Landscape and function of multiple mutations within individual oncogenes.

Sporadic reports have described cancer cases in which multiple driver mutations (MMs) occur in the same oncogene1,2. However, the overall landscape and relevance of MMs remain elusive. Here we carried out a pan-cancer analysis of 60,954 cancer samples, and identified 14 pan-cancer and 6 cancer-type-specific oncogenes in which MMs occur more frequently than expected: 9% of samples with at least one mutation in these genes harboured MMs. In various oncogenes, MMs are preferentially present in cis and show markedly different mutational patterns compared with single mutations in terms of type (missense mutations versus in-frame indels), position and amino-acid substitution, suggesting a cis-acting effect on mutational selection. MMs show an overrepresentation of functionally weak, infrequent mutations, which confer enhanced oncogenicity in combination. Cells with MMs in the PIK3CA and NOTCH1 genes exhibit stronger dependencies on the mutated genes themselves, enhanced downstream signalling activation and/or greater sensitivity to inhibitory drugs than those with single mutations. Together oncogenic MMs are a relatively common driver event, providing the underlying mechanism for clonal selection of suboptimal mutations that are individually rare but collectively account for a substantial proportion of oncogenic mutations.

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.

Subclassification of pT3 upper tract urothelial carcinoma: a multicenter retrospective study.

PURPOSE: The prognosis of patients with pT3 upper tract urothelial carcinoma (UTUC) varies. The current study aimed to further classify patients with pT3 UTUC into different survival outcome groups based on tumor location and site of invasion. METHODS: This retrospective study included 323 patients with pT3 UTUC who underwent nephroureterectomy at 11 hospitals in Japan. Histological and clinical data were obtained via a chart review. Univariate and multivariate Cox proportional hazards analyses showed the effect of different variables on recurrence-free survival (RFS), cancer-specific survival (CSS), and overall survival (OS). RESULTS: The median age of the patients was 72 years. Patients with pT3 UTUCs were divided into two groups: those with renal parenchymal invasion only (pT3a, n = 95) and those with peripelvic or periureteral fat invasion (pT3b, n = 228). pT3b UTUC was significantly associated with hydronephrosis, low preoperative estimated glomerular filtration rate (eGFR), histological nodal metastasis, nuclear grade 3, lymphovascular invasion (LVI), carcinoma in situ, and positive surgical margin. Based on the univariate analyses, patients with pT3b UTUC had a significantly lower 5-year RFS (42.4% vs. 70.1%, p < 0.0001), 5-year CSS (54.3% vs. 80.0%, p = 0.0002), and 5-year OS (47.8% vs. 76.8%, p < 0.0001) than those with pT3a UTUC. According to the multivariate analyses, nodal metastasis, LVI, adjuvant chemotherapy, preoperative eGFR, nuclear grade (RFS only), surgical margin (RFS only), and Charlson comorbidity index (OS only), but not pT3b stage, were associated with survival. CONCLUSION: Compared with pT3a UTUC, pT3b UTUC was significantly associated with worse histological features, consequently resulting in unsatisfactory survival outcomes.

Feasibility and clinical utility of comprehensive genomic profiling of hematological malignancies.

Identification of genetic alterations through next-generation sequencing (NGS) can guide treatment decision-making by providing information on diagnosis, therapy selection, and prognostic stratification in patients with hematological malignancies. Although the utility of NGS-based genomic profiling assays was investigated in hematological malignancies, no assays sufficiently cover driver mutations, including recently discovered ones, as well as fusions and/or pathogenic germline variants. To address these issues, here we have devised an integrated DNA/RNA profiling assay to detect various types of somatic alterations and germline variants at once. Particularly, our assay can successfully identify copy number alterations and structural variations, including immunoglobulin heavy chain translocations, IKZF1 intragenic deletions, and rare fusions. Using this assay, we conducted a prospective study to investigate the feasibility and clinical usefulness of comprehensive genomic profiling for 452 recurrently altered genes in hematological malignancies. In total, 176 patients (with 188 specimens) were analyzed, in which at least one alteration was detected in 171 (97%) patients, with a median number of total alterations of 7 (0-55). Among them, 145 (82%), 86 (49%), and 102 (58%) patients harbored at least one clinically relevant alteration for diagnosis, treatment, and prognosis, respectively. The proportion of patients with clinically relevant alterations was the highest in acute myeloid leukemia, whereas this assay was less informative in T/natural killer-cell lymphoma. These results suggest the clinical utility of NGS-based genomic profiling, particularly for their diagnosis and prognostic prediction, thereby highlighting the promise of precision medicine in hematological malignancies.

Smaller decline of renal function after nephroureterectomy predicts poorer prognosis of upper tract urothelial carcinoma: a multicentre retrospective study.

PURPOSE: Renal function is frequently impaired in the patients with upper tract urothelial carcinoma. We aimed to evaluate the impact of renal function and its change after surgery on survival rates in patients with upper tract urothelial carcinoma after nephroureterectomy. METHODS: The study cohort comprised 755 patients with upper tract urothelial carcinoma who underwent nephroureterectomy between 1995 and 2016 at nine hospitals in Japan. Estimated glomerular filtration rate was calculated using the three-variable Japanese equation for glomerular filtration rate estimation from serum creatinine level and age. Outcomes were recurrence-free, cancer-specific and overall survivals. Univariate and multivariate Cox proportional hazards regression analyses were used. RESULTS: Median patients' age was 72 years old. Pre- and post-surgical median estimated glomerular filtration rate were 55.5 and 42.9 ml/min/1.73 m2, respectively. Median estimated glomerular filtration rate decline after surgery, which represents function of the affected side kidney, was 13.1 ml/min/1.73 m2. The 5-year recurrence-free, cancer-specific and overall survivals were 68.3, 79.4 and 74.0%, respectively. Multivariate analysis indicated that lower preoperative estimated glomerular filtration rate and estimated glomerular filtration rate decline were associated with poorer recurrence-free, cancer-specific and overall survivals, but post-operative estimated glomerular filtration rate was not. Estimated glomerular filtration rate decline was more significant poor-prognosticator than preoperative estimated glomerular filtration rate. Proportions of the patients with estimated glomerular filtration rate <60 ml/min/1.73 m2 before surgery were 50.6 and 73.2% in organ-confined disease and locally advanced disease, respectively (P < 0.0001). After surgery, they were 91.6 and 89.8%, respectively (P = 0.3896). CONCLUSIONS: Lower preoperative renal function, especially of the affected side kidney, was significantly associated with poor prognosis after nephroureterectomy for upper tract urothelial carcinoma. Many patients with locally advanced disease have reduced renal function at diagnosis and even more after surgery.

Prognostic significance of serum neuron-specific enolase in small cell carcinoma of the urinary bladder.

PURPOSE: Small cell carcinoma of the urinary bladder (SCCB) is known for its aggressive clinical features and poor prognosis. No prognostic factor has been established so far. The aim of this study was to assess the significance of possible prognostic factors, including serum neuron-specific enolase (NSE), an established biomarker for small cell lung carcinoma. METHODS: We retrospectively reviewed 31 patients with primary SCCB treated at our eight affiliate institutions between 2001 and 2014. The association of various clinicopathological factors at diagnosis, including the serum NSE value, with cancer-specific survival (CSS) was assessed. The log-rank test and Cox proportional hazards model were used for univariate and multivariate analyses, respectively. RESULTS: Nineteen (61.3 %) died of SCCB during the follow-up, with a median survival time of 12.7 months. Prognostic factors were analyzed for the 25 patients after excluding six with missing data. Univariate analysis demonstrated that stage (extensive disease) and serum NSE ≥25 ng/ml were significantly associated with worse CSS. Multivariate analysis identified increased serum NSE value as a sole independent predictor of CSS (hazard ratio 18.52, p = 0.0022). CONCLUSIONS: Serum NSE value at diagnosis was an independent prognostic factor for primary SCCB and may serve as a useful biomarker in the management of SCCB.

A PATIENT WITH RETROPERITONEAL MYXOID LIPOSARCOMA RECURRENCE WHO ACHIEVED REMARKABLE IMPROVEMENTS IN PERFORMANCE STATUS WHEN TREATED WITH COMBINATION CHEMOTHERAPY WITH GEMCITABINE AND DOCETAXEL.

We report a patient with retroperitoneal myxoid liposarcoma recurrence who achieved remarkable improvements in performance status (PS) and maintained stable disease for approximately 5 months when treated with combination chemotherapy with gemcitabine (GEM) and docetaxel combination chemotherapy (GD). A 51-year-old woman was referred to our hospital with the chief complaint of a palpable mass in the left side of the abdomen. A retroperitoneal liposarcoma was diagnosed on the basis of magnetic resonance imaging and computed tomography results, and tumor resection was performed. The histopathological evaluation showed myxoid liposarcoma, which was classified as grade 2 according to the French Federation of Cancer Centers Sarcoma Group (FNCLCC) system.Two months later, the tumor regionally recurred as peritoneal dissemination with rapid growth. Five months after the surgery, the growing tumor caused appetite loss and pleural effusion in the left lung. GD was administered (800 mg/m2 GEM on days 1 and 8, and 60 mg/m2 docetaxel on day 8) and 4 cycles were administered.The resulting decrease in abdominal girth and in the amount of pleural effusion allowed the patient to regain her appetite, and the patient's PS greatly improved from 3 to 1.Initially, GD was shown to be effective for the treatment of leiomyosarcoma and pleomorphic sarcoma, and it is now recommended as one of the first-line regimens in the National Comprehensive Cancer Network guidelines for soft tissue sarcoma treatment. The patient in this case showed remarkable improvement in PS after tumor recurrence and maintained stable disease for some time, without severe adverse effects.

Impact of adjuvant chemotherapy on patients with pathological Stage T3b and/or lymph node metastatic bladder cancer after radical cystectomy.

OBJECTIVE: To evaluate the effectiveness of adjuvant chemotherapy in patients with pathological Stage T3 bladder cancer who had undergone radical cystectomy, and to determine the prognostic survival factors for adjuvant chemotherapy treatment. METHODS: From January 1990 to October 2013, 202 patients underwent radical cystectomy and pelvic lymphadenectomy. Among them, 65 patients with non-organ-confined disease (pT3, N0-3, M0) diagnosed were investigated in this study. Thirty-one patients (48%) were treated with adjuvant chemotherapy and the remaining 34 patients (52%) were not. RESULTS: Median age of all patients was 66 years, and median follow-up was 26.1 months. For all pT3 patients, overall survival and disease-free survival times were similar in the adjuvant chemotherapy and non-adjuvant chemotherapy groups. However, in the pT3b subgroup, median overall survival (47.0 vs. 10.6 months) and median disease-free survival (35.5 vs. 5.3 months) times were significantly prolonged for those who underwent adjuvant chemotherapy (P = 0.009 and 0.025). In patients with pathological lymph node metastatic (pN+), median overall survival (30.1 vs. 6.4 months) and median disease-free survival (15.7 vs. 3.5 months) times were significantly prolonged in the adjuvant chemotherapy group (P = 0.016 and 0.027). In addition, according to multivariate analysis in pT3b and/or pN+ subgroup patients, adjuvant chemotherapy status was an independent predictive factor for overall survival and disease-free survival. CONCLUSION: Adjuvant chemotherapy did not significantly improve overall survival and disease-free survival when compared with all patients with pT3 who had received radical cystectomy in the non-adjuvant chemotherapy group. However, in the pT3b and pN+ subgroup, adjuvant chemotherapy demonstrated statistically significant benefits regarding overall survival and disease-free survival. Although these results could not support adjuvant chemotherapy use for all pT3 patients, the pT3b substage and/or pN+ may help identify patients with pT3 who could benefit from adjuvant chemotherapy.

Different clinicopathological features between patients who developed early and late recurrence following surgery for renal cell carcinoma.

BACKGROUND: To evaluate the clinicopathological features and identify predictive factors in patients with early and late recurrence following initial surgery for localized renal cell carcinoma. METHODS: From April 1988 to January 2013, 486 patients without metastases at the initial diagnosis underwent either radical nephrectomy or partial nephrectomy and were followed up thereafter. Patients were divided into 3 groups; no recurrence, early recurrence (recurrence within 5 years), and late recurrence (recurrence after 5 years). Cancer-specific survival after recurrence was analyzed by using the Kaplan-Meier method. Multivariate logistic regression analysis was applied to define clinical and pathological factors correlated to early and late recurrence following surgery. RESULTS: Seventy-seven (15.8 %) and 18 (3.7 %) patients developed early and late recurrence, respectively. In multivariate logistic regression analysis, positive symptoms at diagnosis, ≥pT2, positive lymphovascular invasion, and grade 3 were independent predictive factors for early recurrence. Age at surgery and ≥pT2 were significantly correlated to late recurrence. The 5-year cancer-specific survival rate after recurrence was 72.4 and 52.9 % in the late and the early recurrence groups, respectively (P = 0.044). CONCLUSIONS: The risk factors for clinical recurrence differed according to the time that had elapsed between initial surgery and the first metastasis in patients with localized renal cell carcinoma. Our study showed age at initial surgery and the pT stage were independent predictive factors for late recurrence. Further investigation of a larger number of patients is required to predict which patients may develop recurrence in the future and to choose appropriate treatment.

[Clinicopathological Study and Treatment Outcome of Retroperitoneal Soft Tissue Sarcoma].

We analyzed the pathological findings, surgical margin, the first site of local or distant recurrence, treatment for postoperative recurrence and the characteristics of 25 patients who were surgically treated for retroperitoneal sarcomas between December 2000 and January 2014. The median tumor diameter was 11 cm. The pathological diagnosis was liposarcoma (n = 14), leiomyosarcoma (n = 7) and others (n = 4). Tumors were resected en-bloc with adjacent organs in 17 of the patients. In median follow up period of 39 months, 11 of the 14 patients with liposarcoma experienced local tumor recurrence and distant metastasis did not precede local recurrence in any of these patients. Leiomyosarcoma recurred in all patients and distant metastases appeared before local recurrence in four of them. The five-year recurrence-free and over all survival rates were 28 and 58%, respectively. The recurrence-free and overall survival rates significantly differed between well-differentiated and other subtypes of liposarcoma (both p < 0.05). The overall survival was significantly better for patients with a tumor diameter of < 11 cm than for those with ≥ 11 cm (p 0.05). Furthermore, overall survival was significantly better for patients who were able to undergo re-operation at the time of recurrence than for those who could not (p < 0.005). Although we resected adjacent organs when the margin was insufficient, the rate of local recurrence was high in liposarcoma. On the other hand, the rate of distant metastasis was high in leiomyosarcoma.

Pan-Cancer Comparative and Integrative Analyses of Driver Alterations Using Japanese and International Genomic Databases.

Using 48,627 samples from the Center for Cancer Genomics and Advanced Therapeutics (C-CAT), we present a pan-cancer landscape of driver alterations and their clinical actionability in Japanese patients. Comparison with White patients in Genomics Evidence Neoplasia Information Exchange (GENIE) demonstrates high TP53 mutation frequencies in Asian patients across multiple cancer types. Integration of C-CAT, GENIE, and The Cancer Genome Atlas data reveals many cooccurring and mutually exclusive relationships between driver mutations. At pathway level, mutations in epigenetic regulators frequently cooccur with PI3K pathway molecules. Furthermore, we found significant cooccurring mutations within the epigenetic pathway. Accumulation of mutations in epigenetic regulators causes increased proliferation-related transcriptomic signatures. Loss-of-function of many epigenetic drivers inhibits cell proliferation in their wild-type cell lines, but this effect is attenuated in those harboring mutations of not only the same but also different epigenetic drivers. Our analyses dissect various genetic properties and provide valuable resources for precision medicine in cancer. SIGNIFICANCE: We present a genetic landscape of 26 principal cancer types/subtypes, including Asian-prevalent ones, in Japanese patients. Multicohort data integration unveils numerous cooccurring and exclusive relationships between driver mutations, identifying cooccurrence of multiple mutations in epigenetic regulators, which coordinately cause transcriptional and phenotypic changes. These findings provide insights into epigenetic regulator-driven oncogenesis. This article is featured in Selected Articles from This Issue, p. 695.

Modeling NK-cell lymphoma in mice reveals its cell-of-origin and microenvironmental changes and identifies therapeutic targets.

Extranodal NK/T-cell lymphoma (ENKTCL) is an Epstein-Barr virus (EBV)-related neoplasm preferentially involving the upper aerodigestive tract. Here we show that NK-cell-specific Trp53 disruption in mice leads to the development of NK-cell lymphomas after long latency, which involve not only the hematopoietic system but also the salivary glands. Before tumor onset, Trp53 knockout causes extensive gene expression changes, resulting in immature NK-cell expansion, exclusively in the salivary glands. Both human and murine NK-cell lymphomas express tissue-resident markers, suggesting tissue-resident NK cells as their cell-of-origin. Murine NK-cell lymphomas show recurrent Myc amplifications and upregulation of MYC target gene signatures. EBV-encoded latent membrane protein 1 expression accelerates NK-cell lymphomagenesis and causes diverse microenvironmental changes, particularly myeloid propagation, through interferon-γ signaling. In turn, myeloid cells support tumor cells via CXCL16-CXCR6 signaling and its inhibition is effective against NK-cell tumors in vivo. Remarkably, KLRG1-expressing cells expand in the tumor and are capable of repopulating tumors in secondary recipients. Furthermore, targeting KLRG1 alone or combined with MYC inhibition using an eIF4 inhibitor is effective against NK-cell tumors. Therefore, our observations provide insights into the pathogenesis and highlight potential therapeutic targets, including CXCL16, KLRG1, and MYC, in ENKTCL, which can help improve its diagnostic and therapeutic strategies.

Comprehensive Genetic Profiling Reveals Frequent Alterations of Driver Genes on the X Chromosome in Extranodal NK/T-cell Lymphoma.

Extranodal NK/T-cell lymphoma (ENKTCL) is an Epstein-Barr virus (EBV)-related neoplasm with male dominance and a poor prognosis. A better understanding of the genetic alterations and their functional roles in ENKTCL could help improve patient stratification and treatments. In this study, we performed a comprehensive genetic analysis of 178 ENKTCL cases to delineate the landscape of mutations, copy number alterations (CNA), and structural variations, identifying 34 driver genes including six previously unappreciated ones, namely, HLA-B, HLA-C, ROBO1, CD58, POT1, and MAP2K1. Among them, CD274 (24%) was the most frequently altered, followed by TP53 (20%), CDKN2A (19%), ARID1A (15%), HLA-A (15%), BCOR (14%), and MSN (14%). Chromosome X losses were the most common arm-level CNAs in females (∼40%), and alterations of four X-linked driver genes (MSN, BCOR, DDX3X, and KDM6A) were more frequent in males and females harboring chromosome X losses. Among X-linked drivers, MSN was the most recurrently altered, and its expression was lost in approximately one-third of cases using immunohistochemical analysis. Functional studies of human cell lines showed that MSN disruption promoted cell proliferation and NF-κB activation. Moreover, MSN inactivation increased sensitivity to NF-κB inhibition in vitro and in vivo. In addition, recurrent deletions were observed at the origin of replication in the EBV genome (6%). Finally, by integrating the 34 drivers and 19 significant arm-level CNAs, nonnegative matrix factorization and consensus clustering identified two molecular groups with different genetic features and prognoses irrespective of clinical prognostic factors. Together, these findings could help improve diagnostic and therapeutic strategies in ENKTCL. Significance: Integrative genetic analyses and functional studies in extranodal NK/T-cell lymphoma identify frequent disruptions of X-linked drivers, reveal prognostic molecular subgroups, and uncover recurrent MSN alterations that confer sensitivity to NF-κB inhibition.

Landscape of Genetic Alterations Underlying Hallmark Signature Changes in Cancer Reveals TP53 Aneuploidy-driven Metabolic Reprogramming.

The hallmark signatures based on gene expression capture core cancer processes. Through a pan-cancer analysis, we describe the overview of hallmark signatures across tumor types/subtypes and reveal significant relationships between these signatures and genetic alterations. TP53 mutation exerts diverse changes, including increased proliferation and glycolysis, which are closely mimicked by widespread copy-number alterations. Hallmark signature and copy-number clustering identify a cluster of squamous tumors and basal-like breast and bladder cancers with elevated proliferation signatures, frequent TP53 mutation, and high aneuploidy. In these basal-like/squamous TP53-mutated tumors, a specific and consistent spectrum of copy-number alterations is preferentially selected prior to whole-genome duplication. Within Trp53-null breast cancer mouse models, these copy-number alterations spontaneously occur and recapitulate the hallmark signature changes observed in the human condition. Together, our analysis reveals intertumor and intratumor heterogeneity of the hallmark signatures, uncovering an oncogenic program induced by TP53 mutation and select aneuploidy events to drive a worsened prognosis. Significance: Our data demonstrate that TP53 mutation and a resultant selected pattern of aneuploidies cause an aggressive transcriptional program including upregulation of glycolysis signature with prognostic implications. Importantly, basal-like breast cancer demonstrates genetic and/or phenotypic changes closely related to squamous tumors including 5q deletion that reveal alterations that could offer therapeutic options across tumor types regardless of tissue of origin.

Inter- and intra-tumor heterogeneity of genetic and immune profiles in inherited renal cell carcinoma.

Patients with von Hippel-Lindau disease (vHL) are at risk of developing spatially and temporally multiple clear cell renal cell carcinomas (ccRCCs), which offers a valuable opportunity to analyze inter- and intra-tumor heterogeneity of genetic and immune profiles within the same patient. Here, we perform whole-exome and RNA sequencing, digital gene expression, and immunohistochemical analyses for 81 samples from 51 ccRCCs of 10 patients with vHL. Inherited ccRCCs are clonally independent and have less genomic alterations than sporadic ccRCCs. Hierarchical clustering of transcriptome profiles shows two clusters with distinct immune signatures: immune hot and cold clusters. Interestingly, not only samples from the same tumors but also different tumors from the same patients tend to show a similar immune signature, whereas samples from different patients frequently exhibit different signatures. Our findings reveal the genetic and immune landscape of inherited ccRCCs, demonstrating the relevance of host factors in shaping anti-tumor immunity.

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

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. SIGNIFICANCE: Our multimodal single-cell analyses comprehensively dissect the cellular and molecular alterations of the peripheral blood in HTLV-1 infection, with and without progression to leukemia. This study not only sheds light on premalignant clonal expansion in viral carcinogenesis, but also helps to devise novel diagnostic and therapeutic strategies for HTLV-1-related disorders.