Marrow failure

Stress and DNA repair biology of the Fanconi anemia pathway

Fanconi anemia (FA) represents a paradigm of rare genetic diseases, where the quest for cause and cure has led to seminal discoveries in cancer biology. Although a total of 16 FA genes have been identified thus far, the biochemical function of many of the FA proteins remains to be elucidated. FA is rare, yet the fact that 5 FA genes are in fact familial breast cancer genes and FA gene mutations are found frequently in sporadic cancers suggest wider applicability in hematopoiesis and oncology. Establishing the interaction network involving the FA proteins and their associated partners has revealed an intersection of FA with several DNA repair pathways, including homologous recombination, DNA mismatch repair, nucleotide excision repair, and translesion DNA synthesis. Importantly, recent studies have shown a major involvement of the FA pathway in the tolerance of reactive aldehydes. Moreover, despite improved outcomes in stem cell transplantation in the treatment of FA, many challenges remain in patient care.

The inherited bone marrow failure syndromes

Molecular pathogenesis may be elucidated for inherited bone marrow failure syndromes (IBMFS). The study and presentation of the details of their molecular biology and biochemistry is warranted for appropriate diagnosis and management of afflicted patients and to identify the physiology of the normal hematopoiesis and mechanisms of carcinogenesis. Several themes have emerged within each subsection of IBMFS, including the ribosomopathies, which include ribosome assembly and ribosomal RNA processing. The Fanconi anemia pathway has become interdigitated with the familial breast cancer syndromes. In this article, the diseases that account for most IBMFS diagnoses are analyzed.

[Fanconi anemia in 2012: diagnosis, pediatric follow-up and treatment]

Fanconi anemia (FA) is a rare genetic disease, transmitted in an autosomal recessive mode. The clinical phenotype is very broad and heterogeneous, related to the wide range of genes involved in this pathology. The classical triad of short height, physical abnormalities, and bone marrow failure is suggestive. The main physical abnormalities found involve the limbs, spinal column, skin, kidneys and urinary tract, and the ORL zone. Recent progress in molecular biology has identified 15 genes whose mutation causes FA chromosomal instability. FA is diagnosed by cytogenetic examination, then specified by molecular analysis. As FA patients may present multiorgan abnormalities and a high risk for neoplasia development, their medical follow-up has to be multidisciplinary and prolonged throughout life. The main challenges of the follow-up are patient information and education. Bone marrow failure, appearing during the first decade, requires close hematological monitoring and for severe cases requires hematopoietic stem cell transplantation, major and specific care with frequent serious complications and high mortality, but this is the only curative treatment in FA. Extrahematological care consists in screening for organ abnormalities and defects as well as monitoring precancerous lesions and tumors.

Endurance exercise training promotes medullary hematopoiesis

Endurance exercise is a poorly defined yet powerful mediator of hematopoiesis. The purpose of this study was to directly investigate the effects of endurance exercise training on hematopoiesis and to identify potential mechanisms responsible for any observed changes. Four-week-old male C57Bl/6 mice were trained on a treadmill at progressive speeds over a 10-wk period. Tissues were harvested 2 d following the final training session. Flow cytometry, the cobblestone area-forming cell assay, and the methycellulose colony-forming unit assay were used to assess medullary and mobilized hematopoietic stem and progenitor cells. Quantitative real-time PCR and Western blots were used to measure hematopoietic cytokine production. Histochemistry was also used to assess adaptations to exercise in the bone marrow niche. Depending on the cell type, endurance training increased medullary and mobilized hematopoietic stem and progenitor cell content from 50 to 800%. Training also reduced marrow cavity fat by 78%. Skeletal muscle hematopoietic cytokine expression was also increased at least 60% by training. Sedentary mice served as controls for the above experiments. In conclusion, endurance exercise training greatly promotes hematopoiesis and does so through improvements in medullary niche architecture as well as increased skeletal muscle hematopoietic cytokine production.

Fanconi anemia

Fanconi anemia (FA) is an autosomal and X-linked recessive disorder characterized by bone marrow failure, acute myelogenous leukemia, solid tumors, and developmental abnormalities. Recent years have seen a dramatic improvement in FA patient treatment, resulting in a greater survival of children into adulthood. These improvements have been made despite the fact that a definitive cellular function for the proteins in the FA pathway has yet to be elucidated. Delineating the cellular functions of the FA pathway could help further improve the treatment options for FA patients and further reduce the probability of succumbing to the disease. This article reviews the current clinical aspects of FA including presentation, diagnosis, and treatment followed by a review of the molecular aspects of FA as they are currently understood.

HSCT for Fanconi anemia in children: factors that influence early and late results

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by congenital abnormalities, cancer predisposition and progressive BM failure. FA patients present spontaneous and induced chromosome breakage. Hematopoietic SCT (HSCT) represents the unique therapeutic option to restore normal hematopoiesis when marrow failure or clonal hematopoietic abnormality occurs. Conventional myeloablative conditioning regimen, especially including a high dose of irradiation, appeared strongly toxic for FA patients. Then, reduced-intensity conditioning regimens were developed successfully for those patients. However, TRM still remained higher than for other HSCT indications. The development of fludarabine containing a non-myeloablative conditioning regimen appears to be a major progress. Long-term follow-up is absolutely necessary.

Matched sibling donor haematopoietic stem cell transplantation in Fanconi anaemia: an update of the Cincinnati Children's experience

Our results for 18 patients undergoing matched sibling donor stem cell transplant for Fanconi anaemia at Cincinnati Children's Hospital Medical Center were published in 1994. The present report updates our results in 35 consecutive patients. Thirty patients transplanted for marrow aplasia received cyclophosphamide 5 mg/kg for 4 d and 400 cGy thoraco-abdominal irradiation. Five patients with clones involving chromosome 7, myelodysplastic syndrome or leukaemia received a more aggressive regimen with total body irradiation. Horse antithymocyte globulin was administered in the pretransplant period to promote engraftment and in the post-transplant period for additional graft-versus-host disease (GVHD) prophylaxis. The median age at bone marrow transplantation was 7.6 years. Median day of engraftment was day +12 (range 9-49), eight patients developed acute GVHD and four chronic GVHD, one limited and three extensive. Twenty-nine of 35 patients (89% actuarial survival at 10 years) had survived with a median follow up of 10.2 years; two children had developed secondary malignancy. All surviving patients had normal blood counts with full donor engraftment. These data indicate excellent long-term outcomes and serve as a reference for newer radiation-free preparative regimes that may reduce the risk of late secondary malignancy.

Hodgkin lymphoma in a child with Diamond Blackfan anemia

Diamond Blackfan anemia (DBA) is a rare disease characterized by aplasia or hypoplasia of erythroid lineage. Normochromic, usually macrocytic, but occasionally normocytic anemia and reticulocytopenia are characteristic findings of DBA. DBA is associated with an increased risk of malignancy. Most of the reported malignancies are acute myeloid leukemia. Solid tumors including hepatocellular carcinoma and osteosarcoma have also been identified. We could find 29 reported cases with DBA and malignancy. Two of them were diagnosed as Hodgkin lymphoma at 15 and 23 years, respectively. Here we report a 7-year-old boy with DBA who developed Hodgkin disease.

Apoptosis and expression of anti- and pro-apoptotic proteins in peripheral blood mononuclear cells of Fanconi anaemia patients: a study of 73 cases

Fanconi anaemia (FA) is a rare genetic disease whose patients have a high predisposition to haematological abnormalities and cancer. Fas expression levels in peripheral blood lymphocytes samples of 73 FA patients were measured to verify if alterations in Fas expression could lead to predisposition/resistance to spontaneous or PHA induced apoptosis, as well as, to reflect some haematological features of this disease. The anti- and pro-apoptotic proteins Bcl-2 and Bax were also evaluated. FA patients samples could be divided into three different groups based on Fas expression: 20 samples had low, 32 normal and 21 increased Fas levels when compared to 41 control samples. No correlation was found between Fas and Bcl-2 expression but a good association was obtained with Bax, in the subgroup with increased Fas expression. The best correlation was seen between Bax expression and apoptosis. Out of the 15 samples with high Bax expression, 11 underwent apoptosis whereas only one out of seven samples with low levels of Bax displayed increased induced apoptosis. Most patients with normal haematological features expressed Fas within normal levels. It is difficult to establish, however, if Fas-expression is involved in the cause or is a consequence of the effects observed.

Granulocyte-macrophage colony stimulating factor and immunosuppression in the treatment of pediatric acquired severe aplastic anemia

BACKGROUND

Immunosuppressive therapy (IS) is effective in the treatment of patients with acquired severe aplastic anemia (SAA). An enhanced myeloid response and decreased infection risk may be possible with the addition of a hematopoietic cytokine. Published data on the combination of cytokines and IS in patients with SAA are limited. The addition of G-CSF to IS shortens the time to neutrophil count recovery, but may not improve overall survival. Because GM-CSF acts differently than G-CSF, its use in combination with IS may be different.

PROCEDURE

A retrospective chart review was performed on patients diagnosed with SAA and treated with IS and GM-CSF at St. Jude Children's Research Hospital. Hematologic recovery, prognostic factors, and infection data were collected.

RESULTS

Eighteen patients were included in this study. The median age at diagnosis was 7.2 years (range 1.8-17.0). Ten patients (56%) had a complete response, four (22%) a partial response, and four (22%) no response. Median time to erythrocyte and platelet transfusion independence were 90 (18,243) and 64 days (18-243), and to discontinuation of treatment 287 days (90-730). Median time to partial (ANC > 500) and full (ANC > 1,500) neutrophil recovery were 41 and 51 days, respectively. Seventeen documented discrete infections occurred in six patients over 36 patient years.

CONCLUSIONS

GM-CSF, in addition to IS, may shorten time to neutrophil count recovery, may be beneficial in decreasing infection rates, and may improve platelet response in patients with SAA. However, consistent with studies utilizing G-CSF, GM-CSF probably does not affect overall response rate. To fully answer whether or not cytokine therapy is of added value to IS in pediatric patients, a multi-institutional randomized trial is needed.

Comparison of two new classifications for pediatric myelodysplastic and myeloproliferative disorders

BACKGROUND

The category, cytology, cytogenetics (CCC) system for myelodysplastic syndrome (MDS) and the pediatric WHO system for MDS/myeloproliferative disorder (MPD) have recently been proposed to characterize these diseases in pediatrics.

OBJECTIVE

We compare the CCC and pediatric WHO systems against each other and against the French, American, British (FAB) and adult WHO classifications in order to determine which more accurately classifies these diseases and predicts outcome.

METHODS

An 18-year retrospective review identified patients less than 18 years of age meeting CCC and/or pediatric WHO criteria for the diagnosis of MDS or MPD. Resolution, stability, progression, and death in the subcategories of each system were compared.

RESULTS

Twenty-eight patients were included in the study. Pediatric WHO: 17 patients met criteria, 10 died. Eight developed acute myelogenous leukemia (AML) (seven died), one juvenile myelomonocytic leukemia (JMML) (died), one chronic myelomonocytic leukemia (CMML) (currently in relapse), two died of complications, two responded to BMT, three have stable disease, one resolved. Eleven patients were not classifiable by the pediatric WHO system, one of which progressed to AML and died. CCC: 26 patients met criteria, 9 died. Nine developed AML (8 died), 1 died of complications, 10 responded to treatment (BMT and/or chemotherapy). Four are stable without treatment, two resolved. Two patients with MPD were not classifiable by the CCC system.

CONCLUSIONS

Both the pediatric WHO and CCC systems are better able to classify MDS in children than the adult WHO and FAB classifications. The pediatric WHO system is more exclusive. Children meeting these criteria are more likely to progress to AML or death. The restrictive nature of the pediatric WHO system was unable to classify one case of fatal MDS. The CCC system is more inclusive and can stratify patients into a neutral or poor prognosis based upon outcome. However, the CCC system ignores those diseases with a myeloprolifferative component. This resulted in two cases of MPD that were unclassifiable by the CCC system. One of these patients died, the other is currently in relapse.

Nucleophosmin interacts with and inhibits the catalytic function of eukaryotic initiation factor 2 kinase PKR

In normal cells the protein kinase PKR effects apoptosis in response to various extra and intracellular cues and can also function to suppress the neoplastic phenotype. Because most neoplastic cells are resistant to certain apoptotic cues, we reasoned that an early molecular event in carcinogenesis or leukemogenesis might be the inactivation of PKR by expression or activation of intracellular PKR inhibitors. Seeking novel PKR-modulating proteins we report here that nucleophosmin (NPM), a protein frequently overexpressed in a variety of human malignancies, binds to PKR, and inhibits its activation. Co-immunoprecipitation and in vitro binding experiments showed that NPM associated with PKR. Kinase assays demonstrated that recombinant NPM inhibited PKR activation in a dose-dependent manner. In addition, purified recombinant NPM was phosphorylated by activated PKR. Most importantly, overexpression of NPM suppressed PKR activity, enhanced protein synthesis, and inhibited apoptosis. Lymphoblasts from patients with Fanconi anemia (FA) expressed low levels of NPM, which correlated with high ground-state activation of PKR and cellular hypersensitivity to apoptotic cues, but enforced expression of NPM in these mutant cells reduced aberrant apoptotic responses. Inhibition of PKR by NPM may be one mechanism by which neoplastic clones evolve in sporadic malignancies and in neoplastic cells arising in the context of the cancer predisposition syndrome, Fanconi anemia.