title: Mitotane sensitizes adrenocortical cancer cells to ionizing radiations by involvement of the cyclin B1/CDK complex in G2 arrest and mismatch repair enzymes modulation.
abstract: Mitotane inhibits steroid synthesis by an action on steroidogenic enzymes, as 11beta-hydroxylase and cholesterol side chain cleavage. It also has a cytotoxic effect on the adrenocortical cells and represents a primary drug used in the adrenocortical carcinoma (ACC). H295R and SW13 cell lines were treated with mitotane 10(-5) M and ionizing radiations (IR) in combination therapy, inducing an irreversible inhibition of cell growth in both adrenocortical cancer cells. As shown in a previous report, mitotane/IR combination treatment induced a cell accumulation in the G2 phase. Here, we report the radiosensitizing properties of mitotane in two different ACC cell lines. The drug reveals the effectiveness to enhance the cytotoxic effects of IR by attenuating DNA repair and interfering on the activation of mitosis promoting factor (MPF), mainly regulated by the degradation of cyclin B1 in the mitotic process. These events may explain the inappropriate activation of cdc2, implicated in G2/M phase arrest and probably induced by the mitotane and IR in the combined treatment. Indeed, treatment with purvalanol, a cdc2-inhibitor prevents cell cycle arrest, triggering the G2/M transition. The observation that mitotane and IR in combination treatment amplifies the activation level of cyclin B/cdc2 complexes contributing to cell cycle arrest, suggests that the MPF could function as a master signal for controlling the temporal order of different mitotic events. Moreover, we report that mitotane interferes in modulation of mismatch repair (MMR) enzymes, revealing radiosensitizing drug ability.
authors.affiliation: II Faculty of Medicine, Sapienza University of Rome, Endocrinology Sant'Andrea Hospital, Via di Grottarossa 1035, Rome 00189, Italy.
authors.forename: Lidia
authors.initials: L
authors.lastname: Cerquetti
authors.forename: Camilla
authors.initials: C
authors.lastname: Sampaoli
authors.forename: Donatella
authors.initials: D
authors.lastname: Amendola
authors.forename: Barbara
authors.initials: B
authors.lastname: Bucci
authors.forename: Silvia
authors.initials: S
authors.lastname: Misiti
authors.forename: Giorgio
authors.initials: G
authors.lastname: Raza
authors.forename: Ugo
authors.initials: U
authors.lastname: De Paula
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Marchese
authors.forename: Ercole
authors.initials: E
authors.lastname: Brunetti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Toscano
authors.forename: Antonio
authors.initials: A
authors.lastname: Stigliano
mesh_terms: D000306:Adrenal Cortex Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D018268:Adrenocortical Carcinoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D019926:Cyclin B / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053843:DNA Mismatch Repair / Q000187:drug effects / Q000502:physiology; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004353:Drug Evaluation, Preclinical; D016195:G2 Phase / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008939:Mitotane / Q000494:pharmacology*; D046912:Multiprotein Complexes / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: C471843:6-((3-chloro)anilino)-2-(isopropyl-2-hydroxyethylamino)-9-isopropylpurine; D019926:Cyclin B; D046912:Multiprotein Complexes; D047428:Protein Kinase Inhibitors; D011687:Purines; D011838:Radiation-Sensitizing Agents; D008939:Mitotane; D018844:Cyclin-Dependent Kinases; D045643:DNA Repair Enzymes