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The c13orf25/miR‐17 cluster, which is responsible for 13q31‐q32 amplification in malignant lymphoma, contains the microRNA‐17‐18‐19‐20‐92 polycistron. A previous study demonstrated that this polycistron could modulate tumor formation following transplantation of microRNA 17‐19b into Eu‐myc mice. Another study reported that Myc can upregulate the miR‐17 cluster by binding directly upstream of the miR‐17 locus. These findings suggest that Myc and the miR‐17 cluster synergistically contribute to cancer development. In the study presented here, we observed recurrent 13q31‐32 amplification in MYC‐rearranged lymphomas (11 of 47 cases). Quantitative real‐time polymerase chain reaction analysis of c13orf25 for MYC‐rearranged lymphomas demonstrated that cases with 13q31‐32 amplification showed significantly higher expression of c13orf25 than cases without such amplification, although cases without 13q31‐32 amplification still showed slight upregulation of c13orf25. To investigate the relationship between Myc and the miR‐17 polycistron in tumorigenesis, we engineered rat fibroblasts (Rat‐1) that constitutively express the miR‐17 polycistron (miR), Myc, or both miR and Myc. The highest level of miR expression was detected in Rat‐1 transfected with both miR and Myc, whereas Myc transfectant cells alone also showed slight upregulation of miR. Furthermore, we demonstrated that nude mice injected with Rat‐1 transfected with both miR and Myc presented more accelerated tumor growth than those injected with Myc transfectant cells. These results suggest that miR is stably upregulated in the presence of constitutive expression of Myc, and that the deregulation of miR and Myc synergistically contribute to aggressive cancer development, probably by repressing tumor suppressor genes. (Cancer Sci 2007; 98: 1482–1490)

Intravascular large B‐cell lymphoma (IVLBCL) is a rare type of extranodal large B‐cell lymphoma that is characterized by the proliferation of lymphoma cells in the lumina of small vessels. Recent progress uncovering the genetic characteristics associated with MYD88/CD79B mutations has stimulated interest in the use of drugs targeting B‐cell receptor signaling, including Bruton's tyrosine kinase. However, difficulties in culturing ex vivo IVLBCL cells has hampered research on the development of novel therapies. In the present study, we demonstrated the establishment of an ex vivo culture system of IVLBCL cells obtained from patient‐derived xenograft (PDX) models. The spheroid culture enabled us to culture IVLBCL PDX cells for more than 10 days and to explore the efficacy of drug treatments acting on these cells. We found that carfilzomib and ibrutinib were effective for treating IVLBCL in ex vivo experiments and conducted in vivo analyses to assess the efficacy of these drugs. Although the efficacy of carfilzomib was difficult to confirm due to its toxicity in our models, ibrutinib showed comparable efficacy to a standard combination of chemotherapy drugs. Together, our data provide a new culture method for IVLBCL PDX cells and a rationale for translating ibrutinib to clinical use in IVLBCL patients.

Epstein–Barr virus (EBV)‐positive diffuse large B‐cell lymphoma (DLBCL) of the elderly (EBV[+]DLBCL‐E) is classified as a subtype of DLBCL. Until now, its molecular pathogenesis has remained unknown. To identify pathways characteristic of EBV(+)DLBCL‐E, gene expression profiling of five EBV(+)DLBCL‐E and seven EBV‐negative DLBCL (EBV[−]DLBCL) cases was undertaken using human oligonucleotide microarray analysis. Gene set enrichment analysis and gene ontology analysis showed that gene sets of the Janus kinase‐signal transducer and activator of transcription (JAK‐STAT) and nuclear factor kappa B (NF‐κB) pathways were enriched in EBV(+)DLBCL‐E cases. To confirm the results of the expression profiles, in vitro analysis was performed. Expression profiling analysis showed that high activation of the JAK‐STAT and NF‐κB pathways was induced by EBV infection into DLBCL cell lines. Activation of the NF‐κB pathway was confirmed in EBV‐infected cell lines using an electrophoretic mobility shift assay. Western blot analysis revealed an increased protein expression level of phosphorylated signal transducer and activator of transcription 3 (STAT3) in an EBV‐infected cell line. Protein expression of phosphorylated STAT3 was frequently observed in lymphoma cells of EBV(+)DLBCL‐E clinical samples using immunohistochemistry (EBV[+]DLBCL‐E: 80.0% [n = 20/25] versus EBV[−]DLBCL: 38.9% [n = 14/36]; P = 0.001). The results of the present study suggest that activation of the JAK‐STAT and NF‐κB pathways was characteristic of EBV(+)DLBCL‐E, which may reflect the nature of EBV‐positive tumor cells. Targeting these pathways as therapies might improve clinical outcomes of EBV(+)DLBCL‐E. EBV‐positive diffuse large B‐cell lymphoma (DLBCL) of the elderly is newly classified as a subtype of DLBCL in the 4th WHO classification. Comprehensive genetic analysis has not been investigaed. We identified the activation of JAK‐STAT and NF‐κB pathways was characteristic of the disease.

Histopathological distinction between adult T-cell leukemia/lymphoma (ATLL) and other T-cell neoplasms is often challenging. The current gold standard for the accurate diagnosis of ATLL is the Southern blot hybridization (SBH) assay, which detects clonal integration of human T-cell leukemia virus type I (HTLV-1) provirus. However, SBH cannot be performed with small biopsy or formalin-fixed paraffin-embedded (FFPE) tissue samples because this assay requires a large amount of DNA without degradation. Here we developed a new diagnostic algorithm for the accurate diagnosis of ATLL using FFPE samples. This method combines two HTLV-1 detection assays, namely, ultrasensitive RNA in situ hybridization using RNAscope for HTLV-1 bZIP factor (HBZ-RNAscope), and quantitative PCR targeting the tax gene (tax-qPCR). We analyzed 119 FFPE tissue specimens (62 ATLL, and 57 non-ATLL, including 41 HTLV-1 carriers) and compared them with the SBH results using the corresponding fresh-frozen samples. As a result, tax-qPCR had a higher ATLL identification rate than HBZ-RNAscope (88% [52/59], and 63% [39/62], respectively). However, HBZ-RNAscope clearly visualized the localization of HTLV-1-infected tumor cells and its identification rate increased to 94% (17/18) when the analysis was limited to samples up to 2 years old, indicating its usefulness in the daily diagnosis. The diagnostic algorithm combining these two assays successfully evaluated 94% (112/119) of samples and distinguished ATLL from non-ATLL cases including HTLV-1 carriers with 100% sensitivity and specificity. This method is expected to replace SBH and increase the accuracy of the diagnosis of ATLL.

A 34-year-old man became aware of an erythematous nodule on the left nasal wing. He was treated with topical steroids and oral antibacterial agents at his local doctor, but his condition did not improve, and he was referred to our hospital. A skin biopsy revealed diffuse cellular infiltration through the dermis. No epidermotropism was seen. The major infiltrate was small to medium-sized lymphoid cells. The number of CD3+ cells was almost the same as that of CD20+ cells, while CD4+ cells were dominant over CD8+ cells. Atypical lymphocytes were positive for BCL6 and PD-1. Polymerase chain reaction (PCR) analysis of immunoglobulin heavy chain and T-cell receptor gene rearrangements on paraffin-embedded tissue sections revealed a clonal expansion of T-cells. The patient was diagnosed as having primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (PCSM-LPD) and treated with fludroxycortide tape. The red nodule completely disappeared after three months. Nuclear staining for nuclear factor of activated T-cells c1 (NFATc1), which had been suggested to be useful in distinguishing PCSM-LPD from pseudolymphoma, was negative in our case. Our case was considered to be typical of PCSM-LPD among existing reports of PCSM-LPD from Japan, except for the young age of the patient. Our case suggested that young cases with PCSM-LPD may have been misdiagnosed with cutaneous pseudolymphoma (CPL), which may be one of the reasons why this type of lymphoproliferative disorder has been reported to occur in elderly people.

Cyclin D1 is an oncogene frequently overexpressed in human cancers that has a dual function as cell cycle and transcriptional regulator, although the latter is widely unexplored. Here, we investigated the transcriptional role of cyclin D1 in lymphoid tumor cells with cyclin D1 oncogenic overexpression. Cyclin D1 showed widespread binding to the promoters of most actively transcribed genes, and the promoter occupancy positively correlated with the transcriptional output of targeted genes. Despite this association, the overexpression of cyclin D1 in lymphoid cells led to a global transcriptional downmodulation that was proportional to cyclin D1 levels. This cyclin D1-dependent global transcriptional downregulation was associated with a reduced nascent transcription and an accumulation of promoter-proximal paused RNA polymerase II (Pol II) that colocalized with cyclin D1. Concordantly, cyclin D1 overexpression promoted an increase in the Poll II pausing index. This transcriptional impairment seems to be mediated by the interaction of cyclin D1 with the transcription machinery. In addition, cyclin D1 overexpression sensitized cells to transcription inhibitors, revealing a synthetic lethality interaction that was also observed in primary mantle cell lymphoma cases. This finding of global transcriptional dysregulation expands the known functions of oncogenic cyclin D1 and suggests the therapeutic potential of targeting the transcriptional machinery in cyclin D1-overexpressing tumors.

Genetic alterations in adult T‐cell leukemia/lymphoma (ATLL), a T‐cell malignancy associated with HTLV‐1, and their clinical impacts, especially from the perspective of viral strains, are not fully elucidated. We employed targeted next‐generation sequencing and single nucleotide polymorphism array for 89 patients with ATLL in Okinawa, the southernmost islands in Japan, where the frequency of HTLV‐1 tax subgroup‐A (HTLV‐1‐taxA) is notably higher than that in mainland Japan, where most ATLL cases have HTLV‐1‐taxB, and compared the results with previously reported genomic landscapes of ATLL in mainland Japan and the USA. Okinawan patients exhibited similar mutation profiles to mainland Japanese patients, with frequent alterations in TCR/NF‐ĸB (eg, PRKCB, PLCG1, and CARD11) and T‐cell trafficking pathways (CCR4 and CCR7), in contrast with North American patients who exhibited a predominance of epigenome‐associated gene mutations. Some mutations, especially GATA3 and RHOA, were detected more frequently in Okinawan patients than in mainland Japanese patients. Compared to HTLV‐1‐taxB, HTLV‐1‐taxA was significantly dominant in Okinawan patients with these mutations (GATA3, 34.1% vs 14.6%, P = .044; RHOA, 24.4% vs 6.3%, P = .032), suggesting the contribution of viral strains to these mutation frequencies. From a clinical viewpoint, we identified a significant negative impact of biallelic inactivation of PRDM1 (P = .027) in addition to the previously reported PRKCB mutations, indicating the importance of integrated genetic analysis. This study suggests that heterogeneous genetic abnormalities in ATLL depend on the viral strain as well as on the ethnic background. This warrants the need to develop therapeutic interventions considering regional characteristics. Targeted next‐generation sequencing and single nucleotide polymorphism array were applied to analyze aggressive adult T‐cell leukemia/lymphoma in Okinawa, which were not included in prior genomic studies. Our results showed that HTLV‐1 tax subgroup‐A was associated with high alteration frequencies in GATA3 and RHOA. Clinically, biallelic alterations, not heterozygous deletions or mutations, of PRDM1 were significantly associated with poor prognosis.

Despite receiving rituximab‐combined chemotherapy, follicular lymphoma (FL) patients often suffer tumor recurrence and understand that the cause of relapse in FL would thus significantly ameliorate the tumor therapeutics. In the present study, we show that TRA‐1‐60‐expressing cells are a unique population in FL, converge to the conventional stem cell marker Oct3/4 and ALDH1‐positive population, and resist current B‐lymphoma agents. TRA‐1‐60 expression was observed in scattered lymphoma cells in FL tissues only as well as in resting B‐lymphocytes inside germinal centers. Retrospective comparison between recurrent and cognate primary tissues showed that the number of TRA‐1‐60‐positive cells from rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisone (R‐CHOP)‐treated FL had increased relative to primary tissue, a finding corroborated by assays on different rituximab‐treated FL cell lines, FL‐18 and DOHH2, wherein TRA‐positive cell numbers increased over 10‐fold compared to the untreated sample. Concordantly, scanty TRA‐1‐60‐positive FL‐18 cells implanted s.c. into mice evinced potent tumor‐initiating capacity in vivo, where tumors were 12‐fold larger in volume (P = 0.0021 < 0.005) and 13‐fold heavier in weight (P = 0.0015 < 0.005) compared to those xenografted from TRA‐negative cells. To explain these results, gene expression profiling and qPCR analysis indicated that TRA‐1‐60‐positive cells defined a distinct population from that of TRA‐negative cells, with upregulation of multiple drug transporters and therapeutic resistance genes. Hence, TRA‐1‐60‐expressing cells in FL are considered to be vigorously intractable against conventional therapeutic agents, which may explain its refractory recurrence. TRA‐1‐60 should be a prominent focus among cellular markers in follicular lymphoma research, by which we ultimately hope to explain clinical intractability against current rituximab‐combination and other therapies, and to better understand the unique population among a range of lymphoma cell types.

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