Oxidative Stress -a Phenotypic Hallmark of Fanconi Anemia and Down Syndrome: The Effect of Antioxidants

Effects of Deacetylase Inhibition on the Activation of the Antioxidant Response and Aerobic Metabolism in Cellular Models of Fanconi Anemia

Fanconi anemia (FA) is a rare genetic disease characterized by a dysfunctional DNA repair and an oxidative stress accumulation due to defective mitochondrial energy metabolism, not counteracted by endogenous antioxidant defenses, which appear down-expressed compared to the control. Since the antioxidant response lack could depend on the hypoacetylation of genes coding for detoxifying enzymes, we treated lymphoblasts and fibroblasts mutated for the FANC-A gene with some histone deacetylase inhibitors (HDACi), namely, valproic acid (VPA), beta-hydroxybutyrate (OHB), and EX527 (a Sirt1 inhibitor), under basal conditions and after hydrogen peroxide addition. The results show that VPA increased catalase and glutathione reductase expression and activity, corrected the metabolic defect, lowered lipid peroxidation, restored the mitochondrial fusion and fission balance, and improved mitomycin survival. In contrast, OHB, despite a slight increase in antioxidant enzyme expressions, exacerbated the metabolic defect, increasing oxidative stress production, probably because it also acts as an oxidative phosphorylation metabolite, while EX527 showed no effect. In conclusion, the data suggest that VPA could be a promising drug to modulate the gene expression in FA cells, confirming that the antioxidant response modulation plays a pivotal in FA pathogenesis as it acts on both oxidative stress levels and the mitochondrial metabolism and dynamics quality.

A Multidrug Approach to Modulate the Mitochondrial Metabolism Impairment and Relative Oxidative Stress in Fanconi Anemia Complementation Group A

Fanconi Anemia (FA) is a rare recessive genetic disorder characterized by aplastic anemia due to a defective DNA repair system. In addition, dysfunctional energy metabolism, lipid droplets accumulation, and unbalanced oxidative stress are involved in FA pathogenesis. Thus, to modulate the altered metabolism, Fanc-A lymphoblast cell lines were treated with quercetin, a flavonoid compound, C75 (4-Methylene-2-octyl-5-oxotetrahydrofuran-3-carboxylic acid), a fatty acid synthesis inhibitor, and rapamycin, an mTOR inhibitor, alone or in combination. As a control, isogenic FA cell lines corrected with the functional Fanc-A gene were used. Results showed that: (i) quercetin recovered the energy metabolism efficiency, reducing oxidative stress; (ii) C75 caused the lipid accumulation decrement and a slight oxidative stress reduction, without improving the energy metabolism; (iii) rapamycin reduced the aerobic metabolism and the oxidative stress, without increasing the energy status. In addition, all molecules reduce the accumulation of DNA double-strand breaks. Two-by-two combinations of the three drugs showed an additive effect compared with the action of the single molecule. Specifically, the quercetin/C75 combination appeared the most efficient in the mitochondrial and lipid metabolism improvement and in oxidative stress production reduction, while the quercetin/rapamycin combination seemed the most efficient in the DNA breaks decrement. Thus, data reported herein suggest that FA is a complex and multifactorial disease, and a multidrug strategy is necessary to correct the metabolic alterations.

Genotoxic C8-Arylamino-2'-deoxyadenosines Act as Latent Alkylating Agents to Induce DNA Interstrand Cross-Links

DNA interstrand cross-links (ICLs) are extremely deleterious and structurally diverse, driving the evolution of ICL repair pathways. Discovering ICL-inducing agents is, thus, crucial for the characterization of ICL repair pathways and Fanconi anemia, a genetic disease caused by mutations in ICL repair genes. Although several studies point to oxidative stress as a cause of ICLs, oxidative stress-induced cross-linking events remain poorly characterized. Also, polycyclic aromatic amines, potent environmental carcinogens, have been implicated in producing ICLs, but their identities and sequences are unknown. To close this knowledge gap, we tested whether ICLs arise by the oxidation of 8-arylamino-2'-deoxyadenosine (ArNHdA) lesions, adducts produced by arylamino carcinogens. Herein, we report that ArNHdA acts as a latent cross-linking agent to generate ICLs under oxidative conditions. The formation of an ICL from 8-aminoadenine, but not from 8-aminoguanine, highlights the specificity of 8-aminopurine-mediated ICL production. Under the influence of the reactive oxygen species (ROS) nitrosoperoxycarbonate, ArNHdA (Ar = biphenyl, fluorenyl) lesions were selectively oxidized to generate ICLs. The cross-linking reaction may occur between the C2-ArNHdA and N2-dG, presumably via oxidation of ArNHdA into a reactive diiminoadenine intermediate followed by the nucleophilic attack of the N2-dG on the diiminoadenine. Overall, ArNHdA-mediated ICLs represent rare examples of ROS-induced ICLs and polycyclic aromatic amine-mediated ICLs. These results reveal novel cross-linking chemistry and the genotoxic effects of arylamino carcinogens and support the hypothesis that C8-modified adenines with low redox potential can cause ICLs in oxidative stress.

Endoscopic findings and esophageal cancer incidence among Fanconi Anemia patients participating in an endoscopic surveillance program

BACKGROUND AND AIMS

The primary clinical characteristics of Fanconi Anemia (FA) include typical physical features, progressive bone marrow failure, and an increased incidence of neoplasms, including esophageal carcinoma. Currently, there are no data regarding endoscopic findings or the interval time to malignancy in these patients. Data about the contribution of Human Papilloma Virus (HPV) to esophageal carcinoma is conflicting. Our objective is to document the upper gastrointestinal (GI) findings at baseline, document cancer incidence, and evaluate the role of HPV among these cancers.

METHODS

We reviewed endoscopic and clinical data of FA subjects who participated in active surveillance before cancer diagnosis. Incident esophageal cancers were stained for HPV ^p16 protein.

RESULTS

Eight FA patients were included (men 62.5%; median age at first endoscopy 20 years, median endoscopies number: 5.5). At baseline, 8/8 had endoscopic evidence for reflux esophagitis. In 3/8 the reflux esophagitis was mild and in 5/8 it was moderate or severe. During the follow up time (median time 4.5 years 2/8 developed Barrett's esophagus and 2/8 patients had incident esophageal squamous cell carcinoma during follow up, at intervals of eight and eighteen months from the previous upper endoscopy. Both cancers stained negative for HPV ^P16.

CONCLUSIONS

FA subjects have both an extremely high risk for esophageal cancer within short intervals and a very high prevalence of reflux esophagitis with various severities. Active surveillance programs in specialized centers including annual upper endoscopies should be considered in these patients.

Combination therapy with atorvastatin and celecoxib delays tumor formation in a Fanconi anemia mouse model

BACKGROUND

Fanconi anemia is an inherited bone marrow failure disorder associated with a high incidence of leukemia and solid tumors. Currently, no interventions to prevent or delay the formation of solid tumors are available.

PROCEDURE

Two of the most important hallmarks of Fanconi anemia are inflammation and oxidative stress. In this study, we administrated the antioxidant atorvastatin and the anti-inflammatory drug celecoxib to cohorts of Fancd2^-/- /Trp53^+/- mice, a model of Fanconi anemia. Treatment started at weaning and continued until the mice developed a palpable mass or suffered from >20% weight loss. Tumor samples and selected tissues were subjected to histopathological examination. χ² test was performed to analyze tumor incidence, and Kaplan-Meier survival curves were evaluated with log-rank test. In addition, a small cohort of mice was monitored for the safety of the drugs.

RESULTS

The combined oral administration of both drugs significantly delayed tumor onset in Fancd2^-/- /Trp53^+/- mice. Specifically, the treatment delayed the onset of ovarian tumors in Fancd2^-/- /Trp53^+/- mice and increased the mean ovarian tumor-free survival time by 17%, whereas this combinatorial drug regimen did not have a significant effect on other tumor types. In addition, no detrimental effects on hematopoiesis from the drug treatment were observed during a 12-month safety monitoring.

CONCLUSIONS

The data presented here suggest that a combination of atorvastatin and celecoxib may be a good candidate for chemoprevention in Fanconi anemia.