1. ¹Université de Lyon, Université Lyon-I, Lyon, France
2. ²Laboratoire de Radiobiologie Cellulaire et Moléculaire, EA-3738, Faculté de Médecine Lyon-Sud, Oullins, France
3. ³Hospices Civils de Lyon, Lyon, France
4. ⁴Laboratoire d'Anatomie et de Cytologie Pathologiques, Pierre Bénite, France
5. ⁵Ciblage Thérapeutique en Oncologie, EA-3738, Oullins, France
6. ⁶Laboratoire de Biochimie, Centre de Biologie Est, Lyon, France
7. ⁷The Prostate Centre, Vancouver General Hospital, Department of Urological Sciences, Vancouver, British Columbia, Canada
8. ⁸Service de Radiothérapie, Pierre Bénite, France
9. ⁹Laboratoire de Biologie des Tumeurs, Pierre Bénite, France

Correspondence: Claire Rodriguez-Lafrasse, Laboratoire de Radiobiologie Cellulaire et Moléculaire, EA-3738, Faculté de Médecine Lyon-Sud, BP12, 69921 Oullins Cedex, France. E-mail: claire.rodriguez@sante.univ-lyon1.fr

Received 28 November 2008; Accepted 30 March 2009; Published online 12 May 2009.

Abstract

In a wide range of human cancers, increased levels of heat shock protein 27 (Hsp27) are closely associated with tumorigenesis, metastasis, resistance to anticancer therapeutics, and thus poor prognosis. In this study, we evaluate the radiosensitizing effects of Hsp27 gene silencing using OGX-427, a second-generation antisense oligonucleotide (ASO), on the radioresistant head and neck squamous cell carcinoma (HNSCC) SQ20B cells. In vitro, the downregulation of Hsp27 significantly enhanced radiation-induced apoptotic and clonogenic death, and promoted Akt inactivation. In vivo, combining OGX-427 with local tumor irradiation (5 2 Gy) led to a significant regression of SQ20B tumors related to a high rate of apoptosis and decreased levels of glutathione antioxidant defenses. Increasing the total radiation dose (15 2 Gy) significantly amplified the radiosensitizing effect of OGX-427. Treatment of tumors with OGX-427 plus radiation resulted in a decrease in angiogenesis associated with a reduced activation of the Akt pathway. Furthermore, the combined treatment enhanced the survival of SQ20B-bearing mice and showed no signs of acute and delayed toxicity. Our findings demonstrate for the first time that Hsp27 knockdown enhances the cytotoxic effects of radiotherapy in vivo and provide preclinical proof of principle for clinical trials using Hsp27 antisense technology in the treatment of patients with HNSCC radioresistant cancers.