Genetic profile of adult T-cell leukemia/lymphoma in Okinawa: Association with prognosis, ethnicity, and HTLV-1 strains

A Comprehensive Study of the Immunophenotype and its Clinicopathologic Significance in Adult T-Cell Leukemia/Lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a mature T-cell tumor caused by human T-lymphotropic virus type 1 (HTLV-1). The typical ATLL immunophenotypes are described in the 2017 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues (positive: CD2, CD3, CD5, CD4, and CD25; negative: CD7, CD8, and cytotoxic markers; and partially positive: CD30, CCR4, and FOXP3). However, limited studies are available on the expression of these markers, and their mutual relationship remains unknown. Furthermore, the expression status of novel markers associated with T-cell lymphomas, including Th1 markers (T-bet and CXCR3), Th2 markers (GATA3 and CCR4), T follicular helper markers (BCL6, PD1, and ICOS), and T-cell receptor (TCR) markers, and their clinicopathologic significance is unclear. In this study, we performed >20 immunohistochemical stains in 117 ATLL cases to determine the comprehensive immunophenotypic profile of ATLL, which were compared on the basis of clinicopathologic factors, including morphologic variants (pleomorphic vs anaplastic), biopsy locations, treatments, Shimoyama classification-based clinical subtype, and overall survival. CD3+/CD4+/CD25+/CCR4+ was considered a typical immunophenotype of ATLL, but approximately 20% of cases did not conform to this pattern. Simultaneously, the following new findings were obtained: (1) most cases were negative for TCR-β and TCR-δ (104 cases, 88.9%), indicating the usefulness of negative conversion of TCR expression to provide differentiation from other T-cell tumors; (2) the positivity of CD30 and CD15 and the negativity of FOXP3 and CD3 were significantly associated with anaplastic morphology; and (3) atypical cases, such as T follicular helper marker-positive (12 cases, 10.3%) and cytotoxic molecule-positive cases (3 cases, 2.6%), were identified. No single markers could predict the overall survival among patients with acute/lymphoma subtypes of ATLL. The results of this study illustrate the diversity of ATLL phenotypes. In T-cell tumors occurring in HTLV-1 carriers, the possibility of ATLL should not be eliminated even when the tumor exhibits an atypical phenotype, and the confirmation of HTLV-1 in the tissue is recommended.

Protein Kinase C at the Crossroad of Mutations, Cancer, Targeted Therapy and Immune Response

The frequent PKC dysregulations observed in many tumors have made these enzymes natural targets for anticancer applications. Nevertheless, this considerable interest in the development of PKC modulators has not led to the expected therapeutic benefits, likely due to the complex biological activities regulated by PKC isoenzymes, often playing ambiguous and protective functions, further driven by the occurrence of mutations. The structure, regulation and functions of PKCs have been extensively covered in other publications. Herein, we focused on PKC alterations mostly associated with complete functional loss. We also addressed the modest yet encouraging results obtained targeting PKC in selected malignancies and the more frequent negative clinical outcomes. The reported observations advocate the need for more selective molecules and a better understanding of the involved pathways. Furthermore, we underlined the most relevant immune mechanisms controlled by PKC isoforms potentially impacting the immune checkpoint inhibitor blockade-mediated immune recovery. We believe that a comprehensive examination of the molecular features of the tumor microenvironment might improve clinical outcomes by tailoring PKC modulation. This approach can be further supported by the identification of potential response biomarkers, which may indicate patients who may benefit from the manipulation of distinctive PKC isoforms.

A frequent PLCγ1 mutation in adult T-cell leukemia/lymphoma determines functional properties of the malignant cells

BACKGROUND

Development of adult T-cell leukemia/lymphoma (ATL) involves human T-cell leukemia virus type 1 (HTLV-1) infection and accumulation of somatic mutations. The most frequently mutated gene in ATL (36 % of cases) is phospholipase C gamma1 (PLCG1). PLCG1 is also frequently mutated in other T-cell lymphomas. However, the functional consequences of the PLCG1 mutations in cancer cells have not been characterized.

METHODS

We compared the activity of the wild-type PLCγ1 with that of a mutant carrying a hot-spot mutation of PLCγ1 (S345F) observed in ATL, both in cells and in cell-free assays. To analyse the impact of the mutation on cellular properties, we quantified cellular proliferation, aggregation, chemotaxis and apoptosis by live cell-imaging in an S345F+ ATL-derived cell line (KK1) and a KK1 cell line in which we reverted the mutation to the wild-type sequence using CRISPR/Cas9 and homology-directed repair.

FINDINGS

The PLCγ1 S345F mutation results in an increase of basal PLC activity in vitro and in different cell types. This higher basal activity is further enhanced by upstream signalling. Reversion of the S345F mutation in the KK1 cell line resulted in reduction of the PLC activity, lower rates of proliferation and aggregation, and a marked reduction in chemotaxis towards CCL22. The PLCγ1-pathway inhibitors ibrutinib and ritonavir reduced both the PLC activity and the tested functions of KK1 cells.

INTERPRETATION

Consistent with observations from clinical studies, our data provide direct evidence that activated variants of the PLCγ1 enzyme contribute to the properties of the malignant T-cell clone in ATL.

FUNDING

MRC (UK) Project Grant (P028160).

Signaling factors potentially associated to the pathogenesis of Adult T-cell leukemia /lymphoma: A network-analysis and novel findings assessment

Adult T-cell leukemia/lymphoma (ATLL) is a human T-cell leukemia virus (HTLV) type 1-associated disease of TCD4+ cell transformation. Despite extensive studies on ATLL development and progression, the fundamental processes of HTLV-1 oncogenicity are yet to be understood. This study aimed to integrate high-throughput microarray datasets to find novel genes involved in the mechanism of ATLL progression. For this purpose, five microarray datasets were downloaded from the Gene Expression Omnibus database and then profoundly analyzed. Differentially expressed genes and miRNAs were determined using the MetaDE package in the R software and the GEO2R web tool. The STRING database was utilized to construct the protein-protein interaction network and explore hub genes. Gene ontology and pathway enrichment analysis were carried out by employing the EnrichR web tool. Furthermore, flow cytometry was employed to assess the CD4/CD8 ratio, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to confirm the high-throughput data analysis results. Four miRNAs, including hsa-mir-146, hsa-mir-451, hsa-mir-31, and hsa-mir-125, were among the statistically significant differentially expressed miRNAs between healthy individuals and ATLL patients. Moreover, 924 differentially expressed genes were identified between normal and ATLL samples. Further network analysis highlighted 59 hub genes mainly regulating pathways implicated in viral interferences, immunological processes, cancer, and apoptosis pathways. Among the identified hub genes, RhoA and PRKACB were most considerable in the high-throughput analysis and were further validated by qRT-PCR. The RhoA and PRKACB expression were significantly down-regulated in ATLL patients compared to asymptomatic carriers (p<0.0001 and p=0.004) and healthy subjects (p=0.043 and p=0.002). Therefore, these corresponding miRNAs and proteins could be targeted for diagnosis purposes and designing effective treatments.

Mutations Affecting Genes in the Proximal T-Cell Receptor Signaling Pathway in Peripheral T-Cell Lymphoma

Simple Summary

The advent of next-generation sequencing (NGS) has allowed rapid advances in genomic studies on the pathogenesis and biology of peripheral T-cell lymphoma (PTCL). Recurrent mutations and fusions in genes related to the proximal TCR signaling pathway have been identified and show an important pathogenic role in PTCL. In this review, we summarize the genomic alterations in TCR signaling identified in different subgroups of PTCL patients and the functional impact of these alterations on TCR signaling and downstream pathways. We also discuss novel agents that could target TCR-related mutations and may hold promise for improving the treatment of PTCL.

Abstract

Peripheral T-cell lymphoma (PTCL) comprises a heterogeneous group of mature T-cell malignancies. Recurrent activating mutations and fusions in genes related to the proximal TCR signaling pathway have been identified in preclinical and clinical studies. This review summarizes the genetic alterations affecting proximal TCR signaling identified from different subgroups of PTCL and the functional impact on TCR signaling and downstream pathways. These genetic abnormalities include mostly missense mutations, occasional indels, and gene fusions involving CD28, CARD11, the GTPase RHOA, the guanine nucleotide exchange factor VAV1, and kinases including FYN, ITK, PLCG1, PKCB, and PI3K subunits. Most of these aberrations are activating mutations that can potentially be targeted by inhibitors, some of which are being tested in clinical trials that are briefly outlined in this review. Finally, we focus on the molecular pathology of recently identified subgroups of PTCL-NOS and highlight the unique genetic profiles associated with PTCL-GATA3.

Genetic Alterations in Adult T-Cell Leukemia/Lymphoma: Novel Discoveries with Clinical and Biological Significance

Adult T-cell leukemia/lymphoma (ATLL) is a refractory T-cell neoplasm that develops in human T-cell leukemia virus type-I (HTLV-1) carriers. Large-scale comprehensive genomic analyses have uncovered the landscape of genomic alterations of ATLL and have identified several altered genes related to prognosis. The genetic alterations in ATLL are extremely enriched in the T-cell receptor/nuclear factor-κB pathway, suggesting a pivotal role of deregulation in this pathway in the transformation of HTLV-1-infected cells. Recent studies have revealed the process of transformation of HTLV-1-infected cells by analyzing longitudinal samples from HTLV-1 carriers and patients with overt ATLL, an endeavor that might enable earlier ATLL diagnosis. The latest whole-genome sequencing study discovered 11 novel alterations, including CIC long isoform, which had been overlooked in previous studies employing exome sequencing. Our study group performed the targeted sequencing of ATLL in Okinawa, the southernmost island in Japan and an endemic area of HTLV-1, where the comprehensive genetic alterations had never been analyzed. We found associations of genetic alterations with HTLV-1 strains phylogenetically classified based on the tax gene, an etiological virus factor in ATLL. This review summarizes the genetic alterations in ATLL, with a focus on their clinical significance, geographical heterogeneity, and association with HTLV-1 strains.

RHOA takes the RHOad less traveled to cancer

RAS and RHO GTPases function as signaling nodes that regulate diverse cellular processes. Whereas RAS mutations were identified in human cancers nearly four decades ago, only recently have mutations in two RHO GTPases, RAC1 and RHOA, been identified in cancer. RAS mutations are found in a diverse spectrum of human cancer types. By contrast, RAC1 and RHOA mutations are associated with distinct and restricted cancer types. Despite a conservation of RAS and RAC1 residues that comprise mutational hotspots, RHOA mutations comprise highly divergent hotspots. Whereas RAS and RAC1 act as oncogenes, RHOA may act as both an oncogene and a tumor suppressor. Thus, while RAS and RHO each take different mutational paths, they arrive at the same biological destination as cancer drivers.

Deconvolution of Adult T-Cell Leukemia/Lymphoma With Single-Cell RNA-Seq Using Frozen Archived Skin Tissue Reveals New Subset of Cancer-Associated Fibroblast

Adult T-cell Leukemia/Lymphoma (ATLL) is a rare aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) infection. However, little is known about the underlying activated molecular pathways at the single cell level. Moreover, the intercellular communications between the tumor microenvironment (TME) and tumor cells in this malignancy are currently unknown. Difficulties in harvesting fresh tissue in a clinical setting have hampered our deeper understanding of this malignancy. Herein, we examined ATLL using archived fresh frozen tissue after biopsy using single-cell RNA sequencing (scRNA-seq) with T-cell receptor (TCR) clonal analysis. Highly clonal tumor cells showed multiple activating pathways, suggesting dynamic evolution of the malignancy. By dissecting diverse cell types comprising the TME, we identified a novel subset of cancer-associated fibroblast, which showed enriched epidermal growth factor receptor (EGFR)-related transcripts including early growth response 1 and 2 (EGR1 and EGR2). Cancer associated fibroblasts (CAFs) of ATLL play an important role for CD4 T-cell proliferation via FGF7-FGF1 and PDGFA-PDGFRA/B signaling, and CAFs, particularly EGR-enriched, are also associated with CD8 and NKT expansion by EGFR. These findings suggest a potential targeted therapeutic pathway to better treat this neoplasm.

Overarching roles of diacylglycerol signaling in cancer development and antitumor immunity

Diacylglycerol (DAG) is a lipid second messenger that is generated in response to extracellular stimuli and channels intracellular signals that affect mammalian cell proliferation, survival, and motility. DAG exerts a myriad of biological functions through protein kinase C (PKC) and other effectors, such as protein kinase D (PKD) isozymes and small GTPase-regulating proteins (such as RasGRPs). Imbalances in the fine-tuned homeostasis between DAG generation by phospholipase C (PLC) enzymes and termination by DAG kinases (DGKs), as well as dysregulation in the activity or abundance of DAG effectors, have been widely associated with tumor initiation, progression, and metastasis. DAG is also a key orchestrator of T cell function and thus plays a major role in tumor immunosurveillance. In addition, DAG pathways shape the tumor ecosystem by arbitrating the complex, dynamic interaction between cancer cells and the immune landscape, hence representing powerful modifiers of immune checkpoint and adoptive T cell-directed immunotherapy. Exploiting the wide spectrum of DAG signals from an integrated perspective could underscore meaningful advances in targeted cancer therapy.

C-C Chemokine Receptor 7 in Cancer

C-C chemokine receptor 7 (CCR7) was one of the first two chemokine receptors that were found to be upregulated in breast cancers. Chemokine receptors promote chemotaxis of cells and tissue organization. Since under homeostatic conditions, CCR7 promotes migration of immune cells to lymph nodes, questions immediately arose regarding the ability of CCR7 to direct migration of cancer cells to lymph nodes. The literature since 2000 was examined to determine to what extent the expression of CCR7 in malignant tumors promoted migration to the lymph nodes. The data indicated that in different cancers, CCR7 plays distinct roles in directing cells to lymph nodes, the skin or to the central nervous system. In certain tumors, it may even serve a protective role. Future studies should focus on defining mechanisms that differentially regulate the unfavorable or beneficial role that CCR7 plays in cancer pathophysiology, to be able to improve outcomes in patients who harbor CCR7-positive cancers.

CCR7 in Blood Cancers - Review of Its Pathophysiological Roles and the Potential as a Therapeutic Target

According to the classical paradigm, CCR7 is a homing chemokine receptor that grants normal lymphocytes access to secondary lymphoid tissues such as lymph nodes or spleen. As such, in most lymphoproliferative disorders, CCR7 expression correlates with nodal or spleen involvement. Nonetheless, recent evidence suggests that CCR7 is more than a facilitator of lymphatic spread of tumor cells. Here, we review published data to catalogue CCR7 expression across blood cancers and appraise which classical and novel roles are attributed to this receptor in the pathogenesis of specific hematologic neoplasms. We outline why novel therapeutic strategies targeting CCR7 might provide clinical benefits to patients with CCR7-positive hematopoietic tumors.

Genetic profile of adult T-cell leukemia/lymphoma in Okinawa: Association with prognosis, ethnicity, and HTLV-1 strains

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