title: DNA damage responses triggered by a highly cytotoxic monofunctional DNA alkylator, hedamycin, a pluramycin antitumor antibiotic.
abstract: Long-term exposure (72 h) to hedamycin, a monofunctional DNA alkylator of the pluramycin class of antitumor antibiotics, decreased growth of mammalian cells by 50% at subnanomolar concentrations. Short-term treatment (4 h) rapidly reduced DNA synthesis by 50% also at subnanomolar concentrations, but substantially higher levels were needed to block RNA synthesis while protein synthesis even at very high hedamycin concentrations remained unaffected. Hedamycin treatment at concentrations below its growth IC(50) induced only a transient and temporary accumulation of cells in G(2). Somewhat higher concentrations resulted in substantial S-phase arrest, and at increasing concentrations, complete cell cycle arrest in G(1) was observed without the appearance of a sub-G(1) cell population. Neither inhibition of cell growth nor cell cycle arrest appeared to be dependent on ataxia and Rad-related kinase expression. DNA damage checkpoint proteins including p53, chk1, and chk2 were differentially activated by hedamycin depending on the concentration and duration of treatment. The level of downstream cell cycle regulators such as cdc25A, E2F1, cyclin E, and p21 were also altered under conditions that induced cell cycle arrest, but atypically, p21 overexpression was observed only in S-phase-arrested cells. Apoptotic indicators were only observed at moderate hedamycin concentrations associated with S-phase arrest, while increasing concentrations, when cells were arrested in G(1), resulted in a reduction of these signals. Taken together, the responses of cells to hedamycin are distinct with regard to its effect on cell cycle but also in the unusual concentration-dependent manner of activation of DNA damage and cell cycle checkpoint proteins as well as the induction of apoptotic-associated events.
authors.affiliation: Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
authors.forename: Lan Chun
authors.initials: LC
authors.lastname: Tu
authors.forename: Thomas
authors.initials: T
authors.lastname: Melendy
authors.forename: Terry A
authors.initials: TA
authors.lastname: Beerman
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology*; D000617:Aminoglycosides / Q000494:pharmacology*; D000880:Anthraquinones / Q000494:pharmacology*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D019927:Cyclin E / Q000378:metabolism; D003603:Cytotoxins / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D004249:DNA Damage / Q000187:drug effects*; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D045325:HCT116 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D012313:RNA / Q000096:biosynthesis; D016196:S Phase / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D000477:Alkylating Agents; D000617:Aminoglycosides; D000880:Anthraquinones; D000903:Antibiotics, Antineoplastic; D018797:Cell Cycle Proteins; D019927:Cyclin E; D003603:Cytotoxins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D014157:Transcription Factors; C003169:pluramycin; C001328:hedamycin; D012313:RNA; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases; D004253:DNA Nucleotidylexotransferase; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases