV causes AIDS, and human T-cell leukemia virus type 1 (HTLV-1) induces adult T-cell leukemia-lymphoma (ATL). We analyzed the proviral sequences of HTLV-1, HTLV-2, and simian T-cell leukemia virus type 1 (STLV-1) from Japanese macaques (Macaca fuscata) and found that APOBEC3G (A3G) frequently generates G-to-A mutations in the HTLV-1 provirus, whereas such mutations are rare in the HTLV-2 and STLV-1 proviruses. Therefore, we investigated the mechanism of how HTLV-2 is resistant to human A3G (hA3G). HTLV-1, HTLV-2, and STLV-1 encode the so-called antisense proteins, HTLV-1 bZIP factor (HBZ), Antisense protein of HTLV-2 (APH-2), and STLV-1 bZIP factor (SBZ), respectively. APH-2 efficiently inhibits the deaminase activity of both hA3G and simian A3G (sA3G). HBZ and SBZ strongly suppress sA3G activity but only weakly inhibit hA3G, suggesting that HTLV-1 is incompletely adapted to humans. Unexpectedly, hA3G augments the activation of the transforming growth factor (TGF)-β/Smad pathway by HBZ, and this activation is associated with ATL cell proliferation by up-regulating BATF3/IRF4 and MYC. In contrast, the combination of APH-2 and hA3G, or the combination of SBZ and sA3G, does not enhance the TGF-β/Smad pathway. Thus, HTLV-1 is vulnerable to hA3G but utilizes it to promote the proliferation of infected cells via the activation of the TGF-β/Smad pathway. Antisense factors in each virus, differently adapted to control host cellular functions through A3G, seem to dictate the pathogenesis.

Assessment of Bcl-xL, TAX, and HBZ Gene Expression in Adult T cell Leukemia/Lymphoma Patients

Adult T cell leukemia/lymphoma is a malignancy with a poor prognosis caused by human T lymphocyte virus type 1 (HTLV-1) infection. Tax and HBZ are two major viral proteins that may be involved in oncogenesis by disrupting apoptosis. Because Bcl-xL plays an integral role in the anti-apoptotic pathway, this study examines the interaction between host apoptosis and oncoproteins. We investigated 37 HTLV-1-infected individuals, including 18 asymptomatic and 19 adult T cell leukemia/lymphoma (ATLL) subjects. mRNA was extracted and converted to cDNA from peripheral blood mononuclear cells, and then gene expression was determined using TaqMan q-PCR. Moreover, the HTLV-1 proviral load (PVL) was also measured using a commercial absolute quantification kit (Novin Gene, Iran). Data analysis revealed that the mean of TAX, HBZ, and PVL was significantly higher among the study groups (ATLL and carrier groups p = .003, p = .000, and p = .002 respectively). There was no statistical difference in Bcl-xL gene expression between the study groups (p = .323). It is proposed that this anti-apoptotic pathway may not be directly involved in the development of ATLL lymphoma. Bcl-xL, TAX, HBZ gene expression, and PVL can be utilized as prognostic markers.

Clinicopathological features of adult T-cell leukemia/lymphoma with T-follicular helper phenotype

AIMS

T-follicular helper (TFH) cells are effector T-cells that are crucial for B-cell selection and differentiation. T-cell lymphomas derived from TFH cells have distinct characteristics. Additionally, in the World Health Organization (WHO) classification 5th edition, three lymphomas were introduced as independent disease entities with TFH cell origin. We aimed to investigate the clinicopathological features of adult T-cell leukemia/lymphoma (ATLL) with a TFH phenotype (TFHP).

METHODS AND RESULTS

We performed TFH immunohistochemistry analysis of five biomarkers for the biopsy specimen, with TFHP being indicated by a positive result for more than two markers. Among 75 cases of ATLL, 37.3% of them showed TFHP. Compared with cases of ATLL without TFHP, cases of ATLL with TFHP showed higher C-reactive protein levels (p = 0.0219) and increased high endothelial venule proliferation (p = 0.024). However, there were no significant between-group differences in overall survival as well as other clinical and morphological findings. Furthermore, there was no significant between-group difference in TFH markers and FOXP3 expression.

CONCLUSION

Some patients with ATLL may present a TFHP, which should not preclude the diagnosis of ATLL. Although presenting a TFHP does not affect prognosis, it is important to identify cases of ATLL with a TFHP since it may inform future treatment strategies.

Mechanisms of action and resistance in histone methylation-targeted therapy

Epigenomes enable the rectification of disordered cancer gene expression, thereby providing new targets for pharmacological interventions. The clinical utility of targeting histone H3 lysine trimethylation (H3K27me3) as an epigenetic hallmark has been demonstrated1-7. However, in actual therapeutic settings, the mechanism by which H3K27me3-targeting therapies exert their effects and the response of tumour cells remain unclear. Here we show the potency and mechanisms of action and resistance of the EZH1-EZH2 dual inhibitor valemetostat in clinical trials of patients with adult T cell leukaemia/lymphoma. Administration of valemetostat reduced tumour size and demonstrated durable clinical response in aggressive lymphomas with multiple genetic mutations. Integrative single-cell analyses showed that valemetostat abolishes the highly condensed chromatin structure formed by the plastic H3K27me3 and neutralizes multiple gene loci, including tumour suppressor genes. Nevertheless, subsequent long-term treatment encounters the emergence of resistant clones with reconstructed aggregate chromatin that closely resemble the pre-dose state. Acquired mutations at the PRC2-compound interface result in the propagation of clones with increased H3K27me3 expression. In patients free of PRC2 mutations, TET2 mutation or elevated DNMT3A expression causes similar chromatin recondensation through de novo DNA methylation in the H3K27me3-associated regions. We identified subpopulations with distinct metabolic and gene translation characteristics implicated in primary susceptibility until the acquisition of the heritable (epi)mutations. Targeting epigenetic drivers and chromatin homeostasis may provide opportunities for further sustained epigenetic cancer therapies.

Suppression of super-enhancer-driven TAL1 expression by KLF4 in T-cell acute lymphoblastic leukemia

TAL1 is one of the most frequently dysregulated genes in T-ALL and is overexpressed in about 50% of T-ALL cases. One of the molecular mechanisms of TAL1 overexpression is abnormal mutations in the upstream region of the TAL1 promoter that introduce binding motifs for the MYB transcription factor. MYB binding at this location creates a 5' TAL1 super-enhancer (SE), which leads to aberrant expression of TAL1 and is associated with unfavorable clinical outcomes. Although targeting TAL1 is considered to be an attractive therapeutic strategy for patients with T-ALL, direct inhibition of transcription factors is challenging. Here, we show that KLF4, a known tumor suppressor in leukemic cells, suppresses SE-driven TAL1 expression in T-ALL cells. Mechanistically, KLF4 downregulates MYB expression by directly binding to its promoter and inhibits the formation of 5' TAL1 SE. In addition, we found that APTO-253, a small molecule inducer of KLF4, exerts an anti-leukemic effect by targeting SE-driven TAL1 expression in T-ALL cells. Taken together, our results suggest that the induction of KLF4 is a promising strategy to control TAL1 expression and could be a novel treatment for T-ALL patients with a poor prognosis.

[Molecular pathogenesis of adult T-cell leukemia/lymphoma]

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive peripheral T-cell malignancy caused by human T-cell leukemia virus type-1 (HTLV-1) infection. Genetic alterations are thought to contribute to the pathogenesis of ATLL alongside HTLV-1 products such as Tax and HBZ. Several large-scale genetic analyses have delineated the entire landscape of somatic alterations in ATLL, which is characterized by frequent alterations in T-cell receptor/NF-κB pathways and immune-related molecules. Notably, up to one-fourth of ATLL patients harbor structural variations disrupting the 3'-UTR of the PD-L1 gene, which facilitate escape of tumor cells from anti-tumor immunity. Among these alterations, PRKCB and IRF4 mutations, PD-L1 amplification, and CDKN2A deletion are associated with poor prognosis in ATLL. More recently, several single-cell transcriptome and immune repertoire analyses have revealed phenotypic features of premalignant cells and tumor heterogeneity as well as virus- and tumor-related changes of the non-malignant hematopoietic pool in ATLL. Here we summarize the current understanding of the molecular pathogenesis of ATLL, focusing on recent progress made by genetic, epigenetic, and single-cell analyses. These findings not only provide a deeper understanding of the molecular pathobiology of ATLL, but also have significant implications for diagnostic and therapeutic strategies.

Illuminating (HTLV-1)-induced adult T-cell leukemia/lymphoma transcriptomic signature: A systems virology approach

BACKGROUND

Adult T-cell leukemia/lymphoma (ATLL) is a poor prognosis malignancy of peripheral T-cells caused by human T-cell leukemia virus type 1 (HTLV-1). The low survival rates observed in the patients are the result of the lack of sufficient knowledge about the disease pathogenesis.

METHODS

In the present study, we first identified differentially expressed genes in ATLL patients and the cellular signaling pathways affected by them. Then, genes of these pathways were subjected to more comprehensive evaluations, including WGCNA and module validation studies on five external datasets. Finally, potential biomarkers were selected for qRT-PCR validation.

RESULTS

Thirteen signaling pathways, including Apoptosis, Human T-cell leukemia virus 1 infection, IL-17 signaling pathway, pathways in cancer, T cell receptor signaling pathway, Th1 and Th2 cell differentiation, and seven others were selected for deeper investigations. Results of our in-depth bioinformatics evaluations, highlighted pathways related to regulation of immune responses, T-cell receptor and activation, regulation of cell signaling receptors and messengers, Wnt signaling pathway, and apoptosis as key players in ATLL pathogenesis. MAPK3, PIK3CD, KRAS, NFKB1, TNF, PLCB3, PLCB2, PLCB1, MAPK11, JUN, ITPR1, ADCY1, GNAQ, ADCY3, ADCY4, CHEK1, CCND1, SOS2, BAX, FOS and GNA12 were identified as possible biomarkers. Upregulation of ADCY1 and ADCY3 genes was confirmed via qRT-PCR.

CONCLUSIONS

In this study, we performed a deep bioinformatic examination on a limited set of genes with high probabilities of involvement in the pathogenesis of ATLL. Our results highlighted signaling pathways and genes with potential key roles in disease formation and resistance against current treatment strategies. Further studies are required to test the possible benefits of highlighted genes as biomarkers and targets of treatment.

Rigosertib is more potent than wortmannin and rapamycin against adult T-cell leukemia-lymphoma

Human T lymphotropic virus type 1 (HTLV-1) infection can cause adult T-cell lymphoblastic leukemia (ATLL), an incurable, chemotherapy-resistant malignancy. In a quest for new therapeutic targets, our study sought to determine the levels of AKT, mTOR, and PI3K in ATLL MT-2 cells, HTLV-1 infected NIH/3T3 cells (Inf-3T3), and HTLV-1 infected patients (Carrier, HAM/TSP, and ATLL). Furthermore, the effects of rigosertib, wortmannin, and rapamycin on the PI3K/Akt/mTOR pathway to inhibit the proliferation of ATLL cells were examined. The results showed that mRNA expression of Akt/PI3K/mTOR was down-regulated in carrier, HAM/TSP, and ATLL patients, as well as MT-2, and Inf-3T3 cells, compared to the healthy individuals and untreated MT-2 and Inf-3T3 as controls. However, western blotting revealed an increase in the phosphorylated and activated forms of AKT and mTOR. Treating the cells with rapamycin, wortmannin, and rigosertib decreased the phosphorylated forms of Akt and mTOR and restored their mRNA expression levels. Using these inhibitors also significantly boosted the expression of the pro-apoptotic genes, Bax/Bcl-2 ratio as well as the expression of the tumor suppressor gene p53 in the MT-2 and Inf-3T3cells. Rigosertib was more potent than wortmannin and rapamycin in inducing sub-G1 and G2-M cell cycle arrest, as well as late apoptosis in the Inf-3T3 and MT-2 cells. It also synergized the cytotoxic effects of vincristine. These findings demonstrate that HTLV-1 downregulation of the mRNA level may occur as a negative feedback response to increased PI3K-Akt-mTOR phosphorylation by HTLV-1. Therefore, using rigosertib alone or in combination with common chemotherapy drugs may be beneficial in ATLL patients.

The Novel Link between Gene Expression Profiles of Adult T-Cell Leukemia/Lymphoma Patients' Peripheral Blood Lymphocytes and Ferroptosis Susceptibility

Ferroptosis, a regulated cell death dependent on iron, has garnered attention as a potential broad-spectrum anticancer approach in leukemia research. However, there has been limited ferroptosis research on ATL, an aggressive T-cell malignancy caused by HTLV-1 infection. Our study employs bioinformatic analysis, utilizing dataset GSE33615, to identify 46 ferroptosis-related DEGs and 26 autophagy-related DEGs in ATL cells. These DEGs are associated with various cellular responses, chemical stress, and iron-related pathways. Autophagy-related DEGs are linked to autophagy, apoptosis, NOD-like receptor signaling, TNF signaling, and the insulin resistance pathway. PPI network analysis revealed 10 hub genes and related biomolecules. Moreover, we predicted crucial miRNAs, transcription factors, and potential pharmacological compounds. We also screened the top 20 medications based on upregulated DEGs. In summary, our study establishes an innovative link between ATL treatment and ferroptosis, offering promising avenues for novel therapeutic strategies in ATL.

Decoding dysregulated angiogenesis in HTLV-1 asymptomatic carriers compared to healthy individuals

Human T-cell lymphotropic virus type 1 (HTLV-1) is the first identified human retrovirus responsible for two significant diseases: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). Although the majority of infected individuals remain asymptomatic carriers, a small percentage may develop ATLL or HAM/TSP. In tumorigenesis, a crucial process is angiogenesis, which involves the formation of new blood vessels. However, the precise mechanism of HTLV-1 associated angiogenesis remains unclear. This study aims to investigate the gene regulation involved in the angiogenesis signaling pathway associated with HTLV-1 infection. The research enrolled 20 male participants, including asymptomatic carriers and healthy individuals. Blood samples were collected and screened using ELISA for HTLV-1 confirmation, and PCR was performed for both Tax and HBZ for validation. RNA extraction and cDNA synthesis were carried out, followed by RT-qPCR analysis targeting cellular genes involved in angiogenesis. Our findings indicate that gene expression related to angiogenesis was elevated in HTLV-1 ACs patients. However, the differences in gene expression of the analyzed genes, including HSP27, Paxillin, PDK1, PTEN, RAF1, SOS1, and VEGFR2 between ACs and healthy individuals were not statistically significant. This suggests that although angiogenesis-related genes may show increased expression in HTLV-1 infection, they might not be robust indicators of ATLL progression in asymptomatic carriers. The results of our study demonstrate that angiogenesis gene expression is altered in ACs of HTLV-1, indicating potential involvement of angiogenesis in the early stages before ATLL development. While we observed elevated angiogenesis gene expression in ACs, the lack of statistical significance between ACs and healthy individuals suggests that these gene markers may not be sufficient on their own to predict the development of ATLL in asymptomatic carriers.

Gene expression study of host-human T-cell leukaemia virus type 1 (HTLV-1) interactions: adult T-cell leukaemia/lymphoma (ATLL)

BACKGROUND

In HTLV-1-associated malignant disease, adult T-cell leukaemia/lymphoma (ATLL), the interaction of virus and host was evaluated at the chemokines gene expression level. Also, IL-1β and Caspase-1 expressions were evaluated to investigate the importance of pyroptosis in disease development and progression.

METHODS AND RESULTS

The expression of host CCR6 and CXCR-3 and the HTLV-1 proviral load (PVL), Tax, and HBZ were assessed in 17 HTLV-1 asymptomatic carriers (ACs) and 12 ATLL patients using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR), TaqMan method. Moreover, RT-qPCR, SYBR Green assay were performed to measure Caspase-1 and IL-1β expression. HTLV-1-Tax did not express in 91.5% of the ATLLs, while HBZ was expressed in all ATLLs. The expression of CXCR3 dramatically decreased in ATLLs compared to ACs (p = 0.001). The expression of CCR6 was lower in ATLLs than ACs (p = 0.04). The mean of PVL in ATLL patients was statistically higher than ACs (p = 0.001). Furthermore, the expression of the IL-1β between ATLLs and ACs was not statistically significant (p = 0.4). In contrast, there was a meaningful difference between Caspase-1 in ATLLs and ACs (p = 0.02).

CONCLUSIONS

The present study indicated that in the first stage of ATLL malignancy toward acute lymphomatous, CXCR3 and its progression phase may target the pyroptosis process. Mainly, HBZ expression could be a novel therapeutic target.

HTLV-1 bZIP Factor-Induced Reprogramming of Lactate Metabolism and Epigenetic Status Promote Leukemic Cell Expansion

Acceleration of glycolysis is a common trait of cancer. A key metabolite, lactate, is typically secreted from cancer cells because its accumulation is toxic. Here, we report that a viral oncogene, HTLV-1 bZIP factor (HBZ), bimodally upregulates TAp73 to promote lactate excretion from adult T-cell leukemia-lymphoma (ATL) cells. HBZ protein binds to EZH2 and reduces its occupancy of the TAp73 promoter. Meanwhile, HBZ RNA activates TAp73 transcription via the BATF3-IRF4 machinery. TAp73 upregulates the lactate transporters MCT1 and MCT4. Inactivation of TAp73 leads to intracellular accumulation of lactate, inducing cell death in ATL cells. Furthermore, TAp73 knockout diminishes the development of inflammation in HBZ-transgenic mice. An MCT1/4 inhibitor, syrosingopine, decreases the growth of ATL cells in vitro and in vivo. MCT1/4 expression is positively correlated with TAp73 in many cancers, and MCT1/4 upregulation is associated with dismal prognosis. Activation of the TAp73-MCT1/4 pathway could be a common mechanism contributing to cancer metabolism.

SIGNIFICANCE

An antisense gene encoded in HTLV-1, HBZ, reprograms lactate metabolism and epigenetic modification by inducing TAp73 in virus-positive leukemic cells. A positive correlation between TAp73 and its target genes is also observed in many other cancer cells, suggesting that this is a common mechanism for cellular oncogenesis. This article is featured in Selected Articles from This Issue, p. 337.

Gene expression and TCR amino acid sequences selected by HLA-A02:01-restricted CTLs specific to HTLV-1 in ATL patients

Adult T-cell leukaemia/lymphoma (ATL) is an aggressive malignancy of peripheral T cells caused by human T-cell lymphotropic virus type-1 (HTLV-1). Tax is the most important regulatory protein for HTLV-1. We aimed to reveal a unique amino acid sequence (AA) of complementarity-determining region 3 (CDR3) of the T-cell receptor (TCR)β and TCRα chains of HLA-A*02:01-restricted Tax11-19 -specific cytotoxic T cells (Tax-CTLs). The gene expression profiles (GEP) of Tax-CTLs were assessed by the next-generation sequence (NGS) method with SMARTer technology. Tax-CTLs seemed to be oligoclonal, and their gene compositions were skewed. The unique motifs of 'DSWGK' in TCRα and 'LAG' in TCRβ at CDR3 were observed in almost all patients. Tax-CTL clones harbouring the 'LAG' motif with BV28 had a higher binding score than those without either of them, besides a higher binding score associated with longer survival. Tax-CTLs established from a single cell showed killing activities against Tax-peptide-pulsed HLA-A2+ T2 cell lines. GEP of Tax-CTLs revealed that genes associated with immune response activity were well preserved in long-term survivors with stable status. These methods and results can help us better understand immunity against ATL, and should contribute to future studies on the clinical application of adoptive T-cell therapies.

A frequent PLCγ1 mutation in adult T-cell leukemia/lymphoma determines functional properties of the malignant cells

BACKGROUND

Development of adult T-cell leukemia/lymphoma (ATL) involves human T-cell leukemia virus type 1 (HTLV-1) infection and accumulation of somatic mutations. The most frequently mutated gene in ATL (36 % of cases) is phospholipase C gamma1 (PLCG1). PLCG1 is also frequently mutated in other T-cell lymphomas. However, the functional consequences of the PLCG1 mutations in cancer cells have not been characterized.

METHODS

We compared the activity of the wild-type PLCγ1 with that of a mutant carrying a hot-spot mutation of PLCγ1 (S345F) observed in ATL, both in cells and in cell-free assays. To analyse the impact of the mutation on cellular properties, we quantified cellular proliferation, aggregation, chemotaxis and apoptosis by live cell-imaging in an S345F+ ATL-derived cell line (KK1) and a KK1 cell line in which we reverted the mutation to the wild-type sequence using CRISPR/Cas9 and homology-directed repair.

FINDINGS

The PLCγ1 S345F mutation results in an increase of basal PLC activity in vitro and in different cell types. This higher basal activity is further enhanced by upstream signalling. Reversion of the S345F mutation in the KK1 cell line resulted in reduction of the PLC activity, lower rates of proliferation and aggregation, and a marked reduction in chemotaxis towards CCL22. The PLCγ1-pathway inhibitors ibrutinib and ritonavir reduced both the PLC activity and the tested functions of KK1 cells.

INTERPRETATION

Consistent with observations from clinical studies, our data provide direct evidence that activated variants of the PLCγ1 enzyme contribute to the properties of the malignant T-cell clone in ATL.

FUNDING

MRC (UK) Project Grant (P028160).

Molecular insight into the study of adult T-cell leukemia/lymphoma (ATLL): Ten-year studies on HTLV-1 associated diseases in an endemic region

The outcome of successful infection, including human T-cell leukemia virus type 1 (HTLV-1), is determined by the interactions between the host and the infectious agent. Ten years of work on HTLV-1-associated diseases in an endemic region of Iran have been critically compared in the present study. The outstanding findings of RNA-seq, system biology analysis, and gene expression measurements on adult T-cell leukemia/lymphoma (ATLL) and enzootic bovine leukosis(EBL) in our lab encouraged us to investigate the significant role of oncogenes in the ATLL malignancy. Most studies assessed such interactions by the proviral load (PVL), Tax, and HBZ regulatory proteins in HTLV-1 and the host's immunological and cell cycle factors. The current study is a comprehensive comparing view of our previously published and unpublished results investigating the HTLV-1-host interactions leading to the transformation of the infected cell. The main focus has been on the essential proteins implicated in the virus dissemination, cell survival, and proliferation of infected cells toward leukemia development and progression. Similar to its homolog BLV-AS-1-2 in EBL, the HTLV-1-HBZ is a pivotal factor in the maintenance and progression of the ATLL. In addition, the inappropriate activities of the PI3K/Akt pathway, BRCAs, and RAD51 in the DNA repair system, which are orchestrating many other immortalization pathways, might be the central factors in the manifestation of ATLL. HTLV-1-HBZ and the host PI3K/Akt pathway, BCAs, and RAD51 could be suggested as influential targets for the prognosis and proper therapy of ATLL.