The Fanconi anemia/BRCA (FA/BRCA) pathway is a DNA repair pathway that is required for excision of DNA interstrand cross-links. The 17 known FA proteins, along with several FA-associated proteins (FAAPs), cooperate in this pathway to detect, unhook, and excise DNA cross-links and to subsequently repair the double-strand breaks generated in the process. In the current study, we identified a patient with FA with a point mutation in FANCA, which encodes a mutant FANCA protein (FANCAI939S). FANCAI939S failed to bind to the FAAP20 subunit of the FA core complex, leading to decreased stability. Loss of FAAP20 binding exposed a SUMOylation site on FANCA at amino acid residue K921, resulting in E2 SUMO-conjugating enzyme UBC9-mediated SUMOylation, RING finger protein 4-mediated (RNF4-mediated) polyubiquitination, and proteasome-mediated degradation of FANCA. Mutation of the SUMOylation site of FANCA rescued the expression of the mutant protein. Wild-type FANCA was also subject to SUMOylation, RNF4-mediated polyubiquitination, and degradation, suggesting that regulated release of FAAP20 from FANCA is a critical step in the normal FA pathway. Consistent with this model, cells lacking RNF4 exhibited interstrand cross-linker hypersensitivity, and the gene encoding RNF4 was epistatic with the other genes encoding members of the FA/BRCA pathway. Together, the results from our study underscore the importance of analyzing unique patient-derived mutations for dissecting complex DNA repair processes.
Malric A, Defachelles AS, Leblanc T, et al.Fanconi anemia and solid malignancies in childhood: a national retrospective study.
Pediatr Blood Cancer. 2015; 62(3):463-70 [PubMed
] Related Publications
BACKGROUND: Fanconi anemia (FA) predisposes to hematologic disorders and myeloid neoplasia in childhood and to solid cancers, mainly oral carcinomas, in early adulthood. Few cases of solid cancers have been reported in childhood.
PROCEDURES: We conducted a national retrospective study of solid tumors occurring in patients registered with or determined to have FA during childhood in France. Phenotypic features, tumor type, cancer treatment, and outcome were analyzed. Whenever available, fresh-frozen tumors were analyzed by microarray-based comparative genomics hybridization.
RESULTS: We identified eight patients with FA with solid tumor from 1986 to 2012. For two patients, the diagnosis of FA was unknown at the time of cancer diagnosis. Moreover, we identified one fetus with a brain tumor. All patients showed failure to thrive and had dysmorphic features and abnormal skin pigmentation. Seven patients had BRCA2/FANCD1 mutations; five of these featured more than one malignancy and the median age at the time of cancer diagnosis was 11 months (range 0.4-3 years). Solid tumor types included five nephroblastomas, two rhabdomyosarcomas, two neuroblastomas, and three brain tumors. Two children died from the toxic effects of chemotherapy, two patients from the cancer, and one patient from secondary leukemia. Only one BRCA2 patient was alive more than 3 years after diagnosis, after tailored chemotherapy.
CONCLUSION: Solid tumors are rare in FA during childhood, except in patients with BRCA2/FANCD1 mutations. The proper genetic diagnosis is mandatory to tailor the treatment.
Fanconi anemia (FA) patients have an increased risk of head and neck squamous cell carcinoma (HNSCC) at a higher rate with no apparent risk factors. HNSCC of FA patients is an aggressive tumor characterized by multifocal origin, early metastases and frequent recurrences. Given that cancer stem cells (CSC) drive tumorigenesis, tumor recurrence and metastasis, in this study, we characterized the CSC population in FA and sporadic HNSCC. The Aldefluor assay was used to characterize and isolate CSC with high aldehyde dehydrogenase (ALDH) activity (ALDHpos) in cell lines derived from FA and sporadic HNSCC. Isolated ALDHpos and ALDHneg cells were examined for the expression of stemness genes using reverse transcription-polymerase chain reaction (RT-PCR) array. Tumor cell-derived FA and sporadic HNSCC were examined for their ability to form tumorspheres in vitro. Stem-like cell population in FA and sporadic HNSCC in human and mouse xenograft tumors were evaluated using ALDH isoform 1 (ALDH1) immunohistochemistry. FA‑HNSCC cell lines harbor a greater proportion of ALDHpos cells (15-31%) compared to sporadic HNSCC (10%). Expression of Nanog, Oct-3/4 and Stella, molecular markers of undifferentiated embryonic stem (ES) cells were detected in the ALDHpos FA‑HNSCC cells and not in the ALDHneg cells. FA‑HNSCC cell lines revealed enhanced in vitro tumorsphere formation compared to sporadic HNSCC cells. A higher percentage of ALDH1pos tumor cells are noted in the human and mouse xenograft tumors of FA‑HNSCC compared to sporadic HNSCC tumors. FA‑HNSCC are highly enriched for CSC and may serve as a model to develop CSC-targeted therapies for HNSCC.
Cutaneous melanoma (CM) is the most lethal skin cancer. The Fanconi anemia (FA) pathway involved in DNA crosslink repair may affect CM susceptibility and prognosis. Using data derived from published genome-wide association study, we comprehensively analyzed the associations of 2,339 common single-nucleotide polymorphisms (SNPs) in 14 autosomal FA genes with overall survival (OS) in 858 CM patients. By performing false-positive report probability corrections and stepwise Cox proportional hazards regression analyses, we identified significant associations between CM OS and four putatively functional SNPs: BRCA2 rs10492396 (AG vs. GG: adjusted hazard ratio (adjHR)=1.85, 95% confidence interval (CI)=1.16-2.95, P=0.010), rs206118 (CC vs. TT+TC: adjHR=2.44, 95% CI=1.27-4.67, P=0.007), rs3752447 (CC vs. TT+TC: adjHR=2.10, 95% CI=1.38-3.18, P=0.0005), and FANCA rs62068372 (TT vs. CC+CT: adjHR=1.85, 95% CI=1.27-2.69, P=0.001). Moreover, patients with an increasing number of unfavorable genotypes (NUG) of these loci had markedly reduced OS and melanoma-specific survival (MSS). The final model incorporating with NUG, tumor stage, and Breslow thickness showed an improved discriminatory ability to classify both 5-year OS and 5-year MSS. Additional investigations, preferably prospective studies, are needed to validate our findings.
Ayas M, Siddiqui K, Al-Jefri A, et al.Factors affecting the outcome of related allogeneic hematopoietic cell transplantation in patients with Fanconi Anemia.
Biol Blood Marrow Transplant. 2014; 20(10):1599-603 [PubMed
] Related Publications
Hematopoietic cell transplantation (HCT) can cure bone marrow failure in patients with Fanconi Anemia (FA), and it is generally accepted that these patients should receive low-intensity conditioning because of the underlying DNA repair defect in their cells. Outcomes for recipients of matched related HCT have generally been favorable, but only a few studies have scrutinized the factors that may affect the eventual outcome of these patients. This retrospective analysis of 94 pediatric patients with FA who underwent related HCT at King Faisal Specialist Hospital & Research Center was carried out to attempt to identify factors that may affect outcome. Results showed overall survival (OS) probabilities of 92.5%, 89%, and 86% at 1, 5, and 10 years, respectively. In univariate analysis, use of higher dose cyclophosphamide (CY) (60 mg/kg) conditioning was associated with a better 10-year OS than lower dose CY (20 mg/kg) conditioning (91% versus 82%, respectively; P = .035), and use of radiation-containing regimens was associated with a significantly lower 10-year OS than nonradiation regimens (76% versus 91%, respectively; P = .005). Of the 4 regimens used in this study, the fludarabine-based regimen was associated with the highest survival (95.2%; P = .034). The use of the higher dose CY (60 mg/kg) was associated with a significantly increased incidence of hemorrhagic cystitis (HC) (20% versus 5.6% respectively; P = .049). Three patients (3%) developed squamous cell carcinoma (2 oropharyngeal and 1 genitourinary), at 9.4, 5.4, and 13.3 years after HCT; 2 of them had radiation-containing conditioning. In conclusion, our data suggest that although using a higher dose CY (60 mg/kg) conditioning regimen may be associated with better survival, it is also associated with a significantly increased risk of HC. The addition of fludarabine to the low-dose CY (20 mg/kg) is associated with the best survival. On the other hand, radiation-containing regimens are associated with significantly lower survival.
Trejo Bittar HE, Radder JE, Ranganathan S, et al.Clear cell sarcoma of the kidney in a child with Fanconi anemia.
Pediatr Dev Pathol. 2014 Jul-Aug; 17(4):297-301 [PubMed
] Related Publications
Patients with Fanconi anemia subgroup D1, attributable to biallelic mutations in BRCA2, have an increased risk of solid tumors. Tumors in the kidneys of these patients are almost exclusively Wilms tumor. We report the first recorded case, to our knowledge, of a Clear Cell Sarcoma of the Kidney in a patient with this cancer predisposition syndrome. We review different aspects of the need for careful clinical observation in patients of this complementation group, given their risk for malignancy.
Ichikawa T, Hashimoto J, Yabe M, et al.Detection of early esophageal cancer and cervical lymph node metastases by (18)F-FDG PET/CT in a patient with Fanconi anemia.
Clin Nucl Med. 2014; 39(5):459-61 [PubMed
] Related Publications
Fanconi anemia is a rare autosomal recessive disease characterized by multiple congenital anomalies, pancytopenia, and cancer susceptibility, especially to leukemia and squamous cell carcinoma of the head and neck or esophagus. F-FDG PET/CT is a useful tool to assess tumor staging and follow-up of esophageal cancer. We report a rare case of cervical esophageal cancer and lymph node metastases detected on F-FDG PET/CT in a patient with Fanconi anemia after bone marrow transplantation.
Mycoplasma salivarium belongs to the class of the smallest self-replicating Tenericutes and is predominantly found in the oral cavity of humans. In general it is considered as a non-pathogenic commensal. However, some reports point to an association with human diseases. M. salivarium was found e.g. as causative agent of a submasseteric abscess, in necrotic dental pulp, in brain abscess and clogged biliary stent. Here we describe the detection of M. salivarium on the surface of a squamous cell carcinoma of the tongue of a patient with Fanconi anaemia (FA). FA is an inherited bone marrow failure syndrome based on defective DNA-repair that increases the risk of carcinomas especially oral squamous cell carcinoma. Employing high coverage, massive parallel Roche/454-next-generation-sequencing of 16S rRNA gene amplicons we analysed the oral microbiome of this FA patient in comparison to that of an FA patient with a benign leukoplakia and five healthy individuals. The microbiota of the FA patient with leukoplakia correlated well with that of the healthy controls. A dominance of Streptococcus, Veillonella and Neisseria species was typically observed. In contrast, the microbiome of the cancer bearing FA patient was dominated by Pseudomonas aeruginosa at the healthy sites, which changed to a predominance of 98% M. salivarium on the tumour surface. Quantification of the mycoplasma load in five healthy, two tumour- and two leukoplakia-FA patients by TaqMan-PCR confirmed the prevalence of M. salivarium at the tumour sites. These new findings suggest that this mycoplasma species with its reduced coding capacity found ideal breeding grounds at the tumour sites. Interestingly, the oral cavity of all FA patients and especially samples at the tumour sites were in addition positive for Candida albicans. It remains to be elucidated in further studies whether M. salivarium can be used as a predictive biomarker for tumour development in these patients.
BACKGROUND: There is no method routinely used to predict response to anthracycline and cyclophosphamide-based chemotherapy in the clinic; therefore patients often receive treatment for breast cancer with no benefit. Loss of the Fanconi anemia/BRCA (FA/BRCA) DNA damage response (DDR) pathway occurs in approximately 25% of breast cancer patients through several mechanisms and results in sensitization to DNA-damaging agents. The aim of this study was to develop an assay to detect DDR-deficient tumors associated with loss of the FA/BRCA pathway, for the purpose of treatment selection.
METHODS: DNA microarray data from 21 FA patients and 11 control subjects were analyzed to identify genetic processes associated with a deficiency in DDR. Unsupervised hierarchical clustering was then performed using 60 BRCA1/2 mutant and 47 sporadic tumor samples, and a molecular subgroup was identified that was defined by the molecular processes represented within FA patients. A 44-gene microarray-based assay (the DDR deficiency assay) was developed to prospectively identify this subgroup from formalin-fixed, paraffin-embedded samples. All statistical tests were two-sided.
RESULTS: In a publicly available independent cohort of 203 patients, the assay predicted complete pathologic response vs residual disease after neoadjuvant DNA-damaging chemotherapy (5-fluorouracil, anthracycline, and cyclophosphamide) with an odds ratio of 3.96 (95% confidence interval [Cl] =1.67 to 9.41; P = .002). In a new independent cohort of 191 breast cancer patients treated with adjuvant 5-fluorouracil, epirubicin, and cyclophosphamide, a positive assay result predicted 5-year relapse-free survival with a hazard ratio of 0.37 (95% Cl = 0.15 to 0.88; P = .03) compared with the assay negative population.
CONCLUSIONS: A formalin-fixed, paraffin-embedded tissue-based assay has been developed and independently validated as a predictor of response and prognosis after anthracycline/cyclophosphamide-based chemotherapy in the neoadjuvant and adjuvant settings. These findings warrant further validation in a prospective clinical study.
Meyer S, Tischkowitz M, Chandler K, et al.Fanconi anaemia, BRCA2 mutations and childhood cancer: a developmental perspective from clinical and epidemiological observations with implications for genetic counselling.
J Med Genet. 2014; 51(2):71-5 [PubMed
] Related Publications
Fanconi anaemia (FA) is an inherited condition characterised by congenital and developmental abnormalities and a strong cancer predisposition. In around 3-5% of cases FA is caused by biallelic mutations in the BRCA2 gene. Individuals heterozygous for BRCA2 mutations have an increased risk of inherited breast and ovarian cancer. We reviewed the mutation spectrum in BRCA2-associated FA, and the spectrum and frequency of BRCA2 mutations in distinct populations. The rarity of FA due to biallelic BRCA2 mutations supports a fundamental role of BRCA2 for prevention of malignant transformation during development. The spectrum of malignancies seen associated with FA support the concept of a tissue selectivity of BRCA2 mutations for development of FA-associated cancers. This specificity is illustrated by the distinct FA-associated BRCA2 mutations that appear to predispose to specific brain or haematological malignancies. For some populations, the number of FA-patients with biallelic BRCA2 disruption is smaller than that expected from the carrier frequency, and this implies that some pregnancies with biallelic BRCA2 mutations do not go to term. The apparent discrepancy between expected and observed incidence of BRCA2 mutation-associated FA in high-frequency carrier populations has important implications for the genetic counselling of couples with recurrent miscarriages from high-risk populations.
Peffault de Latour R, Porcher R, Dalle JH, et al.Allogeneic hematopoietic stem cell transplantation in Fanconi anemia: the European Group for Blood and Marrow Transplantation experience.
Blood. 2013; 122(26):4279-86 [PubMed
] Related Publications
Although allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for patients with Fanconi anemia (FA), published series mostly refer to single-center experience with limited numbers of patients. We analyzed results in 795 patients with FA who underwent first HSCT between May 1972 and January 2010. With a 6-year median follow-up, overall survival was 49% at 20 years (95% confidence interval, 38-65 years). Better outcome was observed for patients transplanted before the age of 10 years, before clonal evolution (ie, myelodysplastic syndrome or acute myeloid leukemia), from a matched family donor, after a conditioning regimen without irradiation, the latter including fludarabine. Chronic graft-versus-host disease and secondary malignancy were deleterious when considered as time-dependent covariates. Age more than 10 years at time of HSCT, clonal evolution as an indication for transplantation, peripheral blood as source of stem cells, and chronic graft-versus-host disease were found to be independently associated with the risk for secondary malignancy. Changes in transplant protocols have significantly improved the outcome of patients with FA, who should be transplanted at a young age, with bone marrow as the source of stem cells.
Our recently published work suggests that DNA helicases such as the Werner syndrome helicase (WRN) represent a novel class of proteins to target for anticancer therapy. Specifically, pharmacological inhibition of WRN helicase activity in human cells defective in the Fanconi anemia (FA) pathway of interstrand cross-link (ICL) repair are sensitized to the DNA cross-linking agent and chemotherapy drug mitomycin C (MMC) by the WRN helicase inhibitor NSC 617145. (1) The mechanistic basis for the synergistic interaction between NSC 617145 and MMC is discussed in this paper and extrapolated to potential implications for genetic or chemically induced synthetic lethality provoked by cellular exposure to the WRN helicase inhibitor under the context of relevant DNA repair deficiencies associated with cancers or induced by small-molecule inhibitors. Experimental data are presented showing that small-molecule inhibition of WRN helicase elevates sensitivity to MMC-induced stress in human cells that are deficient in both FANCD2 and DNA protein kinase catalytic subunit (DNA-PKcs). These findings suggest a model in which drug-mediated inhibition of WRN helicase activity exacerbates the deleterious effects of MMC-induced DNA damage when both the FA and NHEJ pathways are defective. We conclude with a perspective for the FA pathway and synthetic lethality and implications for DNA repair helicase inhibitors that can be developed for anticancer strategies.
Extremely high cancer incidence in Fanconi anemia (FA) patients has long suggested that the FA signaling pathway is a tumor suppressor pathway. Indeed, our recent findings, for the first time, indicate that the FA pathway plays a significant role in suppressing the development of non-FA human cancer. Also our studies on FA group D2 protein (FANCD2) have, among the first, documented the crosstalks between the FA and Rad6/Rad18 (HHR6) pathways upon DNA damage. In this review, we will discuss how our studies enhance the understanding of the FA tumor suppressor pathway.
In patients with lung cancer whose tumors harbor activating mutations in the EGF receptor (EGFR), increased responses to platinum-based chemotherapies are seen compared with wild-type cancers. However, the mechanisms underlying this association have remained elusive. Here, we describe a cellular phenotype of cross-linker sensitivity in a subset of EGFR-mutant lung cancer cell lines that is reminiscent of the defects seen in cells impaired in the Fanconi anemia pathway, including a pronounced G2-M cell-cycle arrest and chromosomal radial formation. We identified a defect downstream of FANCD2 at the level of recruitment of FAN1 nuclease and DNA interstrand cross-link (ICL) unhooking. The effect of EGFR mutation was epistatic with FANCD2. Consistent with the known role of FANCD2 in promoting RAD51 foci formation and homologous recombination repair (HRR), EGFR-mutant cells also exhibited an impaired RAD51 foci response to ICLs, but not to DNA double-strand breaks. EGFR kinase inhibition affected RAD51 foci formation neither in EGFR-mutant nor wild-type cells. In contrast, EGFR depletion or overexpression of mutant EGFR in wild-type cells suppressed RAD51 foci, suggesting an EGFR kinase-independent regulation of DNA repair. Interestingly, EGFR-mutant cells treated with the PARP inhibitor olaparib also displayed decreased FAN1 foci induction, coupled with a putative block in a late HRR step. As a result, EGFR-mutant lung cancer cells exhibited olaparib sensitivity in vitro and in vivo. Our findings provide insight into the mechanisms of cisplatin and PARP inhibitor sensitivity of EGFR-mutant cells, yielding potential therapeutic opportunities for further treatment individualization in this genetically defined subset of lung cancer.
BACKGROUND AND PURPOSE: We have previously shown that cells with a defective Fanconi anaemia (FA) pathway are hypersensitive to trabectedin, a DNA-binding anti-cancer tetrahydroisoquinoline (DBAT) whose adducts functionally mimic a DNA inter-strand cross link (ICL). Here we expand these observations to new DBATs and investigate whether our findings in primary untransformed cells can be reproduced in human cancer cells.
EXPERIMENTAL APPROACH: Initially, the sensitivity of transformed and untransformed cells, deficient or not in one component of the FA pathway, to mitomycin C (MMC) and three DBATs, trabectedin, Zalypsis and PM01183, was assessed. Then, the functional interaction of these drugs with the FA pathway was comparatively investigated.
KEY RESULTS: While untransformed FA-deficient haematopoietic cells were hypersensitive to both MMC and DBATs, the response of FA-deficient squamous cell carcinoma (SCC) cells to DBATs was similar to that of their respective FA-competent counterparts, even though these FA-deficient SCC cells were hypersensitive to MMC. Furthermore, while MMC always activated the FA pathway, the DBATs inhibited the FA pathway in the cancer cell lines tested and this enhanced their response to MMC.
CONCLUSIONS AND IMPLICATIONS: Our data show that although DBATs functionally interact with DNA as do agents that generate classical ICL, these drugs should be considered as FA pathway inhibitors rather than activators. Moreover, this effect was most significant in a variety of cancer cells. These inhibitory effects of DBATs on the FA pathway could be exploited clinically with the aim of 'fanconizing' cancer cells in order to make them more sensitive to other anti-tumour drugs.
Cappelli E, Ravera S, Vaccaro D, et al.Mitochondrial respiratory complex I defects in Fanconi anemia.
Trends Mol Med. 2013; 19(9):513-4 [PubMed
] Related Publications
Fanconi anemia (FA) is a rare, complex disorder that manifests in childhood. Children with FA suffer bone marrow failure, leukemias, or solid tumors. FA-associated mutations are found in 15 proteins that are involved in DNA repair. Some of these proteins have extranuclear activities involving redox balance, apoptosis, and energy metabolism; and recent data demonstrate respiratory impairment in FA cells, suggesting that altered mitochondrial function is a factor in this disease.
Lin J, Kutler DIWhy otolaryngologists need to be aware of Fanconi anemia.
Otolaryngol Clin North Am. 2013; 46(4):567-77 [PubMed
] Related Publications
Fanconi anemia (FA) is a rare disorder inherited in an autosomal recessive fashion, with an estimated incidence of 1:360,000 births. Although hematologic complications are the most common manifestation of this disease, cancers, especially of the head and neck, are also prominent. The chromosomal fragility of patients with FA necessitates careful planning of therapy and monitoring, and awareness of this rare disorder is crucial to recognizing it in the clinic.
Patients with Fanconi anemia (FA) and dyskeratosis congenita (DC) are at high risk of head and neck squamous cell carcinomas (HNSCC) and anogenital squamous cell carcinomas (SCC). In the general population, these sites (particularly oropharyngeal SCC) may be associated with infection with human papillomavirus (HPV). In FA and DC, however, the majority of HNSCC occur in the oral cavity. We investigated the HPV status of HNSCC and vulvar SCC from nine patients with FA and four with DC using a very sensitive PCR assay, and found HPV16 DNA in only a single vulvar tumor from one patient with FA, and in none of the HNSCC. These results suggest that HPV may not be the cause of SCC in patients with FA or DC, and that vaccination may not reduce the incidence of HNSCC in these patients.
Yao CJ, Du W, Zhang Q, et al.Fanconi anemia pathway--the way of DNA interstrand cross-link repair.
Pharmazie. 2013; 68(1):5-11 [PubMed
] Related Publications
The study of rare genetic diseases usually inspires the research of cancer biology. Fanconi anemia (FA), is a rare cancer susceptibility syndrome with an incidence of only 1 per 350,000 births. FA is an autosomal recessive disease with three main features: chromosome instability, hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC), cisplatin and so on, and susceptible to a number of cancer types, mainly leukemia and squamous cell carcinomas of the head and neck or gynecologic system. DNA crosslinking agents may led to DNA cross-linking lesion, and Fanconi anemia pathway plays a key role in repairing its cross-linking. However, FA pathway is closely linked with carcinogenesis and tumor drug resistance. This paper mainly focuses on the FA pathway and its progress in cancer research.
Böhringer M, Obermeier K, Griner N, et al.siRNA screening identifies differences in the Fanconi anemia pathway in BALB/c-Trp53+/- with susceptibility versus C57BL/6-Trp53+/- mice with resistance to mammary tumors.
Oncogene. 2013; 32(48):5458-70 [PubMed
] Free Access to Full Article Related Publications
BALB/c mice heterozygous for Trp53 develop a high proportion of spontaneous mammary tumors, a phenotype distinct from other mouse strains. BALB/c-Trp53+/- female mice, thus, resemble the hereditary Li-Fraumeni syndrome (LFS) characterized by early-onset of breast cancer, even though LFS involves TP53 mutations, which may involve not only loss- but also gain-of-function. Previous analysis of tumors in BALB/c-Trp53+/- females showed frequent loss of heterozygosity involving the wild-type allele of Trp53 and displayed characteristics indicative of mitotic recombination. Critical involvement of DNA double-strand break (DSB) repair dysfunction, particularly of homologous recombination (HR), was also noticed in the etiology of human breast cancer. To better define functional alterations in BALB/c-Trp53+/- mice, we applied a fluorescence-based DSB repair assay on mouse embryonic fibroblasts (MEFs) from BALB/c-Trp53+/- versus C57BL/6J-Trp53+/- mice. This approach revealed deregulation of HR but not non-homologous end-joining (NHEJ) in BALB/c-Trp53+/-, which was further confirmed for mammary epithelial cells. Screening of a small interfering RNA-library targeting DSB repair, recombination, replication and signaling genes, identified 25 genes causing differences between homologous DSB repair in the two strains upon silencing. Interactome analysis of the hits revealed clustering of replication-related and fanconi anemia (FA)/breast cancer susceptibility (BRCA) genes. Further dissection of the functional change in BALB/c-Trp53+/- by immunofluorescence microscopy of nuclear 53BP1, Replication protein A (RPA) and Rad51 foci uncovered differences in crosslink and replication-associated repair. Chromosome breakage, G2 arrest and biochemical analyses indicated a FA pathway defect downstream of FancD2 associated with reduced levels of BRCA2. Consistent with polygenic models for BRCA, mammary carcinogenesis in BALB/c-Trp53+/- mice may, therefore, be promoted by a BRCA modifier allele in the FA pathway in the context of partial p53 loss-of-function.
Uveal melanoma (UM) is unique among cancers in displaying reduced endogenous levels of sister chromatid exchange (SCE). Here we demonstrate that FANCD2 expression is reduced in UM and that ectopic expression of FANCD2 increased SCE. Similarly, FANCD2-deficient fibroblasts (PD20) derived from Fanconi anaemia patients displayed reduced spontaneous SCE formation relative to their FANCD2-complemented counterparts, suggesting that this observation is not specific to UM. In addition, spontaneous RAD51 foci were reduced in UM and PD20 cells compared with FANCD2-proficient cells. This is consistent with a model where spontaneous SCEs are the end product of endogenous recombination events and implicates FANCD2 in the promotion of recombination-mediated repair of endogenous DNA damage and in SCE formation during normal DNA replication. In both UM and PD20 cells, low SCE was reversed by inhibiting DNA-PKcs (DNA-dependent protein kinase, catalytic subunit). Finally, we demonstrate that both PD20 and UM are sensitive to acetaldehyde, supporting a role for FANCD2 in repair of lesions induced by such endogenous metabolites. Together, these data suggest FANCD2 may promote spontaneous SCE by influencing which double-strand break repair pathway predominates during normal S-phase progression.
Fanconi anaemia (FA) is a rare autosomal recessive or X-linked inherited disease characterised by an increased incidence of bone marrow failure (BMF), haematological malignancies and solid tumours. Cells from individuals with FA show a pronounced sensitivity to DNA interstrand crosslink (ICL)-inducing agents, which manifests as G2-M arrest, chromosomal aberrations and reduced cellular survival. To date, mutations in at least 15 different genes have been identified that cause FA; the products of all of these genes are thought to function together in the FA pathway, which is essential for ICL repair. Rapidly following the discovery of FA genes, mutant mice were generated to study the disease and the affected pathway. These mutant mice all show the characteristic cellular ICL-inducing agent sensitivity, but only partially recapitulate the developmental abnormalities, anaemia and cancer predisposition seen in individuals with FA. Therefore, the usefulness of modelling FA in mice has been questioned. In this Review, we argue that such scepticism is unjustified. We outline that haematopoietic defects and cancer predisposition are manifestations of FA gene defects in mice, albeit only in certain genetic backgrounds and under certain conditions. Most importantly, recent work has shown that developmental defects in FA mice also arise with concomitant inactivation of acetaldehyde metabolism, giving a strong clue about the nature of the endogenous lesion that must be repaired by the functional FA pathway. This body of work provides an excellent example of a paradox in FA research: that the dissimilarity, rather than the similarity, between mice and humans can provide insight into human disease. We expect that further study of mouse models of FA will help to uncover the mechanistic background of FA, ultimately leading to better treatment options for the disease.
Within the last decade, multiple novel congenital human disorders have been described with genetic defects in known and/or novel components of several well-known DNA repair and damage response pathways. Examples include disorders of impaired nucleotide excision repair, DNA double-strand and single-strand break repair, as well as compromised DNA damage-induced signal transduction including phosphorylation and ubiquitination. These conditions further reinforce the importance of multiple genome stability pathways for health and development in humans. Furthermore, these conditions inform our knowledge of the biology of the mechanics of genome stability and in some cases provide potential routes to help exploit these pathways therapeutically. Here, I will review a selection of these exciting findings from the perspective of the disorders themselves, describing how they were identified, how genotype informs phenotype, and how these defects contribute to our growing understanding of genome stability pathways.
Wong WM, Parvathaneni U, Jewell PD, et al.Squamous cell carcinoma of the oral tongue in a patient with Fanconi anemia treated with radiotherapy and concurrent cetuximab: a case report and review of the literature.
Head Neck. 2013; 35(10):E292-8 [PubMed
] Related Publications
BACKGROUND: Fanconi anemia (FA) is a rare autosomal recessive genetic disorder characterized by bone marrow failure and increased risk of cancers including acute myelogenous leukemia and various solid tumors, especially head and neck cancer. Management of head and neck cancer in the setting of FA is complicated by pancytopenia, poor tolerance of chemotherapy, and potentially increased radiosensitivity. There are limited reports on tolerance of radiotherapy (RT) in patients with FA.
METHODS: We report a case of a patient with FA who presented with a small oral tongue cancer that was excised. He rapidly developed extensive locoregional recurrence and underwent surgical resection followed by postoperative RT with concurrent cetuximab.
RESULTS: Both RT and cetuximab were well tolerated with manageable toxicities. Unfortunately, the patient died of early locoregional disease progression.
CONCLUSIONS: RT with concurrent cetuximab was well tolerated and may be an appropriate option in patients with FA. However, many patients have a poor prognosis due to aggressive disease.
Comment on: Panneerselvam J, et al. Cell Cycle 2012; 11:2947-55.
Effectiveness of DNA cross-linking drugs in the treatment of bladder cancer suggests that bladder cancer cells may have harbored an insufficient cellular response to DNA cross-link damage, which will sensitize cells to DNA cross-linking agents. Cell sensitivity benefits from deficient DNA damage responses, which, on the other hand, can cause cancer. Many changed cellular signaling pathways are known to be involved in bladder tumorigenesis; however, DNA cross-link damage response pathway [Fanconi anemia (FA) pathway], whose alterations appear to be a plausible cause of the development of bladder cancer, remains an under-investigated area in bladder cancer research. In this study, we found FAVL (variant of FA protein L--FANCL) was elevated substantially in bladder cancer tissues examined. Ectopic expression of FAVL in bladder cancer cells as well as normal human cells confer an impaired FA pathway and hypersensitivity to Mitomycin C, similar to those found in FA cells, indicating that FAVL elevation may possess the same tumor promotion potential as an impaired FA pathway harbored in FA cells. Indeed, a higher level of FAVL expression can promote the growth of bladder cancer cells in vitro and in vivo, which, at least partly, results from FAVL perturbation of FANCL expression, an essential factor for the activation of the FA pathway. Moreover, a higher level of FAVL expression was found to be associated with chromosomal instability and the invasiveness of bladder cancer cells. Collectively, FAVL elevation can increase the tumorigenic potential of bladder cancer cells, including the invasive potential that confers the development of advanced bladder cancer. These results enhance our understanding the pathogenesis of human bladder cancer, holding a promise to develop additional effective tools to fight human bladder cancer.
Stecklein SR, Jensen RAIdentifying and exploiting defects in the Fanconi anemia/BRCA pathway in oncology.
Transl Res. 2012; 160(3):178-97 [PubMed
] Related Publications
Defects in components of DNA repair pathways are responsible for numerous hereditary cancer syndromes and are also common in many sporadic malignancies. Inherited mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 or components of the Fanconi anemia (FA) complex incite genomic instability and predispose to malignancy. The products of the BRCA and FA genes participate in a conserved DNA damage repair pathway that is responsible for repairing interstrand crosslinks and double-strand DNA breaks by homologous recombination. While the genetic instability resulting from FA/BRCA dysfunction contributes to cancer pathogenesis, deficiency of these genes also lends to therapeutic exploitation. Crosslinking agents and ionizing radiation induce damage in cancer cells that requires the FA/BRCA pathway to be resolved; thus cancers that are deficient in BRCA1, BRCA2, or any other component of the FA/BRCA pathway are hypersensitive to these agents. Moreover, emerging synthetic lethal strategies offer opportunities to selectively target cancer cells with defects in homologous recombination. Conversely, enhanced activity of the FA/BRCA pathway is responsible for acquired resistance to specific therapeutic agents, suggesting that both dysfunction and hyperfunction of the FA/BRCA repair machinery are rational targets for cancer therapy. Selection of specific cytotoxic agents based on repair capacity may improve responses and enable personalized cytotoxic chemotherapy. This article reviews the FA/BRCA pathway and current approaches to identify deficiencies within it, discusses synthetic lethality and enhanced repair capacity as causes of therapeutic hypersensitivity and resistance, respectively, and highlights recent studies that have linked FA/BRCA pathway function with therapeutic efficacy.
Fanconi anemia (FA) is a rare recessive DNA repair disorder that is clinically characterized by congenital malformations, progressive bone marrow failure, and increased incidence of malignancies, especially acute myeloid leukemia and squamous cell carcinomas of the head and neck (HNSCCs) and the anogenital regions. On a cellular level, typical features of the disorder are a high degree of genomic instability and an increased sensitivity to bi-functionally alkylating agents. So far, germ-line defects in 15 different FA genes have been identified. Some of these FA genes are also established as tumor susceptibility genes for familiar cancers.In recent years, the prevention and therapy of HNSCCs in FA patients has become more important as the percentage of patients surviving into adulthood is rising. HNSCCs appear in very young FA patients without common risk factors. Since cisplatin-based chemotherapy in combination with radiotherapy, essential parts of the standard treatment approach for sporadic HNSCCs, cannot be used in FA patients due to therapy-associated toxicities and mortalities even with reduced dosing, surgery is the most important treatment option for HNSCCs, in FA patients and requires an early and efficient detection of malignant lesions. So far, no uniform treatment protocol for the management of HNSCCs in FA patients exists. Therefore, we propose that the information on affected FA patients should be collected worldwide, practical therapeutic guidelines developed and national treatment centers established.
Masserot-Lureau C, Adoui N, Degos F, et al.Incidence of liver abnormalities in Fanconi anemia patients.
Am J Hematol. 2012; 87(5):547-9 [PubMed
] Related Publications
Patients with Fanconi anemia (FA) are prone to liver tumors, especially after androgen treatment, but other liver abnormalities have not been described for these patients. Here, we systematically reviewed liver manifestations in a cohort of 64 adult and pediatric patients with FA followed in a single center. "Significant biological liver abnormalities(SBLA)" in the absence of any androgen treatment were found in five patients, including two children, belonging to rare FA groups; these two patients presented with a very severe chronic cytolysis pattern which may be classified as a new FA phenotype. Liver radiological abnormalities, which include hepatic tumors (n 5 4), hepatomegaly(n 5 1), hyperechogenicity (n 5 2), and a previously undescribed biliary duct dilatation as demonstrated by magnetic resonance cholangiopancreatography(MRCP) (n 5 2), were found in eight patients who received androgen treatment or who had iron overload. Lastly, we found no correlation between cytolysis intensity and high levels of alpha-fetoprotein (AFP); this common finding in FA patients cannot therefore be explained by hepatocyte regeneration.
Rodríguez A, Sosa D, Torres L, et al.A Boolean network model of the FA/BRCA pathway.
Bioinformatics. 2012; 28(6):858-66 [PubMed
] Related Publications
MOTIVATION: Fanconi anemia (FA) is a chromosomal instability syndrome originated by inherited mutations that impair the Fanconi Anemia/Breast Cancer (FA/BRCA) pathway, which is committed to the repair of DNA interstrand cross-links (ICLs). The disease displays increased spontaneous chromosomal aberrations and hypersensitivity to agents that create DNA interstrand cross-links. In spite of DNA damage, FA/BRCA-deficient cells are able to progress throughout the cell cycle, probably due to the activity of alternative DNA repair pathways, or due to defects in the checkpoints that monitor DNA integrity.
RESULTS: We propose a Boolean network model of the FA/BRCA pathway, Checkpoint proteins and some alternative DNA repair pathways. To our knowledge, this is the largest network model incorporating a DNA repair pathway. Our model is able to simulate the ICL repair process mediated by the FA/BRCA pathway, the activation of Checkpoint proteins observed by recurrent DNA damage, as well as the repair of DNA double-strand breaks and DNA adducts. We generated a series of simulations for mutants, some of which have never been reported and thus constitute predictions about the function of the FA/BRCA pathway. Finally, our model suggests alternative DNA repair pathways that become active whenever the FA/BRCA pathway is defective.