Characteristics of chronic lymphocytic leukemia in Japan: Comprehensive analysis of the CLLRSG-01 study

Chronic lymphocytic leukemia (CLL) is rare in Japan. We conducted the nationwide, prospective observational study CLLRSG-01 to clarify the current state of CLL in Japan and to make accurate international comparisons by preparing naturally air-dried smears like those used in other countries. Of the 201 untreated patients enrolled and evaluated, 119 were diagnosed with CLL and 82 with non-CLL mature B-cell neoplasms, based on the WHO classification. Of the 119 CLL patients, 90 were classified as typical and 29 as atypical according to FAB classification morphology, with the proportion of atypical CLL consistent with reports from other countries. Immunophenotypic analyses by flow cytometry showed that 55% of Japanese CLL patients had a Matutes score of 4 or higher, which is lower than the rate of about 90% in Europeans. Mutated IGHV was identified in 80% of Japanese CLL patients, which is a higher rate than in Western patients. The most frequent IGHV gene was VH3-30 (15%), followed by VH3-23 (12%) and VH4-34 (10%). VH1-69, the most common gene in Western countries, was identified in only one patient. These results indicate that the pattern of immunophenotypes and IGHV gene usage in Japanese CLL patients differs from that in Western patients.

Impaired humoral immunity following COVID-19 vaccination in HTLV-1 carriers

BACKGROUND

Whether human T-lymphotropic virus type 1 (HTLV-1) carriers can develop sufficient humoral immunity after coronavirus disease 2019 (COVID-19) vaccination is unknown.

METHODS

To investigate humoral immunity after COVID-19 vaccination in HTLV-1 carriers, a multicenter, prospective observational cohort study was conducted at five institutions in southwestern Japan, an endemic area for HTLV-1. HTLV-1 carriers and HTLV-1-negative controls were enrolled for this study from January to December 2022. During this period, the third dose of the COVID-19 vaccine was actively administered. HTLV-1 carriers were enrolled during outpatient visits, while HTLV-1-negative controls included health care workers and patients treated by participating institutions for diabetes, hypertension, or dyslipidemia. The main outcome was the effect of HTLV-1 infection on the plasma anti-COVID-19 spike IgG (IgG-S) titers after the third dose, assessed by multivariate linear regression with other clinical factors.

RESULTS

We analyzed 181 cases (90 HTLV-1 carriers, 91 HTLV-1-negative controls) after receiving the third dose. HTLV-1 carriers were older (median age 67.0 vs. 45.0 years, p < 0.001) and more frequently had diabetes, hypertension, or dyslipidemia than did HTLV-1-negative controls (60.0% vs. 27.5%, p < 0.001). After the third dose, the IgG-S titers decreased over time in both carriers and controls. Multivariate linear regression in the entire cohort showed that time since the third dose, age, and HTLV-1 infection negatively influenced IgG-S titers. After adjusting for confounders such as age, or presence of diabetes, hypertension, or dyslipidemia between carriers and controls using the overlap weighting propensity score method, and performing weighted regression analysis in the entire cohort, both time since the third dose and HTLV-1 infection negatively influenced IgG-S titers.

CONCLUSIONS

The humoral immunity after the third vaccination dose is impaired in HTLV-1 carriers; thus, customized vaccination schedules may be necessary for them.

Anti-HTLV-1 immunity combined with proviral load as predictive biomarkers for adult T-cell leukemia-lymphoma

Human T-cell leukemia virus type 1 (HTLV-1) establishes chronic infection in humans and induces a T-cell malignancy called adult T-cell leukemia-lymphoma (ATL) and several inflammatory diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Persistent HTLV-1 infection is established under the pressure of host immunity, and therefore the immune response against HTLV-1 is thought to reflect the status of the disease it causes. Indeed, it is known that cellular immunity against viral antigens is suppressed in ATL patients compared to HAM/TSP patients. In this study, we show that profiling the humoral immunity to several HTLV-1 antigens, such as Gag, Env, and Tax, and measuring proviral load are useful tools for classifying disease status and predicting disease development. Using targeted sequencing, we found that several carriers whom this profiling method predicted to be at high risk for developing ATL indeed harbored driver mutations of ATL. The clonality of HTLV-1-infected cells in those carriers was still polyclonal; it is consistent with an early stage of leukemogenesis. Furthermore, this study revealed significance of anti-Gag proteins to predict high risk group in HTLV-1 carriers. Consistent with this finding, anti-Gag cytotoxic T lymphocytes (CTLs) were increased in patients who received hematopoietic stem cell transplantation and achieved remission state, indicating the significance of anti-Gag CTLs for disease control. Our findings suggest that our strategy that combines anti-HTLV-1 antibodies and proviral load may be useful for prediction of the development of HTLV-1-associated diseases.

Performance evaluation of Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test for different diagnostic situations

IMPORTANCE

The World Health Organization estimated that 5-10 million people are infected with human T-cell leukemia virus type 1 (HTLV-1). This number is likely to be underestimated because reliable endemic data are available for only approximately 1.5 billion people worldwide. The point-of-care test is a powerful tool for the easy and quick detection of infections without the requirement for expensive instruments and laboratory equipment. Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test that was evaluated in this study, might significantly advance our understanding of the global epidemiology of HTLV-1 infection.

Outcomes in human T-cell leukemia virus type I carriers after hematopoietic stem cell transplantation for diseases other than adult T cell leukemia/lymphoma: a Japanese national survey

Background

Human T-cell leukemia virus type I (HTLV-1) is a retrovirus known to cause adult T-cell leukemia/lymphoma (ATL). There are few reports on hematopoietic stem cell transplantation (HSCT) for HTLV-1 carriers with diseases other than ATL.

Methods

A total of 25,839 patients (24,399 adults and 1440 children) with pre-transplant HTLV-1 serostatus information recorded in the Japanese National Survey Database who had undergone their first HSCT were analyzed. We investigated the overall survival (OS), transplant-related mortality (TRM), and disease-related mortality (DRM) after HSCT in relation to HTLV-1 serologic status.

Findings

Three hundred and forty-eight patients were HTLV-1 antibody carriers. The number of HTLV-1 carriers and noncarriers among adult patients who received allogeneic HSCT (allo-HSCT) or autologous HSCT (auto-HSCT) was 237/15,777 and 95/8920, respectively, and was 16/1424 among pediatric patients who received allo-HSCT. No pediatric HTLV-1 carrier recipients undergoing auto-HSCT were identified. There were no significant differences between HTLV-1 carriers and non-carriers regarding stem cell source, disease risk, or HCT-CI score prior to allo-HSCT. Multivariate analysis of OS (P = 0.020) and TRM (P = 0.017) in adult patients showed that HTLV-1 positive status was a significant prognostic factor. In children, TRM was significantly higher (P = 0.019), but OS was not significantly different. In adult patients who underwent auto-HSCT, HTLV-1 positive status was not a significant prognostic factor. In adult allo-HSCT patients, cytomegalovirus reactivation was significantly more common in HTLV-1 carriers (P = 0.001).

Interpretation

HTLV-1 antibody positivity was shown to have a poor prognosis in OS and TRM after allo-HSCT in adult patients and in TRM after allo-HSCT in pediatric patients.

Funding

This work was supported in part by the practical research programs of the Japan Agency for Medical Research and Development (AMED) under grant number 17ck0106342h0001.

An open-label, single-arm phase 2 trial of valemetostat for relapsed or refractory adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive non-Hodgkin lymphoma with poor prognosis and few treatment options for patients with relapsed, recurrent, or refractory disease. We evaluated the efficacy and safety of valemetostat, a potent enhancer of zeste homolog 2 (EZH2) and EZH1 inhibitor, in treating relapsed or refractory (R/R) ATL. This multicenter phase 2 trial enrolled patients with R/R aggressive ATL (acute, lymphoma, unfavorable chronic type). Patients received valemetostat 200 mg/day orally until progressive disease or unacceptable toxicity. The primary end point was overall response rate (ORR) centrally assessed by an independent efficacy assessment committee (IEAC). Secondary end points included best response in disease compartments, duration of response (DOR), pharmacokinetics, and safety. Twenty-five patients (median age, 69.0 years) with a median of 3 prior lines of therapy were enrolled; 24 had prior mogamulizumab treatment. The primary end point was met with a centrally reviewed ORR of 48.0% (90% confidence interval [CI], 30.5-65.9), including 5 complete and 7 partial remissions. Patients pretreated with mogamulizumab had an ORR of 45.8% (4 complete and 7 partial remissions). IEAC-assessed median DOR was not reached (NR) (95% CI, 1.87 to NR; months). Treatment-emergent adverse events (TEAEs) were manageable. TEAEs that occurred in ≥20% of patients included thrombocytopenia, anemia, alopecia, dysgeusia, neutropenia, lymphopenia, leukopenia, decreased appetite, and pyrexia. Grade ≥3 TEAEs included thrombocytopenia, anemia, lymphopenia, leukopenia, and neutropenia. Valemetostat demonstrated promising efficacy and tolerability in heavily pretreated patients, warranting further investigation in treating R/R ATL. This trial was registered at www.clinicaltrials.gov as #NCT04102150.

Identification of putative noncanonical driver mutations in patients with essential thrombocythemia

Essential thrombocythemia (ET) cases without canonical JAK2, CALR, or MPL mutations, that is, triple-negative (TN) ET, have been found in 10%-20% of ET cases. Owing to the limited number of TN ET cases, its clinical significance remains unclear. This study evaluated TN ET's clinical characteristics and identified novel driver mutations. Among 119 patients with ET, 20 (16.8%) had no canonical JAK2/CALR/MPL mutations. Patients with TN ET tended to be younger and had lower white blood cell counts and lactate dehydrogenase values. We identified putative driver mutations in 7 (35%): MPL S204P, MPL L265F, JAK2 R683G, and JAK2 T875N were previously reported as candidate driver mutations in ET. Moreover, we identified a THPO splicing site mutation, MPL*636Wext*12, and MPL E237K. Four of the seven identified driver mutations were germline. Functional studies on MPL*636Wext*12 and MPL E237K revealed that they are gain-of-function mutants that increase MPL signaling and confer thrombopoietin hypersensitivity with very low efficiency. Patients with TN ET tended to be younger, although this was thought to be due to the inclusion of germline mutations, hereditary thrombocytosis. Accumulating the genetic and clinical characteristics of noncanonical mutations may help future clinical interventions in TN ET and hereditary thrombocytosis.

Integrated genetic and clinical prognostic factors for aggressive adult T-cell leukemia/lymphoma

The prognosis of aggressive adult T-cell leukemia/lymphoma (ATL) is poor, and allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is a curative treatment. To identify favorable prognostic patients after intensive chemotherapy, and who therefore might not require upfront allo-HSCT, we aimed to improve risk stratification of aggressive ATL patients aged.

A decrease in newly diagnosed patients with adult T-cell leukemia/lymphoma in Kagoshima, a highly endemic area of HTLV-1 in southwestern Japan

Adult T-cell leukemia/lymphoma (ATL) is a peripheral T-cell malignancy caused by human T-cell leukemia virus type-I (HTLV-1). This study investigated whether the number of newly diagnosed patients with ATL is decreasing in the background of a declining number of individuals infected by HTLV-1 in Kagoshima, Japan, one of the most endemic areas of HTLV-1 in the world. We retrospectively analyzed the number of newly diagnosed patients with ATL between January 2001 and December 2021 in three major hospitals. The number of newly diagnosed patients with B-cell non-Hodgkin lymphoma (B-NHL) in the same period was examined as an internal control. One thousand eighteen and 2,029 patients with ATL and B-NHL were registered, respectively. The age-adjusted incidence of ATL steadily increased between 2001 and 2012, whereas that between 2013 and 2021 decreased. Despite the limitation of its retrospective nature, this is the first report indicating a decrease in ATL patients in Japan.

Validation of the iATL-PI prognostic index in therapeutic decision-making for patients with smoldering and chronic ATL: a multicenter study

Adult T cell leukemia-lymphoma (ATL) is clinically heterogeneous and is classified into four subtypes: acute, lymphoma, chronic, and smoldering. Recently, a new prognostic index based on the value of soluble interleukin-2 receptor, denoted the "iATL-PI," has been proposed for patients with smoldering and chronic ATL. To evaluate the effectiveness of the iATL-PI, we re-analyzed our previously published data on 176 patients with smoldering or chronic ATL (76 smoldering, 100 chronic) diagnosed between 2010 and 2011, as well data from the subsequent follow-up study on prognosis between 2016 and 2017. The proportions for the low-, intermediate-, and high-risk iATL-PI groups at the time of ATL diagnosis were 44.7%, 48.7%, and 5% for smoldering ATL; 6.3%, 71.9%, and 21.9% for favorable chronic ATL; and 5.9%, 27.9%, and 66.2% for unfavorable chronic ATL, respectively. The survival of patients with smoldering or chronic ATL as a whole was significantly stratified according to the three iATL-PI groups. Most patients with unfavorable chronic ATL in the low iATL-PI risk group had indolent clinical courses. Our results showed that iATL may become a useful tool to predict the prognosis of smoldering and chronic ATL, which have diverse clinical courses.

The oncogenic driving force of CD30 signaling-induced chromosomal instability in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) develops via stepwise accumulation of gene mutations and chromosome aberrations. However, the molecular mechanisms underlying this tumorigenic process are poorly understood. We previously reported the presence of a biological link between the expression of CD30, which serves as a marker for ATL progression, and the actively proliferating fraction of human T-cell leukemia virus type 1 (HTLV-1)-infected cells that display polylobulation. Here, we demonstrated that CD30 signaling induced chromosomal instability with clonal expansion through DNA double-strand breaks (DSBs) via an increase of intracellular reactive oxygen species. CD30⁺ ATL cells were composed of subclones with additional genomic aberrations compared with CD30^- ATL cells in ATL patients. Furthermore, we found an accumulation of copy number loss of DSB repair-related genes as the disease progressed. Taken together, CD30 expression on ATL cells appears to be correlated with genomic instability, suggesting that CD30 signaling is one of the oncogenic factors of ATL progression with clonal evolution. This study provides new insight into the biological roles of CD30 signaling and could improve our understanding of tumorigenic processes of HTLV-1-infected cells.

CCR7 alterations associated with inferior outcome of adult T-cell leukemia/lymphoma under mogamulizumab treatment

Adult T-cell leukemia/lymphoma (ATL) patients have a very poor prognosis. The humanized anti-CCR4 therapeutic monoclonal antibody, mogamulizumab, is a key agent for ATL treatment. Our previous integrated molecular analysis demonstrated that among all the driver genes in ATL, CCR7 gene alterations were significantly associated with clinical response to mogamulizumab. Accordingly, here we investigated the detailed clinical impact of CCR7 alterations in a larger cohort of ATL patients. These CCR7 alterations, most of which lead to C-terminus truncations, were observed in 27 of 223 patients (12%). For patients receiving mogamulizumab but not allogeneic hematopoietic stem cell transplantation (HSCT), CCR7 alterations were significantly associated with worse survival (median survival from the first dose of mogamulizumab of 0.7 years for 12 patients with CCR7 alterations vs. 1.6 years for 72 patients without, p = 0.020). On the other hand, the presence or absence of CCR7 alterations had no significant impact on survival in the entire cohort (median overall survival of 1.4 and 1.8 years, respectively, p = 0.901), or on the survival of patients receiving allogeneic HSCT (median survival from the day of transplantation of 0.9 years for 6 patients with CCR7 alterations and 1.4 years for 48 without, p = 0.543). Multivariate analysis indicated that patients with CCR4 alterations but lacking CCR7 alterations (n = 20) had significantly better survival after receiving mogamulizumab-containing treatments (hazard ratio for survival, 0.437, 95% confidence interval, 0.192-0.994). This study contributes to the establishment of precision medicine for ATL.

Landscape of <i>immunoglobulin heavy chain gamma</i> gene class switch recombination in patients with adult T-cell leukemia–lymphoma

Not available.

A phase I/II study of 10-min dosing of bendamustine hydrochloride (rapid infusion formulation) in patients with previously untreated indolent B-cell non-Hodgkin lymphoma, mantle cell lymphoma, or relapsed/refractory diffuse large B-cell lymphoma in Japan

Purpose

This phase I/II clinical study was conducted to examine the safety, tolerability, pharmacokinetics, and efficacy of 10-min dosing of bendamustine in patients with previously untreated indolent B-cell non-Hodgkin lymphoma (iNHL) or mantle cell lymphoma (MCL) (Group 1) and patients with relapsed/refractory diffuse large B-cell lymphoma (rrDLBCL) (Group 2).

Methods

Rituximab 375 mg/m² was administered intravenously every 28 days to Group 1 patients on day 1 and every 21 days to Group 2 patients on day 1. Bendamustine 90 mg/m²/day was administered to the former on days 1 and 2; bendamustine 120 mg/m²/day was administered to the latter on days 2 and 3. Each regimen was delivered up to six cycles for both groups. The primary endpoints were safety and tolerability in Groups 1 and 2, respectively.

Results

Among 37 enrolled patients, safety was assessed in 36. In Group 1 (n = 30), 27 patients (90%) had follicular lymphoma. Adverse events (AEs) were observed in all 30 patients in Group 1. Dose-limiting toxicities were observed in two of six patients in Group 2. Common AEs included lymphocyte count decreased (86.7%, 100%). In Group 1, overall response and complete response rates were 93.1% (95% confidence interval [CI] 77.2–99.2%) and 75.9% (95% CI 56.5–89.7%), respectively. The C_max and AUC of bendamustine tended to be higher in Group 2 than in Group 1.

Conclusions

This study showed that bendamustine is safe, well-tolerated and effective for patients with previously untreated iNHL, MCL or rrDLBCL. Pharmacokinetic data were equivalent to those obtained outside of Japan.

Registration numbers

Registration NCT03900377; registered April 3, 2019.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-022-04442-2.

OP0112 THE EVER-LARGEST ASIAN GWAS FOR SYSTEMIC SCLEROSIS AND TRANS-POPULATION META-ANALYSIS IDENTIFIED SEVEN NOVEL LOCI AND A CANDIDATE CAUSAL SNP IN A CIS-REGULATORY ELEMENT OF THE FCGR REGION

Background

Genome-wide association studies (GWASs) have identified 29 disease-associated single nucleotide polymorphisms (SNPs) for systemic sclerosis (SSc) in non-human leukocyte antigen (HLA) regions (1-7). While these GWASs have clarified genetic architectures of SSc, study subjects were mainly Caucasians limiting application of the findings to Asians.

Objectives

The study was conducted to identify novel causal variants for SSc specific to Japanese subjects as well as those shared with European population. We also aimed to clarify mechanistic effects of the variants on pathogenesis of SSc.

Methods

A total of 114,108 subjects comprising 1,499 cases and 112,609 controls were enrolled in the two-staged study leading to the ever-largest Asian GWAS for SSc. After applying a strict quality control both for genotype and samples, imputation was conducted using the reference panel of the phase 3v5 1,000 genome project data combined with a high-depth whole-genome sequence data of 3,256 Japanese subjects. We conducted logistic regression analyses and also combined the Japanese GWAS results with those of Europeans (6) by an inverse-variance fixed-effect model. Polygenicity and enrichment of functional annotations were evaluated by linkage disequilibrium score regression (LDSC), Haploreg and IMPACT programs. We also constructed polygenic risk score (PRS) to predict SSc development.

Results

We identified three (FCRLA-FCGR, TNFAIP3, PLD4) and four (EOMES, ESR1, SLC12A5, TPI1P2) novel loci in Japanese GWAS and a trans-population meta-analysis, respectively. One of Japanese novel risk SNPs, rs6697139, located within FCGR gene clusters had a strong effect size (OR 2.05, P=4.9×10-11). We also found the complete LD variant, rs10917688, was positioned in cis-regulatory element and binding motif for an immunomodulatory transcription factor IRF8 in B cells, another genome-wide significant locus in our trans-ethnic meta-analysis and the previous European GWAS. Notably, the association of risk allele of rs10917688 was significant only in the presence of the risk allele of the IRF8. Intriguingly, rs10917688 was annotated as one enhancer-related histone marks, H3K4me1, in B cells, implying that FCGR gene(s) in B cells may play an important role in the pathogenesis of SSc. Furhtermore, significant heritability enrichment of active histone marks and a transcription factor C-Myc were found in B cells both in European and Japanese populations by LDSC and IMPACT, highlighting a possibility of a shared disease mechanism where abnormal B-cell activation may be one of the key drivers for the disease development. Finally, PRS using effects sizes of European GWAS moderately fit in the development of Japanese SSc (AUC 0.593), paving a path to personalized medicine for SSc.

Conclusion

Our study identified seven novel susceptibility loci in SSc. Downstream analyses highlighted a novel disease mechanism of SSc where an interactive role of FCGR gene(s) and IRF8 may accelerate the disease development and B cells may play a key role on the pathogenesis of SSc.

References

[1]F. C. Arnett et al. Ann Rheum Dis, 2010.

[2]T. R. Radstake et al. Nat Genet, 2010.

[3]Y. Allanore et al. PLoS Genet, 2011.

[4]O. Gorlova et al. PLoS Genet, 2011.

[5]C. Terao et al. Ann Rheum Dis, 2017.

[6]E. López-Isac et al. Nat Commun, 2019.

[7]W. Pu et al. J Invest Dermatol, 2021.

Disclosure of Interests

None declared

Oral HDAC Inhibitor Tucidinostat (HBI-8000) in Patients with Relapsed or Refractory Adult T-cell Leukemia/Lymphoma: Phase IIb Results

This multicenter, prospective phase IIb trial evaluating the efficacy and safety of tucidinostat (HBI‐8000) in patients with relapsed or refractory (R/R) adult T‐cell leukemia/lymphoma (ATLL) was undertaken in Japan. Eligible patients had R/R ATLL and had failed standard of care treatment with chemotherapy and with mogamulizumab. Twenty‐three patients received tucidinostat 40 mg orally twice per week and were included in efficacy and safety analyses. The primary end‐point was objective response rate (ORR) assessed by an independent committee. The ORR was 30.4% (95% confidence interval [CI], 13.2, 52.9]. Median progression‐free survival was 1.7 months (95% CI, 0.8, 7.4), median duration of response was 9.2 months (95% CI, 2.6, not reached), and median overall survival was 7.9 months (95% CI, 2.3, 18.0). All patients experienced adverse events (AEs), which were predominantly hematologic and gastrointestinal. Incidence of grade 3 or higher AEs was 78.3%; most were laboratory abnormalities (decreases in platelets, neutrophils, white blood cells, and hemoglobin). Tucidinostat was well tolerated with AEs that could be mostly managed with supportive care and dose modifications. Tucidinostat is a meaningful treatment option for R/R ATLL patients; further investigation is warranted.

Identification and characterization of a novel enhancer in the HTLV-1 proviral genome

Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus that causes adult T-cell leukemia/lymphoma (ATL), a cancer of infected CD4⁺ T-cells. There is both sense and antisense transcription from the integrated provirus. Sense transcription tends to be suppressed, but antisense transcription is constitutively active. Various efforts have been made to elucidate the regulatory mechanism of HTLV-1 provirus for several decades; however, it remains unknown how HTLV-1 antisense transcription is maintained. Here, using proviral DNA-capture sequencing, we found a previously unidentified viral enhancer in the middle of the HTLV-1 provirus. The transcription factors, SRF and ELK-1, play a pivotal role in the activity of this enhancer. Aberrant transcription of genes in the proximity of integration sites was observed in freshly isolated ATL cells. This finding resolves certain long-standing questions concerning HTLV-1 persistence and pathogenesis. We anticipate that the DNA-capture-seq approach can be applied to analyze the regulatory mechanisms of other oncogenic viruses integrated into the host cellular genome.

Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic virus with constantly active antisense transcription from the proviral genome. Here, Matsuo et al. perform proviral DNA-capture followed by high-throughput sequencing and identify a yet unknown viral enhancer in the middle of the HTLV-1 provirus.

Genomic determinants impacting the clinical outcome of mogamulizumab treatment for adult T-cell leukemia/lymphoma

In order to identify genomic biomarkers for the outcome of mogamulizumab-containing treatment, an integrated molecular analysis of adult T-cell leukemia/lymphoma (ATL) was conducted on 64 mogamulizumab-naïve patients. Among driver genes, CCR4 and CCR7 alterations were observed in 22% and 11% of the patients, respectively, both consisting of single nucleotide variants (SNV)/insertion-deletions (indels) in the C-terminus. Patients with CCR4 alterations or without CCR7 alterations exhibited a more favorable clinical response (complete response [CR] rate 93%, 13/14; P=0.024, and CR rate 71%, 40/56; P=0.036, respectively). Additionally, TP53, CD28, and CD274 alterations were identified in 35%, 16%, and 10% of the patients, respectively. TP53 alterations included SNV/indels or copy number variations (CNV) such as homozygous deletion; CD28 alterations included SNV, CNV such as amplification, or fusion; CD274 alterations included CNV such as amplification, or structural variants. Univariate analysis revealed that TP53, CD28 or CD274 alterations were associated with worse overall survival (OS) (hazard ratio [HR]: 2.330, 95% confidence interval [CI]: 1.183-4.589; HR: 3.191, 95% CI: 1.287-7.911; HR: 3.301, 95% CI: 1.130-9.641, respectively) but that CCR4 alterations were associated with better OS (HR: 0.286, 95% CI: 0.087-0.933). Multivariate analysis indicated that in addition to performance status, TP53, CCR4 or CD274 alterations (HR: 2.467, 95% CI: 1.197-5.085; HR: 0.155, 95% CI: 0.031-0.778; HR: 14.393, 95% CI: 2.437-85.005, respectively) were independently and significantly associated with OS. The present study contributes to the establishment of precision medicine using mogamulizumab in ATL patients.

Whole-genome landscape of adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm immunophenotypically resembling regulatory T cells, associated with human T-cell leukemia virus type-1. Here, we performed whole-genome sequencing (WGS) of 150 ATL cases to reveal the overarching landscape of genetic alterations in ATL. We discovered frequent (33%) loss-of-function alterations preferentially targeting the CIC long isoform, which were overlooked by previous exome-centric studies of various cancer types. Long but not short isoform-specific inactivation of Cic selectively increased CD4+CD25+Foxp3+ T cells in vivo. We also found recurrent (13%) 3'-truncations of REL, which induce transcriptional upregulation and generate gain-of-function proteins. More importantly, REL truncations are also common in diffuse large B-cell lymphoma, especially in germinal center B-cell-like subtype (12%). In the non-coding genome, we identified recurrent mutations in regulatory elements, particularly splice sites, of several driver genes. In addition, we characterized the different mutational processes operative in clustered hypermutation sites within and outside immunoglobulin/T-cell receptor genes and identified the mutational enrichment at the binding sites of host and viral transcription factors, suggesting their activities in ATL. By combining the analyses for coding and noncoding mutations, structural variations, and copy number alterations, we discovered 56 recurrently altered driver genes, including 11 novel ones. Finally, ATL cases were classified into 2 molecular groups with distinct clinical and genetic characteristics based on the driver alteration profile. Our findings not only help to improve diagnostic and therapeutic strategies in ATL, but also provide insights into T-cell biology and have implications for genome-wide cancer driver discovery.

HTLV-1 infection promotes excessive T cell activation and transformation into adult T cell leukemia/lymphoma

Human T cell leukemia virus type 1 (HTLV-1) mainly infects CD4+ T cells and induces chronic, persistent infection in infected individuals, with some developing adult T cell leukemia/lymphoma (ATL). HTLV-1 alters cellular differentiation, activation, and survival; however, it is unknown whether and how these changes contribute to the malignant transformation of infected cells. In this study, we used single-cell RNA-sequencing and T cell receptor-sequencing to investigate the differentiation and HTLV-1-mediated transformation of T cells. We analyzed 87,742 PBMCs from 12 infected and 3 uninfected individuals. Using multiple independent bioinformatics methods, we demonstrated the seamless transition of naive T cells into activated T cells, whereby HTLV-1-infected cells in an activated state further transformed into ATL cells, which are characterized as clonally expanded, highly activated T cells. Notably, the greater the activation state of ATL cells, the more they acquire Treg signatures. Intriguingly, the expression of HLA class II genes in HTLV-1-infected cells was uniquely induced by the viral protein Tax and further upregulated in ATL cells. Functional assays revealed that HTLV-1-infected cells upregulated HLA class II molecules and acted as tolerogenic antigen-presenting cells to induce anergy of antigen-specific T cells. In conclusion, our study revealed the in vivo mechanisms of HTLV-1-mediated transformation and immune escape at the single-cell level.

M-Sec induced by HTLV-1 mediates an efficient viral transmission

Human T-cell leukemia virus type 1 (HTLV-1) infects target cells primarily through cell-to-cell routes. Here, we provide evidence that cellular protein M-Sec plays a critical role in this process. When purified and briefly cultured, CD4⁺ T cells of HTLV-1 carriers, but not of HTLV-1^- individuals, expressed M-Sec. The viral protein Tax was revealed to mediate M-Sec induction. Knockdown or pharmacological inhibition of M-Sec reduced viral infection in multiple co-culture conditions. Furthermore, M-Sec knockdown reduced the number of proviral copies in the tissues of a mouse model of HTLV-1 infection. Phenotypically, M-Sec knockdown or inhibition reduced not only plasma membrane protrusions and migratory activity of cells, but also large clusters of Gag, a viral structural protein required for the formation of viral particles. Taken together, these results suggest that M-Sec induced by Tax mediates an efficient cell-to-cell viral infection, which is likely due to enhanced membrane protrusions, cell migration, and the clustering of Gag.

In the present study, we identified the cellular protein M-Sec as a host factor necessary for de novo infection of human T-cell leukemia virus type 1 (HTLV-1), the causative retrovirus of an aggressive blood cancer known as adult T-cell leukemia/lymphoma. The inhibition or knockdown of M-Sec in infected cells resulted in a reduced viral infection in several culture models and a mouse model. We recently demonstrated a similar role of M-Sec in macrophages infected with another human retrovirus HIV-1, but it has been generally thought that M-Sec is not related to HTLV-1 infection because of the lack of its expression in CD4⁺ T cells, the major target of HTLV-1. In this study, we revealed that CD4⁺ T cells of HTLV-1 asymptomatic carriers, but not those of HTLV-1^- individuals, expressed M-Sec, and that the viral protein Tax mediated the induction of M-Sec. Thus, M-Sec is a new and useful tool for further understanding the process of HTLV-1 transmission.

Clinicopathological significance of CD28 overexpression in adult T-cell leukemia/lymphoma

CD28, one of the costimulatory molecules, has a pivotal role in T‐cell activation, and its expression is strictly regulated in normal T cells. Gain‐of‐function genetic alterations involving CD28 have been frequently observed in adult T‐cell leukemia/lymphoma (ATLL). These abnormalities, such as CD28 fusions and copy number variations, may not only confer continuous, prolonged, and enhanced CD28 signaling to downstream pathways but also induce overexpression of the CD28 protein. In this study, 120 ATLL cases were examined by immunohistochemistry for CD28 and its ligands CD80 and CD86, and their expression on tumor cells was semiquantitatively evaluated. CD28 was overexpressed in 55 (46%) cases, and CD80 or CD86 (CD80/CD86) was infrequently overexpressed in 12 (11%). Compared with non‐overexpressers, CD28 overexpressers showed a higher frequency of CD28 genetic alterations and had an increased number of CD80/CD86‐positive non‐neoplastic cells infiltrating tumor microenvironment. In the entire ATLL patient cohort, CD28 overexpressers showed a significantly poorer overall survival (OS) compared with non‐overexpressers (P = .001). The same was true for a subgroup who were treated with multidrug regimens with or without mogamulizumab. CD28 overexpression had no prognostic impact in the group who received allogeneic hematopoietic stem cell transplantation. In the multivariate analysis for OS, CD28 overexpression was selected as an independent risk factor. These results suggest ATLL patients with CD28 overexpression have more aggressive clinical course and are more refractory to treatment with multidrug chemotherapy. CD28 overexpression appears to be a novel unfavorable prognostic marker in ATLL patients, and further prospective studies are warranted to establish its prognostic significance.

Single-Cell Analysis of the Multicellular Ecosystem in Viral Carcinogenesis by HTLV-1

High-dimensional single-cell landscape of immune alterations during HTLV-1 infection and leukemogenesis identifies hallmarks of premalignant and malignant T-cell states and the accompanying shift of systemic immune state toward myeloid and immunosuppressive.

Premalignant clonal expansion of human T-cell leukemia virus type-1 (HTLV-1)–infected cells occurs before viral carcinogenesis. Here we characterize premalignant cells and the multicellular ecosystem in HTLV-1 infection with and without adult T-cell leukemia/lymphoma (ATL) by genome sequencing and single-cell simultaneous transcriptome and T/B-cell receptor sequencing with surface protein analysis. We distinguish malignant phenotypes caused by HTLV-1 infection and leukemogenesis and dissect clonal evolution of malignant cells with different clinical behavior. Within HTLV-1–infected cells, a regulatory T-cell phenotype associates with premalignant clonal expansion. We also delineate differences between virus- and tumor-related changes in the nonmalignant hematopoietic pool, including tumor-specific myeloid propagation. In a newly generated conditional knockout mouse model recapitulating T-cell–restricted CD274 (encoding PD-L1) gene lesions found in ATL, we demonstrate that PD-L1 overexpressed by T cells is transferred to surrounding cells, leading to their PD-L1 upregulation. Our findings provide insights into clonal evolution and immune landscape of multistep virus carcinogenesis.

Clinical significance of the immunoglobulin G heavy-chain repertoire in peripheral blood mononuclear cells of adult T-cell leukaemia-lymphoma patients receiving mogamulizumab

‘Monitoring of immune responses following mogamulizumab‐containing treatment in patients with adult T‐cell leukaemia–lymphoma (ATL)’ (MIMOGA) is a multicentre prospective clinical study (UMIN000008696). In the MIMOGA study, we found that a lower percentage of CD2⁻CD19⁺ B cells in peripheral blood mononuclear cells (PBMC) was a significant unfavourable prognostic factor for overall survival (OS). Accordingly, we then analysed the immunoglobulin G (IgG) heavy‐chain repertoire in PBMC by high‐throughput sequencing. Of the 101 patients enrolled in the MIMOGA study, for 81 a sufficient amount of PBMC RNA was available for repertoire sequencing analysis. Peripheral IgG B cells in patients with ATL had a restricted repertoire relative to those in healthy individuals. There was a significant positive correlation between the Shannon–Weaver diversity index (SWDI) for the IgG repertoire and proportions of B cells in the PBMC of the patients. Multivariate analysis identified two variables significantly affecting OS: a higher serum soluble interleukin‐2 receptor level, and a lower SWDI for the IgG repertoire [hazard ratio, 2·124; 95% confidence interval, 1·114–4·049; n = 44]. The present study documents the importance of humoral immune responses in patients receiving mogamulizumab‐containing treatment. Further investigation of strategies to enhance humoral immune responses in patients with ATL is warranted.

Improvement of the understanding of blood donors with human T-cell leukaemia virus type 1 using a new information booklet

Background

Human T‐cell leukaemia virus type 1 (HTLV‐1) tests have been mandated in Japan since 1986, and notification of HTLV‐1‐seropositive donors started in 1999. However, donor knowledge and response to notification has not been assessed.

Study design and Methods

A questionnaire survey was conducted among blood donors notified of HTLV‐1 seropositivity regarding their knowledge of HTLV‐1 and unmet information needs. To reduce anxiety among notified individuals and raise awareness of their infection status, we created a booklet containing information that would be useful for these individuals without causing unnecessary anxiety while also requesting that they refrain from donating blood in the future.

Results

A questionnaire survey conducted before the distribution of a new booklet revealed that 15.0% of respondents donated blood again despite receiving an HTLV‐1‐seropositive notification at the previous donation. While 62.2% of respondents reacted to the notification favourably, 40.2% expressed anxiety and 32.5% requested information on related diseases and medical institutions for consultation. In the secondary survey after distribution of the new booklet, 87.9% of respondents reported that the information was comprehensible, and an increase in consultations of medical institutions by notification recipients was observed. Furthermore, no re‐visiting donors were observed among the HTLV‐1‐seropositive recipients who were notified using the new information booklet.

Conclusion

The new information booklet provided enlightenment on HTLV‐1 infection and facilitated the consultation of medical institutions by seropositive donors, leading to an improvement in the health‐related quality of life of seropositive blood donors and the safety of blood products.

Clinical significance of TP53 mutations in adult T-cell leukemia/lymphoma

Adult T‐cell leukaemia/lymphoma (ATL) patients have a poor prognosis. Here, we investigated the impact of TP53 gene mutations on prognosis of ATL treated in different ways. Among 177 patients, we identified 47 single nucleotide variants or insertion‐deletions (SNVs/indels) of the TP53 gene in 37 individuals. TP53 copy number variations (CNVs) were observed in 38 patients. Altogether, 67 of 177 patients harboured TP53 SNVs/indels or TP53 CNVs, and were categorized as having TP53 mutations. In the entire cohort, median survival of patients with and without TP53 mutations was 1·0 and 6·7 years respectively (P < 0·001). After allogeneic haematopoietic stem cell transplantation (HSCT), median survival of patients with (n = 16) and without (n = 29) TP53 mutations was 0·4 years and not reached respectively (P = 0·001). For patients receiving mogamulizumab without allogeneic HSCT, the median survival from the first dose of antibody in patients with TP53 mutations (n = 27) was only 0·9 years, but 5·1 years in those without (n = 42; P < 0·001). Thus, TP53 mutations are associated with unfavourable prognosis of ATL, regardless of treatment strategy. The establishment of alternative modalities to overcome the adverse impact of TP53 mutations in patients with ATL is required.

Epidemiology of adult T-cell leukemia-lymphoma in Japan: An updated analysis, 2012-2013

Adult T‐cell leukemia‐lymphoma (ATL) is a T‐cell malignancy that is endemic to Japan. In this latest nationwide study of ATL, we collected the data from 4 nationwide registries of patients diagnosed in 2012‐2013; the Hematology Blood Disease, the Skin Cancer Society, the Hospital‐Based Cancer Registries, and information from the hospitals that participated in the Japanese nationwide survey of ATL in 2010‐2011. In the present study, 2614 patients with ATL were diagnosed based on the registries, and 117 departments registered 1042 patients. Among these patients, 984 were eligible for analysis. The median age at diagnosis was 69 y. A larger proportion of patients with ATL older than 70 y was diagnosed with the lymphoma subtype, and more than half of the patients with ATL in the metropolitan areas were born in the human T‐cell leukemia virus type I (HTLV‐1)‐endemic areas of Kyushu/Okinawa, which are almost identical to the findings in our 2010‐2011 study. Additionally, we identified that patients with ATL migrated from the endemic areas for HTLV‐1 to the non‐endemic metropolitan areas. The present study was able to reduce the burden of searching each hospital and to update the clinico‐epidemiological characteristics of a large number of patients with ATL in Japan, suggesting the usefulness and feasibility of the novel data collection method. The establishment of a more sophisticated database management system for ATL is necessary for future continuous surveys.

Cord blood transplantation with a reduced-intensity conditioning regimen using fludarabine and melphalan for adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T-cell lymphoma with a poor prognosis when treated with chemotherapy alone; therefore, allogeneic stem cell transplantation is a consideration. We attempted cord blood transplantation (CBT) using a reduced-intensity conditioning regimen without total body irradiation (non-TBI-RIC) to allow for the best possible timing of transplantation and improve survival outcomes, particularly in older patients. Forty-eight patients (27 male, 21 female) underwent CBT using fludarabine (Flu) 125 mg/m² and melphalan (Mel) 140 mg/m² as pre-transplant conditioning. The median age was 32 years (range 44-72), and 21 patients were in complete remission (CR) at the time of CBT. The median duration to neutrophil engraftment (NE) was 19.5 days (range 15-50), with a cumulative incidence of NE of 86.7% at day 50 after CBT. The 1- and 3-year overall survival (OS) rates were 40.4% and 37.7%, respectively. The 3-year OS rate in CR patients was 60.8%, compared with 18.8% in non-CR patients. In ATLL patients, CBT with non-TBI-RIC using Flu/Mel is a promising treatment strategy.

Short-term cultured autologous peripheral blood mononuclear cells as a potential immunogen to activate Tax-specific CTL response in adult T-cell leukemia patients

Activation of CD8⁺ Tax‐specific CTL is a new therapeutic concept for adult T‐cell leukemia (ATL) caused by HTLV‐1. A recent clinical study of the dendritic cell vaccine pulsed with Tax peptides corresponding to CTL epitopes showed promising outcomes in ATL patients possessing limited human leukocyte antigen (HLA) alleles. In this study, we aimed to develop another immunotherapy to activate Tax‐specific CTL without HLA limitation by using patients’ own HTLV‐1‐infected cells as a vaccine. To examine the potential of HTLV‐1‐infected T‐cells to activate CTL via antigen presenting cells, we established a unique co–culture system. We demonstrated that mitomycin C‐treated HLA‐A2‐negative HTLV‐1‐infected T‐cell lines or short‐term cultured peripheral blood mononuclear cells (PBMC) derived from ATL patients induced cross–presentation of Tax antigen in co–cultured HLA‐A2‐positive antigen presenting cells, resulting in activation of HLA‐A2‐restricted CD8⁺ Tax‐specific CTL. This effect was not inhibited by a reverse transcriptase inhibitor. IL‐12 production and CD86 expression were also induced in antigen presenting cells co–cultured with HTLV‐1‐infected cells at various levels, which were improved by pre–treatment of the infected cells with histone deacetylase inhibitors. Furthermore, monocyte‐derived dendritic cells induced from PBMC of a chronic ATL patient produced IL‐12 and expressed enhanced levels of CD86 when co–cultured with autologous lymphocytes that had been isolated from the same PBMC and cultured for several days. These findings suggest that short‐term cultured autologous PBMC from ATL patients could potentially serve as a vaccine to evoke Tax‐specific CTL responses.

Clinical significance of soluble CADM1 as a novel marker for adult T-cell leukemia/lymphoma

Adult T-cell leukemia/leukemia (ATLL) is an aggressive peripheral T-cell malignancy, caused by infection with the human T-cell leukemia virus type 1 (HTLV-1). We recently showed that the cell adhesion molecule 1 (CADM1), a member of the immunoglobulin superfamily, is specifically and consistently overexpressed in ATLL cells, and functions as a novel cell surface marker. In this study, we first show that a soluble form of CADM1 (sCADM1) is secreted from ATLL cells by mainly alternative splicing. After developing the Alpha linked immunosorbent assay (AlphaLISA) for sCADM1, we show that plasma sCADM1 concentrations gradually increased during disease progression from indolent to aggressive ATLL. Although other known biomarkers of tumor burden such as soluble interleukin-2 receptor α (sIL-2Rα) also increased with sCADM1 during ATLL progression, multivariate statistical analysis of biomarkers revealed that only plasma sCADM1 was selected as a specific biomarker for aggressive ATLL, suggesting that plasma sCADM1 may be a potential risk factor for aggressive ATLL. In addition, plasma sCADM1 is a useful marker for monitoring response to chemotherapy as well as for predicting relapse of ATLL. Furthermore, the change in sCADM1 concentration between indolent and aggressive type ATLL was more prominent than the change in the percentage of CD4⁺CADM1⁺ ATLL cells. As plasma sCADM1 values fell within normal ranges in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients with higher levels of serum sIL-2Rα, the measurement of sCADM1 may become a useful tool to discriminate between ATLL and other inflammatory diseases, including HAM/TSP.

Clinical significance of CD28 gene-related activating alterations in adult T-cell leukaemia/lymphoma

Multiple oncogenic events are involved in the development of adult T-cell leukaemia/lymphoma (ATL). Because CD28 plays a pivotal role in T-cell activation, we focused on alterations of the CD28 gene in ATL. We found multiple genetic abnormalities related to CD28 among the 144 patients enrolled in the present study. These involved gene fusions with the cytotoxic T-lymphocyte-associated antigen 4 or the inducible T-cell co-stimulator in 14 patients (10%), CD28-activating mutations in 3 (2%), and CD28 copy number variations in 34 (24%). Patients with such CD28 gene alterations were significantly younger than those without. In patients not receiving allogeneic haematopoietic stem cell transplantation, those with CD28 gene alterations tended to have a worse prognosis than those without. Finally, patients with chronic or smouldering ATL subtypes with CD28 gene alterations had a significantly worse prognosis than those without. These findings indicate that ATL, especially chronic or smouldering subtypes, have a more aggressive clinical course and are more refractory to conventional chemotherapies or mogamulizumab if they harbour CD28 gene alterations, likely because of continuous, prolonged, and enhanced CD28 activatory signalling. Novel treatment strategies to overcome the effects of these CD28 gene alterations are warranted.

Prognosis of patients with adult T-cell leukemia/lymphoma in Japan: A nationwide hospital-based study

Adult T‐cell leukemia/lymphoma (ATL) is a mature T‐cell neoplasm and is classified into four subtypes (acute, lymphoma, chronic, and smoldering) according to the Shimoyama classification, established in 1991 through several nationwide surveys based on the clinical diversity of patients diagnosed in 1983‐1987 in Japan. Thereafter, no such studies have been conducted. Recently, we conducted a nationwide hospital survey using the method of the 1980s studies, collected baseline data on 996 ATL patients diagnosed in 2010‐2011 from 126 hospitals, and reported their unique epidemiological characteristics. Here, we report the follow‐up results of registered ATL patients with the goal of evaluating current prognoses and treatment modalities as of 2016‐2017. Of 770 evaluable patients, 391 (50.8%) had acute‐type, 192 (24.9%) had lymphoma‐type, 106 (13.8%) had chronic‐type, and 81 (10.5%) had smoldering‐type ATL. The initial therapy regimens used for acute/lymphoma‐type ATL were vincristine, cyclophosphamide, doxorubicin and prednisone, followed by doxorubicin, ranimustine, and prednisone and then by vindesine, etoposide, carboplatin, and prednisone (VCAP‐AMP‐VECP)‐like in 38.5/41.7% and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)‐like in 14.6/13.7% of patients. Allogeneic hematopoietic stem cell transplantation was used to treat 15.9/10.4% of acute/lymphoma‐type ATL patients. The 4‐year survival rates (the median survival time, days) for acute‐, lymphoma‐, unfavorable chronic‐, favorable chronic‐, and smoldering‐type ATL were 16.8% (252), 19.6% (305), 26.6% (572), 62.1% (1937), and 59.8% (1851), respectively. The 4‐year survival rates for acute‐ and lymphoma‐type ATL improved compared with those reported in 1991, but those for chronic‐ and smoldering‐type ATL were not. Further efforts are warranted to develop more efficient therapeutic strategies to improve the prognosis of ATL in Japan.

5-aminolevulinic acid-mediated photodynamic therapy can target aggressive adult T cell leukemia/lymphoma resistant to conventional chemotherapy

Photodynamic therapy (PDT) is an emerging treatment for various solid cancers. We recently reported that tumor cell lines and patient specimens from adult T cell leukemia/lymphoma (ATL) are susceptible to specific cell death by visible light exposure after a short-term culture with 5-aminolevulinic acid, indicating that extracorporeal photopheresis could eradicate hematological tumor cells circulating in peripheral blood. As a bridge from basic research to clinical trial of PDT for hematological malignancies, we here examined the efficacy of ALA-PDT on various lymphoid malignancies with circulating tumor cells in peripheral blood. We also examined the effects of ALA-PDT on tumor cells before and after conventional chemotherapy. With 16 primary blood samples from 13 patients, we demonstrated that PDT efficiently killed tumor cells without influencing normal lymphocytes in aggressive diseases such as acute ATL. Importantly, PDT could eradicate acute ATL cells remaining after standard chemotherapy or anti-CCR4 antibody, suggesting that PDT could work together with other conventional therapies in a complementary manner. The responses of PDT on indolent tumor cells were various but were clearly depending on accumulation of protoporphyrin IX, which indicates the possibility of biomarker-guided application of PDT. These findings provide important information for developing novel therapeutic strategy for hematological malignancies.

Immunohistochemistry for CCR4 C-terminus predicts CCR4 mutations and mogamulizumab efficacy in adult T-cell leukemia/lymphoma

Mogamulizumab targets extracellular N‐terminal domain of CCR4, which is expressed in most adult T‐cell leukemia/lymphoma (ATL) cases. Recently, we reported that CCR4 C‐terminal gain‐of‐function mutations were frequent in ATL cases, and a subgroup with these mutations who were treated without allogenic hematopoietic stem cell transplantation (HSCT) and with mogamulizumab‐containing [HSCT (−) and mogamulizumab (+)] regimens had a superior survival rate. Although these mutations are most likely a biomarker for predicting a strong response to mogamulizumab, their detection is time‐consuming and costly. A more convenient screening tool may be necessary in the clinical setting. In this study, the clinicopathological importance of immunohistochemistry for the CCR4 N‐terminus (CCR4‐N‐IHC) and C‐terminus (CCR4‐C‐IHC) was examined in a large ATL cohort (n = 92). We found that CCR4‐C‐IHC, but not CCR4‐N‐IHC, was inversely correlated with the CCR4 mutation status. In ATL patients negative for CCR4‐C‐IHC, a subgroup treated with HSCT (−) and mogamulizumab (+) regimens showed a significantly better prognosis. In addition, CCR4‐C‐IHC was found to be a useful marker for high‐sensitivity screening of the CCR4 mutational status (87%). The present study suggests that CCR4‐C‐IHC may be useful for identifying ATL patients harboring mutated CCR4 who may benefit from the superior efficacy of mogamulizumab‐containing regimens and that CCR4‐C‐IHC may be a rapid and cost‐efficient tool for screening for CCR4 mutation status.

Targeting Excessive EZH1 and EZH2 Activities for Abnormal Histone Methylation and Transcription Network in Malignant Lymphomas

Although global H3K27me3 reprogramming is a hallmark of cancer, no effective therapeutic strategy for H3K27me3-high malignancies harboring EZH2^WT/WT has yet been established. We explore epigenome and transcriptome in EZH2^WT/WT and EZH2^WT/Mu aggressive lymphomas and show that mutual interference and compensatory function of co-expressed EZH1 and EZH2 rearrange their own genome-wide distribution, thereby establishing restricted chromatin and gene expression signatures. Direct comparison of leading compounds introduces potency and a mechanism of action of the EZH1/2 dual inhibitor (valemetostat). The synthetic lethality is observed in all lymphoma models and primary adult T cell leukemia-lymphoma (ATL) cells. Opposing actions of EZH1/2-polycomb and SWI/SNF complexes are required for facultative heterochromatin formation. Inactivation of chromatin-associated genes (ARID1A, SMARCA4/BRG1, SMARCB1/SNF5, KDM6A/UTX, BAP1, KMT2D/MLL2) and oncovirus infection (HTLV-1, EBV) trigger EZH1/2 perturbation and H3K27me3 deposition. Our study provides the mechanism-based rationale for chemical dual targeting of EZH1/2 in cancer epigenome.

Establishment of a novel diagnostic test algorithm for human T-cell leukemia virus type 1 infection with line immunoassay replacement of western blotting: a collaborative study for performance evaluation of diagnostic assays in Japan

BACKGROUND

The reliable diagnosis of human T-cell leukemia virus type 1 (HTLV-1) infection is important, particularly as it can be vertically transmitted by breast feeding mothers to their infants. However, current diagnosis in Japan requires a confirmatory western blot (WB) test after screening/primary testing for HTLV-1 antibodies, but this test often gives indeterminate results. Thus, this collaborative study evaluated the reliability of diagnostic assays for HTLV-1 infection, including a WB-based one, along with line immunoassay (LIA) as an alternative to WB for confirmatory testing.

RESULTS

Using peripheral blood samples from blood donors and pregnant women previously serologically screened and subjected to WB analysis, we analyzed the performances of 10 HTLV-1 antibody assay kits commercially available in Japan. No marked differences in the performances of eight of the screening kits were apparent. However, LIA determined most of the WB-indeterminate samples to be conclusively positive or negative (an 88.0% detection rate). When we also compared the sensitivity to HTLV-1 envelope gp21 with that of other antigens by LIA, the sensitivity to gp21 was the strongest. When we also compared the sensitivity to envelope gp46 by LIA with that of WB, LIA showed stronger sensitivity to gp46 than WB did. These findings indicate that LIA is an alternative confirmatory test to WB analysis without gp21. Therefore, we established a novel diagnostic test algorithm for HTLV-1 infection in Japan, including both the performance of a confirmatory test where LIA replaced WB on primary test-reactive samples and an additional decision based on a standardized nucleic acid detection step (polymerase chain reaction, PCR) on the confirmatory test-indeterminate samples. The final assessment of the clinical usefulness of this algorithm involved performing WB analysis, LIA, and/or PCR in parallel for confirmatory testing of known reactive samples serologically screened at clinical laboratories. Consequently, LIA followed by PCR (LIA/PCR), but neither WB/PCR nor PCR/LIA, was found to be the most reliable diagnostic algorithm.

CONCLUSIONS

Because the above results show that our novel algorithm is clinically useful, we propose that it is recommended for solving the aforementioned WB-associated reliability issues and for providing a more rapid and precise diagnosis of HTLV-1 infection.

Inhibition of ABL1 tyrosine kinase reduces HTLV-1 proviral loads in peripheral blood mononuclear cells from patients with HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-cell leukemia virus type 1 (HTLV-1) causes incurable adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP have increased levels of HTLV-1-infected cells compared with asymptomatic HTLV-1 carriers. However, the roles of cellular genes in HTLV-1-infected CD4+ T cells await discovery. We performed microarray analysis of CD4+ T cells from HAM/TSP patients and found that the ABL1 is an important gene in HAM/TSP. ABL1 is a known survival factor for T- and B-lymphocytes and is part of the fused gene (BCR-ABL) known to be responsible for chronic myelogenous leukemia (CML). ABL1 tyrosine kinase inhibitors (TKIs), including imatinib, nilotinib, and dasatinib, are used clinically for treating CML. To evaluate whether ABL1 is indeed important for HAM/TSP, we investigated the effect of TKIs on HTLV-1-infected cells. We developed a propidium monoazide-HTLV-1 viability quantitative PCR assay, which distinguishes DNA from live cells and dead cells. Using this method, we were able to measure the HTLV-1 proviral load (PVL) in live cells alone when peripheral blood mononuclear cells (PBMCs) from HAM/TSP cases were treated with TKIs. Treating the PBMCs with nilotinib or dasatinib induced significant reductions in PVL (21.0% and 17.5%, respectively) in live cells. Furthermore, ABL1 siRNA transfection reduced cell viability in HTLV-1-infected cell lines, but not in uninfected cell lines. A retrospective survey based on our clinical records found a rare case of HAM/TSP who also suffered from CML. The patient showed an 84.2% PVL reduction after CML treatment with imatinib. We conclude that inhibiting the ABL1 tyrosine kinase specifically reduced the PVL in PBMCs from patients with HAM/TSP, suggesting that ABL1 is an important gene for the survival of HTLV-1-infected cells and that TKIs may be potential therapeutic agents for HAM/TSP.

Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation for ATL with HTLV-1 Antibody-Positive Donors

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is the only available curative treatment option for patients with aggressive adult T cell leukemia-lymphoma (ATL). Donor human T cell leukemia virus (HTLV) 1 seropositivity is a critical concern when choosing relative donors, as they are not usually recommended due solely to the occurrence of donor-derived ATL. A previous report suggested that allo-HCT with an HTLV-1-seropositive donor increased ATL-related mortality. We updated the risk assessment for choosing an HTLV-1-seropositive allo-HCT donor for ATL. Our current registry data, which include larger numbers of HTLV-1-seropositive donors and longer observation periods, revealed no significant difference in overall survival (hazard ratio [HR], 0.93; 95% confidence interval [CI], 0.70-1.24; P = .61) or cumulative incidence of either ATL-related (HR, 0.96; 95% CI, 0.64 to 1.45; P = .80) or non-ATL-related mortality (HR, 0.91; 95% CI, 0.61 to 1.37; P = .66). Similarly, when considering only patients with ATL in complete remission, there was no significant difference in overall survival (HR, 1.02; 95% CI, 0.70 to 1.49; P = .91) or cumulative incidence of either ATL-related (HR, 1.20; 95% CI, 0.66 to 2.20; P=0.54) or non-ATL-related mortality (HR, 0.86; 95% CI, 0.52-1.42; P = .66). These data indicate that selecting HTLV-1-seropositive donors might not be contraindicated for patients with ATL receiving allo-HCT if alternative donors are unavailable. Further risk assessment remains to be performed.

A decision analysis comparing unrelated bone marrow transplantation and cord blood transplantation in patients with aggressive adult T-cell leukemia-lymphoma

Patients with aggressive adult T-cell leukemia-lymphoma (ATL) have dismal outcomes with intensive chemotherapy. Early up-front allogeneic hematopoietic stem cell transplantation (allo-HSCT) is generally recommended. However, the choice of stem cell source, i.e., unrelated bone marrow transplant (UBMT) or cord blood transplantation (CBT), when an HLA-matched related donor is unavailable remains controversial. Thus, we undertook a decision analysis to compare the outcomes of two therapeutic strategies: chemotherapy followed by up-front UBMT at 6 months, and chemotherapy followed by up-front CBT at 3 months. Patients were stratified into low-, intermediate-, and high-risk groups according to the modified ATL-prognostic index. The model simulated life expectancy (LE) and quality-adjusted LE (QALE). LE following up-front UBMT was higher than that following up-front CBT in the low-risk group (2.63 vs. 2.28 years), but was comparable in the intermediate- (2.06 vs. 2.01 years) and high-risk groups (1.25 vs. 1.30 years). The Monte Carlo simulation for LE and QALE in each risk group showed that there was significant uncertainty in all categories. In conclusion, up-front UBMT was superior to up-front CBT in the low-risk group, but the strategies were comparable in the intermediate- and high-risk groups.

Progress in Allogeneic Hematopoietic Cell Transplantation in Adult T-Cell Leukemia-Lymphoma

The prognosis of aggressive adult T-cell leukemia-lymphoma (ATL) remains poor because of frequent infections and drug resistance. Dose-intensified chemotherapy followed by autologous stem cell transplantation failed to improve the prognosis of patients with ATL; however, we first revealed that allogeneic hematopoietic cell transplantation (allo-HCT) might improve their prognosis. We showed that reduced-intensity stem cell transplantation using peripheral blood was feasible for elderly patients. Further, the prognosis of patients in remission, who receive cord blood transplantation, has been recently improved and is equivalent to that of patients who receive transplants from other stem cell sources. As for the timing of HCT, the patients who underwent transplantation early showed better outcomes than those who underwent transplantation late. Based on the analysis of patients with aggressive ATL, including those who received transplants, we identified five prognostic factors for poor outcomes: acute-type ATL, poor performance status, high soluble interleukin-2 receptor levels, hypercalcemia, and high C-reactive protein level. Next, we developed a new prognostic index: the modified ATL-PI. The overall survival (OS) rates were significantly higher in patients who underwent allo-HCT than those who did not in the intermediate and high-risk groups stratified using the modified ATL-PI. Two new anti-cancer agents, mogamulizumab and lenalidomide, were recently approved for ATL patients in Japan. They are expected to induce longer survival in ATL patients when administered along with transplantation. However, a retrospective analysis that the risk of severe, acute, and corticosteroid-refractory graft-versus-host disease was higher in patients who received mogamulizumab before allo-HCT, and that mogamulizumab might increase the transplant-related mortality (TRM) rates and decrease the OS rates compared to those of patients who did not receive mogamulizumab. However, our recent study showed that administration of mogamulizumab before allo-HCT tended to improve the survival of patients with ATL. In conclusion, allo-HCT procedures for patients with aggressive ATL have considerably progressed and have helped improve the prognosis of these patients; however, many concerns still remain to be resolved. Further development of allo-HCT by using new molecular targeting agents is required for the improvement of cure rates in patients with ATL.