The downregulation of PRDM1/Blimp-1 is associated with aberrant expression of miR-223 in extranodal NK/T-cell lymphoma, nasal type

How we treat NK/T-cell lymphomas

Natural killer (NK)/T-cell lymphomas are aggressive malignancies with a predilection for Asian and South American populations. Epstein-Barr virus (EBV) infection in lymphoma cells is universal. Predominantly extranodal, NK/T-cell lymphomas are divided clinically into nasal (involving the nose and upper aerodigestive tract), non-nasal (involving the skin, gastrointestinal tract, testes, and other organs), and aggressive leukaemia/lymphoma (involving the marrow and multiple organs) subtypes. Initial assessment should include imaging with positron emission tomography computed tomography (PET/CT), quantification of plasma EBV DNA as a surrogate marker of lymphoma load, and bone marrow examination with in situ hybridization for EBV-encoded small RNA. Prognostication can be based on presentation parameters (age, stage, lymph node involvement, clinical subtypes, and EBV DNA), which represent patient factors and lymphoma load; and dynamic parameters during treatment (serial plasma EBV DNA and interim/end-of-treatment PET/CT), which reflect response to therapy. Therapeutic goals are to achieve undetectable plasma EBV DNA and normal PET/CT (Deauville score ≤ 3). NK/T-cell lymphomas express the multidrug resistance phenotype, rendering anthracycline-containing regimens ineffective. Stage I/II nasal cases are treated with non-anthracycline asparaginase-based regimens plus sequential/concurrent radiotherapy. Stage III/IV nasal, and non-nasal and aggressive leukaemia/lymphoma cases are treated with asparaginase-containing regimens and consolidated by allogeneic haematopoietic stem cell transplantation (HSCT) in suitable patients. Autologous HSCT does not improve outcome. In relapsed/refractory cases, novel approaches comprise immune checkpoint blockade of PD1/PD-L1, EBV-specific cytotoxic T-cells, monoclonal antibodies, and histone deacetylase inhibitors. Future strategies may include inhibition of signalling pathways and driver mutations, and immunotherapy targeting the lymphoma and its microenvironment.

MiRNAs and lncRNAs in NK cell biology and NK/T-cell lymphoma

The important role of lncRNAs and miRNAs in directing immune responses has become increasingly clear. Recent evidence conforms that miRNAs and lncRNAs are involved in NK cell biology and diseases through RNA-protein, RNA-RNA, or RNA-DNA interactions. In this view, we summarize the contribution of miRNAs and lncRNAs to NK cell lineage development, activation and function, highlight the biological significance of functional miRNAs or lncRNAs in NKTL and discuss the potential of these miRNAs and lncRNAs as innovative biomarkers/targets for NKTL early diagnosis, target treatment and prognostic evaluations.

MicroRNA Expression Differences in Blood-Derived CD19+ B Cells of Methotrexate Treated Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is a complex disease with a wide range of underlying susceptibility factors. Recently, dysregulation of microRNAs (miRNAs) in RA have been reported in several immune cell types from blood. However, B cells have not been studied in detail yet. Given the autoimmune nature of RA with the presence of autoantibodies, CD19+ B cells are a key cell type in RA pathogenesis and alterations in CD19+ B cell subpopulations have been observed in patient blood. Therefore, we aimed to reveal the global miRNA repertoire and to analyze miRNA expression profile differences in homogenous RA patient phenotypes in blood-derived CD19+ B cells. Small RNA sequencing was performed on CD19+ B cells of newly diagnosed untreated RA patients (n=10), successfully methotrexate (MTX) treated RA patients in remission (MTX treated RA patients, n=18) and healthy controls (n=9). The majority of miRNAs was detected across all phenotypes. However, significant expression differences between MTX treated RA patients and controls were observed for 27 miRNAs, while no significant differences were seen between the newly diagnosed patients and controls. Several of the differentially expressed miRNAs were previously found to be dysregulated in RA including miR-223-3p, miR-486-3p and miR-23a-3p. MiRNA target enrichment analysis, using the differentially expressed miRNAs and miRNA-target interactions from miRTarBase as input, revealed enriched target genes known to play important roles in B cell activation, differentiation and B cell receptor signaling, such as STAT3, PRDM1 and PTEN. Interestingly, many of those genes showed a high degree of correlated expression in CD19+ B cells in contrast to other immune cell types. Our results suggest important regulatory functions of miRNAs in blood-derived CD19+ B cells of MTX treated RA patients and motivate for future studies investigating the interactive mechanisms between miRNA and gene targets, as well as the possible predictive power of miRNAs for RA treatment response.

Non-coding RNAs (miRNAs and lncRNAs) and their roles in lymphogenesis in all types of lymphomas and lymphoid malignancies

Contemporary developments in molecular biology have been combined with discoveries on the analysis of the role of all non-coding RNAs (ncRNAs) in human diseases, particularly in cancer, by examining their roles in cells. Currently, included among these common types of cancer, are all the lymphomas and lymphoid malignancies, which represent a diverse group of neoplasms and malignant disorders. Initial data suggest that non-coding RNAs, particularly long ncRNAs (lncRNAs), play key roles in oncogenesis and that lncRNA-mediated biology is an important key pathway to cancer progression. Other non-coding RNAs, termed microRNAs (miRNAs or miRs), are very promising cancer molecular biomarkers. They can be detected in tissues, cell lines, biopsy material and all biological fluids, such as blood. With the number of well-characterized cancer-related lncRNAs and miRNAs increasing, the study of the roles of non-coding RNAs in cancer is bringing forth new hypotheses of the biology of cancerous cells. For the first time, to the best of our knowledge, the present review provides an up-to-date summary of the recent literature referring to all diagnosed ncRNAs that mediate the pathogenesis of all types of lymphomas and lymphoid malignancies.

Differential epigenetic regulation between the alternative promoters, PRDM1α and PRDM1β, of the tumour suppressor gene PRDM1 in human multiple myeloma cells

Multiple myeloma (MM) is a B-cell neoplasm that is characterized by the accumulation of malignant plasma cells in the bone marrow. The transcription factor PRDM1 is a master regulator of plasma cell development and is considered to be an oncosuppressor in several lymphoid neoplasms. The PRDM1β isoform is an alternative promoter of the PRDM1 gene that may interfere with the normal role of the PRDM1α isoform. To explain the induction of the PRDM1β isoform in MM and to offer potential therapeutic strategies to modulate its expression, we characterized the cis regulatory elements and epigenetic status of its promoter. We observed unexpected patterns of hypermethylation and hypomethylation at the PRDM1α and PRDM1β promoters, respectively, and prominent H3K4me1 and H3K9me2 enrichment at the PRDM1β promoter in non-expressing cell lines compared to PRDM1β-expressing cell lines. After treatment with drugs that inhibit DNA methylation, we were able to modify the activity of the PRDM1β promoter but not that of the PRDM1α promoter. Epigenetic drugs may offer the ability to control the expression of the PRDM1α/PRDM1β promoters as components of novel therapeutic approaches.

Extranodal NK/T-Cell Lymphomas: The Role of Natural Killer Cells and EBV in Lymphomagenesis

Natural killer (NK) cells are lymphocytes involved in innate and adaptive immune functions. They are the presumed cell of origin of distinct hematolymphoid malignancies, including aggressive NK-cell leukemia and extranodal NK/T-cell lymphoma (ENKTL). This review focuses on the role of NK cells and Epstein–Barr virus (EBV) in ENKTL pathogenesis.

Epigenetic aberrations in natural killer/T-cell lymphoma: diagnostic, prognostic and therapeutic implications

Natural killer/T-cell lymphoma (NKTCL) is an aggressive malignancy that usually presents in the upper aerodigestive tract. This malignancy shows substantial geographic variability in incidence, and is characterized by Epstein-Barr virus (EBV) infections. Epigenetic aberrations may dysregulate the expression of genes involved in different hallmarks of cancer. A growing body of evidence underscores the importance of epigenetic aberrations in the pathogenesis of NKTCL. Promoter hypermethylation is a common epigenetic mechanism for the inactivation of tumour suppressor genes. Several epigenetically silenced tumour suppressor candidates (e.g. PRDM1, BIM) were identified in this aggressive cancer using locus-specific and genome-wide promoter methylation analyses. Importantly, genes involved in epigenetic modifications were identified to be mutated (e.g. KMT2D) or methylated (e.g. TET2) in NKTCL patients, which may contribute to pathogenesis through global alterations in chromatin states. Cancer-associated microRNAs, some of which are expressed by EBV, and long noncoding RNAs have been observed to be dysregulated in NKTCL. This review focuses on studies investigating epigenetic aberrations in NKTCL to bolster our overall understanding of the role of these abnormalities in disease pathobiology. We also discuss the potential of these epigenetic aberrations to improve diagnosis and prognosis as well as reveal novel targets of therapy for NKTCL.

What we should know about natural killer/T-cell lymphomas

Natural-killer/T cell lymphoma (NKTCL) is the most common extranodal lymphoma with highly aggressive clinical outcome. System biology techniques provide novel insights into the pathogenesis, risk stratification, and clinical management in NKTCL. Comparative genomic hybridization analysis reveal most frequent deletion of chromosome 6q21. Whole-exome sequencing studies identify recurrent somatic gene mutations, involving RNA helicases, tumor suppressors, JAK-STAT pathway molecules, and epigenetic modifiers. Genome-wide association study reports strongest association of HLA-DPB1 rs9277378 with lymphomagenesis. Alterations of oncogenic signaling pathways as well as epigenetic dysregulation of microRNA and long non-coding RNAs are also observed in NKTCL. Epstein-Barr virus (EBV) is the major etiology of NKTCL and the pathogenic mechanism remains unclear. Different risk stratification models are proposed based on clinical parameters (IPI, PINK, and PINK-E, etc.) or biomarkers (Ki67, C-reactive protein level, and EBV DNA, etc.). Therapeutic strategies vary according to disease stage, including radiotherapy, asparaginase-based chemotherapy, hematopoietic stem-cell transplantation, targeted therapy (immune checkpoints inhibitors, and histone deacetylation inhibitors, etc.). Future investigations will be emphasized on EBV-related pathogenesis of NKTCL, prognostic and therapeutic biomarkers, as well as multi-center clinical trials, so as to optimize personalized treatment of NKTCL in the era of precision medicine.

Non-coding RNAs in Natural Killer/T-Cell Lymphoma

Natural killer/T-cell lymphoma (NKTCL) is a rare and aggressive subtype of non-Hodgkin's lymphoma that is associated with a poor outcome. Non-coding RNAs (ncRNAs), which account for 98% of human RNAs, lack the function of encoding proteins but instead have the important function of regulating gene expression, including transcription, translation, RNA splicing, editing, and turnover. However, the roles and mechanisms of aberrantly expressed ncRNAs in NKTCL are not fully clear. Aberrant expressions of microRNA (miRNAs) affect the PI3K/AKT signaling pathways (miRNA-21, miRNA-155, miRNA-150, miRNA-142, miRNA-494), NF-κB (miRNA-146a, miRNA-155) and cell cycle signaling pathways to regulate cell function. Moreover, Epstein-Barr virus (EBV) encoded miRNAs and EBV oncoprotein LMP-1 regulated the expression of cellular genes that induce invasion, metastasis, cell cycle progression and cellular transformation. In addition, NKTCL-associated Long non-coding RNA (lncRNA) ZFAS1 regulated certain pathways and lncRNA MALAT1 acted as a predictive marker. This review article provides an overview of ncRNAs associated with NKTCL, summarizes the function of significantly differentially expressed hotspot non-coding RNAs that contribute to the pathogenesis, diagnoses, treatment and prognosis of NKTCL and discusses the relevance of these ncRNAs to clinical practice.

JAK3/STAT3 oncogenic pathway and PRDM1 expression stratify clinicopathologic features of extranodal NK/T‑cell lymphoma, nasal type

The inactivation of tumor suppressor gene positive regulatory domain containing I (PRDM1) and activation of signal transducer and activator of transcription 3 (STAT3) have been detected in the majority of extranodal NK/T‑cell lymphoma, nasal type (EN‑NK/T‑NT) cases. In the present study, their association with and effects on the clinicopathologic features of EN‑NK/T‑NT are described. PRDM1 was revealed to be expressed in 19 out of 58 patients (32.8%) with EN‑NK/T‑NT, and phosphorylated STAT3 was overexpressed in 42 out of 58 (72.4%). Oncogenic pathways were investigated by NanoString encounter technology in 5 PRDM1(+) and 5 PRDM1(‑) EN‑NK/T‑NT specimens. Multiple oncogenic pathways involved in cell apoptosis, cellcycle (CC) and angiogenesis were discriminately activated in EN‑NK/T‑NT cases, and in PRDM1(+) cases in particular. The sustained activation of the Janus kinase 3 (JAK)/STAT3 pathway was more pronounced. In addition, missense mutations in the SRC homology 2 domain of STAT3 were detected in 7 out of 37 EN‑NK/T‑NT cases (18.92%), and the acquired mutation was related to the activation of the JAK3/STAT3 pathway. The downregulation of PRDM1 and upregulation of phospho‑STAT3 (Tyr705) were associated with angiocentric infiltration of EN‑NK/T‑NT (P=0.039). Notably, the prognosis of patients in the PRDM1(+)/STAT3 [mutated (mut‑)] group was considerably improved than that of patients in the STAT3(mut+)/PRDM(‑) group (P=0.037). In addition, the inhibition of NK/T cell lymphoma cell lines by Stattic and tofacitinib could suppress cell proliferation by inducing cell apoptosis or arresting the CC. The present results revealed that the JAK3/STAT3 oncogenic pathway and PRDM1 expression could stratify clinicopathologic features of EN‑NK/T‑NT. The inhibition of the JAK3/STAT3 pathway may serve as a treatment option for EN‑NK/T‑NT.

[PRDM1 expression and its relationship with PI3K/AKT pathway activation in extranodal NK/T cell lymphoma-nasal type]

目的

探讨抑癌基因PRDM1在结外NK/T细胞淋巴瘤-鼻型（EN-NK/T-NT）中的表达及其与PI3K/AKT通路活化的关系。

方法

以10例EN-NK/T-NT患者病理组织标本和PRDM1阳性细胞系YT细胞、PRDM1缺失细胞系NKL、NK92细胞为研究对象，采用免疫细胞化学和Western blot法检测PRDM1、p-AKT的表达，采用NanoString基因表达谱技术检测PI3K/AKT通路在正常鼻黏膜、PRDM1阴性和阳性EN-NK/T-NT组织中的激活情况，采用MTS法检测YT、NKL和NK92细胞增殖活性，采用流式细胞术检测细胞周期和细胞凋亡。

结果

①NanoString基因表达谱分析结果显示PRDM1阳性组PI3K/AKT信号通路IL-7、BRCA1、ITGA8、IL2RB、FASLG、CDK2、COL27A1、CSF3R、KITLG、IL-6的表达明显高于对照组，差异均有统计学意义（P值均<0.05）。②免疫细胞化学和Western blot法检测结果显示p-AKT在YT细胞系中高表达，而在NK92和NKL细胞中低表达或不表达。③Western blot法检测结果显示，PI3K/AKT通路抑制剂LY294002作用24 h后YT细胞PRDM1和PTEN的表达水平升高，且呈剂量依赖性。④LY294002（20 µmol/L）作用48 h后，与对照组比较，YT细胞增殖率较对照组明显降低（100.00%对58.18%，t=−12.770，P=0.006），G₁期细胞比例明显增高（30.05%对76.93%，t=11.570，P<0.001），差异均有统计学意义；但NKL细胞与对照组比较细胞增殖和细胞周期的差异均无统计学意义（P值均>0.05）。

结论

EN-NK/T-NT中PI3K/AKT通路活化与PRDM1阳性表达相关，抑制PI3K/AKT通路有望成为PRDM1阳性EN-NK/T-NT的治疗手段。

Advances in multiple omics of natural-killer/T cell lymphoma

Natural-killer/T cell lymphoma (NKTCL) represents the most common subtype of extranodal lymphoma with aggressive clinical behavior. Prevalent in Asians and South Americans, the pathogenesis of NKTCL remains to be fully elucidated. Using system biology techniques including genomics, transcriptomics, epigenomics, and metabolomics, novel biomarkers and therapeutic targets have been revealed in NKTCL. Whole-exome sequencing studies identify recurrent somatic gene mutations, involving RNA helicases, tumor suppressors, JAK-STAT pathway molecules, and epigenetic modifiers. Another genome-wide association study reports that single nucleotide polymorphisms mapping to the class II MHC region on chromosome 6 contribute to lymphomagenesis. Alterations of oncogenic signaling pathways janus kinase-signal transducer and activator of transcription (JAK-STAT), nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), WNT, and NOTCH, as well as epigenetic dysregulation of microRNA and long non-coding RNAs, are also frequently observed in NKTCL. As for metabolomic profiling, abnormal amino acids metabolism plays an important role on disease progression of NKTCL. Of note, through targeting multiple omics aberrations, clinical outcome of NKTCL patients has been significantly improved by asparaginase-based regimens, immune checkpoints inhibitors, and histone deacetylation inhibitors. Future investigations will be emphasized on molecular classification of NKTCL using integrated analysis of system biology, so as to optimize targeted therapeutic strategies of NKTCL in the era of precision medicine.

The Genomics and Molecular Biology of Natural Killer/T-Cell Lymphoma: Opportunities for Translation

Extranodal NK/T-cell lymphoma, nasal type (ENKTL), is an aggressive malignancy with a poor prognosis. While the introduction of L-asparaginase in the treatment of this disease has significantly improved the prognosis, the outcome of patients relapsing after asparaginase-based chemotherapy, which occurs in up to 50% of patients with disseminated disease, remains dismal. There is hence an urgent need for effective targeted therapy especially in the relapsed/refractory setting. Gene expression profiling studies have provided new perspectives on the molecular biology, ontogeny and classification of ENKTL and further identified dysregulated signaling pathways such as Janus associated kinase (/Signal Transducer and activation of transcription (JAK/STAT), Platelet derived growth factor (PDGF), Aurora Kinase and NF-κB, which are under evaluation as therapeutic targets. Copy number analyses have highlighted potential tumor suppressor genes such as PR Domain Zinc Finger Protein 1 (PRDM1) and protein tyrosine phosphatase kappa (PTPRK) while next generation sequencing studies have identified recurrently mutated genes in pro-survival and anti-apoptotic pathways. The discovery of epigenetic dysregulation and aberrant microRNA activity has broadened our understanding of the biology of ENKTL. Importantly, immunotherapy via Programmed Cell Death -1 (PD-1) and Programmed Cell Death Ligand1 (PD-L1) checkpoint signaling inhibition is emerging as an attractive therapeutic strategy in ENKTL. Herein, we present an overview of the molecular biology and genomic landscape of ENKTL with a focus on the most promising translational opportunities.

Combinatorial regulation of a Blimp1 (Prdm1) enhancer in the mouse retina

The mouse retina comprises seven major cell types that exist in differing proportions. They are generated from multipotent progenitors in a stochastic manner, such that the relative frequency of any given type generated changes over time. The mechanisms determining the proportions of each cell type are only partially understood. Photoreceptors and bipolar interneurons are derived from cells that express Otx2. Within this population, Blimp1 (Prdm1) helps set the balance between photoreceptors and bipolar cells by suppressing bipolar identity in most of the cells. How only a subset of these Otx2+ cells decides to upregulate Blimp1 and adopt photoreceptor fate is unknown. To understand this, we investigated how Blimp1 transcription is regulated. We identified several potential Blimp1 retinal enhancer elements using DNase hypersensitivity sequencing. Only one of the elements recapitulated Blimp1 spatial and temporal expression in cultured explant assays and within the retinas of transgenic mice. Mutagenesis of this retinal Blimp1 enhancer element revealed four discrete sequences that were each required for its activity. These included highly conserved Otx2 and ROR (retinoic acid receptor related orphan receptor) binding sites. The other required sequences do not appear to be controlled by Otx2 or ROR factors, increasing the complexity of the Blimp1 gene regulatory network. Our results show that the intersection of three or more transcription factors is required to correctly regulate the spatial and temporal features of Blimp1 enhancer expression. This explains how Blimp1 expression can diverge from Otx2 and set the balance between photoreceptor and bipolar fates.

PRDM1 expression levels in marginal zone lymphoma and lymphoplasmacytic lymphoma

PRDM1 (BLIMP1) is a transcription repressor protein shown to be involved in B-cell differentiation into plasma cells. Marginal zone lymphomas (MZL) and lymphoplasmacytic lymphomas (LPL) are B cell lymphomas that both show some degree of plasmacytic differentiation and thus can sometimes constitute a difficult differential diagnosis. In this study, we investigated if MZL and LPL have abnormalities in the expression of PRDM1 beta and if there are any differences in expression between these two entities. After interrogating 42 samples (15 marginal zone lymphomas, 9 lymphoplasmacytic lymphomas, 3 follicular lymphomas, and 13 normal/control samples), we have found that a significant percentage of MZL and LPL cases harbor abnormalities (67% and 44%, respectively) involving the PRDM1-β transcript (P=0.004). By immunohistochemistry, PRDM1 positive staining (>5%) was more common in MZL. We conclude that PRDM1-β may play a role in the pathogenesis of these low-grade lymphomas with plasmacytic differentiation.

New insights into Blimp-1 in T lymphocytes: a divergent regulator of cell destiny and effector function

B lymphocyte-induced maturation protein-1 (Blimp-1) serves as a master regulator of the development and function of antibody-producing B cells. Given that its function in T lymphocytes has been identified within the past decade, we review recent findings with emphasis on its role in coordinated control of gene expression during the development, differentiation, and function of T cells. Expression of Blimp-1 is mainly confined to activated T cells and is essential for the production of interleukin (IL)-10 by a subset of forkhead box (Fox)p3⁺ regulatory T cells with an effector phenotype. Blimp-1 is also required to induce cell elimination in the thymus and critically modulates peripheral T cell activation and proliferation. In addition, Blimp-1 promotes T helper (Th) 2 lineage commitment and limits Th1, Th17 and follicular helper T cell differentiation. Furthermore, Blimp-1 coordinates with other transcription factors to regulate expression of IL-2, IL-21 and IL-10 in effector T lymphocytes. In CD8⁺ T cells, Blimp-1 expression is distinct in heterogeneous populations at the stages of clonal expansion, differentiation, contraction and memory formation when they encounter antigens. Moreover, Blimp-1 plays a fundamental role in coordinating cytokine receptor signaling networks and transcriptional programs to regulate diverse aspects of the formation and function of effector and memory CD8⁺ T cells and their exhaustion. Blimp-1 also functions as a gatekeeper of T cell activation and suppression to prevent or dampen autoimmune disease, antiviral responses and antitumor immunity. In this review, we discuss the emerging roles of Blimp-1 in the complex regulation of gene networks that regulate the destiny and effector function of T cells and provide a Blimp-1-dominated transcriptional framework for T lymphocyte homeostasis.

Whole transcriptome analysis reveals dysregulated oncogenic lncRNAs in natural killer/T-cell lymphoma and establishes MIR155HG as a target of PRDM1

Natural killer/T-cell lymphoma is a rare but aggressive neoplasm with poor prognosis. Despite previous reports that showed potential tumor suppressors, such as PRDM1 or oncogenes associated with the etiology of this malignancy, the role of long non-coding RNAs in natural killer/T-cell lymphoma pathobiology has not been addressed to date. Here, we aim to identify cancer-associated dysregulated long non-coding RNAs and signaling pathways or biological processes associated with these long non-coding RNAs in natural killer/T-cell lymphoma cases and to identify the long non-coding RNAs transcriptionally regulated by PRDM1. RNA-Seq analysis revealed 166 and 66 long non-coding RNAs to be significantly overexpressed or underexpressed, respectively, in natural killer/T-cell lymphoma cases compared with resting or activated normal natural killer cells. Novel long non-coding RNAs as well as the cancer-associated ones such as SNHG5, ZFAS1, or MIR155HG were dysregulated. Interestingly, antisense transcripts of many growth-regulating genes appeared to be transcriptionally deregulated. Expression of ZFAS1, which is upregulated in natural killer/T-cell lymphoma cases, showed association with growth-regulating pathways such as stabilization of P53, regulation of apoptosis, cell cycle, or nuclear factor-kappa B signaling in normal and neoplastic natural killer cell samples. Consistent with the tumor suppressive role of PRDM1, we identified MIR155HG and TERC to be transcriptionally downregulated by PRDM1 in two PRDM1-null NK-cell lines when it is ectopically expressed. In conclusion, this is the first study that identified long non-coding RNAs whose expression is dysregulated in natural killer/T-cell lymphoma cases. These findings suggest that ZFAS1 and other dysregulated long non-coding RNAs may be involved in natural killer/T-cell lymphoma pathobiology through regulation of cancer-related genes, and loss-of-PRDM1 expression in natural killer/T-cell lymphomas may contribute to overexpression of MIR155HG; thereby promoting tumorigenesis.

Hypermethylation of PRDM1/Blimp-1 promoter in extranodal NK/T-cell lymphoma, nasal type: an evidence of predominant role in its downregulation

The loss of PRDM1 expression is common in extranodal NK/T-cell lymphoma, nasal type (EN-NK/T-NT), but the role of promoter methylation in silencing PRDM1 expression remains unclear. Hence, we performed pyrosequencing analysis to evaluate the promoter methylation of PRDM1 gene in vivo and in vitro, to analyze the association between methylation and its expression, and to assess cellular effects of PRDM1 reexpression. The promoter hypermethylation of PRDM1 gene was detected in 11 of 25 EN-NK/T-NT cases (44.0%) and NK92 and NKL cells. The promoter hypermethylation of PRDM1 was significantly correlated with PRDM1 expression in vivo and in vitro, predominantly contributing to the loss of PRDM1 expression compared with genetic deletion and aberrant expression of miR-223 in EN-NK/T-NT. PRDM1 expression was significantly restored by demethylation treatment, which induced cell proliferation suppression, cell cycle arrest, and apoptosis increase. We also found that PRDM1 reexpression could downregulate the expression of Ets-1, T-bet, granzyme B, and c-myc. Our findings demonstrated that the promoter hypermethylation of PRDM1 harbored a predominant role in the downregulation of PRDM1 expression, significantly affecting the biological behavior of tumor cells in EN-NK/T-NT.

Loss of PRDM1/BLIMP-1 function contributes to poor prognosis of activated B-cell-like diffuse large B-cell lymphoma

PRDM1/BLIMP-1, a master regulator of plasma-cell differentiation, is frequently inactivated in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) patients. Little is known about its genetic aberrations and relevant clinical implications. A large series of patients with de novo DLBCL was effectively evaluated for PRDM1/BLIMP-1 deletion, mutation, and protein expression. BLIMP-1 expression was frequently associated with the ABC phenotype and plasmablastic morphologic subtype of DLBCL, yet 63% of the ABC-DLBCL patients were negative for BLIMP-1 protein expression. In these patients, loss of BLIMP-1 was associated with Myc overexpression and decreased expression of p53 pathway molecules. In addition, homozygous PRDM1 deletions and PRDM1 mutations within exons 1 and 2, which encode for domains crucial for transcriptional repression, were found to show a poor prognostic impact in patients with ABC-DLBCL but not in those with germinal center B-cell-like DLBCL (GCB-DLBCL). Gene expression profiling revealed that loss of PRDM1/BLIMP-1 expression correlated with a decreased plasma-cell differentiation signature and upregulation of genes involved in B-cell receptor signaling and tumor-cell proliferation. In conclusion, these results provide novel clinical and biological insight into the tumor-suppressive role of PRDM1/BLIMP-1 in ABC-DLBCL patients and suggest that loss of PRDM1/BLIMP-1 function contributes to the overall poor prognosis of ABC-DLBCL patients.

Esophageal metastasis secondary to extranodal nasal-type natural killer/T-cell lymphoma: A case report

We herein report a case of recurrent nasal natural killer (NK)/T-cell lymphoma in a 21-year-old male patient. The patient presented with an esophageal mass, fever and difficulty in swallowing. There were no other obvious sites of recurrence apart from the esophageal lesion. Metastatic esophageal lesions are extremely rare. The histological analysis demonstrated a highly aggressive tumor with a characteristic angiodestructive growth pattern and nasal cavity necrosis. The lymphoma cells were immunopositive for leukocyte common antigen, T-cell intracytoplasmic antigen 1 and CD68, negative for CD56 and CD3, and positive for Epstein-Barr virus. A computed tomography scan revealed mild thickening of the wall of the lower esophagus. The barium swallow revealed stiffness of the esophageal wall, with limited expansion and mucosal damage. The final diagnosis was primary nasal NK/T-cell lymphoma, with metastasis to the esophagus. Clinically, it is important to distinguish nasal-type NK/T-cell lymphoma from other types of tumors, as its prognosis and treatment of secondary metastases differ significantly.

EBV-miR-BHRF1-2 targets PRDM1/Blimp1: potential role in EBV lymphomagenesis

PRDM1/Blimp1, a master regulator of B-cell terminal differentiation, has been identified as a tumor suppressor gene in aggressive lymphomas, including diffuse large B-cell lymphoma (DLBCL). It has been shown in DLBCL and Hodgkin lymphoma that PRDM1 is downregulated by cellular microRNAs. In this study, we identify the Epstein–Barr virus (EBV) microRNA (miRNA), EBV-miR-BHRF1-2, as a viral miRNA regulator of PRDM1. EBV-miR-BHRF1-2 repressed luciferase reporter activity by specific interaction with the seed region within the PRDM1 3' untranslated region. EBV-miR-BHRF1-2 inhibition upregulated PRDM1 protein expression in lymphoblastoid cell lines (LCL), supporting a role of miR-BHRF1-2 in PRDM1 downregulation in vivo. Discordance of PRDM1 messenger RNA and protein expressions is associated with high EBV-miR-BHRF1-2 levels in LCLs and primary post-transplant EBV-positive DLBCL. Enforced expression of PRDM1-induced apoptosis and cell cycle arrest in LCL cells. Inhibition of EBV-miR-BHRF1-2 negatively regulates cell cycle and decreases expression of SCARNA20, a small nucleolar RNA that is also downregulated by PRDM1 overexpression. The interaction between EBV-miR-BHRF1-2 and PRDM1 may be one of the mechanisms by which EBV-miR-BHRF1-2 promotes EBV lymphomagenesis. Our results support the potential of EBV-miR-BHRF1-2 as a therapeutic target in EBV-associated lymphoma.

The Genetic Deletion of 6q21 and PRDM1 and Clinical Implications in Extranodal NK/T Cell Lymphoma, Nasal Type

6q21 genetic deletion has been frequently detected in extranodal NK/T cell lymphoma, nasal type (EN-NK/T-NT), and PRDM1 is considered as candidate gene. However, direct detection of PRDM1 deletion has not been well documented. We investigated genetic alterations of 6q21 and PRDM1 in 43 cases of EN-NK/T-NT and cell lines by FISH. PRDM1 expression was evaluated by immunohistochemistry and Western blot. The correlation between genetic alteration and PRDM1 expression and the significance in clinic-pathologic were analyzed. Heterozygous deletion of 6q21 and/or PRDM1 was observed in 24 of 43 cases (55.81%) of EN-NK/T-NT including 16 cases (37.21%) for 6q21 deletion and 19 cases (44.19%) for PRDM1 deletion. Similarly, heterozygous codeletion of 6q21 and PRDM1 was identified in NK92 and NKL cells. The heterozygous deletion of 6q21 and/or PRDM1 was correlated with PRDM1 expression. However, genetic deletion of 6q21 and/or PRDM1 was not correlated with clinicopathological features of EN-NK/T-NT, while PRDM1 expression showed positive effect on the outcome of patients as those as disease site, B symptom, and clinical stage. Thus, heterozygous deletion of 6q21 and/or PRDM1 was frequently detected in EN-NK/T-NT and correlated with downregulation of PRDM1. But the prognostic role of genetic deletion needs to be further evaluated in larger cohort.

Icaritin induces lytic cytotoxicity in extranodal NK/T-cell lymphoma

Background

Extranodal NK/T-cell lymphoma (ENKL) is an aggressive hematological malignancy associated with Epstein–Barr virus (EBV) infection. It is often resistant to conventional chemotherapy and has a poor prognosis. Icaritin, a compound derived from Chinese herbal medicine, Herba Epimedii, has been reported to exert antitumor effects on a variety of cancer cell lines. In the present study, we investigated the cytotoxic effects of Icaritin on the two EBV-positive ENKL cell lines SNK-10 and SNT-8, along with the underlying molecular mechanisms.

Methods

ENKL cell lines SNK-10 and SNT-8 were exposed to different concentrations of Icaritin for the indicated time. Treated cells were analyzed for cell proliferation, cell cycle, and cell apoptosis. Phosphorylation of Stat3 and Akt proteins in signaling pathways and the EBV-encoded LMP1 proteins were measured by Western blot. Expression of EBV genes was assessed by Real-Time PCR.

Results

Our results showed that Icaritin dose-dependently inhibits ENKL cell proliferation and induces apoptosis and cell cycle arrest at G₂/M phase. Additionally, Icaritin upregulates Bax, downregulates Bcl-2 and pBad, and activates caspase-3 and caspase-9. The anti-proliferative and pro-apoptotic effects of Icaritin are likely mediated by inhibition of Stat3 and Akt pathways through LMP1 downregulation. Importantly, Icaritin induces EBV lytic gene expression in ENKL cells, and the combination of Icaritin and the antiviral drug ganciclovir (GCV) is more effective in inducing ENKL cells apoptosis than Icaritin or GCV alone.

Conclusions

These findings indicate that EBV-targeted approaches may have significant therapeutic potential for ENKL treatment.