Increased Frequency of Fanconi Anemia Group C Genetic Variants in Children With Sporadic Acute Myeloid Leukemia

Rare germline alterations of myeloperoxidase predispose to myeloid neoplasms

Myeloperoxidase (MPO) gene alterations with variable clinical penetrance have been found in hereditary MPO deficiency, but their leukemia association in patients and carriers has not been established. Germline MPO alterations were found to be significantly enriched in myeloid neoplasms: 28 pathogenic/likely pathogenic variants were identified in 100 patients. The most common alterations were c.2031-2 A > C, R569W, M519fs* and Y173C accounting for about half of the cases. While functional experiments showed that the marrow stem cell pool of Mpo^-/- mice was not increased, using competitive repopulation demonstrated that Mpo^-/- grafts gained growth advantage over MPO wild type cells. This finding also correlated with increased clonogenic potential after serial replating in the setting of H₂O₂-induced oxidative stress. Furthermore, we demonstrated that H₂O₂-induced DNA damage and activation of error-prone DNA repair may result in secondary genetic damage potentially predisposing to leukemia leukemic evolution. In conclusion, our study for the first time demonstrates that germline MPO variants may constitute risk alleles for MN evolution.

Genetic heterogeneity among Fanconi anemia heterozygotes and risk of cancer

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by a greatly increased risk of cancer among those diagnosed with the syndrome. The question as to whether FA heterozygotes are at increased risk for cancer is of great importance to those at risk for being a carrier. To address this question, we formed a cohort of grandparents of probands identified through the International Fanconi Anemia Registry. We obtained informed consent, a short questionnaire, and either blood or buccal swab DNA. After diagnosis of the proband was confirmed and complementation studies or DNA sequencing on the proband were completed, mutation analyses of the putative carriers and noncarriers was carried out. Standardized incidence ratios (SIR) were calculated to compare the observed cancer incidence of the grandparents and other relatives with the expected rates of cancer, using the Surveillance, Epidemiology, and End Results registries and the Connecticut Cancer registry. In the 944 study subjects who participated (784 grandparents and 160 other relatives), there was no suggestion of an increase in overall cancer incidence. On the other hand, a significantly higher rate of breast cancer than expected was observed among carrier grandmothers [SIR, 1.7; 95% confidence interval (95% CI), 1.1-2.7]. Among the grandmothers, those who were carriers of FANCC mutations were found to be at highest risk (SIR, 2.4; 95% CI, 1.1-5.2). Overall, there was no increased risk for cancer among FA heterozygotes in this study of Fanconi relatives, although there is some evidence that FANCC mutations are possibly breast cancer susceptibility alleles.

Fanconi anaemia and leukaemia - clinical and molecular aspects

Fanconi anaemia (FA) is an autosomal recessive chromosomal instability disorder, which is characterized by congenital abnormalities, defective haemopoiesis and a high risk of developing acute myeloid leukaemia and certain solid tumours. It can be caused by mutations in at least eight different genes. Molecular studies have established that a common pathway exists, both between the FA proteins and other proteins involved in DNA damage repair such as NBS1, ATM, BRCA1 and BRCA2. This review summarizes the general clinical and specific haematological features and the current management of FA. Recent molecular advances will also be discussed in the context of the cellular and clinical FA phenotype, with particular emphasis on the haematological aspects of the condition.

DEB test for Fanconi anemia detection in patients with atypical phenotypes

Pancytopenia, hyperpigmentation, small stature, congenital abnormalities, and predisposition to neoplasia characterize Fanconi anemia (FA). The clinical phenotype is extremely variable, therefore the diagnosis is frequently delayed until the pancytopenia appears, making diagnosis difficult on the basis of clinical manifestations alone. Hypersensitivity of FA cells to the clastogenic effect of diepoxybutane (DEB) provides a unique marker for the diagnosis before the beginning of hematological manifestations. Our aim in this study was to detect FA in children with atypical manifestations to define which conditions should be routinely included in the DEB test screening. We performed the chromosomal breakage test in 34 patients with probable FA and 83 patients with clinical conditions that could suggest FA, but are not usually screened by the DEB test: 20 patients with aplastic anemia, 20 patients with VACTERL association, 20 with radial ray abnormalities, 7 with tracheo-esophageal fistulae, 12 with anal atresia, and 4 with myelodysplastic syndrome. We found 18 DEB-positive patients: 12 were in the group of probable FA and 6 in the other groups. Among the last ones: three were included because of aplastic anemia, without any other sign of FA, however when re-examined, other anomalies were detected. The third patient had anal atresia, renal hypoplasia, pre-axial polydactyly, and normal blood cell counts and was diagnosed as having VACTERL association. The other two patients lacking physical or hematological signs were identified among the group of radial ray abnormalities. Thus, our results highlight the need to increase the number of abnormalities indicating need for a DEB test. Delay in the diagnosis of FA may have serious consequences for the patients and their family members.

Constitutional sequence variation in the Fanconi anaemia group C (FANCC) gene in childhood acute myeloid leukaemia

The extent to which genetic susceptibility contributes to the causation of childhood acute myeloid leukaemia (AML) is not known. The inherited bone marrow failure disorder Fanconi anaemia (FA) carries a substantially increased risk of AML, raising the possibility that constitutional variation in the FA (FANC) genes is involved in the aetiology of childhood AML. We have screened genomic DNA extracted from remission blood samples of 97 children with sporadic AML and 91 children with sporadic acute lymphoblastic leukaemia (ALL), together with 104 cord blood DNA samples from newborn children, for variations in the Fanconi anaemia group C (FANCC) gene. We found no evidence of known FANCC pathogenic mutations in children with AML, ALL or in the cord blood samples. However, we detected 12 different FANCC sequence variants, of which five were novel to this study. Among six FANCC variants leading to amino-acid substitutions, one (S26F) was present at a fourfold greater frequency in children with AML than in the cord blood samples (odds ratio: 4.09, P = 0.047; 95% confidence interval 1.08-15.54). Our results thus do not exclude the possibility that this polymorphic variant contributes to the risk of a small proportion of childhood AML.