DNA double-strand breaks (DSBs) are considered as one of the primary causes of cancer but their induction by hydrogen peroxide (H2O2) is still controversial. In this work, we studied whether the high levels of H2O2 produced in the thyroid to oxidize iodide could induce DNA modifications. Scores of DNA damage, in terms of strand breaks, were obtained by comet assay (alkaline condition for single-strand breaks (SSBs) and neutral condition for DSBs). We demonstrated that in a rat thyroid cell line (PCCl3), non-lethal concentrations of H2O2 (0.1–0.5 mmol/l) as well as irradiation (1–10 Gy) provoked a large number of SSBs (∼2–3 times control DNA damage values) but also high levels of DSBs (1.2–2.3 times control DNA damage values). We confirmed the generation of DSBs in this cell line and also in human thyroid in primary culture and in pig thyroid slices by measuring phosphorylation of histone H2AX. l-Buthionine-sulfoximine, an agent that depletes cells of glutathione, decreased the threshold to observe H2O2-induced DNA damage. Moreover, we showed that DNA breaks induced by H2O2 were more slowly repaired than those induced by irradiation. In conclusion, H2O2 causes SSBs and DSBs in thyroid cells. DSBs are produced in amounts comparable with those observed after irradiation but with a slower repair. These data support the hypothesis that the generation of H2O2 in thyroid could also play a role in mutagenesis particularly in the case of antioxidant defense deficiency.
Natacha Driessens, Soetkin Versteyhe, Chiraz Ghaddhab, Agnès Burniat, Xavier De Deken, Jacqueline Van Sande, Jacques-Emile Dumont, Françoise Miot and Bernard Corvilain
Iulia Potorac, Patrick Petrossians, Adrian F Daly, Orsalia Alexopoulou, Sophie Borot, Mona Sahnoun-Fathallah, Frederic Castinetti, France Devuyst, Marie-Lise Jaffrain-Rea, Claire Briet, Florina Luca, Marion Lapoirie, Flavius Zoicas, Isabelle Simoneau, Alpha M Diallo, Ammar Muhammad, Fahrettin Kelestimur, Elena Nazzari, Rogelio Garcia Centeno, Susan M Webb, Marie-Laure Nunes, Vaclav Hana, Véronique Pascal-Vigneron, Irena Ilovayskaya, Farida Nasybullina, Samia Achir, Diego Ferone, Sebastian J C M M Neggers, Brigitte Delemer, Jean-Michel Petit, Christof Schöfl, Gerald Raverot, Bernard Goichot, Patrice Rodien, Bernard Corvilain, Thierry Brue, Franck Schillo, Luaba Tshibanda, Dominique Maiter, Jean-François Bonneville and Albert Beckers
GH-secreting pituitary adenomas can be hypo-, iso- or hyper-intense on T2-weighted MRI sequences. We conducted the current multicenter study in a large population of patients with acromegaly to analyze the relationship between T2-weighted signal intensity on diagnostic MRI and hormonal and tumoral responses to somatostatin analogs (SSA) as primary monotherapy. Acromegaly patients receiving primary SSA for at least 3 months were included in the study. Hormonal, clinical and general MRI assessments were performed and assessed centrally. We included 120 patients with acromegaly. At diagnosis, 84, 17 and 19 tumors were T2-hypo-, iso- and hyper-intense, respectively. SSA treatment duration, cumulative and mean monthly doses were similar in the three groups. Patients with T2-hypo-intense adenomas had median SSA-induced decreases in GH and IGF-1 of 88% and 59% respectively, which were significantly greater than the decreases observed in the T2-iso- and hyper-intense groups (P < 0.001). Tumor shrinkage on SSA was also significantly greater in the T2-hypo-intense group (38%) compared with the T2-iso- and hyper-intense groups (8% and 3%, respectively; P < 0.0001). The response to SSA correlated with the calculated T2 intensity: the lower the T2-weighted intensity, the greater the decrease in random GH (P < 0.0001, r = 0.22), IGF-1 (P < 0.0001, r = 0.14) and adenoma volume (P < 0.0001, r = 0.33). The T2-weighted signal intensity of GH-secreting adenomas at diagnosis correlates with hormone reduction and tumor shrinkage in response to primary SSA treatment in acromegaly. This study supports its use as a generally available predictive tool at diagnosis that could help to guide subsequent treatment choices in acromegaly.