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.
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 G2+M at 1 microM and below and an irreversible arrest in S phase at 2.5 microM 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 microM 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.
Léonce
S
S
Institut de Recherches Servier, Suresnes, France. stephane.leonce@fr.netgrs.com
Pérez
V
V
Lambel
S
S
Peyroulan
D
D
Tillequin
F
F
Michel
S
S
Koch
M
M
Pfeiffer
B
B
Atassi
G
G
Hickman
J A
JA
Pierré
A
A
D000175:Acronine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001973:Bromodeoxyuridine / Q000378:metabolism / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D019927:Cyclin E / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects*; D005434:Flow Cytometry; D019073:HT29 Cells; D006801:Humans; D016196:S Phase / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D019927:Cyclin E; C436732:S 23906-1; D004247:DNA; D001973:Bromodeoxyuridine; D000175:Acronine