Alterations in ATR in nasal NK/T-cell lymphoma and chronic active Epstein-Barr virus infection

Extranodal NK-/T-cell lymphoma, nasal type: what advances have been made in the last decade?

Extranodal NK-/T-cell lymphoma (ENKTCL) is a rare and highly aggressive malignancy with significant racial and geographic variations worldwide. In addition to the formerly "nasal-type" initial description, these lymphomas are predominantly extranodal in origin and typically cause vascular damage and tissue destruction, and although not fully understood, Epstein-Barr virus (EBV) has an important role in its pathogenesis. Initial assessment must include a hematopathology review of representative and viable tumor areas without necrosis for adequate immunohistochemistry studies, including EBV-encoded small RNA (EBER) in situ hybridization (ISH). Positron emission tomography with 18-fluorodeoxyglucose (¹⁸F-FDG-PET/CT) for accurate staging is essential, and most patients will have localized disease (IE/IIE) at diagnosis. Apart from other T-cell malignancies, the best treatment even for localized cases is combined modality therapy (chemotherapy plus radiotherapy) with non-anthracycline-based regimens. For advanced-stage disease, l-asparaginase-containing regimens have shown improved survival, but relapsed and refractory cases have very poor outcomes. Nowadays, even with a better understanding of pathogenic pathways, up-front therapy is completely based on chemotherapy and radiotherapy, and treatment-related mortality is not low. Future strategies targeting signaling pathways and immunotherapy are evolving, but we need to better identify those patients with dismal outcomes in a pre-emptive way. Given the rarity of the disease, international collaborations are urgently needed, and clinical trials are the way to change the future.

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.

Resveratrol activates DNA damage response through inhibition of polo-like kinase 1 (PLK1) in natural killer/T cell lymphoma

Background

Extranodal natural killer/T cell lymphoma (NKTCL) is a highly aggressive non-Hodgkin lymphoma with a poor prognosis. Resveratrol (REV), a natural nontoxic pleiotropic agent, has antitumor effects, yet not being studied in NKTCL.

Methods

We performed immunohistochemical (IHC) staining with NKTCL tumor tissues. Apoptosis and cell cycle of NKTCL cell line NK-92 were detected by using flow cytometry. Then we detected the cellular expression level of polo-like kinase 1 (PLK1) and key molecules in DNA damage response (DDR) pathway by using RNA sequencing (RNA-seq) technology, real-time PCR, and Western blot.

Results

In this study, we found distinguishingly expressed phosphorylated ataxia telangiectasia mutated (ATM) in human NKTCL tumor tissues compared to normal lymph nodes samples. But low levels of phosphorylated checkpoint kinase 2 (Chk2) and phosphorylated p53 were shown, suggesting that DDR pathway is blocked midway in NKTCL. REV inhibited the proliferation of NK-92 cells in a time- and dose-dependent manner, arrested cell cycle at G1 phase, and induced mitochondrial apoptosis. PLK1 was inhibited in both mRNA and protein levels by REV in NK-92 cells. At the same time, phosphorylation levels of Chk2 and p53 were upregulated.

Conclusions

DDR pathway plays an important role in the pathogenesis of NKTCL. REV shows anti-NKTCL activity. The inhibition of PLK1 and the activation of DDR are vital for REV induced tumor cell apoptosis.

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.

Transcriptomic Abnormalities in Epstein Barr Virus Associated T/NK Lymphoproliferative Disorders

Epstein Barr virus positive T/NK lymphoproliferative disorders (EBV-TNKLPD) comprise a spectrum of neoplasms ranging from cutaneous lymphoid proliferations to aggressive lymphomas. The spectrum includes extranodal NK/T-cell lymphoma (ENKTL), aggressive NK-cell leukemia, and a group of EBV-TNKLPDs affecting children which are poorly characterized in terms of their molecular biology. Gene and miRNA expression profiling has elucidated RNA abnormalities which impact on disease biology, classification, and treatment of EBV-TNKLPD. Pathways promoting proliferation, such as Janus associated kinase/ Signal Transducer and Activator of Transcription (JAK/STAT) and nuclear factor kB, are upregulated in ENKTL while upregulation of survivin and deregulation of p53 inhibit apoptosis in both ENKTL and chronic active EBV infection (CAEBV). Importantly, immune evasion via the programmed cell death-1 and its ligand, PD-1/PD-L1 checkpoint pathway, has been demonstrated to play an important role in ENKTL. Other pathogenic mechanisms involve EBV genes, microRNA deregulation, and a variety of other oncogenic signaling pathways. The identification of EBV-positive Peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) as a tumor with a distinct molecular signature and clinical characteristics highlights the important contribution of the knowledge derived from gene and miRNA expression profiling in disease classification. Novel therapeutic targets identified through the study of RNA abnormalities provide hope for patients with EBV-TNKLPD, which often has a poor prognosis. Immune checkpoint inhibition and JAK inhibition in particular have shown promise and are being evaluated in clinical trials. In this review, we provide an overview of the key transcriptomic aberrancies in EBV-TNKLPD and discuss their translational potential.

Allogeneic hematopoietic stem cell transplantation for Epstein-Barr virus-associated T/natural killer-cell lymphoproliferative disease in Japan

Epstein-Barr virus (EBV)-associated T/NK-cell lymphoproliferative disease (LPD) has been linked to several different disorders. Its prognosis is generally poor and a treatment strategy has yet to be established. There are reports, however, that hematopoietic stem cell transplantation (HSCT) can cure this disease. To clarify the current situation regarding allogeneic hematopoietic stem cell transplantation (allo-HSCT) for EBV-associated T/NK-LPD, a nationwide survey was performed in Japan. Data for 74 patients were collected. There were 42 cases of chronic active EBV infection (CAEBV), 10 cases of EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), and 22 cases of EBV-associated lymphoma/leukemia (EBV-lymphoma/leukemia). Of those with CAEBV, 54% had the EBV-infected T-cell type and 59% with EBV-lymphoma/leukemia had the EBV-infected NK-cell type. Most patients with EBV-HLH and EBV-lymphoma/leukemia received allo-HSCT within 1 year after onset compared to only 14% of patients with CAEBV. The event-free survival (EFS) rate following allo-HSCT was 0.561 +/- 0.086 for CAEBV, 0.614 +/- 0.186 for EBV-HLH, and 0.309 +/- 0.107 for EBV-lymphoma/leukemia. The EFS of allo-HSCT with conventional conditioning was 0.488 +/- 0.074 and with reduced-intensity conditioning was 0.563 +/- 0.124. Thus, in a substantial number of cases, EBV-associated T/NK-LPD can be cured by either allogeneic conventional stem cell transplantation or reduced-intensity stem cell transplantation.

Progress in understanding and managing natural killer-cell malignancies

The World Health Organization classification of haematolymphoid tumours recognizes three categories of natural killer (NK)-cell neoplasms: blastic NK-cell lymphoma, aggressive NK-cell leukaemia, and extranodal NK/T-cell lymphoma, nasal-type. Recent studies indicate that CD4+CD56+ blastic NK-cell lymphoma is of plasmacytoid dendritic cell origin, and true tumours of precursor NK-cell origin may be present mainly in the CD4-CD56+ subset. Myeloid/NK-cell precursor acute leukaemia may also develop from precursor NK cells. However, because the developmental pathway of normal NK cells is not well understood, tumours of precursor NK-cell origin are not clearly identified. Among mature NK-cell tumours, extranodal NK/T-cell lymphoma is relatively common in Asia and Latin America. In localized disease, chemoradiotherapy seems to be promising, and in advanced disease, new combination chemotherapies are under active investigation. Aggressive NK-cell leukaemia is rare and has a poor prognosis. Because NK-cell neoplasms are rare and difficult to manage, rigorous studies are required for their understanding and management.

Periphere NK/T-Zell-Lymphome

Peripheral T-cell lymphomas comprise 8% of the malignant lymphomas in Germany. About 25% of these cases present primarily in extranodal localizations. Such localizations are typical for the respective disease and form the basis for the classification of extranodal peripheral T-cell lymphoma. The morphology, immunophenotype and lineage specificity of the tumor cells (originating from T- or NK-cells) is only secondary for the classification. Extranodal NK/T-cell lymphomas of the nasal type are characterized by an angiocentric growth pattern and large confluent areas of necrosis. In addition, there is a clonal infection by Epstein-Barr virus in the T-lymphocytes. In the differential diagnosis, B-cell lymphomas are more frequent at all localizations than T- or NK-cell lymphomas.