cytochrome-c-t and amonafide

In the course of screening for novel anticancer compounds, B1 (N-(2-(Dimethylamino)ethyl)-2-aminothiazonaphthalimide), a novel naphthalimide-based DNA intercalator, was generated as a new anticancer candidate. For the first time, our investigation demonstrates that B1 inhibited the growth of HeLa cells by the induction of cell cycle arrest and apoptosis. Analysis of flow cytometry and western blots of HeLa cells treated with B1 revealed an appreciable cell cycle arrest and apoptotic induction in dose and time-dependent manner via the p53-dependent pathway. Furthermore, the release of cytochrome c from mitochondria was detected using confocal microscopy in HeLa cells treated with B1. Accordingly, these data demonstrate that the anticancer activity of B1 is associated with the activation of p53 and the release of cytochrome c, which suggest that B1 might have therapeutic potential against cervix carcinoma as an effective lead compound.

Topics: Adenine; Apoptosis; Benzothiazoles; Caspases; Cell Cycle; Cell Cycle Proteins; Cell Proliferation; Cell Shape; Cell Survival; Cytochromes c; DNA, Neoplasm; Dose-Response Relationship, Drug; Flow Cytometry; Fluorescence; Gene Expression Regulation, Neoplastic; HeLa Cells; Humans; Intercalating Agents; Mitochondria; Naphthalimides; Necrosis; Organophosphonates; RNA, Messenger; RNA, Small Interfering; Staining and Labeling; Time Factors; Tumor Stem Cell Assay; Tumor Suppressor Protein p53

Amonafide, a naphthalimide derivative, although selected for exploratory clinical trials for its potent anticancer activity, has long been challenged by its unpredictable side effects. In the present study, a novel amonafide analogue, 2-(2-dimethylamino)-6-thia-2-aza-benzo-[def]-chrysene-1,3-diones (R16) was synthesized by substituting 5'-NH(2) of the naphthyl with a heterocyclic group to amonafide, with additional introduction of a thiol group. In a panel of various human tumor cell lines, R16 was more cytotoxic than its parent compound amonafide. It was also effective against multidrug-resistant cells. Importantly, the i.p. administration of R16 inhibited tumor growth in mice implanted with S-180 sarcoma and H(22) hepatoma. The molecular and cellular machinery studies showed that the R16 functions as a topoisomerase II (topo II) poison via binding to the ATPase domain of human topo IIalpha. The superior cytotoxicity of R16 to amonafide was ascribed to its potent effects on trapping topo II-DNA cleavage complexes. Moreover, using a topo II catalytic inhibitor aclarubicin, ataxia-telangiectasia-mutated (ATM)/ATM- and Rad3-related (ATR) kinase inhibitor caffeine and topo II-deficient HL-60/MX2 cells, we further showed that R16-triggered DNA double-strand breaks, tumor cell cycle arrest, and apoptosis were in a topo II-dependent manner. Taken together, R16 stood out by its improved anticancer activity, appreciable anti-multidrug resistance activities, and well-defined topo II poisoning mechanisms, as comparable with the parent compound amonafide. All these collectively promise the potential value of R16 as an anticancer drug candidate, which deserves further development.

Topics: Adenine; Animals; Antineoplastic Agents; Apoptosis; Caspases; Cell Division; Cell Proliferation; Cytochromes c; DNA Topoisomerases, Type II; Enzyme Inhibitors; Female; Flow Cytometry; G2 Phase; Humans; Imides; In Situ Nick-End Labeling; Isoquinolines; Liver Neoplasms, Experimental; Mice; Mice, Inbred Strains; Naphthalimides; Organophosphonates; Poly(ADP-ribose) Polymerases; Sarcoma, Experimental; Thiophenes; Topoisomerase II Inhibitors; Tumor Cells, Cultured