1. ¹Centre National de la Recherche Scientifique, UMR CNRS 6101, Faculté de Médecine de Limoges, Université de Limoges, CHU Dupuytren, Laboratoire d'Hématologie, Limoges, France, Equipe labellisée de la Ligue Nationale Contre le Cancer
2. ²UPRES EA 3406, Université Paris 13, Service de Biochimie, Hôpital Avicenne, Assistance Publique Hôpitaux de Paris, Bobigny, France
3. ³Service d'Hématologie Biologique, Hôpital Avicenne, Assistance Publique Hôpitaux de Paris, Bobigny, France
4. ⁴Service d'Hématologie Clinique, CHU Dupuytren, Limoges, France
5. ⁵FRE CNRS 2937, Institut André Lwoff, France
6. ⁶GSF, Institute of Clinical Molecular Biology and Tumour Genetics, 81377 Munich, Germany

Correspondence: J Feuillard, Laboratoire d'Hématologie et UMR CNRS 6101, CNRS, Faculté de Médecine, Université de Limoges, CHU Dupuytren, 2 Avenue Martin Luther King, Limoges 87042, France. Tel: +33 5 55 05 61 80; Fax: 33 5 55 05 61 85; E-mail: jean.feuillard@chu-limoges.fr

Received 16 April 2007; Revised 13 September 2007; Accepted 1 October 2007; Published online 9 November 2007.

Abstract

Chemotherapeutic drugs such as fludarabine^*, doxorubicin or cisplatin are very potent activators of the anti-oncogene p53. Convergent studies suggest that p53 and STAT1 (signal transducer and activator of transcription 1) cooperate in the induction of cell death. We show that these drugs are also activators of STAT1 in p53-expressing cells, but not in p53-null cells. STAT1 activation was obtained in the presence of both the secretion inhibitor brefeldine A and the inhibitor of RNA synthesis, actinomycin D. p53-dependent STAT1 activation was reversed by overexpression of MDM2 and siRNAs against p53. Genetic analysis of p53 showed that expression of transcriptionally inactive p53 punctual mutants markedly increased Y701-STAT1 phosphorylation, and suggests that the p53 DNA-binding domain was alternatively involved in STAT1 activation or p53 multimerization. Immunoprecipitation experiments showed that ataxia telangiectasia mutated, p53, STAT1 and c-Abl1 (Abelson murine leukaemia viral oncogene homologue 1) were associated together. Treatment of cells with the c-Abl1 tyrosine kinase inhibitor STI571 decreased STAT1 activation by genotoxic drugs. Finally, genotoxic agents sensitized cells in response to very low doses of both interferon and (IFN and ). These results show that genotoxic drugs induce STAT1 activation, an effect that depends on p53 protein but not on p53 transcriptional activity, and point to a novel pathway of STAT1 activation by genotoxic drugs, with involvement of c-Abl1 tyrosine kinase in sensitizing cells to IFN response.