Induction of Cyclin E and Inhibition of DNA Synthesis by the Novel Acronycine Derivative S23906-1 Precede the Irreversible Arrest of Tumor Cells in S Phase Leading to Apoptosis

• Published in: Molecular pharmacology 2001-12, Vol.60 (6), p.1383-1391
• Main Authors: Léonce, S, Pérez, V, Lambel, S, Peyroulan, D, Tillequin, F, Michel, S, Koch, M, Pfeiffer, B, Atassi, G, Hickman, J A, Pierré, A
• Format: Article
• Language: English
• Subjects: Acronine - analogs & derivatives; Acronine - pharmacology; Antineoplastic Agents - pharmacology; Apoptosis; Bromodeoxyuridine - metabolism; Bromodeoxyuridine - pharmacology; Cell Division - drug effects; Cyclin E - biosynthesis; DNA - biosynthesis; DNA - drug effects; Flow Cytometry; HT29 Cells; Humans; S Phase - drug effects; Tumor Cells, Cultured
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.60.6.1383

S23906 -1 is a diester derivative of 1,2-dihydrobenzo[ b ]acronycine with an unknown mechanism of action. This cytotoxic compound was 20-fold more potent than acronycine in inhibiting the proliferation of six tumor cell lines. Using a clonogenic assay of cell survival, the HT29 human colon carcinoma cell line was 100-fold more sensitive to S23906 -1 than acronycine. Cell cycle analysis, by flow cytometry, showed that S23906 -1 induced a partially reversible arrest of HT29 cells in G 2 +M at 1 μM and below and an irreversible arrest in S phase at 2.5 μM and above. These cell cycle effects were followed by cell death through apoptosis, quantified by annexin-V labeling. Inhibition of DNA synthesis was observed by complete prevention of bromodeoxyuridine (BrdU) incorporation after only 4 h of incubation with 5 μM S23906 -1. Interestingly, under the same experimental conditions, a significant increase of cyclin E protein level was observed without any modification of cyclins D1, D2, D3, or A. This overexpressed cyclin E protein was not complexed with Cdk2, as shown by western blotting for Cdk2 in immunoprecipitates of cyclin E. Similar inhibition of BrdU incorporation and elevation of cyclin E protein were observed after treatment with cytosine arabinoside, which reversibly inhibited progression into S phase, but not after DNA damage induced by cisplatin. S23906 -1 thus has a novel mechanism of action. A cell line resistant to S23906 -1 showed that overexpression of cyclin E was implicated in the novel cytotoxic activity of this compound.