Hiaki Sato

Multi-Step Aberrant CpG Island Hyper-Methylation Is Associated with the Progression of Adult T–Cell Leukemia/Lymphoma

Aberrant CpG island methylation contributes to the pathogenesis of various malignancies. However, little is known about the association of epigenetic abnormalities with multistep tumorigenic events in adult T cell leukemia/lymphoma (ATLL). To determine whether epigenetic abnormalities induce the progression of ATLL, we analyzed the methylation profiles of the SHP1, p15, p16, p73, HCAD, DAPK, hMLH-1, and MGMT genes by methylation specific PCR assay in 65 cases with ATLL patients. The number of CpG island methylated genes increased with disease progression and aberrant hypermethylation in specific genes was detected even in HTLV-1 carriers and correlated with progression to ATLL. The CpG island methylator phenotype (CIMP) was observed most frequently in lymphoma type ATLL and was also closely associated with the progression and crisis of ATLL. The high number of methylated genes and increase of CIMP incidence were shown to be unfavorable prognostic factors and correlated with a shorter overall survival by Kaplan-Meyer analysis. The present findings strongly suggest that the multistep accumulation of aberrant CpG methylation in specific target genes and the presence of CIMP are deeply involved in the crisis, progression, and prognosis of ATLL, as well as indicate the value of CpG methylation and CIMP for new diagnostic and prognostic biomarkers.

Duodenal follicular lymphomas share common characteristics with mucosa-associated lymphoid tissue lymphomas.

Background: Follicular lymphomas occasionally arise in the extra-nodal organs and are frequently found in the duodenum. They are often localised tumours with multiple polyps around the ampulla of Vater. Aims: To examine a IgH/bcl-2 hybrid gene and VH gene to investigate the nature of the lymphoma cells and how they differ from nodal follicular lymphomas and MALT lymphomas. Methods: Of 40 patients reported previously, 35 with duodenal follicular lymphoma were studied in detail with respect to clinicopathological characteristics. Results: 37/40 patients were in clinical stage I (n = 30) or stage II (n = 7). Clonal immunoglobulin gene rearrangement was detected in 53.3% of examined cases, and rearrangement of IgH/bcl-2 gene at the major break point was detected in 27% of cases. Three of 8 examined cases were VH4 (38%); 2 out of them were VH4-34. As VH4 deviation is one of the common characteristics of MALT lymphomas and 2/3 were identical, duodenal follicular lymphomas have a similar aetiology to MALT lymphomas. Clinical course was also similar to that of MALT lymphomas. Conclusions: Results suggest that duodenal follicular lymphomas have intermediate characteristics of MALT lymphomas and nodal follicular lymphomas.

In aggressive variants of non-Hodgkin lymphomas, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2

Polycomb group (PcG) proteins are important for the regulation of hematopoiesis by regulating chromatin compaction and silencing genes related to differentiation and cell cycle. Overexpression of enhancer of zeste homologue 2 (Ezh2) and Bmi-1/PCGF4 has been implicated in solid organ cancers, while Mel-18/PCGF2 has been reported as a tumor suppressor. Detailed expression profiles of PcG proteins and their diagnostic significance in malignant lymphomas are still unknown. In this study, we analyzed the expression levels of Ezh2, Bmi-1, Mel-18, and Ki67 in 197 Hodgkin’s and non-Hodgkin’s lymphoma patient samples and in lymphoma cell lines using immunohistochemistry, fluorescent immunocytochemistry, and Western blotting. Immunohistochemical staining showed that Ezh2 expression was significantly increased in aggressive compared to indolent subtypes of B cell neoplasms (P = 0.000–0.030), while no significant differences in Bmi-1 expression were found between these subtypes. Compared to the normal counterpart, T cell lymphomas showed significant overexpression of Bmi-1 (P = 0.011) and Ezh2 (P = 0.000). The Ki67 labeling index showed a positive correlation with Ezh2 expression in B cell lymphomas (correlation coefficient (Co) = 0.983, P = 0.000) and T/NK cell lymphomas (Co = 0.629, P = 0.000). Fluorescent immunohistochemical staining showed coexpression of Ezh2 and Ki67 in the same tumor cells, indicating that Ezh2 expression correlates with cell proliferation. Both B and T/NK cell neoplasms showed low expression of Mel-18 and high expression of both Bmi-1 and Ezh2. In conclusion, in aggressive lymphoma variants, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2. Coexpression of Bmi-1 and Ezh2 is a characteristic of aggressive lymphomas. Ezh2 correlates with the proliferation and aggressive nature of non-Hodgkin’s lymphomas.

Identification and characterization of human thymic cortical dendritic macrophages that may act as professional scavengers of apoptotic thymocytes

We identify and characterize a special type of macrophage in the human thymic cortex that may act as professional scavengers of apoptotic thymocytes. These are large cells with clear cytoplasm, evenly distributed exclusively in the thymic cortex, and usually contain degraded nuclei in their cytoplasm. They are distinct from ordinary macrophages (OM) in the thymic cortex in expressing fascin, an actin-bundling protein specific for dendritic cells (DC), and in lacking lysozyme (LZM) and CD68. They are also different from DC in lacking major histocompatibility complex (MHC)-class II molecules. To distinguish them from OM and DC, we called them thymic cortical dendritic macrophages (TCDM). Both TCDM and OM are positive for DC-SIGN (CD209) and HAM56, whereas fascin(hi) MHC-class II(hi) medullary DC (mDC) are negative for these antigens. TCDM exhibit either dendritic or plump feature depending on cases examined. Plump TCDM usually contain several degraded nuclei, while dendritic TCDM contain one or two. These degraded nuclei are positive for active caspase-3 (aCasp-3), indicating that they are apoptotic thymocytes. In contrast to TCDM, LZM(hi) CD68(hi) OM are smaller round cells, distributed unevenly throughout the thymus, and do not contain apoptotic thymocytes at all. TCDM tend to adhere to capillaries with their dendrites or they make extensive contacts covering a large portion of the capillaries. Electron microscopic analysis confirmed the extensive contact between TCDM and capillaries and indicated that TCDM possess extremely electron-lucent, abundant cytoplasm with numerous tubulovesicular structures and secondary lysosomes. The finding of numerous condensed nuclei in most of the TCDM indicates that these cells represent a special type of fixed macrophages in the human thymic cortex, and that they play a central role in the clearance of apoptotic thymocytes.

Dendritic cells interacting mainly with B cells in the lymphoepithelial symbiosis of the human palatine tonsil

The lymphoepithelial symbiosis (LES) of the human palatine tonsil is composed of spindle- or star-shaped epithelial cells forming a loose meshwork, containing numerous lymphocytes and dendritic cells (DCs). In the present study, we immunohistochemically characterized DCs in the LES (LES-DCs). LES-DCs were phenotypically immature DCs that were S100β+, fascin−, HLA-DR+, CD1a−, CD80−, CD83−, CD86−, and CD123−. The most characteristic feature of LES-DCs was that they contacted many B cells, which were mostly IgM+ IgD+ resting naive B cells. Langerhans cells (LCs) located in the nonsymbiotic squamous epithelium were immature DCs that were S100β+, fascin−, and CD1a+ and did not contact lymphocytes. In contrast to LES-DCs, interdigitating dendritic cells (IDCs) in the T zone were mature DCs that were HLA-DR+, CD1a−, fascin+, CD80+, CD83+, and CD86+ and contacted numerous CD4+ T cells. Two subsets of IDC, S100β+ fascin+ IDC (IDC-1) and S100β− fascin+ IDC (IDC-2), were identified, and the majority of IDCs are IDC-2. In contrast to IDCs, which were distributed in the T-cell area in groups, LES-DCs were distributed along the crypt as if forming a barrier. These findings suggest that LES-DCs are a novel type of DC playing an important role in the induction of humoral immune response against incoming air- or food-borne pathogenic antigens.

Morphologic, flow cytometric, functional, and molecular analyses of S100B positive lymphocytes, unique cytotoxic lymphocytes containing S100B protein

Little is known about the S100B+ lymphocytes, which are unique human peripheral blood lymphocytes (PBL) containing the S100B protein. It has recently been shown that S100B is released from various types of S100B+ cells and exhibits varied cytokine‐like activities. In this study, we precisely characterized the S100B+ lymphocytes of healthy adults with respect to the proportion in the whole PBL, immunophenotypes, function, and their S100B mRNA expression and also evaluated their S100B‐releasing activity upon stimulation. S100B+ lymphocytes were detected in all individuals examined, and the proportion of S100B+ lymphocytes in the whole PBL ranged from 0.42% to 16.15% (mean, 4.21%). In addition, two subtypes of S100B+ lymphocytes, a CTL subtype (CD3+ CD8+ CD16‐) and a NK subtype (CD3‐ CD8‐ CD16+), were detected. The majority of the CTL subtype of S100B+ lymphocytes expressed the αβ‐T‐cell receptor. Surprisingly, S100B mRNA was detected not only in S100B+ lymphocytes, but also in every S100B‐ lymphocytes, although the expression levels of S100B mRNA in S100B‐ lymphocytes were much lower than those of S100B+ lymphocytes. The CTL subtype of S100B+ lymphocytes exhibited blastic morphological changes, proliferated and released S100B upon stimulation with phytohemagglutinin. The NK subtype of S100B+ lymphocytes exhibited morphological NK activity when cocultivated with NK‐sensitive target, K‐562 cells. Thus, the CTL subtype of S100B+ lymphocytes exhibit the biological characteristics of T cells, while the NK subtype of S100B+ lymphocytes exhibit the characteristics of NK cells. These results suggest that S100B+ lymphocytes are a particular subtype of cytotoxic lymphocytes that play a unique role in antitumor immunity.

Cumulative Epigenetic Abnormalities in Host Genes with Viral and Microbial Infection during Initiation and Progression of Malignant Lymphoma/Leukemia.

Although cancers have been thought to be predominantly driven by acquired genetic changes, it is becoming clear that microenvironment-mediated epigenetic alterations play important roles. Aberrant promoter hypermethylation is a prevalent phenomenon in human cancers as well as malignant lymphoma/leukemia. Tumor suppressor genes become frequent targets of aberrant hypermethylation in the course of gene-silencing due to the increased and deregulated DNA methyltransferases (DNMTs). The purpose of this article is to review the current status of knowledge about the contribution of cumulative epigenetic abnormalities of the host genes after microbial and virus infection to the crisis and progression of malignant lymphoma/leukemia. In addition, the relevance of this knowledge to malignant lymphoma/leukemia assessment, prevention and early detection will be discussed.

A possible new morphological variant of mantle cell lymphoma with plasma-cell type Castleman disease-like features

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma characterized by overexpression of cyclin D1 resulting from t(11;14)(q13;q32) translocation. Herein, we report 3 cases of MCL with features of plasma cell-type Castleman disease (CD). The 3 patients were all men, ranging from 51 to 74 years in age, and they all presented with systemic lymphadenopathy with anemia, hypoalbuminemia, elevated serum levels of C-reactive protein, and polyclonal hypergammaglobulinemia. Lymph node biopsy specimens of the 3 cases showed histological features of plasma cell-type CD, including atrophic germinal centers and interfollicular plasmacytosis, with no light chain restriction. However, flow cytometric analysis demonstrated an abnormal B-cell population with CD5 expression, and further analysis using cyclin D1 immunostaining highlighted a neoplastic component that was restricted to the mantle zone. These neoplastic cells were immunohistochemically positive for CD20, CD5, and SOX11, and negative for CD3, CD10, and HHV8. The Ki67 index was low. All patients were finally diagnosed with MCL. This rare type of MCL can be misdiagnosed clinically and histologically as CD. Therefore, it is important to recognize this rare type of MCL, and careful examination is required using both histological and flow cytometric analyses.

Gene expression analysis of hypersensitivity to mosquito bite, chronic active EBV infection and NK/T-lymphoma/leukemia

Abstract The human herpes virus, Epstein-Barr virus (EBV), is a known oncogenic virus and plays important roles in life-threatening T/NK-cell lymphoproliferative disorders (T/NK-cell LPD) such as hypersensitivity to mosquito bite (HMB), chronic active EBV infection (CAEBV), and NK/T-cell lymphoma/leukemia. During the clinical courses of HMB and CAEBV, patients frequently develop malignant lymphomas and the diseases passively progress sequentially. In the present study, gene expression of CD16(−)CD56(+)-, EBV(+) HMB, CAEBV, NK-lymphoma, and NK-leukemia cell lines, which were established from patients, was analyzed using oligonucleotide microarrays and compared to that of CD56brightCD16dim/− NK cells from healthy donors. Principal components analysis showed that CAEBV and NK-lymphoma cells were relatively closely located, indicating that they had similar expression profiles. Unsupervised hierarchal clustering analyses of microarray data and gene ontology analysis revealed specific gene clusters and identified several candidate genes responsible for disease that can be used to discriminate each category of NK-LPD and NK-cell lymphoma/leukemia.

Cumulative kinetics of epigenetic abnormalities during initiation and progression of Adult T-cell Leukemia/Lymphoma (ATLL)

HTLV-1 causes ATLL in 3-5% of infected individuals after a long latent period of 40-60 years. ATLL is divided into four stages: namely, smoldering, chronic, lymphoma and acute types. The smoldering and chronic types are indolent, but the acute and lymphoma types are aggressive ATLL characterized by resistance to chemotherapy and a poor prognosis. Such a long latent period suggests that a multi-step leukemogenic/lymphomagenic mechanism is involved in the development of ATLL, although the critical events in the progression have not been characterized. To determine whether epigenetic abnormalities are playing important roles in the progression of ATLL, we analyzed the methylation profiles, showing that number of CpG island methylated genes increased with disease progression and aberrant hyper-methylation in specific genes was detected even in HTLV-1 carriers and correlated with progression to ATLL. The CpG island methylator phenotype (CIMP) was observed most frequently in lymphoma type ATLL and was also closely associated with the progression and crisis of ATLL. The high number of methylated genes and increase of CIMP incidence were shown to be unfavorable prognostic factors and correlated with a shorter overall survival with the Kaplan-Meyer analysis. Increase of aberrant DNA methylation density was observed during the progression of an ATLL patient. The present findings strongly suggest that the multi-step accumulation of aberrant CpG methylation in specific target genes and the presence of CIMP are deeply involved in the initiation and progression of ATLL not only epidemiologically but also in the clinical course of a specific ATLL patient.