PRDM1 is a tumor suppressor gene in natural killer cell malignancies

Resistance mechanisms and potential therapeutic strategies in relapsed or refractory natural killer/T cell lymphoma

ABSTRACT

Natural killer/T cell lymphoma (NKTCL) is a malignant tumor originating from NK or T cells, characterized by its highly aggressive and heterogeneous nature. NKTCL is predominantly associated with Epstein-Barr virus infection, disproportionately affecting Asian and Latin American populations. Owing to the application of asparaginase and immunotherapy, clinical outcomes have improved significantly. However, for patients in whom first-line treatment fails, the prognosis is exceedingly poor. Overexpression of multidrug resistance genes, abnormal signaling pathways, epigenetic modifications and active Epstein-Barr virus infection may be responsible for resistance. This review summarized the mechanisms of resistance for NKTCL and proposed potential therapeutic approaches.

Prdm1 positively regulates liver Group 1 ILCs cancer immune surveillance and preserves functional heterogeneity

Group 1 innate lymphoid cells (ILCs) comprise conventional natural killer (cNK) cells and type 1 innate lymphoid cells (ILC1s). The main functions of liver cNK cells and ILC1s not only include directly killing target cells but also regulating local immune microenvironment of the liver through the secretion of cytokines. Uncovering the intricate mechanisms by which transcriptional factors regulate and influence the functions of liver cNK cells and ILC1s, particularly within the context of liver tumors, presents a significant opportunity to amplify the effectiveness of immunotherapies against liver malignancies. Using Ncr1-drived conditional knockout mouse model, our study reveals the regulatory role of Prdm1 in shaping the composition and maturation of cNK cells. Although Prdm1 did not affect the killing function of cNK cells in an in vivo cytotoxicity model, a significant increase in cancer metastasis was observed in Prdm1 knockout mice. Interferon-gamma (IFN-γ), granzyme B, and perforin secretion decreased significantly in Prdm1-deficient cNK cells and liver ILC1s. Single-cell RNA sequencing (scRNA-seq) data also provided evidences that Prdm1 maintains functional subsets of cNK cells and liver ILC1s and facilitates communications between cNK cells, liver ILC1s, and macrophages. The present study unveiled a novel regulatory mechanism of Prdm1 in cNK cells and liver ILC1s, showing promising potential for developing innovative immune therapy strategies against liver cancer.

Identification of multiple organ metastasis-associated hub mRNA/miRNA signatures in non-small cell lung cancer

Metastasis remains major cause of treatment failure in non-small cell lung cancer (NSCLC). A comprehensive characterization of the transcriptomic landscape of NSCLC-cells with organ-specific metastatic potentials would advance our understanding of NSCLC metastasis process. In this study, we established NSCLC bone-metastatic (BoM), brain-metastatic (BrM), and lymph-metastatic (LnM) cells by an in vivo spontaneous metastatic model. Subsequently, by analyzing the entire transcriptomic profiles of BoM, BrM, LnM, LuM, in comparison with their parental cell line L9981, we identified miR-660-5p as a key driver that is associated with NSCLC progression and distant metastasis, potentially through its targeting of LIMCH1, SMARCA5 and TPP2. In addition, a six-gene signature (ADRB2, DPYSL2, IL7R, LIMCH1, PIK3R1, and SOX2) was subsequently established to predict NSCLC metastasis based on differentially expressed genes, three of which (DPYSL2, PIK3R1, LIMCH1) along with the transcriptional factors RB1 and TP63, were ultimately validated by experiments. Taken together, aberrant gene signature and miRNA can serve as biomarkers for predicting NSCLC distant metastasis, and targeting them could potentially contribute to the development of novel therapeutic strategies.

Forkhead box protein D2 suppresses colorectal cancer by reprogramming enhancer interactions

Somatic stem cells contribute to normal tissue homeostasis, and their epigenomic features play an important role in regulating tissue identities or developing disease states. Enhancers are one of the key players controlling chromatin context-specific gene expression in a spatial and temporal manner while maintaining tissue homeostasis, and their dysregulation leads to tumorigenesis. Here, epigenomic and transcriptomic analyses reveal that forkhead box protein D2 (FOXD2) is a hub for the gene regulatory network exclusive to large intestinal stem cells, and its overexpression plays a significant role in colon cancer regression. FOXD2 is positioned at the closed chromatin and facilitates mixed-lineage leukemia protein-4 (MLL4/KMT2D) binding to deposit H3K4 monomethylation. De novo FOXD2-mediated chromatin interactions rewire the regulation of p53-responsive genes and induction of apoptosis. Taken together, our findings illustrate the novel mechanistic details of FOXD2 in suppressing colorectal cancer growth and suggest its function as a chromatin-tuning factor and a potential therapeutic target for colorectal cancer.

Rational Targets of Therapy in Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive extranodal non-Hodgkin lymphoma (NHL) with poor outcomes, particularly in advanced-stage and relapsed/refractory disease. Emerging research on molecular drivers of ENKTL lymphomagenesis by next-generation and whole genome sequencing has revealed diverse genomic mutations in multiple signaling pathways, with the identification of multiple putative targets for novel therapeutic agents. In this review, we summarize the biological underpinnings of newly-understood therapeutic targets in ENKTL with a focus on translational implications, including epigenetic and histone regulatory aberrations, activation of cell proliferation signaling pathways, suppression of apoptosis and tumor suppressor genes, changes in the tumor microenvironment, and EBV-mediated oncogenesis. In addition, we highlight prognostic and predictive biomarkers which may enable a personalized medicine approach toward ENKTL therapy.

Extranodal natural killer/T-cell lymphoma: An overview on pathology and clinical management

Natural killer (NK)/T-cell lymphomas arise mainly from NK-cells and occasionally T-cells, and are universally infected with Epstein Barr virus (EBV). They are uncommon lymphomas more prevalent in Asian and Central/South American populations. NK/T-cell lymphomas are clinically aggressive and predominantly extranodal. The most commonly involved sites are the nasal cavity, followed by non-nasal sites including the skin, gastrointestinal tract and testis. The diagnosis of extranodal NK/T-cell lymphoma is established with histological and immunohistochemical examination, together with the demonstration of EBV in the tumour cells. Staging by positron emission tomography computed tomography is essential to inform the optimal management. Plasma EBV DNA quantification should be performed as it serves as a marker for prognostication and treatment response. Survival outcomes of patients with early-stage disease are good following treatment with nonanthracycline based chemotherapy, together with sequential/concurrent radiotherapy. For advanced-stage disease, asparaginase-containing regimens are mostly used and allogeneic haematopoietic stem cell transplantation should be considered for those at high risk of relapse. Salvage chemotherapy is largely ineffective for relapsed/refractory disease, which has a grave prognosis. Novel therapeutic approaches including immune check-point blockade, EBV-specific cytotoxic T-cells, and monoclonal antibodies are being investigated to improve outcomes for those with high risk and relapsed/refractory disease.

Genomic profiling identifies distinct genetic subtypes in extra-nodal natural killer/T-cell lymphoma

Extra-nodal NK/T-cell lymphoma, nasal type (ENKTCL) is a highly aggressive Epstein-Barr virus associated lymphoma, typically presenting in the nasal and paranasal areas. We assembled a large series of ENKTCL (n = 209) for comprehensive genomic analysis and correlative clinical study. The International Lymphoma Prognostic Index (IPI), site of disease, stage, lymphadenopathy, and hepatomegaly were associated with overall survival. Genetic analysis revealed frequent oncogenic activation of the JAK/STAT3 pathway and alterations in tumor suppressor genes (TSGs) and genes associated with epigenomic regulation. Integrated genomic analysis including recurrent mutations and genomic copy number alterations using consensus clustering identified seven distinct genetic clusters that were associated with different clinical outcomes, thus constituting previously unrecognized risk groups. The genetic profiles of ENTKCLs from Asian and Hispanic ethnic groups showed striking similarity, indicating shared pathogenetic mechanism and tumor evolution. Interestingly, we discovered a novel functional cooperation between activating STAT3 mutations and loss of the TSG, PRDM1, in promoting NK-cell growth and survival. This study provides a genetic roadmap for further analysis and facilitates investigation of actionable therapeutic opportunities in this aggressive lymphoma.

Clinicopathologic and Genetic Features of Primary T-cell Lymphomas of the Central Nervous System: An Analysis of 11 Cases Using Targeted Gene Sequencing

Primary central nervous system lymphoma (PCNSL) of peripheral T-cell lineage (T-PCNSL) is rare, and its genetic and clinicopathologic features remain unclear. Here, we present 11 cases of T-PCNSL in immunocompetent individuals from a single institute, focusing on their genetic alterations. Seven cases were subject to targeted panel sequencing covering 120 lymphoma-related genes. Nine of the eleven cases were classified as peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), of which one was of γδT-cell lineage. There was one case of anaplastic lymphoma kinase-positive anaplastic large cell lymphoma and another of extranodal natural killer (NK)/T-cell lymphoma (ENKTL) of αβT-cell lineage. The male to female ratio was 7 : 4 and the age ranged from 3 to 75 years (median, 61 y). Most patients presented with neurological deficits (n=10) and showed multifocal lesions (n=9) and deep brain structure involvement (n=9). Tumor cells were mostly small-to-medium, and T-cell monoclonality was detected in all nine evaluated cases. PTCL-NOS was CD4-positive (n=4), CD8-positive (n=3), mixed CD4-positive and CD8-positive (n=1), or CD4/CD8-double-negative (n=1, γδT-cell type). Cytotoxic molecule expression was observed in 4 (67%) of the 6 evaluated cases. Pathogenic alterations were found in 4 patients: one PTCL-NOS case had a frameshift mutation in KMT2C, another PTCL-NOS case harbored a truncating mutation in TET2, and another (γδT-cell-PTCL-NOS) harbored NRAS G12S and JAK3 M511I mutations, and homozygous deletions of CDKN2A and CDKN2B. The ENKTL (αβT-cell lineage) case harbored mutations in genes ARID1B, FAS, TP53, BCOR, KMT2C, POT1, and PRDM1. In conclusion, most of the T-PCNSL were PTCL-NOS, but sporadic cases of other subtypes including γδT-cell lymphoma, anaplastic lymphoma kinase-positive anaplastic large cell lymphoma, and ENKTL were also encountered. Immunophenotypic analysis, clonality test, and targeted gene sequencing along with clinicoradiologic evaluation, may be helpful for establishing the diagnosis of T-PCNSL. Moreover, this study demonstrates genetic alterations with potential diagnostic and therapeutic utility in T-PCNSL.

Conserved and Unique Functions of Blimp1 in Immune Cells

B-lymphocyte-induced maturation protein-1 (Blimp1), is an evolutionarily conserved transcriptional regulator originally described as a repressor of gene transcription. Blimp1 crucially regulates embryonic development and terminal differentiation in numerous cell lineages, including immune cells. Initial investigations of Blimp1’s role in immunity established its non-redundant role in lymphocytic terminal effector differentiation and function. In B cells, Blimp1 drives plasmablast formation and antibody secretion, whereas in T cells, Blimp1 regulates functional differentiation, including cytokine gene expression. These studies established Blimp1 as an essential transcriptional regulator that promotes efficient and controlled adaptive immunity. Recent studies have also demonstrated important roles for Blimp1 in innate immune cells, specifically myeloid cells, and Blimp1 has been established as an intrinsic regulator of dendritic cell maturation and T cell priming. Emerging studies have determined both conserved and unique functions of Blimp1 in different immune cell subsets, including the unique direct activation of the igh gene transcription in B cells and a conserved antagonism with BCL6 in B cells, T cells, and myeloid cells. Moreover, polymorphisms associated with the gene encoding Blimp1 (PRDM1) have been linked to numerous chronic inflammatory conditions in humans. Blimp1 has been shown to regulate target gene expression by either competing with other transcription factors for binding to the target loci, and/or by recruiting various chromatin-modifying co-factors that promote suppressive chromatin structure, such as histone de-acetylases and methyl-transferases. Further, Blimp1 function has been shown to be essentially dose and context-dependent, which adds to Blimp1’s versatility as a regulator of gene expression. Here, we review Blimp1’s complex roles in immunity and highlight specific gaps in the understanding of the biology of this transcriptional regulator, with a major focus on aspects that could foster the description and understanding of novel pathways regulated by Blimp1 in the immune system.

Recent Advances in the Diagnosis and Treatment of Natural Killer Cell Malignancies

Simple Summary

Natural killer (NK)/T-cell lymphomas are aggressive extranodal Epstein–Barr virus (EBV)-positive malignancies. They can be divided into three subtypes: nasal (involving the nose and upper aerodigestive tract), non-nasal (involving skin, gastrointestinal tract, testis and other organs) and disseminated (involving multiple organs). Lymphoma cells are positive for CD3ε, CD56, cytotoxic molecules and EBV-encoded small RNA. There is a predilection for Asian and Central/South American populations. Genome-wide association studies have identified lymphoma susceptibility loci in Asians. Positron emission tomography computed tomography and plasma EBV DNA quantification are crucial at diagnosis and follow-up. Stage I/II patients receive non-athracycline asparaginse-containing regimens, together with sequential/concurrent radiotherapy. Anthracycline-containing regimens are ineffective. Stage III/IV patients receive asparaginase-containing regimens, followed by allogeneic haematopoietic stem cell transplantation (HSCT). Autologous HSCT does not improve outcome. In relapsed/refractory patients, novel approaches include PD1/PD-L1 targeting, EBV-specific cytotoxic T-cells, and monoclonal antibodies. Small molecules including histone deacetylase inhibitors may be beneficial.

Abstract

Natural killer (NK)/T-cell lymphomas are aggressive malignancies. Epstein–Barr virus (EBV) infection in lymphoma cells is invariable. NK/T-cell lymphomas are divided into nasal, non-nasal, and disseminated subtypes. Nasal NK/T-cell lymphomas involve the nasal cavity and the upper aerodigestive tract. Non-nasal NK/T-cell lymphomas involve the skin, gastrointestinal tract, testis and other extranodal sites. Disseminated NK/T-cell lymphoma involves multiple organs, rarely presenting with a leukaemic phase. Lymphoma cells are positive for CD3ε (not surface CD3), CD56, cytotoxic molecules and EBV-encoded small RNA. There is a predilection for Asian and Central/South American populations. Genome-wide association studies have identified lymphoma susceptibility loci in Asian patients. Positron emission tomography computed tomography and plasma EBV DNA quantification are crucial evaluations at diagnosis and follow-up. Stage I/II patients typically receive non-athracycline regimens containing asparaginse, together with sequential/concurrent radiotherapy. Anthracycline-containing regimens are ineffective. Stage III/IV patients are treated with asparaginase-containing regimens, followed by allogeneic haematopoietic stem cell transplantation (HSCT) in suitable cases. Autologous HSCT does not improve outcome. In relapsed/refractory patients, novel approaches are needed, involving PD1/PD-L1 targeting, EBV-specific cytotoxic T-cells, and monoclonal antibodies. Small molecules including histone deacetylase inhibitors may be beneficial in selected patients. Future strategies may include targeting of signalling pathways and driver mutations.

The Pathologic and Genetic Characteristics of Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma is a neoplasm of NK cells or cytotoxic T cells presenting in extranodal sites, most often in the nasal cavity. The typical immunophenotypes are cCD3+, sCD3-, CD4-, CD5-, CD8-, CD16-, and CD56+ with the expression of cytotoxic molecules. Tumor subsets express NK cell receptors, CD95/CD95L, CD30, MYC, and PDL1. Virtually all the tumor cells harbor the EBV genome, which plays a key role in lymphomagenesis as an epigenetic driver. EBV-encoded oncoproteins modulate the host-cell epigenetic machinery, reprogramming the viral and host epigenomes using host epigenetic modifiers. NGS analysis revealed the mutational landscape of ENKTL, predominantly involving the JAK-STAT pathway, epigenetic modifications, the RNA helicase family, the RAS/MAP kinase pathway, and tumor suppressors, which indicate an important role of these pathways and this group of genes in the lymphomagenesis of ENKTL. Recently, three molecular subtypes were proposed, the tumor-suppressor/immune-modulator (TSIM), MGA-BRDT (MB), and HDAC9-EP300-ARID1A (HEA) subtypes, and they are well-correlated with the cell of origin, EBV pattern, genomic alterations, and clinical outcomes. A future investigation into the function and interaction of discovered genes would be very helpful for better understanding the molecular pathogenesis of ENKTL and establishing better treatment strategies.

Genetic manipulation of primary human natural killer cells to investigate the functional and oncogenic roles of PRDM1

Extra-nodal natural killer (NK)/T-cell lymphoma, nasal type (ENKTCL) is a highly aggressive lymphoma, in which the tumor suppressor gene PRDM1 is frequently lost or inactivated. We employed two different CRISPR/Cas9 approaches to generate PRDM1-/- primary NK cells to study the role of this gene in NK-cell homeostasis. PRDM1-/- NK cells showed a marked increase in cloning efficiency, higher proliferation rate and less apoptosis compared with their wild-type counterparts. Gene expression profiling demonstrated a marked enrichment in pathways associated with proliferation, cell cycle, MYC, MYB and TCR/NK signaling in PRDM1-/- NK cells, but pathways associated with normal cellular functions including cytotoxic functions were downregulated, suggesting that the loss of PRDM1 shifted NK cells toward proliferation and survival rather than the performance of their normal functions. We were also able to further modify a PRDM1-deleted clone to introduce heterozygous deletions of common tumor suppressor genes in ENKTCL such as TP53, DDX3X, and PTPN6. We established an in vitro model to elucidate the major pathways through which PRDM1 mediates its homeostatic control of NK cells. This approach can be applied to the study of other relevant genetic lesions and oncogenic collaborations in lymphoma pathogenesis.

The synergistic proapoptotic effect of PARP-1 and HDAC inhibition in cutaneous T-cell lymphoma is mediated via Blimp-1

The therapy of advanced mycosis fungoides (MF) presents a therapeutic challenge, and the search for new therapeutic targets is ongoing. Poly(ADP-ribose) polymerase 1 was shown to be upregulated in patients with advanced MF and could be druggable by a new class of chemotherapeutic agents, PARP-1 inhibitors, which are already in clinical trials for other malignancies; however, the role of PARP-1 inhibitors in MF has never been established. We examined the efficacy of talazoparib in the murine model of cutaneous T-cell lymphoma. The cytotoxic effect of talazoparib on Moloney MuLV-induced T-cell lymphoma (MBL2) cells was a result of G2/M cell cycle arrest via the upregulation of p53. The in vivo experiments confirmed the clinical impact of talazoparib on MF tumors. When talazoparib was combined with the histone deacetylase (HDAC) inhibitor, romidepsin, the cytotoxic effect was synergized via downregulation of the DNA-repair genes Fanconianemia complementation group A (FANCA), Fanconi anemia complementation group D2 (FANCD2), and DNA topoisomerase II binding protein 1(TOPBP1)and stimulation of apoptosis via Blimp-1 (PRDM1)/Bax axis. Romidepsin increased the expression of IRF8 and Bcl-6, leading to upregulation of Blimp1and Bax; whereas talazoparib upregulated Blimp-1 and Bax via upregulation of interferon regulatory factor 4 (IRF4), leading to cleavage of caspases 6 and 7. Thus, a combination of talazoparib with romidepsin demonstrated the synergistic antilymphoma effect and warranted further investigation in a clinical trial.

Mucosal ribosomal stress-induced PRDM1 promotes chemoresistance via stemness regulation

The majorities of colorectal cancer (CRC) cases are sporadic in origin and a large proportion of etiologies are associated with environmental stress responses. In response to external and internal stress, the ribosome stands sentinel and stress-driven ribosomal dysfunction triggers the cellular decision pathways via transcriptional reprogramming. In the present study, PR domain zinc finger protein (PRDM) 1, a master transcriptional regulator, was found to be closely associated with ribosomal actions in patients with CRC and the murine models. Stress-driven ribosomal dysfunction enhanced PRDM1 levels in intestinal cancer cells, which contributed to their survival and enhanced cancer cell stemness against cancer treatment. Mechanistically, PRDM1 facilitated clustering modulation of insulin-like growth factor (IGF) receptor-associated genes, which supported cancer cell growth and stemness-linked features. Ribosomal dysfunction-responsive PRDM1 facilitated signaling remodeling for the survival of tumor progenitors, providing compelling evidence for the progression of sporadic CRC.

PRDM1 decreases sensitivity of human NK cells to IL2-induced cell expansion by directly repressing CD25 (IL2RA)

IL2 receptor signaling is crucial for human NK cell activation and gain of effector functions. The molecular mechanisms involved in termination of IL2 activation are largely unknown in human NK cells. PR/SET domain 1 was previously reported to decrease cell growth and increase apoptosis in an IL2-dependent manner in malignant NK cell lines, suggesting the possibility of down-regulation of IL2 signaling pathway gene(s) through direct transcriptional repression. Using ChIP-Seq, we identified a PRDM1 binding site on the first intron of CD25 (IL2RA), which codes for the IL2 receptor subunit regulating sensitivity to IL2 signaling, in primary NK cells activated with engineered K562 cells or IL2. Ectopic expression of PRDM1 down-regulated CD25 expression at transcript and protein levels in two PRDM1 nonexpressing NK cell lines. shRNA-mediated knockdown of CD25 in two malignant NK cell lines led to progressive depletion of NK cells in low IL2 concentrations. By contrast, ectopic CD25 expression in primary human NK cells led to progressive increase in cell number in CD25-transduced cells in low IL2 concentrations. Altogether these results reveal a pivotal role of PRDM1 in inhibition of IL2-induced NK cell expansion through direct repression of CD25 in activated human NK cells. These observations provide additional support for the role of PRDM1 in attenuation of NK cell activation and growth, with implications on neoplastic transformation or NK cell function when it is deregulated.

Positive Regulatory Domain I-binding Factor 1 Mediates Peripheral Nerve Injury-induced Nociception in Mice by Repressing Kv4.3 Channel Expression

BACKGROUND

The transcriptional repressor positive regulatory domain I-binding factor 1 (PRDM1) is expressed in adult mouse dorsal root ganglion and regulates the formation and function of peripheral sensory neurons. The authors hypothesized that PRDM1 in the dorsal root ganglion may contribute to peripheral nerve injury-induced nociception regulation and that its mechanism may involve Kv4.3 channel transcriptional repression.

METHODS

Nociception was induced in C57BL/6 mice by applying chronic constriction injury, complete Freund's adjuvant, or capsaicin plantar injection. Nociceptive response was evaluated by mechanical allodynia, thermal hyperalgesia, cold hyperalgesia, or gait analysis. The role of PRDM1 was evaluated by injection of Prdm1 knockdown and overexpression adeno-associated viruses. The interaction of PRDM1 at the Kv4.3 (Kcnd3) promoter was evaluated by chromatin immunoprecipitation assay. Excitability of dorsal root ganglion neurons was evaluated by whole cell patch clamp recordings, and calcium signaling in spinal dorsal horn neurons was evaluated by in vivo two-photon imaging.

RESULTS

Peripheral nerve injury increased PRDM1 expression in the dorsal root ganglion, which reduced the activity of the Kv4.3 promoter and repressed Kv4.3 channel expression (injured vs. uninjured; all P < 0.001). Knockdown of PRDM1 rescued Kv4.3 expression, reduced the high excitability of injured dorsal root ganglion neurons, and alleviated peripheral nerve injury-induced nociception (short hairpin RNA vs. Scram; all P < 0.05). In contrast, PRDM1 overexpression in naive mouse dorsal root ganglion neurons diminished Kv4.3 channel expression and induced hyperalgesia (PRDM1 overexpression vs. control, mean ± SD; n = 13; all P < 0.0001) as evaluated by mechanical allodynia (0.6 ± 0.3 vs. 1.2 ± 0.2 g), thermal hyperalgesia (5.2 ± 1.3 vs. 9.8 ± 1.7 s), and cold hyperalgesia (3.4 ± 0.5 vs. 5.3 ± 0.6 s). Finally, PRDM1 downregulation in naive mice reduced the calcium signaling response of spinal dorsal horn neurons to thermal stimulation.

CONCLUSIONS

PRDM1 contributes to peripheral nerve injury-induced nociception by repressing Kv4.3 channel expression in injured dorsal root ganglion neurons.

EDITOR’S PERSPECTIVE

Sildenafil prevents HDACi-induced Epstein-Barr virus reactivation through the PKG pathway in NK/T cell lymphoma; potential implications for HDACi-mediated fatal complications

Romidepsin, a histone deacetylase (HDAC) inhibitor, has been approved for the treatment of relapsed and refractory peripheral T-cell lymphoma. However the use of romidepsin reportedly causes potent EBV (Epstein-Barr virus) reactivation leading to severe adverse events in patients with natural killer (NK)/T-cell lymphoma (NKTL). As inhibition of EBV lytic cycle reactivation may help prevent romidepsin-induced adverse events in NKTL, we herein set out to identify a safe and effective drug for inhibiting EBV reactivation and examine its mechanism of inhibition. EBV reactivation was evaluated by qRT-PCR of BZLF1 and BRLF1 mRNA expression, qPCR of EBV DNA, and immunoblotting of viral EA-D protein. High-throughput screening of FDA-approved drugs was performed to identify safe and effective molecules and test their effect on romidepsin-induced EBV reactivation in the EBV-positive NKTL cell lines, SNK6 and NK92MI. We found that phosphodiesterase 5 (PDE5) inhibitors, including sildenafil (Viagra; Pfizer), appeared to be nontoxic and effective inhibitors of romidepsin-induced EBV reactivation. Clinical relevance was investigated by qPCR of EBV in two primary effusion samples of NKTL patients. We also investigated the molecular consequences downstream of sildenafil-induced PDE5 inhibition in NKTL cells. A negative correlation was established between the cGMP/PKG pathway and EBV reactivation in NKTL cells. On a molecular level, PDE5 inhibition downregulates BZLF1 and BRLF1 through cGMP/PKG signaling-induced ZNF overexpression. Co-treatment with romidepsin and sildenafil (inhibiting HDAC and PDE5, respectively) showed a synergistic inhibitory effect on NKTL cells, highlighting PDE5 as an attractive target for future therapy in NKTL.

Emerging Roles of PRDM Factors in Stem Cells and Neuronal System: Cofactor Dependent Regulation of PRDM3/16 and FOG1/2 (Novel PRDM Factors)

PRDI-BF1 (positive regulatory domain I-binding factor 1) and RIZ1 (retinoblastoma protein-interacting zinc finger gene 1) (PR) homologous domain containing (PRDM) transcription factors are expressed in neuronal and stem cell systems, and they exert multiple functions in a spatiotemporal manner. Therefore, it is believed that PRDM factors cooperate with a number of protein partners to regulate a critical set of genes required for maintenance of stem cell self-renewal and differentiation through genetic and epigenetic mechanisms. In this review, we summarize recent findings about the expression of PRDM factors and function in stem cell and neuronal systems with a focus on cofactor-dependent regulation of PRDM3/16 and FOG1/2. We put special attention on summarizing the effects of the PRDM proteins interaction with chromatin modulators (NuRD complex and CtBPs) on the stem cell characteristic and neuronal differentiation. Although PRDM factors are known to possess intrinsic enzyme activity, our literature analysis suggests that cofactor-dependent regulation of PRDM3/16 and FOG1/2 is also one of the important mechanisms to orchestrate bidirectional target gene regulation. Therefore, determining stem cell and neuronal-specific cofactors will help better understanding of PRDM3/16 and FOG1/2-controlled stem cell maintenance and neuronal differentiation. Finally, we discuss the clinical aspect of these PRDM factors in different diseases including cancer. Overall, this review will help further sharpen our knowledge of the function of the PRDM3/16 and FOG1/2 with hopes to open new research fields related to these factors in stem cell biology and neuroscience.

TGF-β1-regulated miR-3691-3p targets E2F3 and PRDM1 to inhibit prostate cancer progression

Transforming growth factor-β1 (TGF-β1) acts as a tumor promoter in advanced prostate cancer (PCa). We speculated that microRNAs (miRNAs) that are inhibited by TGF-β1 might exert anti-tumor effects. To assess this, we identified several miRNAs downregulated by TGF-β1 in PCa cell lines and selected miR-3691-3p for detailed analysis as a candidate anti-oncogene miRNA. miR-3691-3p was expressed at significantly lower levels in human PCa tissue compared with paired benign prostatic hyperplasia tissue, and its expression level correlated inversely with aggressive clinical pathological features. Overexpression of miR-3691-3p in PCa cell lines inhibited proliferation, migration, and invasion, and promoted apoptosis. The miR-3691-3p target genes E2F transcription factor 3 (E2F3) and PR domain containing 1, with ZNF domain (PRDM1) were upregulated in miR-3691-3p-overexpressing PCa cells, and silencing of E2F3 or PRDM1 suppressed PCa cell proliferation, migration, and invasion. Treatment of mice bearing PCa xenografts with a miR-3691-3p agomir inhibited tumor growth and promoted tumor cell apoptosis. Consistent with the negative regulation of E2F3 and PRDM1 by miR-3691-3p, both proteins were overexpressed in clinical PCa specimens compared with noncancerous prostate tissue. Our results indicate that TGF-β1-regulated miR-3691-3p acts as an anti-oncogene in PCa by downregulating E2F3 and PRDM1. These results provide novel insights into the mechanisms by which TGF-β1 contributes to the progression of PCa.

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.

Loss of prdm1a accelerates melanoma onset and progression

Melanoma is an aggressive, deadly skin cancer derived from melanocytes, a neural crest cell derivative. Melanoma cells mirror the developmental program of neural crest cells in that they exhibit the same gene expression patterns and utilize similar cellular mechanisms, including increased cell proliferation, epithelial-mesenchymal transition, and migration. Here we studied the role of neural crest regulator PRDM1 in melanoma onset and progression. In development, Prdm1a functions to promote neural crest progenitor fate, and in melanoma, we found that PRDM1 has reduced copy number and is recurrently deleted in both zebrafish and humans. When examining expression of neural crest and melanocyte development genes, we show that sox10 progenitor expression is high in prdm1a-/- mutants, while more differentiated melanocyte markers are reduced, suggesting that normally Prdm1a is required for differentiation. Data mining of human melanoma datasets indicates that high PRDM1 expression in human melanoma is correlated with better patient survival and decreased PRDM1 expression is common in metastatic tumors. When one copy of prdm1a is lost in the zebrafish melanoma model Tg(mitfa:BRAFV600E );p53-/- ;prdm1a+/- , melanoma onset occurs more quickly, and the tumors that form have a larger area with increased expression of sox10. These data demonstrate a novel role for PRDM1 as a tumor suppressor in melanoma.

The landscape of new drugs in extranodal NK/T-cell lymphoma

To date, much progress has been made in early-stage extranodal NK/T-cell lymphoma (ENKTCL), and risk-adapted therapy with radiotherapy (RT) alone for the low-risk group and RT combined with asparaginase-based chemotherapy (CT) for the high-risk group yields favorable outcomes. However, optimal treatment strategies have not been defined yet for advanced-stage ENKTCL. Historically, ENKTCL responded poorly to conventional anthracycline-based chemotherapy probably because of inherent multidrug resistance (MDR). The fact that ENKTCL cells lack asparagine synthetase (ASNS) activity warranted the use of L-asparaginase or pegaspargase as frontline chemotherapies. Even though, due to high mortality of the disease, approximately 50% patients failing the frontline therapy arrived at dismal clinical outcomes with a median progression-free survival (PFS) less than 8 months. As distinctive molecular and biological subgroups are increasingly discovered within the disease entity of ENKTCL, novel targeted therapies and immunotherapy are of the urgent need for those heterogeneous subgroups. In this review, we sought to summarize the preclinical and clinical results of 6 categories of promising targeted therapy and immunotherapy for the treatment of ENKTCL, including monoclonal antibodies, immune checkpoint inhibitors, small-molecular inhibitors, epigenetic therapy, immunomodulatory drugs, and adoptive T-cell therapy, and these might change the landscape of treatment for ENKTCL in the near future.

Multifaceted Role of PRDM Proteins in Human Cancer

The PR/SET domain family (PRDM) comprise a family of genes whose protein products share a conserved N-terminal PR [PRDI-BF1 (positive regulatory domain I-binding factor 1) and RIZ1 (retinoblastoma protein-interacting zinc finger gene 1)] homologous domain structurally and functionally similar to the catalytic SET [Su(var)3-9, enhancer-of-zeste and trithorax] domain of histone methyltransferases (HMTs). These genes are involved in epigenetic regulation of gene expression through their intrinsic HMTase activity or via interactions with other chromatin modifying enzymes. In this way they control a broad spectrum of biological processes, including proliferation and differentiation control, cell cycle progression, and maintenance of immune cell homeostasis. In cancer, tumor-specific dysfunctions of PRDM genes alter their expression by genetic and/or epigenetic modifications. A common characteristic of most PRDM genes is to encode for two main molecular variants with or without the PR domain. They are generated by either alternative splicing or alternative use of different promoters and play opposite roles, particularly in cancer where their imbalance can be often observed. In this scenario, PRDM proteins are involved in cancer onset, invasion, and metastasis and their altered expression is related to poor prognosis and clinical outcome. These functions strongly suggest their potential use in cancer management as diagnostic or prognostic tools and as new targets of therapeutic intervention.

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.

Epstein - Barr virus positive T and NK-cell lymphoproliferations: Morphological features and differential diagnosis

The spectrum of Epstein-Barr virus (EBV)-positive T and NK-cell lymphoproliferations is broad and ranges from reactive self-limited disorders to neoplastic processes with a fulminant clinical course. EBV plays an important role promoting lymphomagenesis, although the precise mechanisms remain elusive. EBV-positive lymphoproliferative disorders (LPD) are more common in East Asia (China, Japan, Korea and Taiwan), and Latin America suggesting a strong genetic predisposition. The revised 2016 World Health Organization (WHO) lymphoma classification recognizes the following malignant NK- and T-cell lymphomas; extranodal NK/T-cell lymphoma, nasal type (ENKTCL), aggressive NK-cell leukemia (ANKL), and the provisional entity within the group of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) "primary EBV-positive nodal T or NK cell lymphoma". Disorders presenting mainly in children and young adults include chronic active EBV infection (CAEBV) - systemic and cutaneous forms - which are not considered malignant disorders but were included in the WHO classification for the first time because of the differential diagnosis with other T- or NK-cell lymphomas. CAEBV, cutaneous form, includes hydroa vacciniforme-like LPD (HV-LPD) and severe mosquito bite allergy (SMBA). Finally, systemic EBV-positive T-cell lymphoma of childhood was recognized as lymphoma because of its fulminant clinical course. Given the shared pathogenesis of these disorders, overlapping features are common demanding a close clinical, morphological and molecular correlation for an accurate diagnosis. This review summarizes the clinical, histopathological and molecular features of EBV-associated T and NK-cell LPD, highlighting the main features that might aid in the differential diagnosis.

Rare, functional, somatic variants in gene families linked to cancer genes: GPCR signaling as a paradigm

Oncodriver genes are usually identified when mutations recur in multiple tumours. Different drivers often converge in the activation or repression of key cancer-relevant pathways. However, as many pathways contain multiple members of the same gene family, individual mutations might be overlooked, as each family member would necessarily have a lower mutation frequency and thus not identified as significant in any one-gene-at-a-time analysis. Here, we looked for mutated, functional sequence positions in gene families that were mutually exclusive (in patients) with another gene in the same pathway, which identified both known and new candidate oncodrivers. For instance, many inactivating mutations in multiple G-protein (particularly Gi/o) coupled receptors, are mutually exclusive with Gαs oncogenic activating mutations, both of which ultimately enhance cAMP signalling. By integrating transcriptomics and interaction data, we show that the Gs pathway is upregulated in multiple cancer types, even those lacking known GNAS activating mutations. This suggests that cancer cells may develop alternative strategies to activate adenylate cyclase signalling in multiple cancer types. Our study provides a mechanistic interpretation for several rare somatic mutations in multi-gene oncodrivers, and offers possible explanations for known and potential off-label cancer treatments, suggesting new therapeutic opportunities.

PRDM1 rs1010273 polymorphism is associated with overall survival of patients with hepatitis B virus-related hepatocellular carcinoma

T cell exhaustion is involved in the pathogenesis of chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). B lymphocyte-induced maturation protein 1 (BLIMP-1), encoded by the PRDM1 gene, plays a crucial role in T cell exhaustion. This study investigated PRDM1 rs1010273 and rs2185379 polymorphisms in 403 patients with chronic HBV infection (171 chronic hepatitis, 119 liver cirrhosis and 113 HCC), 70 spontaneous HBV infection resolvers and 196 healthy controls. The results showed that the rs1010273 and rs2185379 polymorphisms had no significant differences between patients with chronic HBV infection and healthy controls or between patients with different clinical diseases. However, PRDM1 rs1010273 polymorphism was shown to be significantly associated with the overall survival of patients with HBV-related HCC. The 1-, 3-, and 5-year survival rates of HCC patients were 70.5%, 34.6%, and 11.5%, respectively, in genotype GG carriers and 91.4%, 51.4% and 31.4%, respectively, in genotypes AA + GA carriers (p =  0.008). Multivariate analysis showed that PRDM1 rs1010273 polymorphism was an independent factor associated with the overall survival of patients with HCC (odds ratio, 0.529; 95% confidence interval, 0.126-0.862; p =  0.002). These results provide novel evidence for a role of PRDM1 rs1010273 in the pathogenesis of HBV-related HCC. Additional studies are needed to replicate and extend the findings of this study and to elucidate the underlying mechanisms.

Activation of the NF-κB Pathway and Heterozygous Deletion of TNFAIP3 (A20) Confer Superior Survival in Extranodal Natural Killer/T-Cell Lymphoma, Nasal Type

OBJECTIVES

To investigate the role of TNFAIP3 deletions and NF-κB activation in extranodal natural killer/T-cell lymphoma (ENKTCL), nasal type.

METHODS

In total, 138 patients with ENKTCL were included. Activation of NF-κB pathway and expression of TNFAIP3 (A20) were examined by immunohistochemistry. TNFAIP3 was analyzed for deletions using FICTION (fluorescence immunophenotyping and interphase cytogenetics as a tool for investigating neoplasms), for mutations using Sanger sequencing, and for promoter methylation using methylation-specific sequencing.

RESULTS

NF-κB pathway activation was observed in 31.2% of cases (43/138), TNFAIP3 expression was negative in 15.2% of cases (21/138), and heterozygous TNFAIP3 deletion was observed in 35% of cases (35/100). TNFAIP3 exons 2 to 9 mutations and promoter methylation were not observed. Kaplan-Meier analysis showed patients with NF-κB pathway activation or TNFAIP3 heterozygous deletion to have a longer overall survival.

CONCLUSIONS

Our study demonstrated that NF-κB activation and TNFAIP3 heterozygous deletion confer superior survival in patients with ENKTCL.

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.

NK/T-cell lymphomas

NK/T-cell lymphomas are extranodal EBV-related malignancies, mostly of NK-cell and occasionally of T-cell lineage. They are divided into nasal, non-nasal, and disseminated subtypes. Nasal NK/T-cell lymphomas involve the nose, nasopharynx and the upper aerodigestive tract. Non-nasal NK/T-cell lymphomas involve the skin, gastrointestinal tract, testis and other sites. Disseminated NK/T-cell lymphoma involves multiple organs, and may present with a leukemic phase. Initial evaluation requires positron emission tomography computed tomography (PET/CT) and quantification of circulating EBV DNA. Radiotherapy alone is inadequate with frequent relapses. Anthracycline-containing regimens are ineffective. Regimens incorporating asparaginase are currently the standard. For stage I/II disease, combined chemotherapy and radiotherapy is recommended. For stage III/IV disease, asparaginase-containing regimens are needed. Autologous hematopoietic stem cell transplantation (HSCT) is of limited efficacy, whereas allogeneic HSCT may be useful in patients with stage III/IV and relapsed diseases. Immunotherapy with antibodies against CD30, programmed cell death protein 1 and CD38 is promising.

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.

Molecular pathogenic pathways in extranodal NK/T cell lymphoma

Extranodal NK/T cell lymphoma, nasal type (ENKTL) is an aggressive malignancy with a dismal prognosis. Although L-asparaginase-based chemotherapy has resulted in improved response rates, relapse occurs in up to 50% of patients with disseminated disease. There is hence an urgent need for effective targeted therapy, especially for patients with relapsed or refractory disease. Novel insights gleaned from high-throughput molecular and genomic profiling studies in recent years have contributed significantly to the understanding of the molecular biology of ENKTL, which exemplifies many of the hallmarks of cancer. Deregulated pro-proliferative signaling pathways, such as the Janus-associated kinase/signal transducer and activator of transcription (JAK/STAT), platelet-derived growth factor (PDGF), Aurora kinase, MYC, and NF-κB, have been identified as potential therapeutic targets. The discovery of the non-canonical function of EZH2 as a pro-proliferative transcriptional co-activator has shed further light on the pathogenesis of ENKTL. Loss of key tumor suppressor genes located on chromosome 6q21 also plays an important role. The best-studied examples include PR domain zinc finger protein 1(PRDM1), protein tyrosine phosphatase kappa (PTPRK), and FOXO3. Promoter hypermethylation has been shown to result in the downregulation of other tumor suppressor genes in ENKTL, which may be potentially targeted through hypomethylating agents. Deregulation of apoptosis through p53 mutations and upregulation of the anti-apoptotic protein, survivin, may provide a further growth advantage to this tumor. A deranged DNA damage response as a result of the aberration of ataxia telangiectasia-related (ATR) kinases can lead to significant genomic instability and may contribute to chemoresistance of ENKTL. Recently, immune evasion has emerged as a critical pathway for survival in ENKTL and may be a consequence of HLA dysregulation or STAT3-driven upregulation of programmed cell death ligand 1 (PD-L1). Immunotherapy via inhibition of programmed cell death 1 (PD-1)/PD-L1 checkpoint signaling holds great promise as a novel therapeutic option. In this review, we present an overview of the key molecular and pathogenic pathways in ENKTL, organized using the framework of the "hallmarks of cancer" as described by Hanahan and Weinberg, with a focus on those with the greatest translational potential.

[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。

Gene Regulatory Programs Conferring Phenotypic Identities to Human NK Cells

Natural killer (NK) cells develop from common progenitors but diverge into distinct subsets, which differ in cytokine production, cytotoxicity, homing, and memory traits. Given their promise in adoptive cell therapies for cancer, a deeper understanding of regulatory modules controlling clinically beneficial NK phenotypes is of high priority. We report integrated "-omics" analysis of human NK subsets, which revealed super-enhancers associated with gene cohorts that may coordinate NK functions and localization. A transcription factor-based regulatory scheme also emerged, which is evolutionarily conserved and shared by innate and adaptive lymphocytes. For both NK and T lineages, a TCF1-LEF1-MYC axis dominated the regulatory landscape of long-lived, proliferative subsets that traffic to lymph nodes. In contrast, effector populations circulating between blood and peripheral tissues shared a PRDM1-dominant landscape. This resource defines transcriptional modules, regulated by feedback loops, which may be leveraged to enhance phenotypes for NK cell-based therapies.

Molecular and Genomic Landscape of Peripheral T-Cell Lymphoma

Peripheral T-cell lymphoma (PTCL) is an uncommon group of lymphoma covering a diverse spectrum of entities. Little was known regarding the molecular and genomic landscapes of these diseases until recently but the knowledge is still quite spotty with many rarer types of PTCL remain largely unexplored. In this chapter, the recent findings from gene expression profiling (GEP) studies, including profiling data on microRNA, where available, will be presented with emphasis on the implication on molecular diagnosis, prognostication, and the identification of new entities (PTCL-GATA3 and PTCL-TBX21) in the PTCL-NOS group. Recent studies using next-generation sequencing have unraveled the mutational landscape in a number of PTCL entities leading to a marked improvement in the understanding of their pathogenesis and biology. While many mutations are shared among PTCL entities, the frequency varies and certain mutations are quite unique to a specific entity. For example, TET2 is often mutated but this is particularly frequent (70-80%) in angioimmunoblastic T-cell lymphoma (AITL) and IDH2 R172 mutations appear to be unique for AITL. In general, chromatin modifiers and molecular components in the CD28/T-cell receptor signaling pathways are frequently mutated. The major findings will be summarized in this chapter correlating with GEP data and clinical features where appropriate. The mutational landscape of cutaneous T-cell lymphoma, specifically on mycosis fungoides and Sezary syndrome, will also be discussed.

Extranodal NK/T-cell lymphoma: Updates in biology and management strategies

Extranodal NK/T-cell lymphoma, nasal type (ENKL), is a rare lymphoma subtype of peripheral T/NK-cell lymphoma that is very common in East Asia and Latin America. Two-thirds of patients have localized disease in the nasal cavity or adjacent sites. Large retrospective studies have revealed the clinicopathologic features of ENKL patients, identified risk factors for short survival time, and developed prognostic models. Next-generation sequencing studies have provided a comprehensive list of recurrent mutations in ENKL. Since the early 2000s, disease-specific therapeutic approaches have been developed, and the standard of care for ENKL has markedly changed. Non-anthracycline-containing chemotherapy with or without radiotherapy is the current standard approach for ENKL treatment. Emerging therapies, including the use of immune checkpoint inhibitors, are being investigated.

Recurrent Cytogenetic Abnormalities in Intravascular Large B-Cell Lymphoma

OBJECTIVES

Data characterizing the cytogenetic landscape of intravascular large B-cell lymphoma (ILBCL) are limited. Here, we developed a comprehensive karyotypic data set to identify recurrent cytogenetic abnormalities in ILBCL.

METHODS

Cases of ILBCL with complete cytogenetic analysis were identified from an institutional database and the literature. The combined data were systematically reviewed for the presence of recurrent abnormalities.

RESULTS

Four new cases were identified and combined with 25 karyotypes previously published in the literature. Karyotypes were uniformly complex with a median of 10 aberrations. In total, 72.4% had abnormalities involving chromosome 1, with 31.0% involving rearrangements of 1p13 or 1q21; 58.6% had abnormalities involving chromosome 6, which in almost all cases involved 6q; 34.5% had abnormalities involving chromosome 14, with 27.6% involving rearrangements of 14q32; and 55.2% had abnormalities of chromosome 18, with 37.9% harboring trisomy 18.

CONCLUSIONS

Recurrent cytogenetic abnormalities involving chromosomes 1, 6q, and 18 are present in greater than 50% of ILBCL.

PRDM1 silences stem cell-related genes and inhibits proliferation of human colon tumor organoids

PRDM1 is a tumor suppressor that plays an important role in B and T cell lymphomas. Our previous studies demonstrated that PRDM1β is a p53-response gene in human colorectal cancer cells. However, the function of PRDM1β in colorectal cancer cells and colon tumor organoids is not clear. Here we show that PRDM1β is a p53-response gene in human colon organoids and that low PRDM1 expression predicts poor survival in colon cancer patients. We engineered PRDM1 knockouts and overexpression clones in RKO cells and characterized the PRDM1-dependent transcript landscapes, revealing that both the α and β transcript isoforms repress MYC-response genes and stem cell-related genes. Finally, we show that forced expression of PRDM1 in human colon cancer organoids prevents the formation and growth of colon tumor organoids in vitro. These results suggest that p53 may exert tumor-suppressive effects in part through a PRDM1-dependent silencing of stem cell genes, depleting the size of the normal intestinal stem cell compartment in response to DNA damage.

Genetic Landscape and Classification of Peripheral T Cell Lymphomas

PURPOSE OF REVIEW

Peripheral T cell lymphomas (PTCLs) are markedly heterogeneous at the clinical, pathological, and molecular levels. This review will discuss genetic findings in PTCL with special emphasis on how they impact lymphoma classification.

RECENT FINDINGS

Sequencing studies have identified recurrent genetic alterations in nearly every PTCL subtype. In anaplastic large cell lymphoma, these studies have revealed novel chromosomal rearrangements and mutations that have prognostic significance and may suggest new therapeutic approaches. Angioimmunoblastic T cell lymphoma has been found to have mutations overlapping some cases of PTCL, not otherwise specified with a T follicular helper cell phenotype. Across various subtypes, recurrent mutations and structural alterations affecting genes involved in epigenetic regulation, T cell receptor signaling, and immune response may represent targets for precision therapy approaches. New genetic findings are refining the classification of PTCLs and are beginning to be used clinically for diagnosis, risk stratification, and individualized therapy.

NKL homeobox gene MSX1 acts like a tumor suppressor in NK-cell leukemia

NKL homeobox gene MSX1 is physiologically expressed in lymphoid progenitors and subsequently downregulated in developing T- and B-cells. In contrast, elevated expression levels of MSX1 persist in mature natural killer (NK)-cells, indicating a functional role in this compartment. While T-cell acute lymphoblastic leukemia (T-ALL) subsets exhibit aberrant overexpression of MSX1, we show here that in malignant NK-cells the level of MSX1 transcripts is aberrantly downregulated. Chromosomal deletions at 4p16 hosting the MSX1 locus have been described in NK-cell leukemia patients. However, NK-cell lines analyzed here showed normal MSX1 gene configurations, indicating that this aberration might be uncommon. To identify alternative MSX1 regulatory mechanisms we compared expression profiling data of primary normal NK-cells and malignant NK-cell lines. This procedure revealed several deregulated genes including overexpressed IRF4, MIR155HG and MIR17HG and downregulated AUTS2, EP300, GATA3 and HHEX. As shown recently, chromatin-modulator AUTS2 is overexpressed in T-ALL subsets where it mediates aberrant transcriptional activation of MSX1. Here, our data demonstrate that in malignant NK-cell lines AUTS2 performed MSX1 activation as well, but in accordance with downregulated MSX1 transcription therein we detected reduced AUTS2 expression, a small genomic deletion at 7q11 removing exons 3 and 4, and truncating mutations in exon 1. Moreover, genomic profiling and chromosomal analyses of NK-cell lines demonstrated amplification of IRF4 at 6p25 and deletion of PRDM1 at 6q21, highlighting their potential oncogenic impact. Functional analyses performed via knockdown or forced expression of these genes revealed regulatory network disturbances effecting downregulation of MSX1 which may underlie malignant development in NK-cells.

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.

The diagnosis and management of NK/T-cell lymphomas

Extranodal natural killer (NK)/T-cell lymphoma is an aggressive malignancy of putative NK-cell origin, with a minority deriving from the T-cell lineage. Pathologically, the malignancy occurs in two forms, extranodal NK/T-cell lymphoma, nasal type; and aggressive NK-cell leukaemia. Lymphoma occur most commonly (80%) in the nose and upper aerodigestive tract, less commonly (20%) in non-nasal areas (skin, gastrointestinal tract, testis, salivary gland), and rarely as disseminated disease with a leukemic phase. Genetic analysis showed mutations of genes involved in the JAK/STAT pathway, RNA assembly, epigenetic regulation, and tumor suppression. In initial clinical evaluation, positron emission tomography computed tomography, and quantification of plasma EBV DNA are mandatory as they are useful for response monitoring and prognostication. In stage I/II diseases, combined chemotherapy and radiotherapy (sequentially or concurrently) is the best approach. Conventional anthracycline-containing regimens are ineffective and should be replaced by non-anthracycline-containing regimens, preferably including L-asparaginase. Radiotherapy alone is associated with high systemic relapse rates and should be avoided. In stage III/IV diseases, non-anthracycline-regimens-containing L-asparaginase are the standard. In relapsed/refractory cases, blockade of the programmed death protein 1 has recently shown promising results with high response rates. In the era of effective non-anthracycline-containing regimens, autologous haematopoietic stem cell transplantation (HSCT) has not been shown to be beneficial. However, allogeneic HSCT may be considered for high-risk or advanced-stage patients in remission or relapsed/refractory patients responding to salvage therapy. Prognostic models taking into account presentation, interim, and end-of-treatment parameters are useful in triaging patients to different treatment strategies.

Downregulation of PRDM1 promotes cellular invasion and lung cancer metastasis

The zinc-finger transcription factor PRDM1 (PR domain containing 1) plays key roles in the development of malignant lymphoma, leukaemia and some non-haematopoietic cancers, including breast cancer, colorectal cancer and glioma. However, little is known regarding the function of PRDM1 in the progression of lung cancer. Here, we found that PRDM1 is expressed in normal human lung epithelium but is downregulated in lung cancer cells. Decreased expression of PRDM1 correlates with poor prognosis in lung cancer. Depletion of PRDM1 in lung cancer cells promotes cellular invasion and anoikis resistance in vitro and lung metastasis in vivo. PRDM1 is silenced by an ectopically expressed lymphocyte-specific transcription factor Aiolos. The transcription of these two genes is negatively correlated in 206 lung epithelial cell lines. Our results indicate that PRDM1 functions as a tumour suppressor in lung cancer.

Cutaneous EBV-related lymphoproliferative disorders

This article will focus on the cutaneous lymphoproliferative disorders associated with EBV, with an emphasis on the upcoming changes in the revised 4th Edition of the WHO classification of tumors of the hematopoietic system, many of which deal with cutaneous disorders derived from NK-cells or T-cells. Extranodal NK/T-cell lymphoma usually presents in the upper aerodigestive tract, but can involve the skin secondarily. EBV-associated T- and NK-cell lymphoproliferative disorders (LPD) in the pediatric age group include the systemic diseases, chronic active EBV infection (CAEBV) and systemic EBV+ T-cell lymphoma of childhood. Hydroa vacciniforme (HV)-like LPD is a primarily cutaneous form of CAEBV and encompasses the lesions previously referred to as HV and HV-like lymphoma (HVLL). All the T/NK-cell-EBV-associated diseases occur with higher frequency in Asians, and indigenous populations from Central and South America and Mexico. Among the B-cell EBV-associated LPD two major changes have been introduced in the WHO. The previously designated EBV-positive diffuse large B-cell lymphoma (EBV-DLBCL) of the elderly, has been changed to EBV-DLBCL with 'not otherwise specified' as a modifier (NOS). A new addition to the WHO system is the more recently identified EBV+ mucocutaneous ulcer, which involves skin and mucosal-associated sites.

Varicella-Zoster Virus Downregulates Programmed Death Ligand 1 and Major Histocompatibility Complex Class I in Human Brain Vascular Adventitial Fibroblasts, Perineurial Cells, and Lung Fibroblasts

Varicella-zoster virus (VZV) vasculopathy produces stroke, giant cell arteritis, and granulomatous aortitis, and it develops after virus reactivates from ganglia and spreads transaxonally to arterial adventitia, resulting in persistent inflammation and pathological vascular remodeling. The mechanism(s) by which inflammatory cells persist in VZV-infected arteries is unknown; however, virus-induced dysregulation of programmed death ligand 1 (PD-L1) may play a role. Specifically, PD-L1 can be expressed on virtually all nucleated cells and suppresses the immune system by interacting with the programmed cell death protein receptor 1, found exclusively on immune cells; thus, downregulation of PD-L1 may promote inflammation, as seen in some autoimmune diseases. Both flow cytometry and immunofluorescence analyses to test whether VZV infection of adventitial cells downregulates PD-L1 showed decreased PD-L1 expression in VZV-infected compared to mock-infected human brain vascular adventitial fibroblasts (HBVAFs), perineural cells (HPNCs), and fetal lung fibroblasts (HFLs) at 72 h postinfection. Quantitative RT-PCR analyses showed no change in PD-L1 transcript levels between mock- and VZV-infected cells, indicating a posttranscriptional mechanism for VZV-mediated downregulation of PD-L1. Flow cytometry analyses showed decreased major histocompatibility complex class I (MHC-I) expression in VZV-infected cells and adjacent uninfected cells compared to mock-infected cells. These data suggest that reduced PD-L1 expression in VZV-infected adventitial cells contribute to persistent vascular inflammation observed in virus-infected arteries from patients with VZV vasculopathy, while downregulation of MHC-I prevents viral clearance.

IMPORTANCE

Here, we provide the first demonstration that VZV downregulates PD-L1 expression in infected HBVAFs, HPNCs, and HFLs, which, together with the noted VZV-mediated downregulation of MHC-I, might foster persistent inflammation in vessels, leading to pathological vascular remodeling during VZV vasculopathy and persistent inflammation in infected lungs to promote subsequent infection of T cells and hematogenous virus spread. Identification of a potential mechanism by which persistent inflammation in the absence of effective viral clearance occurs in VZV vasculopathy and VZV infection of the lung is a step toward targeted therapy of VZV-induced disease.

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.

Molecular Pathogenesis of Peripheral T Cell Lymphoma

Understanding the molecular pathogenesis of peripheral T cell lymphomas (PTCLs) has lagged behind that of B cell lymphomas due to disease rarity. However, novel approaches are gradually clarifying these mechanisms, and gene profiling has identified specific signaling pathways governing PTCL cell survival and growth. For example, genetic alterations have been discovered, including signal transducer and activator of transcription (STAT)3 and STAT5b mutations in several PTCLs, disease-specific ras homolog family member A (RHOA) mutations in angioimmunoblastic T cell lymphoma (AITL), and recurrent translocations at the dual specificity phosphatase 22 (DUSP22) locus in anaplastic lymphoma receptor tyrosine kinase (ALK)-negative anaplastic large cell lymphomas (ALCLs). Intriguingly, some PTCL-relevant mutations are seen in apparently normal blood cells as well as tumor cells, while others are confined to tumor cells. These data have dramatically changed our understanding of PTCL origins: once considered to originate from mature T lymphocytes, some PTCLs are now believed to emerge from immature hematopoietic progenitor cells.

PRDM1 overexpression induce G0/G1 arrest in DF-1 cell line

PRDM1 (PR domain containing 1) is a transcriptional repressor that affects the expression of numerous genes involved in cell proliferation, differentiation and metabolism. However, the molecular mechanisms underlying PRDM1-regulated gene expression in the DF-1 cell line remain to be elucidated. In this study, we explored the role of PRDM1 in cell proliferation and cell cycle by forced expression of PRDM1 in DF-1 cells. Our results showed an absence of endogenous PRDM1 in this cell line, while exogenous PRDM1 was specifically localized to the nucleus. Ectopic expression of PRDM1 inhibited DF-1 cell proliferation and altered clonal morphology. Furthermore, PRDM1 overexpression caused an increase in the G0/G1 phase population. The levels of p53 mRNA and the p53-regulated p21(WAF1) and MDM2 genes were significantly increased in DF-1 cells transfected with the PRDM1 expression vector. Examination of the Rb pathway further revealed that Rb, E2F-1 and p15(INK4b) alternate reading frame (ARF) mRNA were also significantly increased after transient transfection. Interestingly, the mRNA expression levels of multiple chicken cyclin genes were also increased. These results show that PRDM1 overexpression induced G0/G1 arrest in DF-1 cells through multiple parallel mechanisms, including the p53 and Rb pathways.

Diagnosis and management of extranodal NK/T cell lymphoma nasal type

INTRODUCTION

Extranodal NK/T-cell lymphoma nasal type is a distinct clinicopathologic entity. The most common initial site of presentation is the nasopharyngeal area, but non-nasals sites including the skin and the gastrointestinal tract may be affected.

AREAS COVERED

The diagnosis and management of NK/T-cell lymphoma is discussed, based on a literature search on PubMed. NK/T-cell lymphoma are typically positive for CD3 (cytoplasmic), CD56, cytotoxic markers (granzyme B, TIA1) and Epstein Barr virus (EBV). Plasma EBV DNA is an accurate surrogate biomarker for lymphoma load. For stage I/II nasal lymphoma, a combination of chemotherapy and radiotherapy yields the best results. Concomitant chemoradiotherapy and sequential chemotherapy and radiotherapy give similar response rates and survivals. For stage III/IV nasal lymphoma and non-nasal lymphomas, chemotherapy is the mainstay of treatment. Conventional anthracycline-based regimens are ineffective. Recommended chemotherapy protocols are based on the use of L-asparaginase combined with other effective drugs. Durable remission can be expected in at least 60% of patients irrespective of stage. Prognostically models based on clinicopathologic parameters and EBV DNA load are useful in stratification of patients for therapy. Expert commentary: Current treatment leads to long-term survival in a significant proportion of patients. For relapsed patients, novel strategies are needed.