Epigenetic changes in therapy-related MDS/AML

Epigenetic signature of ionizing radiation in therapy-related AML patients

Therapy-related acute myeloid leukaemia (t-AML) is a late side effect of previous chemotherapy (ct-AML) and/or radiotherapy (rt-AML) or immunosuppressive treatment. t-AMLs, which account for ∼10-20 % of all AML cases, are extremely aggressive and have a poor prognosis compared to de novo AML. Our hypothesis is that exposure to radiation causes genome-wide epigenetic changes in rt-AML. An epigenome-wide association study was undertaken, measuring over 850K methylation sites across the genome from fifteen donors (five healthy, five de novo, and five t-AMLs). The study predominantly focussed on 94K sites that lie in CpG-rich gene promoter regions. Genome-wide hypomethylation was discovered in AML, primarily in intergenic regions. Additionally, genes specific to AML were identified with promoter hypermethylation. A two-step validation was conducted, both internally, using pyrosequencing to measure methylation levels in specific regions across fifteen primary samples, and externally, with an additional eight AML samples. We demonstrated that the MEST and GATA5 gene promoters, which were previously identified as tumour suppressors, were noticeably hypermethylated in rt-AML, as opposed to other subtypes of AML and control samples. These may indicate the epigenetic involvement in the development of rt-AML at the molecular level and could serve as potential targets for drug therapy in rt-AML.

A retrospective validation of the IPSS-M molecular score in primary and therapy-related myelodysplastic syndromes (MDS)

A molecular scoring system (IPSS-M) was recently proposed for myelodysplastic syndrome (MDS). We conducted a retrospective study of adults with MDS referred 2019-2021. The primary outcomes were leukemia-free survival (LFS) and overall survival (OS). One hundred and forty-four patients diagnosed between 2011 and 2021 were analyzed. After IPSS-M re-stratification, 33% of patients were up-staged and 11% down-staged. Median follow-up was 2.8 years and 53 patients died (37%). Cumulative incidence of acute myeloid leukemia (AML) transformation was 20% at 3 years post-diagnosis. International Prognostic Scoring System (IPSS), revised version (IPSS-R) was significantly associated with LFS (log-rank p = 9.2e-05; 'very high' vs. 'low' risk HR = 3.85, p = 5.8e-04) and OS (log-rank p = 7.2e-06; 'very high' vs. 'low' HR = 5.09, p = 1.7e-04). IPSS-M was also a significant predictor of LFS (log-rank p = 1.1e-06; 'very high' vs. 'low' HR = 4.97, p = 2.2e-05) and OS (log-rank p = 4.8e-07; 'very high' vs. 'low' HR = 6.42, p = 2.5e-05) while providing better discrimination than IPSS-R for both outcomes. This mutation-incorporating prognostic index has greater discriminative potential than IPSS-R to predict AML transformation and any-cause mortality.

SPAG6-silencing enhances decitabine-induced apoptosis and demethylation of PTEN in SKM-1 cells and in a xenograft mouse model

Myelodysplastic syndromes (MDS) are a group of malignant diseases that are characterized by disordered hematopoiesis with a high risk of transforming into leukemia. In the present study, SPAG6-knockdown and decitabine (DAC) treatment resulted in a decreased DNA methyltransferases and methyl-CpG-binding domain protein expression. In addition, DAC and LBH589 were shown to promote apoptosis in SKM-1 cells, and SPAG6-knockdown to enhance the pro-apoptotic effect of DAC. DAC could reduce PTEN methylation and increase PTEN expression in SKM-1 cells. SPAG6-knockdown and LBH589 treatment could increase DAC-mediated demethylation of PTEN promoter. Finally, a mouse model was constructed, and an enhanced efficacy of DAC following SPAG6-knockdown was confirmed in vivo. In conclusion, DAC-mediated apoptosis and PTEN promoter demethylation may be synergistically enhanced by SPAG6-silencing. Therefore, in the present study it was indicated that SPAG6 may be a potential target for demethylation therapy in MDS.

A non-viral nano-delivery system targeting epigenetic methyltransferase EZH2 for precise acute myeloid leukemia therapy

Acute myeloid leukemia (AML), which is common in the elderly population, accounts for poor long-term survival with a high possibility of relapse. The associated lack of currently developed therapeutics is directing the search for new therapeutic targets relating to AML. EZH2 (Enhancer of Zeste Homolog 2) is a histone methyltransferase member of the polycomb-group (PcG) family, and its significant overexpression in AML means it has emerged as a potential epigenetic target. Here, we propose the human serum albumin (HSA) nanoparticle based delivery of small interfering RNA (siRNA), which can target EZH2-expressing genes in AML. EZH2 specific siRNA loaded in a polyethyleneimine (PEI) conjugated HSA nanocarrier can overcome the systemic instability of siRNA and precisely target the AML cell population for increased EZH2 gene silencing. A stable nanosized complex (HSANPs-PEI@EZH2siRNA), achieved via the electrostatic interaction of PEI and EZH2 siRNA, shows increased systemic stability and hemocompatibility, and enhanced EZH2 gene silencing activity in vitro, compared to conventional transfection reagents. HSANPs-PEI@EZH2siRNA-treated AML cells showed downregulated EZH2, which is associated with a reduced level of Bmi-1 protein, and H3K27me3 and H2AK119ub modification. The ubiquitin-mediated proteasomal degradation pathway plays a critical role in the downregulation of associated proteins following HSANPs-PEI@EZH2siRNA exposure to AML cells. c-Myb is the AML-responsive transcription factor that directly binds on the EZH2 promoter and was downregulated in HSANPs-PEI@EZH2siRNA-treated AML cells. The systemic exposure to HSANPs-PEI@EZH2siRNA of AML engrafted immunodeficient nude mice displayed efficient EZH2 gene silencing and a reduced AML cell population in peripheral blood and bone marrow. The present study demonstrates a non-viral siRNA delivery system for epigenetic targeting based superior anti-leukemic therapy.

Utility of 5-Methylcytosine Immunohistochemical Staining to Assess Global DNA Methylation and Its Prognostic Impact in MDS Patients

Background:

DNA methylation plays a vital role in the pathogenesis of the myelodysplastic syndrome (MDS), a heterogeneous group of clonal hematopoietic stem cell (HSC) disorders. It is reported to be an independent prognostic factor affecting overall survival (OS). Our aim was to analyze the role of global DNA methylation using an anti-5-methylcytosine (5-MC) antibody by immunohistochemistry (IHC) of bone marrow biopsy (BM Bx) specimens in MDS patients, assessing correlations with various clinical and biological prognostic factors.

Material and methods:

A total of 59 MDS cases, classified as per the World Health Organization (WHO) 2008 guidelines, were evaluated over a period of 4 years. Clinical data were retrieved from departmental case records and anti-5-MC expression was analyzed with formalin fixed paraffin embedded sections of BM Bx specimens of MDS patients and controls.

Results:

The median age at diagnosis was 52 years (15-85years). Patients were categorized into low risk (59%) and high risk (41%) according to International Prognostic Scoring System (IPSS). The median follow-up time was 10 months (1 to 37 months). We generated a methylation score (M-score) using anti-5-MC and with the derived cut-off of 30.5 from the receiver operator curve (ROC), there was a significant difference between the two groups in the percentage of BM blasts (p=0.01), WHO sub-type (p=0.01), IPSS (p=0.004), progression to AML (p=0.04) on univariate analysis. Interestingly, patients showing a high M-score (M-score ≥ 30.5) demonstrated a significantly shorter OS and progression to AML. However, on multivariate analysis, only BM blasts (p=0.01) and IPSS (p=0.02) remained independent variables for progression to AML and OS respectively.

Conclusion:

Immunostaining with anti-5-MC antibody with BM Bx samples is a simple and cost effective technique to detect global methylation, a powerful tool to predict overall survival in patients with MDS.

[Clinical characteristics and prognosis of 35 patients with therapy-related hematological neoplasms]

目的

探讨治疗相关血液肿瘤的临床特征及预后。

方法

采用细胞形态学、流式细胞术、间期荧光原位杂交技术（I-FISH）、染色体核型分析对35例治疗相关血液肿瘤患者进行诊断和分型并回顾性分析其临床特征及预后。

结果

35例患者中，治疗相关急性髓系白血病（t-AML）20例，治疗相关急性淋巴细胞白血病（t-ALL）4例，治疗相关急性混合细胞白血病1例，治疗相关非霍奇金淋巴瘤（t-NHL) 8例，治疗相关骨髓增生异常综合征（t-MDS）2例。第一肿瘤至治疗相关恶性血液肿瘤的中位发病间隔期为29(16~90）个月，中位生存时间14(1~60）个月，3年累积生存率为17.1%。在25例治疗相关性急性白血病患者中，40.0%（10/25）合并复杂核型，36.0%（9/25）合并MLL断裂基因重排，12.0%（3/25）合并AML-ETO融合基因阳性，1例合并NPM1点突变，1例合并P16基因缺失。

结论

治疗相关血液肿瘤患者的预后差。

TP53 mutation characteristics in therapy-related myelodysplastic syndromes and acute myeloid leukemia is similar to de novo diseases

Background

TP53 mutation is more prevalent in therapy-related myeloid neoplasms (t-MN) than their de novo counterparts; however, the pattern of mutations involving TP53 gene in t-MN versus de novo diseases is largely unknown.

Methods

We collected 108 consecutive patients with therapy-related myelodysplastic syndrome (t-MDS)/acute myeloid leukemia (t-AML). Clinical, hematological, and cytogenetic data were collected by searching the electronic medical record. TP53 sequencing was performed in all patients using a clinically validated next-generation sequencing-based gene panel assay. A previously published patient cohort consisting of 428 patients with de novo MDS/AML was included for comparison.

Results

We assessed 108 patients with t-MN, in which 40 patients (37%) had TP53 mutations. The mutation frequency was similar between t-MDS and t-AML; but significantly higher than de novo MDS/AML (62/428 patients, 14.5%) (p < 0.0001). TP53 mutations in t-MN were mainly clustered in DNA-binding domains, with an allelic frequency of 37.0% (range, 7.1 to 98.8). Most mutations involved single nucleotide changes, of which, transitions (65.9%) were more common than transversions (34.1%). Missense mutations were the most frequent, followed by frameshift and nonsense mutations. This TP53 mutation pattern was strikingly similar to that observed in de novo MDS/AML. TP53 mutations in t-MN were associated with a complex karyotype (p < 0.0001), a higher number of chromosomal abnormalities (p < 0.0001), and an inferior overall survival in affected patients (6.1 vs 14.1 months) by univariate (p < 0.0001) and multivariate analyses (p = 0.0020).

Conclusions

Our findings support the recent notion that heterozygous TP53 mutation may be a function of normal aging and that mutated cells are subject to selection upon exposure to cytotoxic therapy. t-MN carrying TP53 mutation have an aggressive clinical course independent of other confounding factors.

Rare Cytogenetic Abnormalities and Alteration of microRNAs in Acute Myeloid Leukemia and Response to Therapy

Acute myeloid leukemia (AML) is the most common acute leukemia in adults, which is heterogeneous in terms of morphological, cytogenetic and clinical features. Cytogenetic abnormalities, including karyotype aberrations, gene mutations and gene expression abnormalities are the most important diagnostic tools in diagnosis, classification and prognosis in acute myeloid leukemias. Based on World Health Organization (WHO) classification, acute myeloid leukemias can be divided to four groups. Due to the heterogeneous nature of AML and since most therapeutic protocols in AML are based on genetic alterations, gathering further information in the field of rare disorders as well as common cytogenetic abnormalities would be helpful in determining the prognosis and treatment in this group of diseases. Recently, the role of microRNAs (miRNAs) in both normal hematopoiesis and myeloid leukemic cell differentiation in myeloid lineage has been specified. miRNAs can be used instead of genes for AML diagnosis and classification in the future, and can also play a decisive role in the evaluation of relapse as well as response to treatment in the patients. Therefore, their use in clinical trials can affect treatment protocols and play a role in therapeutic strategies for these patients. In this review, we have examined rare cytogenetic abnormalities in different groups of acute myeloid leukemias according to WHO classification, and the role of miRNA expression in classification, diagnosis and response to treatment of these disorders has also been dealt with.

Mutational profiling of therapy-related myelodysplastic syndromes and acute myeloid leukemia by next generation sequencing, a comparison with de novo diseases

In this study we used a next generation sequencing-based approach to profile gene mutations in therapy-related myelodysplastic syndromes (t-MDS) and acute myeloid leukemia (t-AML); and compared these findings with de novo MDS/AML. Consecutive bone marrow samples of 498 patients, including 70 therapy-related (28 MDS and 42 AML) and 428 de novo (147 MDS and 281 AML) were analyzed using a modified-TruSeq Amplicon Cancer Panel (Illumina) covering mutation hotspots of 53 genes. Overall, mutation(s) were detected in 58.6% of t-MDS/AML and 56.8% of de novo MDS/AML. Of therapy-related cases, mutations were detected in 71.4% of t-AML versus 39.3% t-MDS (p=0.0127). TP53 was the most common mutated gene in t-MDS (35.7%) as well as t-AML (33.3%), significantly higher than de novo MDS (17.7%) (p=0.0410) and de novo AML (12.8%) (p=0.0020). t-AML showed more frequent PTPN11 but less NPM1 and FLT3 mutations than de novo AML. In summary, t-MDS/AML shows a mutation profile different from their de novo counterparts. TP53 mutations are highly and similarly prevalent in t-MDS and t-AML but mutations in genes other than TP53 were more frequent in t-AML than t-MDS. The molecular genetic profiling further expands our understanding in this group of clinically aggressive yet heterogeneous myeloid neoplasms.

-7/7q- syndrome in myeloid-lineage hematopoietic malignancies: attempts to understand this complex disease entity

The recurrence of chromosomal abnormalities in a specific subtype of cancer strongly suggests that dysregulated gene expression in the corresponding region has a critical role in disease pathogenesis. -7/7q-, defined as the entire loss of chromosome 7 and partial deletion of its long arm, is among the most frequently observed chromosomal aberrations in myeloid-lineage hematopoietic malignancies such as myelodysplastic syndrome and acute myeloid leukemia, particularly in patients treated with cytotoxic agents and/or irradiation. Tremendous efforts have been made to clarify the molecular mechanisms underlying the disease development, and several possible candidate genes have been cloned. However, the study is still underway, and the entire nature of this syndrome is not completely understood. In this review, we focus on the attempts to identify commonly deleted regions in patients with -7/7q-; isolate the candidate genes responsible for disease development, cooperative genes and the factors affecting disease prognosis; and determine effective and potent therapeutic approaches. We also refer to the possibility that the accumulation of multiple gene haploinsufficiency, rather than the loss of a single tumor suppressor gene, may contribute to the development of diseases with large chromosomal deletions such as -7/7q-.

Increased p16 DNA methylation in mouse thymic lymphoma induced by irradiation

DNA methylation is an important part of epigenetics. In this study, we examined the methylation state of two CpG islands in the promoter of the p16 gene in radiation-induced thymic lymphoma samples. The mRNA and protein levels of P16 were significantly reduced in radiation-induced thymic lymphoma tissue samples. Twenty-three CpG sites of the CpG islands in the p16 promoter region were detected, and the methylation percentages of −71, −63, −239, −29, −38, −40, −23, 46 CpG sites were significantly higher in radiation-induced thymic lymphoma tissue samples than those in matched non-irradiated thymus tissue samples. This study provides new evidence for the methylation state of p16 in the radiation-induced thymic lymphoma samples, which suggests that the methylation of these CpG sites in the p16 promoter may reduce its expression in the thymic lymphoma after irradiation.

The clinical importance of moderate/severe bone marrow fibrosis in patients with therapy-related myelodysplastic syndromes

The presence of moderate to severe bone marrow (BM) fibrosis has been shown to be an adverse feature in patients with primary myelodysplastic syndromes (MDS). However, the clinical importance of BM fibrosis is not clear in therapy-related MDS. We retrieved all therapy-related MDS (t-MDS) cases (n = 266) diagnosed at our hospital over a 10-year period (2003-2012). Reticulin and trichrome stains were performed in cases in which BM fibrosis was suspected on initial evaluation of hematoxylin and eosin-stained slide. BM fibrosis was graded according to European consensus guidelines, and a score of MF2/MF3 was defined as moderate/severe fibrosis. Moderate/severe BM fibrosis was found in 47 (17%) patients. Compared to 219 patients with no/mild BM fibrosis, the patients with moderate/severe fibrosis presented with severer thrombocytopenia (p = 0.039) and higher numbers of circulating blasts (p = 0.051) but with similar degrees of anemia and neutropenia, transfusion requirements, and similar incidences of hepatosplenomegaly and constitutional symptoms. Histological examination revealed a comparable BM cellularity and BM blast percentage, but markedly increased megakaryocytes (p < 0.001) in the fibrotic group. Although the risk distribution of cytogenetic data was similar according to the New Comprehensive Cytogenetic Scoring criteria, -5 and -17 were more frequently observed in t-MDS with moderate/severe BM fibrosis (p = 0.031 and p = 0.043, respectively). With a median follow-up of 11.5 months, patients with moderate/severe BM fibrosis showed a similar risk of acute myeloid leukemia transformation and a comparable overall survival in univariate and multivariate analyses. Moderate/severe BM fibrosis in patients with t-MDS is associated with certain clinicopathological and genetic features. However, unlike the situation in patients with primary MDS, moderate/severe BM fibrosis does not add additional risk to patients with therapy-related MDS.

Propofol induces DNA damage in mouse leukemic monocyte macrophage RAW264.7 cells

Propofol is one of the most widely clinically used intravenous anesthetic, and it induces apoptosis in human and murine leukemia cell lines. Yet, whether propofol causes DNA damage and affects the mRNA expression of repair-associated genes in cancer cells remains undetermined. In the present study, we investigated the effects of propofol on DNA damage and associated mRNA gene expression in RAW264.7 cells. Comet assay and DNA gel electrophoresis were used to evaluate DNA damage in RAW264.7 cells and propofol-inhibited cell growth in vitro. The results revealed a longer DNA tail and DNA fragmentation. Real-time PCR assay was used to examine mRNA gene expression of DNA damage and DNA repair-associated genes. Following exposure to propofol for 48 h, a decrease in the mRNA expression of DNA-PK, BRCA1, MGMT and p53 was noted in the RAW264.7 cells. Results from the western blotting indicated that p53, MGMT, 14-3-3-σ, BRCA1 and MDC1 proteins were decreased while p-p53 and p-H2A.X(S140) were increased in the RAW264.7 cells following exposure to propofol. In conclusion, exposure to propofol caused DNA damage and inhibited mRNA expression and protein levels of repair-associated genes in RAW264.7 cells.

Epigenetic aspects of MDS and its molecular targeted therapy

The term "epigenetics" refers to clonally inherited stable variability in gene expression without underlying genetic changes. There are two well-known molecular mechanisms for epigenetic information: DNA methylation and histone modifications. Epigenetic changes have been recognized in the past decade as critical factors for physiological phenomena such as embryogenesis and the differentiation of normal cells. There is recent interest regarding the involvement of aberrant DNA methylation and histone modifications in mediating altered physiology in cancer. MDS is characterized by epigenetic changes, mutations in epigenetic regulators, and response to DNA methylation inhibitors, suggesting that epigenetic changes are unique features of MDS patients. In this article, recent progress in the understanding of MDS epigenetics and epigenetics-based therapies is reviewed.

Involvement of p53 in the cytotoxic activity of the NAMPT inhibitor FK866 in myeloid leukemic cells

FK866 is a specific inhibitor of NAMPT and induces apoptosis of leukemic cells by depletion of intracellular NAD⁺. Since up-regulation of NAMPT is associated with several cases of cancers, including leukemias, we asked whether in leukemic cells inhibition of NAMPT involves p53 pathway. We observed that FK866 induced apoptosis and reduced cell proliferation in NB-4, OCI-AML3 and MOLM-13 cell lines. In contrast, the leukemia cell lines, K-562 and Kasumi, containing nonfunctional p53 were relatively unaffected by FK866 treatment. Importantly, direct inhibition of sirtuins significantly reduced the viability of NB-4, OCI-AML3 and MOLM-13 cell lines. Activation of p53 by FK866 involved increased acetylation of p53 at lysine 382 with subsequent increase in the expression of p21 and BAX. Further, knockdown of p53 attenuated the effects of FK866 on apoptosis and cell cycle arrest, which was partly associated with decreased expression of p21 and BAX. Our results suggest the role of p53 acetylation pathway in the anti-leukemic effect of FK866.

Outcome of therapy-related myeloid neoplasms treated with azacitidine

BACKGROUND

Therapy-related myeloid neoplasms (t-MN), including myelodysplastic syndromes and acute myeloid leukemia (t-MDS and t-AML) are associated to clinical and biologic unfavorable prognostic features, including high levels of DNA methylation.

METHODS

We retrospectively evaluated 50 t-MN patients (34 MDS and 16 AML) selected among all patients receiving azacitidine (AZA) at 10 Italian Hematology Centers. Patients had developed a t-MN at a median of 6.5 years (range 1.7- 29) after treatment of the primary tumor (hematological neoplasm, 27 patients; solid tumor, 23 patients).

RESULTS

The overall response rate was 42% (complete remission: 10 patients, partial remission: 2 and hematological improvement: 8 patients) and was obtained after a median of 3 cycles (range 1-6). Median overall survival (OS) was 21 months (range 1-53.6+) from AZA start. OS was significantly better in patients with less than 20% blasts, in normal karyotype t-AML and when AZA was used as front-line treatment. This was confirmed by the multivariate analysis.

CONCLUSIONS

This study reports efficacy of AZA in the largest series of therapy-related MN patients treated with 5-AZA. Our data show that blasts and karyotype maintain their important prognostic role in t-MN also in the azacitidine era.

Using bioinformatic approaches to identify pathways targeted by human leukemogens

We have applied bioinformatic approaches to identify pathways common to chemical leukemogens and to determine whether leukemogens could be distinguished from non-leukemogenic carcinogens. From all known and probable carcinogens classified by IARC and NTP, we identified 35 carcinogens that were associated with leukemia risk in human studies and 16 non-leukemogenic carcinogens. Using data on gene/protein targets available in the Comparative Toxicogenomics Database (CTD) for 29 of the leukemogens and 11 of the non-leukemogenic carcinogens, we analyzed for enrichment of all 250 human biochemical pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The top pathways targeted by the leukemogens included metabolism of xenobiotics by cytochrome P450, glutathione metabolism, neurotrophin signaling pathway, apoptosis, MAPK signaling, Toll-like receptor signaling and various cancer pathways. The 29 leukemogens formed 18 distinct clusters comprising 1 to 3 chemicals that did not correlate with known mechanism of action or with structural similarity as determined by 2D Tanimoto coefficients in the PubChem database. Unsupervised clustering and one-class support vector machines, based on the pathway data, were unable to distinguish the 29 leukemogens from 11 non-leukemogenic known and probable IARC carcinogens. However, using two-class random forests to estimate leukemogen and non-leukemogen patterns, we estimated a 76% chance of distinguishing a random leukemogen/non-leukemogen pair from each other.

Epigenetic mechanisms in tumorigenesis, tumor cell heterogeneity and drug resistance

Resistance of cancer cells to chemotherapeutics and emerging targeted drugs is a devastating problem in the treatment of cancer patients. Multiple mechanisms contribute to drug resistance such as increased drug efflux, altered drug metabolism, secondary mutations in drug targets, and activation of downstream or parallel signal transduction pathways. The rapid kinetics, the reversibility of acquired drug resistance and the absence of genetic mutations suggest an epigenetic basis for drug insensitivity. Similar to the cellular variance seen in the human body, epigenetic mechanisms, through reversible histone modifications and DNA methylation patterns, generate a variety of transcriptional states resulting in a dynamic heterogeneous tumor cell population. Consequently, epigenomes favoring survival in the presence of a drug by aberrant transcription of drug transporters, DNA-repair enzymes and pro-apoptotic factors render cytotoxic and targeted drugs ineffective and allow selection of rare drug-resistant tumor cells. Recent advances in charting cancer genomes indeed strongly indicate a role for epigenetic regulators in driving cancer, which may result in the acquisition of additional (epi)genetic modifications leading to drug resistance. These observations have important clinical consequences as they provide an opportunity for "epigenetic drugs" to change reversible drug-resistance-associated epigenomes to prevent or reverse non-responsiveness to anti-cancer drugs.

The co-presence of deletion 7q, 20q and inversion 16 in therapy-related acute myeloid leukemia developed secondary to treatment of breast cancer with cyclophosphamide, doxorubicin, and radiotherapy: a case report

Introduction

Therapy-related acute myeloid leukemia occurs as a complication of treatment with chemotherapy, radiotherapy, immunosuppressive agents or exposure to environmental carcinogens.

Case presentation

We report a case of therapy-related acute myeloid leukemia in a 37-year-old Turkish woman in complete remission from breast cancer. Our patient presented to our facility with fatigue, fever, sore throat, peripheral lymphadenopathy, and moderate hepatosplenomegaly. On peripheral blood and bone marrow aspirate smears, monoblasts were present. Immunophenotypic analysis of the bone marrow showed expression of CD11b, CD13, CD14, CD15, CD33, CD34, CD45 and human leukocyte antigen-DR, findings compatible with the diagnosis of acute monoblastic leukemia (French-American-British classification M5a). Therapy-related acute myeloid leukemia developed three years after adjuvant chemotherapy consisting of an alkylating agent, cyclophosphamide and DNA topoisomerase II inhibitor, doxorubicin and adjuvant radiotherapy. Cytogenetic analysis revealed a 46, XX, deletion 7 (q22q34), deletion 20 (q11.2q13.1) karyotype in five out of 20 metaphases and inversion 16 was detected by fluorescence in situhybridization. There was no response to chemotherapy (cytarabine and idarubicin, FLAG-IDA protocol, azacitidine) and our patient died in the 11th month after diagnosis.

Conclusions

The median survival in therapy-related acute myeloid leukemia is shorter compared to de novoacute myeloid leukemia. Also, the response to therapy is poor. In therapy-related acute myeloid leukemia, complex karyotypes have been associated with abnormalities of chromosome 5, rather than 7. To the best of our knowledge, this is the first case of therapy-related acute myeloid leukemia showing the co-presence of deletion 7q, 20q and the inversion 16 signal.

Similarities and differences between therapy-related and elderly acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal disorder of the hematopoietic stem cell, typical of the elderly, with a median age of over 60 years at diagnosis. In AML, older age is one of the strongest independent adverse prognostic factor, associated with decreased complete response rate, worse disease-free and overall survival, with highest rates of treatment related mortality, resistant disease and relapse, compared to younger patients. Outcomes are compromised in older patients not only by increased comorbidities and susceptibility to toxicity from therapy, but it is now recognized that elderly AML has peculiar biologic characteristics with a negative impact on treatment response.

In older individuals prolonged exposure to environmental carcinogens may be the basis for similarities to therapy-related myeloid malignancies (t-MN), which result from toxic effects of previous cytotoxic treatments on hematopoietic stem cells. Age is itself a risk factor for t-MN, which are more frequent in elderly patients, where also a shorter latency between treatment of primary tumor and t-MN has been reported. t-MN following chemotherapy with alkylating agents and elderly AML frequently present MDS-related cytogenetic abnormalities, including complex or monosomal karyotype, and a myelodysplastic phase preceding the diagnosis of overt leukemia. Similarly, t-MN and elderly-AML share common molecular abnormalities, such as reduced frequency of NPM1, FLT3 and CEBPA mutations and increased MDR1 expression.

Given the unfavorable prognosis of elderly and t-MN and the similar clinical and molecular aspects, this is a promising field for implementation of new treatment protocols including alternative biological drugs.

Epigenetic therapy for breast cancer

Both genetic and epigenetic alterations can control the progression of cancer. Genetic alterations are impossible to reverse, while epigenetic alterations are reversible. This advantage suggests that epigenetic modifications should be preferred in therapy applications. DNA methyltransferases and histone deacetylases have become the primary targets for studies in epigenetic therapy. Some DNA methylation inhibitors and histone deacetylation inhibitors are approved by the US Food and Drug Administration as anti-cancer drugs. Therefore, the uses of epigenetic targets are believed to have great potential as a lasting favorable approach in treating breast cancer.

Therapy-Related Myeloid Neoplasms in Chronic Lymphocytic Leukemia and Waldenstrom's Macroglobulinemia

Secondary myelodysplasia (MDS) and acute myeloid leukemia (AML) are frequent long term complications in Chronic Lymphocytic Leukemia (CLL) and Waldenström Macroglobulinemia (WM) patients. Although disease-related immune-suppression plays a crucial role in leukemogenesis there is great concern that therapy may further increase the risk of developing these devastating complications.Nucleoside analogs (NA) and alkylating agents are considered appropriate agents in the treatment of both CLL and WM patients. Prolonged immunosuppression related to NA therapy and the incorporation of these agents or their metabolites into DNA, with potentially mutagenic action, leads to speculation that their therapeutic use might be responsible for an increased incidence of second cancer especially when combined with other DNA damaging agents like alkylating agents.In this review the published studies considering the occurrence of secondary MDS and AML in CLL and WM patients are reported and the potential role of chemotherapeutic agents in leukemogenesis is discussed.

Therapy-related myeloid neoplasms: pathobiology and clinical characteristics

Therapy-related myeloid neoplasms (t-MNs) are serious long-term consequences of cytotoxic treatments for an antecedent disorder. t-MNs are observed after ionizing radiation as well as conventional chemotherapy including alkylating agents, topoisomerase-II-inhibitors and antimetabolites. In addition, adjuvant use of recombinant human granulocyte-colony stimulating factor may also increase the risk of t-MNs. There is clinical and biological overlap between t-MNs and high-risk de novo myelodysplastic syndromes and acute myeloid leukaemia suggesting similar mechanisms of leukaemogenesis. Human studies and animal models point to a prominent role of genetic susceptibilty in the pathogenesis of t-MNs. Common genetic variants have been identified that modulate t-MN risk, and t-MNs have been observed in some cancer predisposition syndromes. In either case, establishing a leukaemic phenotype requires acquisition of somatic mutations - most likely induced by the cytotoxic treatment. Knowledge of the specific nature of the initiating exposure has allowed the identification of crucial pathogenetic mechanisms and for these to be modelled in vitro and in vivo. Prognosis of patients with t-MNs is dismal and at present, the only curative approach for the majority of these individuals is haematopoietic stem cell transplantation, which is characterized by high transplant-related mortality rates. Novel transplantation strategies using reduced intensity conditioning regimens as well as novel drugs - demethylating agents and targeted therapies - await clinical testing and may improve outcome. Ultimately, individual assessment of genetic risk factors may translate into tailored therapies and establish a strategy for reducing t-MN incidences without jeopardizing therapeutic success rates for the primary disorders.

Proposed mode of action of benzene-induced leukemia: Interpreting available data and identifying critical data gaps for risk assessment

Mode of action is defined as a series of key biological events leading to an observed toxicological effect (for example, metabolism to a toxic entity, cell death, regenerative repair and tumors). It contrasts with mechanism of action, which generally involves a detailed understanding of the molecular basis for an effect. A framework to consider the weight of evidence for hypothesized modes of action in animals and their relevance to humans, has been widely adopted and used by government agencies and international organizations. The framework, developed and refined through its application in case studies for principally non-DNA-reactive carcinogens, has more recently been extended to DNA-reactive carcinogens, non-cancer endpoints and different life stages. In addition to increasing transparency, use of the framework promotes consistency in decision-making concerning adequacy of weight of evidence, facilitates peer input and review and identifies critical research needs. The framework provides an effective tool to facilitate discussion between the research and risk assessment communities on critical data gaps, which if filled, would permit more refined estimates of risk. As a basis for additionally coordinating and focusing research on critical data gaps in a risk assessment context, five key events in the mode of action for benzene-induced leukemia are proposed: (1) benzene metabolism via Cytochrome P450, (2) the interaction of benzene metabolites with target cells in the bone marrow, (3) formation of initiated, mutated target cells, (4) selective proliferation of the mutated cells and (5) production of leukemia. These key events are considered in a framework analysis of human relevance as a basis to consider appropriate next steps in developing research strategies.