Clinical and cytogenetic diversity in Fanconi's anaemia

Squamous cell carcinoma of base of tongue in a patient with Fanconi's anemia treated with radiation therapy: case report and review of literature

BACKGROUND

Fanconi's anemia (FA) is a rare autosomal recessive genetic disorder characterized by congenital anomalies, progressive aplastic anemia, and a predisposition for malignancies. Solid tumors in the head and neck region, especially in the tongue, are rarely observed. Management of these patients is a challenge because of hematological complications and increased toxicities.

METHODS

We report a case of Fanconi's anemia in a 27-year-old man with carcinoma of the base of tongue (T2N0M0) who was treated with radical radiation therapy to a dose of 70 Gy/35 fractions/51 days. We have also done in vitro radiosensitivity tests.

RESULTS

The patient tolerated the radiation treatment well and completed it without any interruptions. In vitro studies did not show any increased radiosensitivity in this patient.

CONCLUSION

Head and neck cancer in a patient with FA requires individualized treatment. The decision about opting for different modalities should be based on a balanced approach with respect to locoregional control and toxicities of the treatment.

Association of biallelic BRCA2/FANCD1 mutations with spontaneous chromosomal instability and solid tumors of childhood

The clinical, cytogenetic, and molecular findings of 2 Fanconi anemia (FA) subtype D1 kindreds, initially identified through a young child with a solid tumor (medullobastoma, Wilms tumor), are described. Each kindred subsequently had a second affected child; one developed Wilms tumor followed by a medulloblastoma, and the other developed T-lineage acute lymphoblastic leukemia. Cytogenetic studies revealed an unusually high spontaneous chromosome aberration rate, contrasting with other FA subtypes. Molecular analysis revealed biallelic BRCA2/FANCD1 mutations. The patients did not exhibit bone marrow failure. Our studies suggest that the D1 subtype represents a severe end of the cytogenetic spectrum within FA, consistent with a critical downstream role of BRCA2 in the FA pathway. Furthermore, this FA subgroup may be preferentially associated with an increased predisposition to solid tumors in early childhood. Recognition of this constellation of findings has significant implications for medical management and genetic counseling of FA families.

Differential effects in cells exposed to ultra-short, high intensity electric fields: cell survival, DNA damage, and cell cycle analysis

High power, nanosecond pulsed electric field (nsPEF) effects have been focused on bacterial decontamination, but the impact on mammalian cells is now being revealed. During nsPEF applications, electrical pulses of 10, 60 or 300 ns durations were applied to cells using electric field amplitudes as high as 300 kV/cm. Because of the ultra-short pulse durations, the energy transferred to cells is negligible, and only non-thermal effects are observed. We investigated the genotoxicity of nsPEF on adherent and non-adherent cell lines including 10 human lines and one mouse cell line with different origin and growth characteristics. We present data examining the effects of nsPEF exposure on cell survival assessed by clonogenic formation or live cell count; DNA damage determined by the comet assay and chromosome aberrations; and cell cycle parameters by measuring the mitotic indices of exposed cells. Using each of these indicators, we observed differential effects among cell types with non-adherent cells being more sensitive to the genotoxic effects of nsPEF exposures than adherent cells. Non-adherent cultures showed a rapid decrease in cell viability (90%), induction of DNA damage, and a decrease in the number of cells reaching mitosis after one 60 ns pulse with an electric field intensity of 60 kV/cm. These effects were not observed in cells grown as adherent cultures, with the exception of the mouse 3T3 cell line, which showed survival characteristics similar to non-adherent cultures. These data suggest that nsPEF genotoxicity may be cell type specific, and therefore have potential applications in the selective removal of one cell type from another, for example, in diseased states.

Chromosome instability syndromes

The chromosome instability syndromes, ataxia telangiectasia (A-T), Fanconi anaemia (FA) and Bloom syndrome (BS) have been known for many years. More recently Nijmegen breakage syndrome (NBS) and ataxia telangiectasia-like disorder (ATLD) have been identified. A-T, ATLD and NBS form a group of disorders all of which show very similar cellular features that result from the consequences of increased sensitivity to ionizing radiation (IR). They also share some clinical features, particularly A-T and ATLD, and all show an immunodeficiency. A-T and NBS both show a predisposition to lymphoid tumours. Fanconi anaemia can be caused by mutations in eight different genes, although the majority of mutations are accounted for by FANCA and FANCC. The very rare Bloom syndrome is caused by mutation in a single gene, BLM. An important feature which all of these disorders have in common is that the genes identified are involved in aspects of recombination repair of DNA damage.

Normal cellular radiosensitivity in an adult Fanconi anaemia patient with marked clinical radiosensitivity

BACKGROUND

Fanconi anaemia is a rare disease associated with cellular sensitivity to chemicals (e.g. mitomycin C and diepoxybutane); variable but mild cellular radiosensitivity has also been reported.

MATERIALS AND METHODS

A 32-year-old patient with Fanconi anaemia and tonsillar carcinoma, treated by radiotherapy, was found to exhibit profound clinical radiosensitivity. Confluent, ulcerating oropharyngeal mucositis developed after a conventionally fractionated dose of 34Gy and healing was incomplete by 2 months after cessation of therapy.

RESULTS

Cellular radiosensitivity assays and RPLD studies from this patient did not suggest any major detectable radiosensitivity.

CONCLUSION

There is a discrepancy between the observed clinical radiosensitivity and the usual "predictive" radiosensitivity assays in this patient with Fanconi anaemia.

Fanconi anemia. a statistical evaluation of cytogenetic results obtained from South African families

Fanconi anemia (FA) is a rare autosomal recessive genetic disorder showing progressive bone marrow failure, and various phenotypic abnormalities. The lymphocytes show an increased sensitivity to the clastogenic agents diepoxybutane (DEB) or mytomycin C (MMC), measured as chromosomal aberrations. Statistical analysis of chromosome aberration yield showed that: (i) differentiation between obligate carriers and the control group was not possible; (ii) homozygotes were clearly distinguishable from heterozygotes as well as from controls by analyzing only 20 metaphase spreads per person; (iii) most of the FA patients had only one cell line present as measured by distribution of chromosomal damage among cells analyzed; (iv) and when the DEB sensitivity of a patient was high, the amount of cells without damage was low.

Growth hormone deficiency caused by pituitary stalk interruption in Fanconi's anemia

Fanconi's anemia can be associated with growth retardation. We describe biologic growth hormone deficiency, isolated or associated with thyrotropin abnormality, and pituitary stalk interruption syndrome on magnetic resonance imaging of 5 patients with Fanconi's anemia. Growth hormone treatment produced catch-up growth in all cases. These findings suggest a common genetic origin.

Body proportions in Fanconi anemia heterozygotes

To study the anthropometric ratios in parents (heterozygotes) of children with Fanconi anemia. The study was carried out in the Department of Hematology, Institute of Child Health & Hospital for Children, Chennai. Parents of children with Fanconi anemia were the subjects of the study. Applying standard instruments and methods, various body measurements were recorded. 31 fathers and 37 mothers were included in the study. A hundred male and female controls of the same ethnic group were also studied for the same parameters. The ratios were calculated and statistically analyzed. It was observed that fathers (male heterozygotes) had shorter forearms, the ratio of upper arm: forearm was significantly increased compared to male controls. In mothers (female heterozygotes) the inter-pupillary distance was increased, the ratio of head circumference to inter-pupillary distance was decreased compared to female controls.

Comparative study of Fanconi anemia in children of different ethnic origin in South Africa

A comparative study of clinical, hematologic, and cytogenetic findings was made in 40 black and 35 white children with Fanconi anemia. The black children were Bantu-speaking Negroid stock of diverse tribal origin. The white children were predominantly Afrikaans stock of Dutch/German/French Huguenot origin. All of the patients had IFAR scores of 2 to 4+ and over 80% in each group had increased spontaneous and/or mutagen-induced chromosomal breakage (CB-positive). There were no significant clinical differences between black and white patients or between CB-pos and CB-neg patients, with the exception of white children in whom significantly more CB-pos patients had thumb and radial anomalies than the CB-neg patients. The age-at-onset of hematologic manifestations was the same for all groups, but more black than white CB-pos patients were severely anemic at the time of diagnosis. Response to androgen and steroid therapy occurred in only 33% of black children compared with 86-90% of white children; 81% of black patients died during the 18 year study period compared with 30% of white children, but the age at death was similar. More sophisticated studies are required to determine whether these differences are genetically determined or related to cultural, educational, and socio-economic differences between the two ethnic groups.

Monozygotic twin girls with congenital malformations resembling fanconi anemia

Monozygotic (MZ) twin girls, diagnosed at birth to have Fanconi anemia (FA) on the basis of multiple anomalies and an apparently increased baseline chromosomal breakage frequency in one twin, have been followed prospectively for 13 years. They have not developed aplastic anemia or other hematologic manifestations of FA. There was no evidence for increased baseline or diepoxybutane (DEB)-induced chromosomal breakage in either twin when the studies were repeated in Denver as well as in New York. Since the cellular phenotype must be considered in establishing the diagnosis of FA, these MZ twins should not be classified as affected with FA. Using the scoring system for FA diagnosis developed by Auerbach et al. [1989], the probability coefficients of their having FA based solely on clinical findings, prior to DEB testing, were .75 and .92, respectively. When the combination of their anomalies are taken together, their FA probability coefficient is .98. Through the International FA Registry, 15 additional patients have been identified with an FA probability score of .75 or greater, but who have not developed aplastic anemia and who are DEB negative. These patients, as well as the twins described in this report, are most likely a heterogeneous group and may represent other syndromes like Holt-Oram, VATER, VACTERL and IVIC, with genetic as well as nongenetic etiologies. These cases demonstrate the importance of testing with DEB or other DNA crosslinking agent in order to discriminate between FA and other syndromes with a similar phenotype.

Sister chromatid exchange evaluation as an aid to the diagnosis and exclusion of Fanconi's anaemia by induced chromosome damage analysis

Evaluation of chromatid aberrations induced in culture by DNA cross linking agents provides the most reliable method currently available for the diagnosis and exclusion of Fanconi's anaemia. However, at appropriate concentrations of clastogenic agent the aberration frequency in an unaffected subject may be very low and thus it may be difficult to confirm that the treatment was effective. Data are presented to show that sister chromatid exchange analysis can be used to monitor the effectiveness of the clastogen treatment and thereby increase the reliability and efficiency of the assay.

Physical and laboratory characteristics of heterozygote carriers of the Fanconi aplasia gene

Fanconi anaemia (FA) is a recessively inherited disorder associated with a typical physical appearance and a spectrum of clinical and laboratory characteristics. Parental heterozygotes of FA patients are superficially normal in appearance and lack overt laboratory abnormalities. Furthermore, they are indistinguishable from normal subjects on chromosome analysis. In order to determine if any of the clinical or laboratory abnormalities seen in FA patients were detectable to a lesser degree in heterozygotes, we carried out detailed skeletal measurement and laboratory investigation on 16 obligate FA heterozygotes and compared the results with 40 normal control subjects. Skeletal proportions in FA heterozygotes showed significant differences from normal subjects in the ratio of the height to the inter-acromial distance (p less than 0.001), and in having significantly shorter forearms (p less than 0.05). Apart from two patients with presumed iron deficiency, haemoglobin levels were normal, but three patients showed neutropenia (less than 1.5 X 10(9)/l). Foetal haemoglobin measurements were significantly higher (p less than 0.01) and natural killer cell subsets lower (p less than 0.05) in heterozygotes. Significantly reduced mitogenetic responses to phytohaemagglutinin and interleukin-2 of peripheral blood lymphocytes in heterozygotes was also demonstrated. These results suggest that heterozygotes show minor physical and haematological abnormalities consistent with partial expression of the Fanconi gene in the heterozygote.

Fanconi anemia in black African children

Fanconi anemia (FA) has rarely been reported in black children either in the United States or Africa. This report describes 25 black African children with FA seen in Johannesburg over an 11-year period. The prevalence of homozygotes was estimated to be 1:476,000. Clinical manifestations, mean age at diagnosis, and hematologic and chromosome abnormalities were similar to those described in other ethnic groups. Response to androgens was poor and most patients required regular transfusions. Seventeen (68%) of the children died during the 11-year observation period. Leukemia was the terminal event in 2 patients. The mean age at death was 9.8 years and the mean time between diagnosis and death 2.3 years. The poor response to androgens, high mortality, and early mean age at death would favor consideration of early bone marrow transplantation in these children.

Dominantly transmitted hematologic dysfunction clinically similar to Fanconi's anemia

We report a family with a dominantly transmitted syndrome resembling Fanconi's anemia and spanning two generations. This syndrome was characterized by an ill-defined hematologic stem cell disorder, immune dysfunction, poor dentition, hyperpigmented skin, warts, and multiple second trimester spontaneous abortions and included one case of acute myelomonocytic leukemia (acute non-lymphocytic leukemia, M4). This family lacks the characteristic chromosomal aberrations of Fanconi's anemia. We believe this constellation of findings represents an entity not previously described.

Cultured skin keratinocytes from both normal individuals and basal cell naevus syndrome patients are more resistant to gamma-rays and UV light compared with cultured skin fibroblasts

Measurement of colony-forming ability following exposure to gamma-rays was performed on cultured skin keratinocytes and skin fibroblasts obtained from normal individuals, basal cell naevus syndrome patients (BCNS) and ataxia telangiectasia (A-T) patients. The most striking observation was the radiation resistance of 8/8 keratinocyte strains compared with fibroblasts whether from BCNS patients or normals. The single A-T keratinocyte cell strain showed the same radiosensitivity as A-T fibroblast cell strains. The differential survival of keratinocytes and fibroblasts was also observed following exposure to 254 nm UV light. The survival curves of SV40 immortalized keratinocytes and retinoblasts derived from normal individuals or BCNS patients showed large shoulder regions following exposure to gamma-rays or 254 nm UV light. An increased D37 rather than an increased D0 was therefore the feature of such curves. This contrasted with the SV40 immortalized A-T keratinocytes or fibroblasts which showed a minimal shoulder effect and an increased D0. No difference in survival was observed between BCNS and normal cells following exposure to either UV or gamma-rays.

The fate of 8-methoxypsoralen-photoinduced DNA interstrand crosslinks in Fanconi's anemia cells of defined genetic complementation groups

The fate of 8-methoxypsoralen (8-MOP)-photoinduced DNA interstrand crosslinks was followed by alkaline elution in Fanconi's anemia (FA) fibroblasts belonging to complementation groups A (FA 150 and FA 402) and B (FA 145) in comparison to a normal (1 BR/3) and a heterozygote (F 311) cell line. Clonogenic cell survival to 8-MOP photoaddition was established in parallel for all cell lines. In comparison to normal cells, group A FA cells demonstrated a higher photosensitivity than group B cells (sensitivity index 2.3 and 1.5, respectively), the heterozygote cell line being only slightly more sensitive. FA cells from both groups A and B demonstrated an incision capacity of crosslinks, the kinetics and extent of which being, however, different from that of normal or heterozygote cells. The incision is slower in FA cells and, at 24 h of post-treatment incubation, the amount of crosslinks incised is clearly lower than that observed in normal cells for group A cells, whereas in group B cells incision approaches the level of normal cells. These results correlate with survival as well as with rates of DNA semi-conservative synthesis after 8-MOP photoaddition.

Two complementation groups of Fanconi's anemia differ in their phenotypic response to a DNA-crosslinking treatment

The two genetic complementation groups reported for Fanconi's anemia (FA) correspond to two phenotypic classes as characterized by measurements of the rate of DNA semiconservative synthesis after 8-methoxypsoralen photoaddition. This test allows a rapid genetic classification of FA patients which appears to be a prerequisite for investigations of the biochemical defect(s) in FA.

Fanconi anemia, dyskeratosis congenita, and WT syndrome

The association of congenital anomalies and pancytopenia is encountered in several clinical syndromes. Among these, Fanconi anemia is by far the most prevalent, and consequently best known. As a result, other similar conditions, such as dyskeratosis congenita and particularly WT syndrome, are often mistaken for Fanconi anemia. However, at a closer look, the type of congenital anomalies, the mode of inheritance, cytogenic and other laboratory findings allow clear differentiation between these 3 syndromes.

Characterization of a simian virus 40-transformed Fanconi anemia fibroblast cell line

We have characterized a SV40-transformed human fibroblast cell line (GM6914) derived from a patient with Fanconi anemia (FA) in order to establish its usefulness for biochemical and genetic experiments, including DNA-mediated gene transfer. GM6914 cells have a growth rate similar to that of SV40-transformed normal human fibroblasts and an indefinite lifespan in culture. As has been established for other FA cell types, GM6914 cells have an increased sensitivity to DNA-crosslinking agents such as mitomycin C (MMC). The D10 for GM6914 cells is 8 times lower than for equivalent controls. GM6914 cells also have an elevated frequency of spontaneous chromosome aberrations and this frequency can be increased by MMC concentrations which show no effect on control cells. Genetic complementation studies with lymphoblasts derived from two affected sibs of the donor of GM6914 cells show that GM6914 belongs to FA complementation group A. In DNA-transfection studies using plasmid pRSVneo, colonies of GM6914 cells resistant to the drug G-418 were observed at frequencies ranging from 1.7 to 16 X 10(-4), values similar to those observed with several other SV40-transformed human cell lines. GM6914 should be a useful recipient cell line in experiments using DNA-mediated gene transfer to clone the normal allele of the gene which is defective in FA complementation group A. GM6914 would also be an excellent cell line for studies on mutagenesis, recombination and repair using plasmid vectors.

Human DNA repair defects

A number of human genetic diseases have come to be described as being defective in DNA repair. The minimum criterion on which this assignment is based is hypersensitivity to the clastogenic or lethal action of specific DNA damaging agents. In one disease, xeroderma pigmentosum, the molecular evidence for a defect in DNA repair is unequivocal. This condition then acts as a model for dissecting others. For the other diseases the formal evidence for defects in repair is less secure or even lacking. The evidence for repair in each disease is assembled together with any methods that have been used to support the differential diagnosis or for prenatal diagnosis. Attempts to clone human DNA repair genes are in hand and may provide the necessary evidence to decide if all the putative DNA repair defective diseases are genuine. Neoplastic disease and neurological degeneration together with immune defects are frequent clinical features linking this set of diseases, suggesting that effective DNA repair may be important in many aspects of human health.

Spontaneous 6-thioguanine-resistant lymphocytes in Fanconi anemia patients and their heterozygous parents

The incidence of spontaneous 6-thioguanine-resistant (TGr) lymphocytes was studied in the peripheral blood collected from seven Fanconi anemia (FA) patients and five of their heterozygous parents using an autoradiographic or a lymphocyte cloning method. Five of the seven patients showed a significantly elevated incidence of TGr lymphocytes as compared to age- and sex-matched healthy controls. There was, however, no difference between FA heterozygotes and controls. These results suggest some variability among the patients similar to those reported in clinical and cytogenetic investigations. The basis for the increase in TGr cells in the patients is not known, but the inherent genomic instability reflected as increased frequencies of chromosomal aberrations is one possible explanation.

Cytogenetic analyses utilizing various clastogens in two sibs with Fanconi anemia, their relatives, and control individuals

Structural chromosome damage, sister chromatid exchange (SCE), and proliferation kinetics were studied on lymphocyte cultures from the peripheral blood of two sibs exhibiting signs of Fanconi anemia, their relatives, and control individuals. While the rate of spontaneous chromosome breakage was at the lower limit of that known for Fanconi anemia in our patients, a distinctly greater increase than in controls of breakage frequency could be induced by isoniazid (INH), 4-nitroquinoline-1-oxide (NQO), and diepoxybutane (DEB) in their lymphocytes. Increased aberration frequencies as compared with controls were also observed in the clastogen-exposed lymphocyte cultures of the parents of both sibs, but in some experiments (NQO, DEB 24 h) only in the cells of the healthy brother. There was an increase in the breakage rate of bromodeoxyuridine (BrdU)-labeled consecutive mitoses under the action of NQO, but a decrease with INH as the test clastogen. No significantly higher SCE frequency was found throughout the study in untreated and clastogen-exposed FA lymphocytes as compared with the respective controls. Proliferation was clearly inhibited by INH and NQO as indicated by a distinct increase of the percentage of BrdU-labeled first and a drastic decrease of third metaphases. The present test clastogens were shown not only to be suitable for ensuring the diagnosis of FA in patients with a low incidence of spontaneous breakage but also for determining clastogen-sensitive heterozygotes. According to these results cross-link repair cannot be the only mechanism affected by the basic defect of Fanconi anemia.

Effect of oxidants and antioxidants on chromosomal breakage in Fanconi anemia lymphocytes

Peripheral blood lymphocytes from eight Fanconi anemia (FA) patients, 14 FA heterozygotes, and nine normal subjects have been tested for their susceptibility to chromosomal breakage induction by diepoxybutane (DEB) and by two peroxides. In addition, the effect of five antioxidants was investigated in standard cultures and in cultures stressed either with DEB or with butylhydroperoxide (BHP) or with hydrogen peroxide (H2O2). DEB, BHP, and H2O2 dramatically increased the chromosomal breakage levels in homozygous and heterozygous FA cells. A partial correction of chromosomal instability was obtained by treating the patients' lymphocytes with antioxidants. A "protective" effect was also noted in the DEB or peroxide-stressed lymphocytes of patients and heterozygotes, grown in the presence of antioxidants.

Identification of two complementation groups in Fanconi anemia

Considerable variation can be observed in the clinical presentation of Fanconi anemia (FA) patients and in the degree of sensitivity of their cells to DNA damaging agents. We have examined the hypothesis that genetic heterogeneity underlies this variation by testing for complementation in somatic cell hybrids constructed from FA cells. Hybrids were formed by fusing lymphoblastoid cell lines derived from four different FA patients. Complementation of the cellular defects in FA was tested by examining sensitivity to growth inhibition by mitomycin C(MMC), spontaneous chromosome breakage, and MMC-induced chromosome breakage in the hybrid cells. These studies revealed the presence of at least two complementation groups, suggesting that there may be two or more different FA genes.