Monosomy 7 in myeloid malignancies: parental origin and monitoring by real-time quantitative PCR

Genetic Characterization and Risk Stratification of Acute Myeloid Leukemia

The most common acute leukemia in adults is acute myeloid leukemia (AML). The pathophysiology of the disease associates with cytogenetic abnormalities, gene mutations and aberrant gene expressions. At the molecular level, the disease manifests as changes in both epigenetic and genetic signatures. At the clinical level, two aspects of AML should be taken into account. First, the molecular changes occurring in the disease are important prognostic and predictive markers of AML. Second, use of novel therapies targeting these molecular changes. Currently, cytogenetic abnormalities and molecular alterations are the common biomarkers for the prognosis and choice of treatment for AML. Finding a panel of multiple biomarkers is a crucial diagnostic step for patient classification and serves as a prerequisite for individualized treatment strategies. Furthermore, the most important way of identifying relevant targets for new treatment approaches is defining specific patterns or a spectrum of driver gene mutations occurring in AML. Then, an algorithm can be established by the use of several biomarkers, to be used for personalized medicine. This review deals with molecular alterations, risk stratification, and relevant therapeutic decision-making in AML.

Bone marrow failure may be caused by chromosome anomalies exerting effects on RUNX1T1 gene

Background

The majority of the cases of bone marrow failure syndromes/aplastic anaemias (BMFS/AA) are non-hereditary and considered idiopathic (80–85%). The peripheral blood picture is variable, with anaemia, neutropenia and/or thrombocytopenia, and the patients with idiopathic BMFS/AA may have a risk of transformation into a myelodysplastic syndrome (MDS) and/or an acute myeloid leukaemia (AML), as ascertained for all inherited BMFS. We already reported four patients with different forms of BMFS/AA with chromosome anomalies as primary etiologic event: the chromosome changes exerted an effect on specific genes, namely RUNX1, MPL, and FLI1, leading to the disease.

Results

We report two further patients with non-hereditary BM failure, with diagnosis of severe aplastic anaemia and pancytopenia caused by two different constitutional structural anomalies involving chromosome 8, and possibly leading to the disorder due to effects on the RUNX1T1 gene, which was hypo-expressed and hyper-expressed, respectively, in the two patients. The chromosome change was unbalanced in one patient, and balanced in the other one.

Conclusions

We analyzed the sequence of events in the pathogenesis of the disease in the two patients, including a number of non-haematological signs present in the one with the unbalanced anomaly. We demonstrated that in these two patients the primary event causing BMFS/AA was the constitutional chromosome anomaly. If we take into account the cohort of 219 patients with a similar diagnosis in whom we made cytogenetic studies in the years 2003–2017, we conclude that cytogenetic investigations were instrumental to reach a diagnosis in 52 of them. We postulate that a chromosome change is the primary cause of BMFS/AA in a not negligible proportion of cases, as it was ascertained in 6 of these patients.

Electronic supplementary material

The online version of this article (10.1186/s13039-017-0352-2) contains supplementary material, which is available to authorized users.

Enhancing acute myeloid leukemia therapy - monitoring response using residual disease testing as a guide to therapeutic decision-making

INTRODUCTION

Current standards for monitoring the response of acute myeloid leukemia (AML) are based on morphologic assessments of the bone marrow and recovery of peripheral blood counts. A growing experience is being developed to enhance the detection of small amounts of AML, or minimal residual disease (MRD). Areas covered: Available techniques include multi-color flow cytometry (MFC) of leukemia associated immunophenotypes (LAIP), quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) for detecting fusion and mutated genes (RUNX1-RUNX1T1, CBFB-MYH11, and NPM1), overexpression of genes such as WT1, and next generation sequencing (NGS) for MRD. Expert commentary: While MRD monitoring is standard of care in some leukemia subsets such as acute promyelocytic leukemia, this approach for the broader AML population does not universally predict outcomes as some patients may experience relapse in the setting of undetectable leukemia while others show no obvious disease progression despite MRD positivity. However, there are instances where MRD can identify patients at increased risk for relapse that may change recommended therapy. Currently, prospective investigations to define clinically relevant MRD thresholds are ongoing. Risk-adapted trials are needed to best define the use of MRD in the follow up of AML patients after initial induction therapy.

A Comprehensive Review of Pediatric Tumors and Associated Cancer Predisposition Syndromes

An understanding of the role of inherited cancer predisposition syndromes in pediatric tumor diagnoses continues to develop as more information is learned through the application of genomic technology. Identifying patients and their relatives at an increased risk for developing cancer is an important step in the care of this patient population. The purpose of this review is to highlight various tumor types that arise in the pediatric population and the cancer predisposition syndromes associated with those tumors. The review serves as a guide for recognizing genes and conditions to consider when a pediatric cancer referral presents to the genetics clinic.

Array-CGH in childhood MDS

To study genomic imbalances potentially involved in disease development and/or progression of childhood MDS, array-based comparative genomic hybridization (aCGH) is a helpful tool. Copy number alterations (CNA) of subtle chromosomal regions containing potential candidate genes, e.g., TP53 or RUNX1 can be detected. However, characterizing small and/or heterogeneous tumor subpopulations by high-resolution aCGH within a majority of normal cells is a challenge in MDS and requires validation by independent methods like FISH or quantitative PCR. For the identification of tumor-relevant CNA, the analysis of DNA isolated from purified granulocytes or myeloid populations instead of DNA from whole bone marrow (BM) cells is helpful to overcome some of these limitations.

Aneuploid human embryonic stem cells: origins and potential for modeling chromosomal disorders

Chromosomal aneuploidies are widely recognized genetic disorders in humans that often lead to spontaneous abortion. Aneuploid fetuses that survive to term commonly exhibit impaired developmental growth and mental retardation in addition to multiple congenital malformations. Preimplantation genetic screening is used to detect chromosomal aneuploidies in early embryos. Human embryonic stem cell (ESC) cell lines generated from aneuploid embryos created a unique repository of cell lines. The spectrum of aneuploidies in these ESC lines reflects the range of common embryonic chromosomal aberrations and significantly differs from the spectrum of aneuploid human ESC lines generated by cell adaptation in culture. The aneuploid human ESC lines represent an excellent model to study human chromosomal abnormalities especially in the early stages of development.

Comparative genomic hybridization on microarray (a-CGH) in constitutional and acquired mosaicism may detect as low as 8% abnormal cells

Background

The results of cytogenetic investigations on unbalanced chromosome anomalies, both constitutional and acquired, were largely improved by comparative genomic hybridization on microarray (a-CGH), but in mosaicism the ability of a-CGH to reliably detect imbalances is not yet well established. This problem of sensitivity is even more relevant in acquired mosaicism in neoplastic diseases, where cells carrying acquired imbalances coexist with normal cells, in particular when the proportion of abnormal cells may be low.

We constructed a synthetic mosaicism by mixing the DNA of three patients carrying altogether seven chromosome imbalances with normal sex-matched DNA. Dilutions were prepared mimicking 5%, 6%, 7%, 8%, 10% and 15% levels of mosaicism. Oligomer-based a-CGH (244 K whole-genome system) was applied on the patients' DNA and customized slides designed around the regions of imbalance were used for the synthetic mosaics.

Results and conclusions

The a-CGH on the synthetic mosaics proved to be able to detect as low as 8% abnormal cells in the tissue examined. Although in our experiment some regions of imbalances escaped to be revealed at this level, and were detected only at 10-15% level, it should be remarked that these ones were the smallest analyzed, and that the imbalances recurrent as clonal anomalies in cancer and leukaemia are similar in size to those revealed at 8% level.

Emberger syndrome-primary lymphedema with myelodysplasia: report of seven new cases

Four reports have been published on an association between acute myeloid leukaemia (AML) and primary lymphedema, with or without congenital deafness. We report seven new cases, including one extended family, confirming this entity as a genetic syndrome. The lymphedema typically presents in one or both lower limbs, before the hematological abnormalities, with onset between infancy and puberty and frequently affecting the genitalia. The AML is often preceded by pancytopenia or myelodysplasia with a high incidence of monosomy 7 in the bone marrow (five propositi and two relatives). Associated anomalies included hypotelorism, epicanthic folds, long tapering fingers and/or neck webbing (four patients), recurrent cellulitis in the affected limb (four patients), generalized warts (two patients), and congenital, high frequency sensorineural deafness (one patient). Children with lower limb and genital lymphedema should be screened for hematological abnormalities and immunodeficiency.

Clonal heterogeneity in childhood myelodysplastic syndromes--challenge for the detection of chromosomal imbalances by array-CGH

To evaluate whether copy number alterations (CNAs) are present that may contribute to disease development and/or progression of childhood myelodysplastic syndromes (MDS), 36 pediatric MDS patients were analyzed using array-based comparative genome hybridization (aCGH). In addition to monosomy 7, the most frequent chromosome aberration in childhood MDS, novel recurrent CNAs were detected. They included a loss of 3p14.3-p12.3, which contains the putative tumor suppressor gene FHIT, a loss of 7p21.3-p15.3, a loss of 9q33.3-q34.3 (D184) and microdeletions in 17p11.2, 6q23 containing MYB, and 17p13 containing TP53. In this small patient cohort, patients without CNA, patients with monosomy 7 only and patients with one CNA in addition to monosomy 7 did not differ in their survival. As expected, all patients with complex karyotypes, including two patients with deletions of TP53, died. A challenge inherent to aCGH analysis of MDS is the low percentage of tumor cells. We evaluated several approaches to overcome this limitation. Genomic profiles from isolated granulocytes were of higher quality than those from bone marrow mononuclear cells. Decreased breakpoint calling stringency increased recognition of CNAs present in small clonal populations. However, further analysis using a custom-designed array showed that these CNAs often did not confirm the findings from 244k arrays. In contrast, constitutional CNVs were reliably detected on both arrays. Moreover, aCGH on amplified DNA from distinct myeloid clusters is a new approach to determine CNAs in small subpopulations. Our results clearly emphasize the need to verify array-CGH results by independent methods like FISH or quantitative PCR.

Familial childhood monosomy 7 and associated myelodysplasia

Familial monosomy 7 is defined as bone marrow monosomy 7 occurring as a sole cytogenetic abnormality affecting 2 or more siblings. It manifests usually in childhood with neurologic disorder (cerebellar ataxia or atrophy) and/or hematologic disorder (marrow hypoplasia, myelodysplasia, acute myeloid leukemia, or pancytopenia). Partial or complete monosomy 7 with hematologic disorder has been reported in 13 families/pedigrees to date. Here we report the 14th family.

Molecular monitoring of residual disease in chronic myeloid leukemia by genomic DNA compared with conventional mRNA analysis

Translocation t(9;22), which produces the BCR-ABL gene, is pathognomonic of chronic myeloid leukemia. For clinical purposes, the amount of chimeric transcript is considered proportional to the leukemic clone; thus, mRNA is commonly used for molecular monitoring of patients. However, there is no consensus regarding the degree of increase in mRNA that should cause concern or whether the absence of transcript indicates a "cure." In this study, we analyzed 57 samples from 10 chronic myeloid leukemia patients undergoing imatinib treatment. For each sample, we compared BCR-ABL mRNA levels with the actual proportion of leukemic cells, which were measured through a novel genomic approach based on the quantitative amplification of DNA breakpoints. The two approaches gave similar patterns of residual disease, and the majority of patients were still positive after an average treatment period of 2 years. Nevertheless, in one of two patients with confirmed undetectable levels of chimeric transcript, DNA still revealed the persistence of leukemic cells at 42 months. These findings appear to justify the clinical practice of maintaining imatinib treatment indefinitely. However, the absence of leukemic DNA (observed in 1 of 10 patients) could be used to identify possible candidates for drug discontinuation. In conclusion, DNA analysis proved to be a reliable index of residual disease with potential applications in the field of clinical diagnostics and research.