Disabling the Fanconi Anemia Pathway in Stem Cells Leads to Radioresistance and Genomic Instability.

Fanconi anemia is an inherited genome instability syndrome characterized by interstrand cross-link hypersensitivity, congenital defects, bone marrow failure, and cancer predisposition. Although DNA repair mediated by Fanconi anemia genes has been extensively studied, how inactivation of these genes leads to specific cellular phenotypic consequences associated with Fanconi anemia is not well understood. Here we report that Fanconi anemia stem cells in the C. elegans germline and in murine embryos display marked nonhomologous end joining (NHEJ)-dependent radiation resistance, leading to survival of progeny cells carrying genetic lesions. In contrast, DNA cross-linking does not induce generational genomic instability in Fanconi anemia stem cells, as widely accepted, but rather drives NHEJ-dependent apoptosis in both species. These findings suggest that Fanconi anemia is a stem cell disease reflecting inappropriate NHEJ, which is mutagenic and carcinogenic as a result of DNA misrepair, while marrow failure represents hematopoietic stem cell apoptosis. SIGNIFICANCE: This study finds that Fanconi anemia stem cells preferentially activate error-prone NHEJ-dependent DNA repair to survive irradiation, thereby conferring generational genomic instability that is instrumental in carcinogenesis.

Amelioration of Mucositis in Proton Therapy of Fanconi Anemia Fanca-/- Mice by JP4-039.

BACKGROUND/AIM: We tested JP4-039, a GS-nitroxide radiation damage mitigator in proton therapy of Fanconi anemia (FA) mice. MATERIALS AND METHODS: Fanca-/- and Fanca+/+ bone marrow stromal cells were pre-treated with JP4-039 and irradiated with either protons or photons (0-10 GyRBE) followed by clonogenic survival and ß-Galactosidase senescence analysis. Fanca-/- and Fanca+/+ mice were pretreated with JP4-039 for 10 min prior to oropharyngeal irradiation with either protons or photons (0 or 30 GyRBE) followed by sacrifice and measurement of oral cavity ulceration, distant hematopoietic suppression, and real-time polymerase chain reaction analysis. RESULTS: JP4-039 reduced oral cavity ulceration in Fanca-/- mice, transcripts Nfkb, Ap1, Sp1, and Nrf2, and proton therapy induced distant marrow suppression. CONCLUSION: JP4-039 protected Fanca-/- and Fanca+/+ cells and mouse oral cavity from both proton and photon radiation.

Induction of TGF-ß by Irradiation or Chemotherapy in Fanconi Anemia (FA) Mouse Bone Marrow Is Modulated by Small Molecule Radiation Mitigators JP4-039 and MMS350.

BACKGROUND/AIM: Total-body irradiation and/or administration of chemotherapy drugs in bone marrow transplantation induce cytokines that can suppress engraftment. Fanconi Anemia (FA) patients have a hyperactive responsiveness to the inhibitory cytokine, transforming growth factor-beta (TGF-ß). Small molecule radiation mitigator drugs, JP4-039 and MMS350, were evaluated for suppression of irradiation or drug-induced TGF-ß. MATERIALS AND METHODS: In vivo induction of TGF-ß by total-body ionizing irradiation (TBI), L-phenylalanine mustard (L-PAM), busulfan or fludarabine, was quantified. In parallel, mitigator drug amelioration of TGF-ß induction in FA D2-/- (FANCD2-/-) mouse bone marrow, was studied in vitro. Tissue culture medium, cell lysates, and mouse plasma were analyzed for TGF-ß levels. RESULTS: Induction of TGF-ß levels in FANCD2-/- and FANCD2+/+ mice and in mouse bone marrow were modulated by both JP4-039 and MMS350. CONCLUSION: Bone marrow transplantation in FA recipients may benefit from administration of small molecule agents that suppress TGF-ß induction.

A flow cytometry assay that measures cellular sensitivity to DNA-damaging agents, customized for clinical routine laboratories.

OBJECTIVES: The clonogenic assay examines cell sensitivity to toxic agents and has been shown to correlate with normal tissue sensitivity to radiotherapy in cancer patients. The clonogenic assay is not clinically applicable due to its intra-individual variability and the time frame of the protocol. We aimed to develop a clinically applicable assay that correlated with the clonogenic assay. DESIGN AND METHODS: We have developed a faster and less labor-intensive cell division assay (CD assay) using flow cytometry and incorporation of a fluorescent thymidine analogue. The CD assay was calibrated to the clonogenic assay and optimized for peripheral blood lymphocytes. RESULTS: Following ionizing radiation of primary human skin fibroblasts, the four-day CD assay gave similar results as the 14-day clonogenic survival assay. In lymphocytes isolated from patient blood samples, the CD assay was able to detect increased radiosensitivity in ataxia telangiectasia patients and increased radiosensitivity after in vitro treatment with DNA-PK and ATM inhibitors. The CD assay found a variation in the intrinsic radiosensitivity of lymphocytes isolated from healthy control samples. The CD assay was able to measure the anti-proliferation effect of different chemotherapeutic drugs in lymphocytes. CONCLUSIONS: Our results indicate that the CD assay is a fast and reliable method to measure the anti-proliferation effect of DNA-damaging agents with a potential to find the most sensitive patients in the work-up before cancer treatment.

FANCD2 influences replication fork processes and genome stability in response to clustered DSBs.

Fanconi Anemia (FA) is a cancer predisposition syndrome and the factors defective in FA are involved in DNA replication, DNA damage repair and tumor suppression. Here, we show that FANCD2 is critical for genome stability maintenance in response to high-linear energy transfer (LET) radiation. We found that FANCD2 is monoubiquitinated and recruited to the sites of clustered DNA double-stranded breaks (DSBs) specifically in S/G2 cells after high-LET radiation. Further, FANCD2 facilitated the repair of clustered DSBs in S/G2 cells and proper progression of S-phase. Furthermore, lack of FANCD2 led to a reduced rate of replication fork progression and elevated levels of both replication fork stalling and new origin firing in response to high-LET radiation. Mechanistically, FANCD2 is required for correct recruitment of RPA2 and Rad51 to the sites of clustered DSBs and that is critical for proper processing of clustered DSBs. Significantly, FANCD2-decifient cells exhibited defective chromosome segregation, elevated levels of chromosomal aberrations, and anchorage-independent growth in response to high-LET radiation. These findings establish FANCD2 as a key factor in genome stability maintenance in response to high-LET radiation and as a promising target to improve cancer therapy.

Long-term results of non-fludarabine versus fludarabine-based stem cell transplantation without total body irradiation in Fanconi anemia patients.

BACKGROUND AND OBJECTIVE: Hematopoietic cell transplantation (HCT) is the only therapeutic modality capable of correcting the hematologic manifestations of Fanconi anemia (FA). The development of well-tolerated immunosuppressive conditioning regimens for FA patients undergoing HCT has proven to be a challenging task for hematologists. DESIGN AND SETTINGS: Retrospective, patients referred to the hematology, oncology and stem cell transplantation research center. PATIENTS AND METHODS: We analyzed the outcome of 53 FA patients who had undergone HCT between 1992 and 2010. The median age at transplantation was 9 years. Patients received transplants from an HLA-identical sibling (n=39) or matched relative (n=9) and one-antigen locus mismatched other relative/sibling (n=5). All of the patients underwent transplantation with fludarabine and non-fludarabine-based conditioning regimens. No radiation therapy was given. RESULTS: The median follow-up period for survivors was 13.5 months (range, 3 months-13.5 years). The 3-year overall survival (OS) was 60.6%. The 3-year OS for patients who did or did not receive fludarabine-based preparative regimens for the allograft was 36.4%, and 70%, respectively. However, there were no statistically significant differences in OS rates between these two groups (P=.112). Graft failure occurred in 4 patients (7.5%). All of these 4 patients had received fludarabine-based conditioning regimens. The incidence of acute GVHD after fludarabine-based regimens was 45% versus 79% in non-fludarabine-based regimens (P=.03). CONCLUSION: Despite the high incidence of acute GVHD (78.6%) in the non-fludarabine group, which resulted in the death of some patients, the OS rate was significantly better than in fludarabine recipients. Therefore, in spite of the fact that recent studies advocate the fludarabine-based conditioning regimens, we propose to conduct a multicenter, prospective study to evaluate the outcomes of regimens employed in FA patients.

Neoadjuvant chemotherapy with reduced-dose carboplatin and gemcitabine for non-small cell lung cancer in a patient with Fanconi anemia.

Fanconi anemia (FA) is characterized by pancytopenia, congenital malformations, and susceptibility to malignancies. We describe a 31-year-old man with FA, who had undergone bone marrow transplantation and whole body irradiation at the age 17 years for FA. Fourteen years later, he presented with squamous cell carcinoma of the bronchus intermedius in the right lung. The tumor was located next to the main pulmonary artery and between the superior and inferior pulmonary veins. Two cycles of neoadjuvant therapy were given in an attempt to decrease tumor size and avoid a potential right pneumonectomy. Treatment consisted of a 21-day cycle with carboplatin (area under the curve 3) given on day 1 and gemcitabine (1250 mg/m) on day 1 and 8. Because FA cells are hypersensitive to DNA crosslinking agents, we reduced the carboplatin dose to minimize treatment-related toxicity. The tumor regressed sufficiently to permit performance of a right middle and lower lobectomy. In our case, neoadjuvant therapy with gemcitabine and low-dose carboplatin exhibited antitumor activity with manageable side-effects, suggesting that this chemotherapy regimen can be safely and effectively used in the treatment of NSCLC in FA patients who have achieved hematopoietic reconstitution after bone marrow transplantation.

Second stem cell transplantation in patients with Fanconi anemia using antithymocyte globulin alone for conditioning.

Despite the promising data on the outcome of allogeneic stem cell transplantation (SCT) in patients with Fanconi anemia (FA), a certain percentage of these patients still experience graft failure; some of these patients undergo second transplants, but the existing data on the outcome of the second SCT in FA patients are scarce, with no long-term follow-up provided in many of the publications addressing this issue. This is a review of our experience in 4 such patients who underwent second stem cell transplants using rabbit ATG only for conditioning. Three engrafted promptly and are alive and free of disease at 25, 23, and 21 months, respectively. We conclude, therefore, that the use of ATG alone for conditioning before a second SCT may offer a chance of long-term disease-free survival for FA patients who fail their first transplant.

Allogeneic haematopoietic cell transplantation from alternative donors with a conditioning regimen of low-dose irradiation, fludarabine and cyclophosphamide in Fanconi anaemia.

A pilot study was undertaken using a fludarabine-based conditioning regimen to improve haematopoietic cell transplantation (HCT) from alternative donors in 27 Fanconi anaemia (FA) patients. Patients were conditioned with 150-180 mg/m2 of fludarabine, 40 mg/kg of cyclophosphamide, 5-10 mg/kg of antithymocyte globulin, and 300-450 cGy of thoracoabdominal/total body irradiation. One patient who received unrelated cord blood transplantation failed to engraft, another patient died of sepsis. The 1-year overall survival was 96.3% (95% CI, 89-100). This conditioning regimen exerted an immunosuppressive effect that enabled durable engraftment in alternative donor HCT without severe toxicity.

The inherited basis of human radiosensitivity.

Certain individuals cannot tolerate 'conventional' doses of radiation therapy. This is known to be true of patients with ataxia-telangiectasia and ligase IV deficiency. Although in vitro testing may not correlate completely with clinical radiosensitivity, fibroblasts and lymphoblasts from patients with both of these disorders have been clearly shown to be radiosensitive. Using a colony survival assay (CSA) to test lymphoblastoid cells after irradiation with 1 Gy, a variety of other genetic disorders have been identified as strong candidates for clinical radiosensitivity, such as Nijmegen breakage syndrome, Mre 11 deficiency, and Fanconi's anemia. These data are presented and considered as a starting-point for the inherited basis of human radiosensitivity.

Haematopoietic cell transplantation in patients with Fanconi anaemia using alternate donors: results of a total body irradiation dose escalation trial.

Allogeneic haematopoietic cell transplantation (HCT) is the only therapeutic modality capable of correcting the haematologic manifestations of Fanconi anaemia (FA). However, HCT from alternative donors has been associated with poor survival. Between June 1993 and July 1998, 29 FA patients (median age 12.1 years; range 3.7-48.5 years) were enrolled in a prospective phase I-II dose escalation study. All patients were treated with cyclophosphamide 40 mg/kg, total body irradiation (TBI) 450 cGy or 600 cGy and antithymocyte globulin (ATG), followed by HCT from an alternative donor. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporin A for 6 months, short course methylprednisolone (2 mg/kg/day) between days +5 and +19 and marrow T-cell depletion by counterflow elutriation. The probability of developing grade III-IV toxicity was 17% (95% CI 3-31%). For the 25 marrow recipients, the probability of neutrophil engraftment (ANC 0.5 x 109/l by day 45) was 63% (95% CI 42-82%). Probabilities of grade II-IV acute GVHD and chronic GVHD were 32% (95%CI 10-54%) and 0% respectively. With a median follow-up of 18 months, the probability of survival for the entire cohort at 1 year was 34% (95% CI 17-51%). The presence of lymphocyte somatic mosaicism [i.e. the presence of diepoxybutane (DEB)-insensitive cells] was associated with a significantly increased risk of graft failure. Disappointingly, the use of higher dose TBI and post-transplant ATG did not improve engraftment. More effective peritransplant immunosuppression, especially in FA patients with somatic mosaicism, was required to overcome the barrier of graft rejection. New conditioning regimens adapted to each individual's alkylator sensitivity are needed to improve the outcome of alternative donor HCT for FA.

Loss of the Fanconi anemia group C protein activity results in an inability to activate caspase-3 after ionizing radiation.

Fanconi anemia (FA) is a human genetic disease featuring cancer predisposition, genetic instability and DNA damage hypersensitivity. Although abnormalities in DNA repair and cell cycle checkpoint have been proposed as the underlying defect in this syndrome, these hypotheses did not provide full explanations of the complex phenotype. Although not exclusive of such possibilities, alterations in the control of apoptosis might account for the pleiotropic phenotype of this syndrome. We and others have previously reported a deregulation of the apoptotic response to mitomycin C, suggesting that the products of the Fanconi anemia group C protein (FANCC) contribute to the regulation of apoptosis. To explore the functional importance of the apoptotic alterations in FA we analyzed biochemical steps of the execution phase of apoptosis stimulated by another DNA damaging agent, the gamma-ray using FA cell lines derived from complementation group C (FA-C) independent patients. It is shown that the poly(ADP-ribose) polymerase, a target of caspase-3, is not cleaved in FA-C after ionizing radiation (IR). Moreover, caspase-3 is not processed in its active form and, its activity is not increased by IR in FA-C cells compared to normal cells. Altogether, these results demonstrate that loss of the FANCC activity results in a deficiency of the IR-induced apoptosis which is due to an inability to activate caspase-3. Our work suggests that apoptosis signaling induced by mitomycin C and IR is subject to common regulation involving the FANCC protein.

Transplantation for Fanconi's anaemia: long-term follow-up of fifty patients transplanted from a sibling donor after low-dose cyclophosphamide and thoraco-abdominal irradiation for conditioning.

We describe the long-term follow-up of 50 Fanconi's anaemia patients who were transplanted from a related donor with a median follow-up of >6 years. The survival estimate was 74.4% at 54 months and 58.5% at 100 months. All patients were conditioned with low-dose cyclophosphamide and thoraco-abdominal irradiation. Acute graft-versus-host disease (GvHD) of grade II or more developed in 26 patients and chronic GvHD developed in 30/43 (69.9%) patients. The survival of patients without chronic GvHD (n = 13) was 100%. In addition to chronic GvHD, 20 pre-transplant transfusions was shown to have an adverse impact on survival by multivariate analysis (relative risk = 7.08, P = 0.0003). Prospective follow-up of growth and endocrine function could be performed in 31 patients. Of 20 boys, six have already reached normal puberty within the expected time. Among the 11 girls, three were at the pubertal age at the time of analysis. Growth retardation was common, whereas late complications (e.g. peripheral hypothyroidism, cataract) were rare. However, the most important long-term complication was the occurrence of cancer in seven patients (8-year projected incidence 24%). Among the 32 survivors, 27 (84.5%) had a normal and four a moderately reduced performance status, and all achieved complete engraftment with donor cells. Therefore transplantation was able to cure these patients who remain at high risk for developing late complications. Clearly, a genetic predisposition and chronic GvHD could have led to the development of these cancers. However, we cannot completely rule out irradiation as a cofactor in the genesis of these cancers, and therefore no longer use irradiation for the conditioning of Fanconi's anaemia patients.

Radiosensitivity in Fanconi anemia: application to the conditioning for bone marrow transplantation.

Fanconi anemia is characterised by pancytopenia, malformations and chromosomal breaks probably related to a congenital defect of DNA repair mechanisms. The evolution is always fatal unless, the patient receives a bone marrow transplant from an HLA identical sibling. According to preliminary work on sensitivity of FA cells to alkylating agents and to in vivo radiosensitivity tests, we used a modified conditioning regimen with cyclophosphamide 20 mg/kg and 5 Grays thoraco-abdominal irradiation. Nineteen patients are reported. The actuarial survival is 74% with a median follow-up time of 4 years (range 6 months to 6 years). GVH was the main complication (58%). It was responsible directly or indirectly for 4 deaths. These results show that BMT in FA is successful in the large majority of cases. The decrease of the dose cyclophosphamide allowed a good engraftment without major toxicity. Studies are in progress for using this type of protocol in situations without a HLA matched sibling donor.