DNA methylation of microRNA genes in multiple myeloma

DNA methylation is one of the heritable epigenetic modifications, leading to repressed gene expressions and consequent phenotypic alterations without changing the DNA sequence. MicroRNA (miRNA) is a novel class of short non-coding RNA molecules regulating a wide range of cellular functions through translational repression of their target genes. Recently, epigenetic dysregulation of tumor-suppressor miRNA genes by promoter DNA methylation has been implicated in human cancers, including multiple myeloma (MM). This article presents a brief overview of the pathogenesis of MM, the role of DNA methylation in cancer biology, methods of DNA methylation analysis, miRNA biology and dysregulation of miRNAs in MM and summaries the current data on the role of DNA methylation of tumor-suppressive miRNAs in MM.postprin

Methylation of cyclin-dependent kinase inhibitors, XAF1, JUNB, CDH13 and soluble Wnt inhibitors in essential thrombocythaemia

Background: Methylation of genes regulating cell-cycle check-point (INK4 cyclin-dependent kinase inhibitors), apoptosis (XAF1), adhesion (CDH13), JUNB and Wnt signalling (soluble Wnt inhibitors) has been implicated in pathogenesis of haematological and epithelial cancers. Method The authors studied the methylation status of CDKN2A, CDKN2B, XAF1, CDH13, JUNB and a panel of soluble Wnt inhibitors including WIF1, DKK3, APC, SFRP1, SFRP2, SFRP4 and SFRP5 by methylation-specific PCR in 31 bone marrow and 21 peripheral blood samples of patients with essential thrombocythaemia. Results and discussion: There was no evidence of hypermethylation of all these genes in both the BM and PB samples. Therefore, in contrast to myeloid leukaemias, methylation of these genes regulating the cell cycle, apoptosis, adhesion and Wnt signalling does not play an important role in the pathogenesis of myeloproliferative diseases. Whether differential methylation may occur in the progenitor or mature blood cell compartments remains to be verified. Our study contributes to the literature on methylation in chronic myeloproliferatve diseases.published_or_final_versio

Methylation of TET2, CBL and CEBPA in Ph-negative myeloproliferative neoplasms

A loss-of-function mutation of TET2, CBL and CEBPA has been implicated in the pathogenesis or leukaemic transformation of myeloproliferative neoplasm. As tumour suppressor genes may potentially be inactivated by promoter hypermethylation, the authors studied the methylation status of these genes in three cell lines and diagnostic marrow samples from 45 patients with myeloproliferative neoplasm (MPN) (essential thrombocythaemia, N=34; polycythaemia vera, N=7 and primary myelofibrosis, N=4) by methylation-specific PCR. TET2 was heterozygously methylated in MEG-01 and K562 but completely unmethylated in HEL. On the other hand, both CBL and CEBPA were completely unmethylated in all three cell lines. In the primary marrow samples, methylation of TET2 occurred in two (5.9%) patients with essential thrombocythaemia (4.4% of all patients), both without JAK2 V617 mutation, but not in polycythaemia vera or primary myelofibrosis. There was no association between TET2 methylation with the type of MPN (p=0.713). Hypermethylation of CBL or CEBPA was not detected in any patients. In summary, methylation of TET2, CBL and CEBPA is infrequent in MPN at diagnosis. The role of methylation of these genes at the time of leukaemic transformation warrants further study.published_or_final_versio

Kimura's disease: No evidence of clonality [4]

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Electronic clinical practice guidelines: Current status and future prospects in Hong Kong

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Methylation of miR-34a, miR-34b/c, miR-124-1 and miR-203 in Ph-negative myeloproliferative neoplasms

BACKGROUND: MicroRNA (miR) miR-34a, -34b/c, -124-1 and -203 are tumor suppressor miRs implicated in carcinogenesis. METHODS: We studied DNA methylation of these miRs in Philadelphia-negative (Ph-ve) myeloproliferative neoplasms (MPNs). Methylation-specific PCR (MSP), verified by direct sequencing of the methylated MSP products, was performed in cell lines, normal controls and diagnostic marrow samples of patients with MPNs. RESULTS: Methylation of these miRs was absent in the normal controls. miR-34b/c were homozygously methylated in HEL cells but heterozygously in MEG-01. In HEL cells, homozygous miR-34b/c methylation was associated with miR silencing, and 5-aza-2'-deoxycytidine treatment led to re-expression of both miR-34b and miR-34c, consistent with that both miRs are under the regulation of the same promoter CpG island. miR-34a was heterozygously methylated in MEG-01 and K-562. miR-203 was completely unmethylated in K-562 and SET-2 but no MSP amplification was found in both HEL and MEG-01, suggestive of miR deletion. In primary samples, four each had miR-34b/c and -203 methylation, in which two had concomitant methylation of miR-34b/c and -203. miR-34a was methylated in one patient and none had methylation of miR-124-1. Seven patients (15.6%) had methylation of at least one of the four miRs. miR methylation did not correlate with clinical parameters, disease complications or JAK2 V617F mutation. CONCLUSION: This is the first report of miR hypermethylation in MPNs. miR-203 hypermethylation is not specific to Ph+ve leukemias but also present in Ph-ve MPNs. miR-34b/c methylation was associated with reversible miR silencing. There was no correlation of miR methylation with clinical demographic data or outcome.published_or_final_versio

Non-gastric marginal zone B cell lymphoma: Clinicopathologic features and treatment results

The optimal treatment strategy and outcome of non-gastric marginal zone lymphoma (MZL) remains undefined. The role of rituximab and fludarabine in MZL has not been critically appraised and compared with conventional chemotherapy. We retrospectively analyzed 81 consecutive patients with non-gastric MZL (mucosa-associated lymphoid tissue lymphoma, n = 66; splenic MZL, n = 11; nodal MZL, n = 4). As a group, the treatment results were favorable, with an overall response rate of 87% and a complete response (CR) rate of 73%. The CR rate was similar for conventional chemotherapy, and rituximab- and fludarabine-containing regimens. However, the relapse rate was significantly decreased in rituximab- and fludarabine-containing regimens. The use of rituximab and fludarabine was associated with acceptable side effects. For splenic MZL, splenectomy was significantly associated with a superior CR rate. Early stage, good performance status, and low international prognostic index risk scores significantly impacted on CR rate and survivals. Rituximab and fludarabine were safe for non-gastric MZL and resulted in more durable remissions. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Non-myeloablative allogeneic peripheral stem cell transplantation for multiple myeloma

Objective. To present an institution's 2-year experience of non-myeloablative allogeneic stem cell transplantation among Chinese patients. Design. Retrospective study. Setting. Bone marrow transplantation unit at a university hospital, Hong Kong. Patients. Ten patients with multiple myeloma who received non-myeloablative allogeneic stem cell transplantation between March 2000 and October 2002. Intervention. Fludarabine (90 mg/m 2) and total body irradiation (300 cGy) were given as conditioning regimens, followed by non-myeloablative allogeneic stem cell transplantation. Main outcome measures. Engraftment, regimen-related toxicity, treatment-related mortality (in the first 100 days), incidence of graft-versus-host disease, chimerism, disease response, and survival rate. Results. All 10 patients had active disease before transplantation. The donors were eight human leukocyte antigen-matched siblings, a mismatched sibling, and a matched daughter. Satisfactory engraftment before day 21 was achieved without early treatment-related mortality. Five patients developed full donor chimerism by day 28 and three other patients had 100% donor chimerism by day 100. Acute graft-versus-host disease developed in six patients (five with grade III and one with grade IV disease), and chronic graft-versus-host disease developed in eight patients (four with extensive disease). Complete remission and partial response were achieved in three and four patients, respectively. Three patients did not respond to treatment, and one case of relapse was observed. Only one patient, who had shown a partial response, received donor lymphocyte infusion; seven patients received thalidomide for graft-versus-host disease with or without graft-versus-myeloma effect. All patients were alive after a median follow-up of 1 year. Conclusion. Non-myeloablative allogeneic stem cell transplantation for multiple myeloma is effective, has low toxicity, and results in low treatment-related mortality. Studies of more cases with longer follow-up durations are required.published_or_final_versio

Epigenetic inactivation of miR-9 family microRNAs in chronic lymphocytic leukemia--implications on constitutive activation of NFκB pathway

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Epigenetic inactivation of the miR-34a in hematological malignancies

miR-34a is a transcriptional target of p53 and implicated in carcinogenesis. We studied the role of miR-34a methylation in a panel of hematological malignancies including acute leukemia [acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL)], chronic leukemia [chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML)], multiple myeloma (MM) and non-Hodgkin's lymphoma (NHL). The methylation status of miR-34a promoter was studied in 12 cell lines and 188 diagnostic samples by methylation-specific polymerase chain reaction. miR-34a promoter was unmethylated in normal controls but methylated in 75% lymphoma and 37% myeloma cell lines. Hypomethylating treatment led to re-expression of pri-miR-34a transcript in lymphoma cells with homozygous miR-34a methylation. In primary samples at diagnosis, miR-34a methylation was detected in 4% CLL, 5.5% MM samples and 18.8% of NHL at diagnosis but none of ALL, AML and CML (P = 0.011). In MM patients with paired samples, miR-34a methylation status remained unchanged at progression. Amongst lymphoid malignancies, miR-34a was preferentially methylated in NHL (P = 0.018), in particular natural killer (NK)/T-cell lymphoma. In conclusion, amongst hematological malignancies, miR-34a methylation is preferentially hypermethylated in NHL, in particular NK/T-cell lymphoma, in a tumor-specific manner, therefore the role of miR-34a in lymphomagenesis warrants further study. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]