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

Development of Acute Adult T-cell Leukemia Following PD-1 Blockade Therapy for Lung Cancer

Immune checkpoint inhibitors (ICIs) are widely used for the treatment of various cancers. However, paradoxical exacerbation of neoplasms, referred to as "hyperprogressive disease," has been reported in a proportion of patients treated with anti-programmed cell death-1 (PD-1)/PD-1 ligand (PD-L1) blockade. We herein report a case of acute adult T-cell leukemia (ATL) that developed shortly after the administration of nivolumab, a PD-1 inhibitor, to treat non-small-cell lung cancer. There were no signs of ATL before the administration of nivolumab, and seropositivity for human T-cell leukemia virus type-1 (HTLV-1) was confirmed after the development of acute ATL. We speculate that nivolumab likely contributed to the development of acute ATL.

Allogeneic hematopoietic stem cell transplantation for adult T-cell leukemia/lymphoma with HTLV-1-associated myelopathy

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can be curative for adult T-cell leukemia/lymphoma (ATL), but comorbidities increase transplant-related mortality. Here we report the outcome of allo-HSCT in a patient with ATL with human T-cell leukemia virus type I (HTLV-1)-associated myelopathy-tropical spastic paraparesis (HAM/TSP). A 48-year-old man was diagnosed with HAM/TSP and started prednisolone therapy. Ten years later, he developed lymphoma-type ATL. At the diagnosis of ATL, Osame's Motor Disability Score (OMDS) was 4. When prednisolone was gradually tapered and stopped following chemotherapy for ATL, HAM/TSP symptoms recurred (OMDS 7). Bone marrow transplantation from a human leukocyte antigen allele 8/8 matched unrelated donor was performed while ATL was in partial remission. Neutrophil engraftment with complete donor chimerism was achieved on day 19 after allo-HSCT. Mild gait improvement (OMDS 5) was observed on day 30. Although ATL relapsed on day 275, progression of HAM/TSP symptoms was not observed. Furthermore, there was no clear progression of HAM/TSP symptoms after donor lymphocyte infusions. The outcome of this case suggests that ATL patients with HAM/TSP tolerate allo-HSCT and donor lymphocyte infusions.

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

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

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

Clonality of HTLV-1-infected T cells as a risk indicator for development and progression of adult T-cell leukemia

Adult T-cell leukemia (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) that develops along a carcinogenic process involving 5 or more genetic events in infected cells. The lifetime incidence of ATL among HTLV-1-infected individuals is approximately 5%. Although epidemiologic studies have revealed risk factors for ATL, the molecular mechanisms that determine the fates of carriers remain unclear. A better understanding of clonal composition and related longitudinal dynamics would clarify the process of ATL leukemogenesis and provide insights into the mechanisms underlying the proliferation of a malignant clone. Genomic DNA samples and clinical information were obtained from individuals enrolled in the Joint Study for Predisposing Factors for ATL Development, a Japanese prospective cohort study. Forty-seven longitudinal samples from 20 individuals (9 asymptomatic carriers and 11 patients with ATL at enrollment) were subjected to a clonality analysis. A method based on next-generation sequencing was used to characterize clones on the basis of integration sites. Relationships were analyzed among clonal patterns, clone sizes, and clinical status, including ATL onset and progression. Among carriers, those exhibiting an oligoclonal or monoclonal pattern with largely expanded clones subsequently progressed to ATL. All indolent patients who progressed to acute-type ATL exhibited monoclonal expansion. In both situations, the major expanded clone after progression was derived from the largest pre-existing clone. This study has provided the first detailed information regarding the dynamics of HTLV-1-infected T-cell clones and collectively suggests that the clonality of HTLV-1-infected cells could be a useful predictive marker of ATL onset and progression.

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

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

Transition of adult T-cell leukemia/lymphoma clones during clinical progression

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T-cell neoplasm caused by the transformation of HTLV-1-infected T cells. ATLL, especially its aggressive form, is known for its poor prognosis, even with intensive chemotherapy. ATLL cells are considered to be monoclonal; however, multiclonal proliferation or emergence of a new clone over time has been reported based on Southern blot analysis, although direct molecular evidence remains elusive. Furthermore, it is thought that clonal change may be a cause of early drug resistance in ATLL. To directly analyze potential clonal changes in ATLL during its clinical course, we used inverse PCR to detect integration sites in combination with a newly developed method using next-generation sequencing, and compared ATLL cell clonality at different time points. The results of inverse PCR indicated that the major clone was altered in three of 19 patients. Together with results from five patients, using this new method, we found direct evidence of clonal change occurring during the clinical course or in response to chemotherapy in ATLL. These results also highlight the importance of clonality analysis for understanding the mechanisms of ATLL development and drug resistance.

Advanced human T-cell leukemia virus type 1 carriers and early-stage indolent adult T-cell leukemia-lymphoma are indistinguishable based on CADM1 positivity in flow cytometry

We previously reported that the cell adhesion molecule 1 (CADM1) versus CD7 plot in flow cytometry reflects disease progression in human T-cell leukemia virus type 1 (HTLV-1) infection. In CD4⁺ cells from peripheral blood, CADM1⁻CD7⁺ (P), CADM1⁺CD7^dim (D) and CADM1⁺CD7⁻ (N) subpopulations are observed. The D and N subpopulations increase as asymptomatic HTLV-1 carriers (AC) progress to indolent adult T-cell leukemia-lymphoma (ATL) and the N subpopulation then expands in aggressive ATL. In the present study we examined whether the analysis can estimate the risk of developing ATL in advanced AC. Peripheral blood samples from AC (N = 41) and indolent ATL patients (N = 19) were analyzed by flow cytometry using the CADM1 versus CD7 plot for CD4⁺ cells and inverse long PCR (clonality analysis) of FACS-sorted subpopulations. Almost all AC with a high HTLV-1 proviral load (>4 copies/100 cells) had a CADM1⁺ (D + N) frequency of >10%. AC with 25% < CADM1⁺ ≤ 50% contained expanded clones similar to smoldering-type ATL. In many patients in the 25% < CADM1⁺ ≤ 50% group, the proportion of abnormal lymphocytes was distributed around the 5% line, which divides AC and smoldering-type ATL in Shimoyama's classification. In conclusion, the CADM1 versus CD7 plot is useful for selection of putative high-risk AC. The characteristics of some AC and smoldering ATL are said to be similar; however, long-term follow up is required and the clinical outcome (e.g. rate of transformation) of these cases should be used to determine whether to include them in the same clinical category.

Development and validation of a new high-throughput method to investigate the clonality of HTLV-1-infected cells based on provirus integration sites

Transformation and clonal proliferation of T-cells infected with human T-cell leukemia virus type-I (HTLV-1) cause adult T-cell leukemia. We took advantage of next-generation sequencing technology to develop and internally validate a new methodology for isolating integration sites and estimating the number of cells in each HTLV-1-infected clone (clone size). Initial analysis was performed with DNA samples from infected individuals. We then used appropriate controls with known integration sites and clonality status to confirm the accuracy of our system, which indeed had the least errors among the currently available techniques. Results suggest potential clinical and biological applications of the new method.

CADM1 expression and stepwise downregulation of CD7 are closely associated with clonal expansion of HTLV-I-infected cells in adult T-cell leukemia/lymphoma

PURPOSE

Cell adhesion molecule 1 (CADM1), initially identified as a tumor suppressor gene, has recently been reported to be ectopically expressed in primary adult T-cell leukemia-lymphoma (ATL) cells. We incorporated CADM1 into flow-cytometric analysis to reveal oncogenic mechanisms in human T-cell lymphotrophic virus type I (HTLV-I) infection by purifying cells from the intermediate stages of ATL development.

EXPERIMENTAL DESIGN

We isolated CADM1- and CD7-expressing peripheral blood mononuclear cells of asymptomatic carriers and ATLs using multicolor flow cytometry. Fluorescence-activated cell sorted (FACS) subpopulations were subjected to clonal expansion and gene expression analysis.

RESULTS

HTLV-I-infected cells were efficiently enriched in CADM1(+) subpopulations (D, CADM1(pos)CD7(dim) and N, CADM1(pos)CD7(neg)). Clonally expanding cells were detected exclusively in these subpopulations in asymptomatic carriers with high proviral load, suggesting that the appearance of D and N could be a surrogate marker of progression from asymptomatic carrier to early ATL. Further disease progression was accompanied by an increase in N with a reciprocal decrease in D, indicating clonal evolution from D to N. The gene expression profiles of D and N in asymptomatic carriers showed similarities to those of indolent ATLs, suggesting that these subpopulations represent premalignant cells. This is further supported by the molecular hallmarks of ATL, that is, drastic downregulation of miR-31 and upregulation of abnormal Helios transcripts.

CONCLUSION

The CADM1 versus CD7 plot accurately reflects disease progression in HTLV-I infection, and CADM1(+) cells with downregulated CD7 in asymptomatic carriers have common properties with those in indolent ATLs.

Molecular diagnosis of infection-related cancers in dermatopathology

The association between viruses and skin cancer is increasingly recognized in a number of neoplasms, that is, cutaneous squamous cell carcinoma, Kaposi sarcoma, nasopharyngeal carcinoma, and Merkel cell carcinoma, as well as hematolymphoid malignancies such as adult T-cell leukemia/lymphoma and NK/T-cell lymphoma (nasal type) and post-transplant lymphoproliferative disorders. Molecular assays are increasingly used to diagnose and manage these diseases. In this review, molecular features of tumor viruses and related host responses are explored. The tests used to identify such features are summarized. Evaluation of the utility of these assays for diagnosis and/or management of specific tumor types is presented.

Adult T-cell leukemia: a review of epidemiological evidence

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