Expression of activating natural killer-cell receptors is a hallmark of the innate-like T-cell neoplasm in peripheral T-cell lymphomas

Clinical and Histopathological Features of an Italian Monocentric Series of Primary Small Bowel T-Cell Lymphomas

The gastrointestinal (GI) tract is the most common extranodal site of occurrence of non-Hodgkin lymphomas. Most GI lymphomas are of B-cell lineage, while T-cell lymphomas are less frequent. The aim of our retrospective study was to depict the clinical-pathological profile of a series of patients affected by intestinal T-cell lymphomas (ITCL) and possibly define hallmarks of these neoplasms. A total of 28 patients were included: 17 enteropathy-associated T-cell lymphomas (EATL), 5 monomorphic epitheliotropic T-cell lymphomas (MEITL), 3 indolent T-cell lymphoproliferative disorders of the gastrointestinal tract (ITCLDGT), and 3 intestinal T-cell lymphomas not otherwise specified (ITCL-NOS). Celiac disease (CD) was diagnosed in around 70% of cases. Diagnosis of EATL showed a significant correlation with CD30 expression, whereas MEITL with angiotropism and CD56 positivity. ITCLDGT cases showed plasma cells infiltration. Peripheral lymphocytosis, the absence of a previous diagnosis of CD, an advanced Lugano clinical stage, and the histological subtype ITCL-NOS were significantly associated with worse survival at multivariate analysis. Our findings about the epidemiological, clinical, and histopathological features of ITCL were in line with the current knowledge. Reliable prognostic tools for these neoplasms are still lacking but according to our results lymphocytosis, diagnosis of CD, Lugano clinical stage, and histological subtype should be considered for patient stratification.

Cellular Origins and Pathogenesis of Gastrointestinal NK- and T-Cell Lymphoproliferative Disorders

The intestinal immune system, which must ensure appropriate immune responses to both pathogens and commensal microflora, comprises innate lymphoid cells and various T-cell subsets, including intra-epithelial lymphocytes (IELs). An example of innate lymphoid cells is natural killer cells, which may be classified into tissue-resident, CD56bright NK-cells that serve a regulatory function and more mature, circulating CD56dim NK-cells with effector cytolytic properties. CD56bright NK-cells in the gastrointestinal tract give rise to indolent NK-cell enteropathy and lymphomatoid gastropathy, as well as the aggressive extranodal NK/T cell lymphoma, the latter following activation by EBV infection and neoplastic transformation. Conventional CD4+ TCRαβ+ and CD8αβ+ TCRαβ+ T-cells are located in the lamina propria and the intraepithelial compartment of intestinal mucosa as type 'a' IELs. They are the putative cells of origin for CD4+ and CD8+ indolent T-cell lymphoproliferative disorders of the gastrointestinal tract and intestinal T-cell lymphoma, NOS. In addition to such conventional T-cells, there are non-conventional T-cells in the intra-epithelial compartment that express CD8αα and innate lymphoid cells that lack TCRs. The central feature of type 'b' IELs is the expression of CD8αα homodimers, seen in monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL), which primarily arises from both CD8αα+ TCRαβ+ and CD8αα+ TCRγδ+ IELs. EATL is the other epitheliotropic T-cell lymphoma in the GI tract, a subset of which arises from the expansion and reprograming of intracytoplasmic CD3+ innate lymphoid cells, driven by IL15 and mutations of the JAK-STAT pathway.

Chronic T cell receptor stimulation unmasks NK receptor signaling in peripheral T cell lymphomas via epigenetic reprogramming

Peripheral T cell lymphomas (PTCLs) represent a significant unmet medical need with dismal clinical outcomes. The T cell receptor (TCR) is emerging as a key driver of T lymphocyte transformation. However, the role of chronic TCR activation in lymphomagenesis and in lymphoma cell survival is still poorly understood. Using a mouse model, we report that chronic TCR stimulation drove T cell lymphomagenesis, whereas TCR signaling did not contribute to PTCL survival. The combination of kinome, transcriptome, and epigenome analyses of mouse PTCLs revealed a NK cell-like reprogramming of PTCL cells with expression of NK receptors (NKRs) and downstream signaling molecules such as Tyrobp and SYK. Activating NKRs were functional in PTCLs and dependent on SYK activity. In vivo blockade of NKR signaling prolonged mouse survival, demonstrating the addiction of PTCLs to NKRs and downstream SYK/mTOR activity for their survival. We studied a large collection of human primary samples and identified several PTCLs recapitulating the phenotype described in this model by their expression of SYK and the NKR, suggesting a similar mechanism of lymphomagenesis and establishing a rationale for clinical studies targeting such molecules.

Epstein-Barr virus BART microRNAs in EBV- associated Hodgkin lymphoma and gastric cancer

Background

EBV produces miRNAs with important functions in cancer growth, tumor invasion and host immune surveillance. The discovery of EBV miR-BARTs is recent, and most of their functions are still unknown. Nonetheless, some new studies underline their key roles in EBV-associated malignancies.

Main body

In EBV-associated tumors, the expression profile of miR-BARTs varies according to the cell type, autophagic process and signals received from the tumor microenvironment. By the same way of interest is the interaction between tumor cells and the tumor environment by the release of selected EBV miR-BARTs in addition to the tumor proteins trough tumor exosomes.

Conclusion

In this review, we discuss new findings regarding EBV miR-BARTs in Hodgkin lymphoma and gastric cancer. The recent discovery that miRNAs are released by exosomes, including miR-BARTs, highlights the importance of tumor and microenvironment interplay with more specific effects on the host immune response.

Nasal NK/T cell lymphoma mimicking mucosa-associated lymphoid tissue lymphoma in morphology: A case report

The objective of the present study was to describe the clinicopathological features of a patient with nasal NK/T cell lymphoma that was similar in morphology to mucosa-associated lymphoid tissue lymphoma (MALToma). The clinicopathological data of a patient diagnosed with nasal NK/T cell lymphoma mimicking MALToma was collected, and the clinicopathological characteristics were discussed. The female patient was 43 years old and had suffered from persistent congestion for ten days. The mucosa in the left nasal cavity was inflamed, resulting in congestion and it was also purulent on the surface, as observed by nasal endoscopy. The disease was considered to be inflammatory based on CT scan. A biopsy after operation showed that the tumor consisted of small lymphoid cells that resembled MALToma in morphology. On the basis of the immunohistochemistry and in situ hybridization laboratory tests, a diagnosis of left nasal NK/T cell lymphoma was made. The patient received chemotherapy and radiotherapy, and remission was achieved six months after diagnosis. The patient was in a good condition at 16 months follow-up. In conclusion, NK/T cell lymphoma composed of small cells may be a type of indolent lymphoma with special characteristics of clinical presentation, image, pathology and prognosis. This case highlights that more attention is required by radiologists, pathologists and hematologists to diagnose this type of lymphoma.

NKp46 is a diagnostic biomarker and may be a therapeutic target in gastrointestinal T-cell lymphoproliferative diseases: a CELAC study

OBJECTIVES

Primary GI T-cell lymphoproliferative diseases (T-LPD) are heterogeneous entities, which raise difficult diagnosis and therapeutic challenges. We have recently provided evidences that lymphomas complicating coeliac disease (CD) arise from innate-like lymphocytes, which may carry NK receptors (NKRs).

DESIGN

NKRs expression was compared by flow cytometry in intraepithelial lymphocytes (IEL) from CD, type I or type II refractory CD (RCD). NKp46 was next assessed by immunohistochemistry in paraffin-embedded biopsies from 204 patients with CD, RCDI, RCDII or GI T-cell lymphomas and from a validation cohort of 61 patients. The cytotoxic properties of an anti-NKp46 monoclonal antibody conjugated to pyrrolobenzodiazepine (PBD) was tested ex vivo in human primary tumour cells isolated from fresh duodenal biopsies.

RESULTS

NKp46 (but not CD94, NKG2A, NKG2C, NKG2D) was significantly more expressed by malignant RCDII IEL than by normal IEL in CD and RCDI. In paraffin biopsies, detection of >25 NKp46+ IEL per 100 epithelial cells discriminated RCDII from CD and RCDI. NKp46 was also detected in enteropathy-associated T-cell lymphomas (EATL, 24/29) and in monomorphic epitheliotropic intestinal T-cell lymphomas (MEITL, 4/4) but not in indolent T-LPD (0/15). Treatment with anti-NKp46-PBD could efficiently and selectively kill human NKp46+ primary IEL ex vivo.

CONCLUSION

NKp46 is a novel biomarker useful for diagnosis and therapeutic stratification of GI T-LPD. Strong preclinical rationale identifies anti-NKp46-PBD as a promising therapy for RCDII, EATL and MEITL.

Expression of activating natural killer-cell receptors is a hallmark of the innate-like T-cell neoplasm in peripheral T-cell lymphomas

Peripheral T‐ or natural killer (NK)‐cell lymphomas are rare and difficult‐to‐recognize diseases. It remains arduous to distinguish between NK cell‐ and cytotoxic T‐lymphocyte‐derived lymphomas through routine histological evaluation. To clarify the cells of origin, we focused on NK‐cell receptors and examined the expression using immunohistochemistry in 22 cases with T‐ and NK‐cell neoplasms comprising angioimmunoblastic T‐cell lymphoma, anaplastic lymphoma kinase (ALK)‐positive and ‐negative anaplastic large‐cell lymphomas, extranodal NK/T‐cell lymphoma, nasal type, monomorphic epitheliotropic intestinal T‐cell lymphoma, aggressive NK‐cell leukemia, and other peripheral T‐cell lymphomas. Inhibitory receptor leukocyte immunoglobulin‐like receptor subfamily B member 1 (LILRB1) was detected in 14 (64%) cases, whereas activating receptors DNAM1, NKp46, and NKG2D were expressed in 7 (32%), 9 (41%), and 5 (23%) cases, respectively. Although LILRB1 was detected regardless of the disease entity, the activating NK‐cell receptors were expressed predominantly in TIA‐1‐positive neoplasms (DNAM1, 49%; NKp46, 69%; and NKG2D, 38%). In addition, NKp46 and NKG2D were detected only in NK‐cell neoplasms and cytotoxic T‐lymphocyte‐derived lymphomas including monomorphic epitheliotropic intestinal T‐cell lymphoma. One Epstein‐Barr virus‐harboring cytotoxic T‐lymphocyte‐derived lymphoma mimicking extranodal NK/T‐cell lymphoma, nasal type lacked these NK‐cell receptors, indicating different cell origin from NK and innate‐like T cells. Furthermore, NKG2D expression showed a negative impact on survival among the 22 examined cases, which mainly received the standard chemotherapy regimen (log‐rank test, P = .024). We propose that the presence of activating NK‐cell receptors may provide new insights into understanding peripheral T‐cell lymphomas and characterizing them as innate‐like T‐cell neoplasm.