P15INK4B gene methylation and expression in normal, myelodysplastic, and acute myelogenous leukemia cells and in the marrow cells of cured lymphoma patients

Role of p15(INK4B) Methylation in Patients With Myelodysplastic Syndromes: A Systematic Meta-Analysis

BACKGROUND

Tumor suppressor gene cyclin-dependent kinase inhibitor 2B (p15(INK4B)) methylation has been frequently reported in myelodysplastic syndromes (MDS). However, the association between p15(INK4B) methylation and MDS remains elusive. Thus, this meta-analysis was first conducted to evaluate the clinical significance of p15(INK4B) methylation in MDS.

MATERIALS AND METHODS

Eligible studies were identified via an online electronic databases search. The overall odds ratios (ORs) or hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Twenty-eight studies published between 1997 and 2017 were identified, including 1205 MDS patients and 243 nontumor controls. No evidence of heterogeneity was found in our study. p15(INK4B) methylation was significantly elevated in MDS compared with nontumor controls (OR, 10.37; P < .001). In addition, p15(INK4B) methylation was significantly higher in advanced MDS than in early MDS (OR, 4.70; P < .001) and was linked to an unfavorable overall survival (multivariate analysis: HR, 1.78; 95% CI, 1.23-2.71). Subgroup analyses on the basis of ethnicity and detection method showed that the results remained significant in different subgroups (all Ps < .05).

CONCLUSION

Our findings suggest that p15(INK4B) methylation might play an important role in the development, progression, and poor prognosis of MDS. More prospective studies with larger study populations are needed.

p15Ink4b Loss of Expression by Promoter Hypermethylation Adds to Leukemogenesis and Confers a Poor Prognosis in Acute Promyelocytic Leukemia Patients

PURPOSE

The p15^Ink4b gene exerts its influence as an inhibitor of cyclin-dependent kinases and is frequently associated with hematological malignancies. Inactivation of this gene through DNA methylation has been found to be the most prevalent epigenetic alteration reported, with a high frequency in all French-American-British subtypes of acute myeloid leukemias, including acute promyelocytic leukemia (APL). In this study,we investigated the prognostic significance of p15 gene promoter hypermethylation and its expression in APL patients of Kashmir (North India).

MATERIALS AND METHODS

p15 gene promoter hypermethylation was conducted by methylation-specific polymerase chain reaction, while its subsequent expression analysiswas carried out by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Of the 37 patients, 16 (43.2%) were found to have methylated p15 genes. Of these 16 cases, seven (43.8%) were methylated partially and nine (56.2%) were found to have complete methylation. Moreover, nine of the 37 patients (24.3%) who presented with leukocytosis at their baseline had complete p15 gene methylation as well (p < 0.05). Semiquantitative RT-PCR showed a complete loss of p15 expression in nine patients with complete methylation coupled with leukocytosis (p=0.031), while seven patients with partial methylation showed decreased p15 expression. Six patients relapsed during the maintenance phase of treatment and were found to have a completely methylated p15 gene and no p15 mRNA.

CONCLUSION

Complete methylation and loss of p15 gene expression causes susceptibility to relapse and decreased survival in APL patients. Thus, p15 promoter hypermethylation is a prospective prognostic indicator and a reliable clinical aid in assessment of patients with APL.

Hypermethylation of p15 gene associated with an inferior poor long-term outcome in childhood acute lymphoblastic leukemia

PURPOSE

To quantitate methylation of the CpG island of the promoter region of the p15 gene in childhood acute lymphoblastic leukemia (ALL) and explore its effect on prognosis.

METHODS

We assessed methylation of the CpG island on the p15 gene in bone marrow mononuclear cells in 93 ALL cases and in a control group of 20 children with idiopathic thrombocytopenia (ITP) by restriction enzyme Eco52I digestion combined with polymerase chain reaction techniques. We explored the effect of varying levels of methylation on event-free survival (EFS).

RESULTS

The mean methylation level was 25 % in de novo ALL and significantly higher than the control group 2 %, P < 0.01). Forty-two percent of cases (39/93) had hypermethylation (level over 10 %). Fifty-seven percent (12/21) and 38 % (27/72) T- and precursor-B ALL patients had hypermethylation (not significant). For all patients, the 8-year EFS was (83 ± 4) %, standard risk (91 ± 4) %, intermediate risk (IR) (82 ± 5) %, and high risk (HR) (43 ± 19) % (χ(2) = 11.58, P < 0.01). Hypermethylation was associated with a lower 8-year EFS (71 ± 7 vs. 91 ± 4 %, P = 0.02) in univariate analyses.

CONCLUSIONS

Children with ALL have higher levels of p15 CpG island methylation than a control group of children with ITP. Among children with ALL, hypermethylation was associated with inferior EFS. Higher levels of p15 CpG island methylation may be a poor prognostic marker in childhood ALL.

tp53-dependent G2 arrest mediator candidate gene, Reprimo, is down-regulated by promoter hypermethylation in pediatric acute myeloid leukemia

Reprimo (RPRM) is a novel tumor suppressor. However, the expression and molecular function of RPRM in pediatric acute myeloid leukemia (AML) is still unknown. We observed hypermethylation of the RPRM promoter in 8/11 leukemia cell lines and in 44.8% (47/105) of pediatric AML samples compared with 6.7% (2/30) of control samples. Bisulfite genomic sequencing analysis showed that the RPRM promoter was methylated in the majority of AML samples (66.2-83.1%), whereas RPRM was almost unmethylated in normal bone marrow samples (20.0-27.7%). Kaplan-Meier survival analysis revealed poor survival outcomes in samples with RPRM promoter methylation (p < 0.001). Proliferation of AML cells was inhibited in a dose-dependent manner (p < 0.05) after RPRM overexpression with lentivirus transfection. Apoptosis was up-regulated in RPRM-overexpressing AML cells. Real-time polymerase chain reaction array analysis revealed 50 dysregulated genes that might be implicated in apoptosis of RPRM-induced AML cells. RPRM may be a putative tumor suppressor in pediatric AML.

Genomic impact of transient low-dose decitabine treatment on primary AML cells

Acute myeloid leukemia (AML) is characterized by dysregulated gene expression and abnormal patterns of DNA methylation; the relationship between these events is unclear. Many AML patients are now being treated with hypomethylating agents, such as decitabine (DAC), although the mechanisms by which it induces remissions remain unknown. The goal of this study was to use a novel stromal coculture assay that can expand primary AML cells to identify the immediate changes induced by DAC with a dose (100nM) that decreases total 5-methylcytosine content and reactivates imprinted genes (without causing myeloid differentiation, which would confound downstream genomic analyses). Using array-based technologies, we found that DAC treatment caused global hypomethylation in all samples (with a preference for regions with higher levels of baseline methylation), yet there was limited correlation between changes in methylation and gene expression. Moreover, the patterns of methylation and gene expression across the samples were primarily determined by the intrinsic properties of the primary cells, rather than DAC treatment. Although DAC induces hypomethylation, we could not identify canonical target genes that are altered by DAC in primary AML cells, suggesting that the mechanism of action of DAC is more complex than previously recognized.

Analyzing the gene expression profile of pediatric acute myeloid leukemia with real-time PCR arrays

Background

The Real-time PCR Array System is the ideal tool for analyzing the expression of a focused panel of genes. In this study, we will analyze the gene expression profile of pediatric acute myeloid leukemia with real-time PCR arrays.

Methods

Real-time PCR array was designed and tested firstly. Then gene expression profile of 11 pediatric AML and 10 normal controls was analyzed with real-time PCR arrays. We analyzed the expression data with MEV (Multi Experiment View) cluster software. Datasets representing genes with altered expression profile derived from cluster analyses were imported into the Ingenuity Pathway Analysis Tool.

Results

We designed and tested 88 real-time PCR primer pairs for a quantitative gene expression analysis of key genes involved in pediatric AML. The gene expression profile of pediatric AML is significantly different from normal control; there are 19 genes up-regulated and 25 genes down-regulated in pediatric AML. To investigate possible biological interactions of differently regulated genes, datasets representing genes with altered expression profile were imported into the Ingenuity Pathway Analysis Tool. The results revealed 12 significant networks. Of these networks, Cellular Development, Cellular Growth and Proliferation, Tumor Morphology was the highest rated network with 36 focus molecules and the significance score of 41. The IPA analysis also groups the differentially expressed genes into biological mechanisms that are related to hematological disease, cell death, cell growth and hematological system development. In the top canonical pathways, p53 and Huntington’s disease signaling came out to be the top two most significant pathways with a p value of 1.5E-8 and2.95E-7, respectively.

Conclusions

The present study demonstrates the gene expression profile of pediatric AML is significantly different from normal control; there are 19 genes up-regulated and 25 genes down-regulated in pediatric AML. We found some genes dyes-regulated in pediatric AML for the first time as FASLG, HDAC4, HDAC7 and some HOX family genes. IPA analysis showed the top important pathways for pediatric AML are p53 and Huntington’s disease signaling. This work may provide new clues of molecular mechanism in pediatric AML.

Reexpression of epigenetically silenced AML tumor suppressor genes by SUV39H1 inhibition

Reexpression of hypermethylated tumor suppressor genes using DNA methyltransferase (DNMT) and histone deacetylase inhibitors occurs by a mechanism whereby promoter demethylation is the dominant event. In support of this model, we found in acute myeloid leukemia cells with hypermethylated p15INK4B and E-cadherin promoters that the DNMT inhibitor, 5-aza-2'-deoxycytidine, induced p15INK4B and E-cadherin expression, and decreased levels of DNA methylation, histone H3 lysine 9 (H3K9) methylation and SUV39H1 associated with p15INK4B and E-cadherin promoters. On the basis of these observations, we examined whether promoter demethylation was dominant to H3K9 demethylation in p15INK4B and E-cadherin reexpression. We observed that SUV39H1 short hairpin RNA and chaetocin, a SUV39H1 inhibitor, induced p15INK4B and E-cadherin expression and H3K9 demethylation without promoter demethylation. Reexpression of hypermethylated p15INK4B and E-cadherin required histone H3K9 demethylation that was achieved directly by inhibiting SUV39H1 expression or activity, or indirectly by decreasing the amount of SUV39H1 associated with the p15INK4B and E-cadherin promoters using 5-aza-2'-deoxycytidine. The results from this study highlight the potential of H3K9 methyltransferases as therapeutic targets for reactivating expression of hypermethylated genes.

Analysis of histone modification around the CpG island region of the p15 gene in acute myeloblastic leukemia

Seven of 11 patients with acute myeloblastic leukemia (AML) had allele(s) in which more than half of 27 CpG sites in the p15 gene were methylated. The p15 CpG island region was surrounded with both the acetylated histone H3 (AcH3) and dimethylated histone H3-lysine 9 (MeH3K9) in bone marrow cells of AML patients, whereas with AcH3 alone in normal marrow cells. The p15 CpG islands of DNA immunoprecipitated with anti-AcH3 antibody and anti-MeH3K9 antibody were not always unmethylated and methylated, respectively, in the patients. These results suggest perturbed modifications of histone H3 around the p15 CpG island region in AML.

DNA Methylation of Tumor Suppressor Genes in Clinical Remission Predicts the Relapse Risk in Acute Myeloid Leukemia

Epigenetic changes play an important role in leukemia pathogenesis. DNA methylation is among the most common alterations in leukemia. The potential role of DNA methylation as a biomarker in leukemia is unknown. In addition, the lack of molecular markers precludes minimal residual disease (MRD) estimation for most patients with hematologic malignancies. We analyzed the potential of aberrant DNA promoter methylation as a biomarker for MRD in acute leukemias. Quantitative real-time PCR methods with bisulfite-modified DNA were established to quantify MRD based on estrogen receptor alpha (ERalpha) and/or p15(INK4B) methylation. Methylation analyses were done in >370 DNA specimens from 180 acute leukemia patients and controls. Methylation of ERalpha and/or p15(INK4B) occurred frequently and specifically in acute leukemia but not in healthy controls or in nonmalignant hematologic diseases. Aberrant DNA methylation was detectable in >20% of leukemia patients during clinical remission. In pediatric acute lymphoblastic leukemia, methylation levels during clinical remission correlated closely with T-cell receptor/immunoglobulin MRD levels (r = +0.7, P < 0.01) and were associated with subsequent relapse. In acute myelogenous leukemia patients in clinical remission, increased methylation levels were associated with a high relapse risk and significantly reduced relapse-free survival (P = 0.003). Many patients with acute leukemia in clinical remission harbor increased levels of aberrant DNA methylation. Analysis of methylation MRD might be used as a novel biomarker for leukemia patients' relapse risk.

Epigenetics and chronic lymphocytic leukemia

The DNA methylation level in patients with chronic lymphocytic leukemia is generally lower than healthy individuals. Although DNA methylation is globally decreased, regional hypermethylation of gene promoters leads to gene silencing. Many of these genes have tumor suppressor phenotypes. Unlike mutations or deletions, hypermethylation is potentially reversible after inhibition with DNA methylation modulators. Myelodysplastic syndrome has been a model disease in which treatment of patients results in demethylation of specific genes. The story in patients with chronic lymphocytic leukemia is slowly unraveling as epigenetic modifications likely also play an important role. Ongoing clinical trials correlating clinical response to gene expression after treatment with DNA methylation inhibitors will ultimately allow us to better risk stratify and predict the subgroup of patients who will benefit from treatment with this class of drugs.

Management of patients with higher risk myelodysplastic syndromes

Higher risk myelodysplastic syndromes (MDS) include patients in the Intermediate-2 and high-risk categories of the International Prognostic Scoring System, as well as patients with MDS secondary to radiation or chemical exposure. Ideally, the goal of therapy is to alter the natural history of disease in these patients to achieve cure or durable remission. High-intensity chemotherapy can achieve moderate rates of complete remission, however, durability of remission and overall survival tend to be short. Hematopoietic stem cell transplantation (HSCT) offers the possibility of cure, with long-term disease-free survival inversely related to age. Patients who are elderly or have poor functional status are candidates for reduced intensity HSCT, although this is still an experimental modality. Azacitidine is a hypomethylating agent that is a reasonable option for many patients ineligible for high-intensity therapies. Other therapies, such as immunomodulatory agents, arsenic trioxide, and farnesyl transferase inhibitors have thus far shown limited usefulness in higher risk MDS. This paper reviews the various therapeutic options for higher risk MDS, providing rationale for specific management approaches for these patients.

Absence of p16 and p27 gene rearrangements and mutations in de novo myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a group of clonal hematopoietic disorders characterized by dyshemopoiesis and frequent evolution to acute leukemia. Tumor suppressor gene inactivation may be involved in MDS pathogenesis. The two families of cyclin-dependent kinase inhibitors (CDKIs) (INK4 family of p15, p16, p18 and p19 and CIP/KIP family of p21, p27 and p57) that negatively regulate cell cycle progression are known tumor suppressor genes. To determine whether genetic alterations of p16 and p27 genes play an important role in MDS pathogenesis, we examined DNA from 51 patients classified as 17 refractory anemias (RA), four refractory anemias with ringed sideroblasts (RARS), 19 refractory anemias with an excess of blasts (RAEB), 5 refractory anemias with excess of blasts in transformation (RAEB-t) and 6 chronic myelomonocytic leukemias (CMML). Southern blot analysis detected no homozygous deletions of p16 and p27. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequencing did not reveal point mutations for both genes with the exception of two allelic polymorphisms, namely a C --> G transition at 447 bp of p16exon3 and a T --> A transition at 791 bp of p27exon1 genes. Our results suggest that mutations of p16 and p27 genes resulting in abnormal p16 and p27 proteins do not represent a mechanism of gene inactivation involved in the pathogenesis of MDS.

Distinct methylation patterns of benign and malignant liver tumors revealed by quantitative methylation profiling

PURPOSE

A comparative quantitative methylation profiling of hepatocellular carcinoma and the most frequent benign liver tumor, hepatocellular adenoma, was set up for the identification of tumor-specific methylation patterns.

EXPERIMENTAL DESIGN

The quantitative methylation levels of nine genes (RASSF1A, cyclinD2, p16INK4a, DAP-K, APC, RIZ-1, HIN-1, GSTpi1, SOCS-1) were analyzed in hepatocellular carcinoma and adjacent normal tissue (n = 41), hepatocellular adenoma and adjacent normal tissue (n = 26), focal nodular hyperplasia (n = 10), and unrelated normal liver tissue (n = 28). Accumulated methylation data were analyzed using various statistical algorithms, including hierarchical clustering, to detect tumor-specific methylation patterns.

RESULTS

Cluster analysis revealed that hepatocellular adenoma displays a methylation profile much more similar to that found in normal liver tissue and focal nodular hyperplasia than to that found in hepatocellular carcinoma. Many characteristic differences were not detected when using mere qualitative methylation assays. The cyclinD2 gene was identified as a new and frequent target for aberrant hypermethylation in hepatocellular carcinoma (68%). In the control group of 28 liver specimens from healthy donors, a clear correlation between age of patient and frequency and level of aberrant methylation was seen, which could not be detected in the group of hepatocellular carcinoma specimens.

CONCLUSIONS

Methylation profiling can clearly contribute to the unequivocal classification of suspicious lesions, but only if done in a quantitative manner applying cell type and gene-specific thresholds. In hepatocellular carcinoma, the altered methylation patterns accompanying malignant transformation override the age-dependent increase in gene methylation.

Genetic testing in the myelodysplastic syndromes: molecular insights into hematologic diversity

The myelodysplastic syndromes (MDS) are associated with a diverse set of acquired somatic genetic abnormalities. Bone marrow karyotyping provides important diagnostic and prognostic information and should be attempted in all patients who are suspected of having MDS. Fluorescent in situ hybridization (FISH) studies on blood or marrow may also be valuable in selected cases, such as patients who may have 5q- syndrome or those who have undergone hematopoletic stem cell transplantation. The MDS-associated cytogenetic abnormalities that have been defined by karyotyping and FISH studies have already contributed substantially to our current understanding of the biology of malignant myeloid disorders, but the pathobiological meaning of common, recurrent chromosomal lesions such as del(5q), del(20q), and monosomy 7 is still unknown. The great diversity of the cytogenetic findings described in MDS highlights the molecular heterogeneity of this cluster of diseases. We review the common and pathophysiologically interesting genetic abnormalities associated with MDS, focusing on the clinical utility of conventional cytogenetic assays and selected FISH studies. In addition, we discuss a series of well-defined MDS-associated point mutations and outline the potential for further insights from newer techniques such as global gene expression profiling and array-based comparative genomic hybridization.

Methylation status of the p15 and p16 genes in paediatric myelodysplastic syndrome and juvenile myelomonocytic leukaemia

Aberrant DNA methylation is frequently observed in adults with myelodysplastic syndrome (MDS), and is recognized as a critical event in the disease's pathogenesis and progression. This is the first report to investigate the methylation status of p15 and p16, cell cycle regulatory genes, in children with MDS (n = 9) and juvenile myelomonocytic leukaemia (JMML; n = 18) by using a methylation-specific polymerase chain reaction. The frequency of p15 hypermethylation in paediatric MDS was 78% (7/9), which was comparable to that in adult MDS. In contrast, p15 hypermethylation in JMML was a rare event (17%; 3/18). In JMML, clinical and laboratory characteristics including PTPN11 mutations and aberrant colony formation were not different between the three patients with hypermethylated p15 and the others. Aberrant methylation of p16 was not detected in children with either MDS or JMML. Since p15 and p16 genes were unmethylated in two children with JMML, in whom the disease had progressed with an increased number of blasts, a condition referred to as blastic crisis, we infer that the aberrant methylation of these genes is not responsible for the progression of JMML. The results suggest that demethylating agents may be effective in most children with MDS and a few patients with JMML.

Epigenetic Inactivation of Tumor Suppressor Genes in Hematologic Malignancies

A number of genetic alterations are involved in the development of hematologic malignancies. These alterations include the activation of oncogenes by chromosomal translocation or gene amplification and the inactivation of tumor suppressor genes by gene deletion or mutations. Recently, epigenetic change has been proven to be another important means of inactivating tumor suppressor genes in tumor cells, and hypermethylation of promoter DNA is one of the most important mechanisms. In hematologic malignancies, many kinds of tumor suppressor genes and candidate suppressor genes are epigenetically inactivated. Inactivation of tumor suppressor genes usually occurs in a disease-specific manner and plays important roles in the development and progression of the disease. Some of these alterations have clinical effects on treatment results or the prognoses of the patients.

Epigenetic targets in hematopoietic malignancies

Frequent genetic alterations in hematopoietic neoplasias (chromosomal translocations, point mutations, etc.) have provided biologic targets for the development of effective novel therapies. A rapidly increasing body of knowledge provides evidence also for multiple epigenetic alterations in these disorders, which can complement or even precede genetic aberrations. Gene inactivation ('silencing') of tumor suppressor and growth inhibitory genes (e.g. the cyclin-dependent kinase inhibitors p16, p15, p21) is frequently mediated by DNA methylation of gene promoters. The acetylation state of histones (functionally linked to the DNA methylation state by the methylcytosine binding protein 2, recruiting histone deacetylases) provides a second major epigenetic silencing mechanism. Therapeutic reversal strategies are being developed for acute leukemias, myelodysplastic syndromes and malignant lymphomas. Since the discovery of the DNA methyltransferase (Dnmt) inhibitory activity of two azanucleosides (5-azacytidine, 5-aza-2'-deoxycytidine/decitabine) even at doses with minimal nonhematologic toxicity, both have been clinically studied in several myeloid neoplasias, particularly in elderly patients unable to tolerate aggressive treatment. Further development of agents counteracting aberrant methylation is directed at more targeted approaches, for example, antisense molecules against Dnmts. Histone deacetylases (HDACs) can be inhibited by numerous compounds (sodium phenylbutyrate, valproic acid, novel compounds such as depsipeptide), which have entered the clinical arena in similar indications as Dnmt inhibitors. Impressive effects of HDAC inhibition in acute promyelocytic leukemia models (PML/RARA expression) translate the finding of HDAC recruitment by this chimeric transcription factor to its target genes. The recent discovery of recruitment by PML/RARA also of Dnmt activity to the retinoic acid receptor-beta promoter makes it an interesting candidate for Dnmt inhibitors. Studies combining a 're-expressor' strategy with inhibitors of Dnmts and HDACs are underway. Thus, resensitization to biological agents such as retinoids, colony-stimulating factors and other differentiation inducers may be envisioned.

Methylation of p15INK4B is common, is associated with deletion of genes on chromosome arm 7q and predicts a poor prognosis in therapy-related myelodysplasia and acute myeloid leukemia

The p14(ARF), p15(INK4B), and p16(INK4A) genes are important negative cell-cycle regulators often inactivated by deletions, mutations, or hypermethylation in malignancy. Hypermethylation of the three genes was studied in 81 patients with therapy-related myelodysplasia (t-MDS) or acute myeloid leukemia (t-AML) by methylation-specific PCR, and p15 methylation additionally by bisulfite genomic sequencing. In all, 55 patients disclosed p15 methylation, five patients showed p16 methylation, whereas p14 methylation was not observed. Methylation of p15 was closely associated with deletion or loss of chromosome arm 7q (P=0.0006). In t-MDS, the p15 methylation frequency and the p15 methylation density both increased significantly by stage (P=0.004 and 0.0002), and p15 methylation frequency increased with an increasing percentage of myeloblasts in the bone marrow (P=0.006). In a two-variable Cox model including the percentage of myeloblasts, p15 methylation was an independent prognostic factor (P=0.005). Methylation of p15 was less common in t-AML of subtype M5 than in other FAB subtypes (P=0.03). Methylation of p15 was unrelated to type of previous therapy, to latent period from start of therapy, to platelet count, and to p53 mutations. Inactivation of p15 and deletion of genes on chromosome arm 7q possibly cooperate in leukemogenesis.

Aberrant methylation and impaired expression of the p15(INK4b) cell cycle regulatory gene in chronic myelomonocytic leukemia (CMML)

The important cell cycle regulatory gene p15(INK4b) has been shown to be inactivated in acute myeloid leukemia and myelodysplastic syndrome. Little is known about the expression and epigenetic modification of this gene in chronic myelomonocytic leukemia (CMML) that belongs to the myelodysplastic/myeloproliferative disorders (MDS/MPD) with a high proportion of blastic transformation. Analysis of bone marrow trephines in a series of 33 CMML cases showed an aberrant p15(INK4b) gene methylation in up to 58% of cases. Methylation was analyzed employing different methylation-specific PCR and genomic sequencing protocols. It turned out to be spread over a broad area of the 5' region and exhibited substantial heterogeneity between cases and even in individual patients. The degree of aberrant methylation was correlated with a reduced mRNA as well as reduced protein expression, and was associated with a higher expression of DNA methyltransferase DNMT 3A. We conclude that aberrant gene methylation is a frequent event in CMML that might contribute to the pathogenesis of this MDS/MPD.

Hypermethylation of GpG islands in the promoter region of p15(INK4b) in acute promyelocytic leukemia represses p15(INK4b) expression and correlates with poor prognosis

We evaluated the methylation status of p15 gene in a series of 65 patients with newly diagnosed acute promyelocytic leukemia (APL) receiving homogeneous treatment. Moreover, in 32 of them, the methylation status of p15 gene was correlated to the p15 m-RNA expression. In total, 31 patients had no p15 methylation (U group). An abnormal methylation pattern was found in 34 patients: in seven of these patients only methylated DNA was detected (M group), while in the remaining 27 patients (M/U group), both methylated and unmethylated DNA were amplified. Patients from M group showed a higher incidence of relapses and a lower disease-free survival (DSF) with respect to patients from U and M/U groups (29, 64 and 79% at 5 years for M, U/M and U patients, respectively, P=0.03), while p15 methylation had no impact on overall survival. The p15 expression was detectable in all patients with unmethylated DNA, in none of patients with fully methylated DNA and in 60% of patients with partially methylated DNA. The DFS estimate at 5 years for p15-negative patients was significantly lower than that of p15-positive patients (P=0.03). These data confirm that the presence of p15 methylation negatively influences the prognosis of APL, mainly when it represses the p15 gene transcription.

Characterization of gene expression of CD34+ cells from normal and myelodysplastic bone marrow

Gene patterns of expression in purified CD34(+) bone marrow cells from 7 patients with low-risk myelodysplastic syndrome (MDS) and 4 patients with high-risk MDS were compared with expression data from CD34(+) bone marrow cells from 4 healthy control subjects. CD34(+) cells were isolated by magnetic cell separation, and high-density oligonucleotide microarray analysis was performed. For confirmation, the expression of selected genes was analyzed by real-time polymerase chain reaction. Class membership prediction analysis selected 11 genes. Using the expression profile of these genes, we were able to discriminate patients with low-risk from patients with high-risk MDS and both patient groups from the control group by hierarchical clustering (Spearman confidence). The power of these 11 genes was verified by applying the algorithm to an unknown test set containing expression data from 8 additional patients with MDS (3 at low risk, 5 at high risk). Patients at low risk could be distinguished from those at high risk by clustering analysis. In low-risk MDS, we found that the retinoic-acid-induced gene (RAI3), the radiation-inducible, immediate-early response gene (IEX1), and the stress-induced phosphoprotein 1 (STIP1) were down-regulated. These data suggest that CD34(+) cells from patients with low-risk MDS lack defensive proteins, resulting in their susceptibility to cell damage. In summary, we propose that gene expression profiling may have clinical relevance for risk evaluation in MDS at the time of initial diagnosis. Furthermore, this study provides evidence that in MDS, hematopoietic stem cells accumulate defects that prevent normal hematopoiesis.

Effect of etafenone on total and regional myocardial blood flow

The distribution of blood flow to the subendocardial, medium and subepicardial layers of the left ventricular free wall was studied in anaesthetized dogs under normoxic (A), hypoxic (B) conditions and under pharmacologically induced (etafenone) coronary vasodilation (C). Regional myocardial blood flow was determined by means of the particle distribution method. In normoxia a transmural gradient of flow was observed, with the subendocardial layers receiving a significantly higher flow rate compared with the subepicardial layers. In hypoxia induced vasodilation this transmural gradient of flow was persistent. In contrast a marked redistribution of regional flow was observed under pharmacologically induced vasodilation. The transmural gradient decreased. In contrast to some findings these experiments demonstrate that a considerable vasodilatory capacity exists in all layers of the myocardium and can be utilized by drugs. The differences observed for the intramural distribution pattern of flow under hypoxia and drug induced vasodilation support the hypothesis that this pattern reflects corresponding gradients of regional myocardial metabolism.