DELETION AND METHYLATION OF THE TUMOR-SUPPRESSOR GENE P16 CDKN2 IN PRIMARY HEAD AND NECK SQUAMOUS-CELL CARCINOMA/

Aims-To study the homozygous deletion and methylation status of the 5' CpG island of the p16 and p15 genes (9p21) in a set of primary advanc ed head and neck squamous cell carcinomas (SCC) and to test whether in activation of these genes by these mechanisms contributes to head and neck SCC development. Methods-DNA was extracted from fresh tumours. Ho mozygous deletion was determined by the polymerase chain reaction (PCR ) followed by hybridisation with the corresponding probe, radioactivel y labelled by the random priming method. Methylation status of the CpG island of the 5' region of these genes was assessed by digestion with the appropiate restriction enzymes followed by PCR and subsequent hyb ridisation with the corresponding probe. The presence of point mutatio ns was determined by PCR-SSCP (single strand conformation polymorphism ). Results-The p16 and p15 genes were homozygously deleted in 20% and 10% of the tumours, respectively. No point mutations were found at p16 and p15. The 5' CpG island at the p16 gene was methylated in 20% of t he cases. Conclusions-The tumour suppressor gene p16 is inactivated th rough homozygous deletion or methylation in a significant proportion o f cases of head and neck SCC.