The use of Nutlin‐3 as a radiosensitiser in laryngeal carcinoma cells harbouring wild‐type p53

Abstract

Objectives. Radiotherapy is one of the mainstays of treatment for squamous cell carcinoma of the larynx but is often associated with severe morbidity. Providing patients with targeted treatment according to tumour type is a major goal of clinicians treating the disease. It has previously been shown that p53 is a critical mediator of radiation response and thus we investigated its influence on radiosensitivity and also whether Nutlin‐3 (the small molecule inhibitor of p53/MDM2 interaction) could radiosensitise tumours. Methods. Seven cell lines derived exclusively from patients with laryngeal carcinoma and with defined p53 status (determined by direct sequencing of exons 2–11 and intron/exon boundaries) were examined. Radiosensitivity was determined by clonogenic assays following treatment with gamma irradiation in the presence and absence of Nutlin‐3. Flow cytometry was used to determine cell cycle characteristics and the levels of apoptosis and senescence were also measured. Results. Cells with p53 homozygous mutations were relatively radiosensitive (SF2 < 20%). Cell lines with wild‐type p53, heterozygous and homozygous non‐sense mutations were relatively radioresistant (SF2 > 60%). Wild‐type p53 cells were made significantly more radiosensitive after treatment with Nutlin‐3. Neither apoptosis nor cell cycle responses corresponded with radiosensitivity. Interestingly, cells that displayed senescence were radioresistant whereas those that did not were radiosensitive suggesting a possible role for senescence in determining radiosensitivity. Conclusions. This is the first study to demonstrate that Nutlin‐3 may be an effective radiosensitiser in laryngeal cancer cell lines with wild‐type p53. The clinical application of Nutlin‐3 might improve survival rates or reduce therapeutic doses in these patients.