DELETION ANALYSIS OF THE P16 TUMOR-SUPPRESSOR GENE IN PHEOCHROMOCYTOMAS

BACKGROUND AND OBJECTIVES The molecular pathogenesis of phaeochromocyt oma has not yet been fully established. The p16 tumour suppressor gene is often inactivated in a wide variety of primary human malignancies, including tumours of ectodermal origin. We have therefore examined th e status of the p16 gene in a series of phaeochromocytomas. DESIGN We studied tumour and constitutive DNA from 26 phaeochromocytoma patients , Twenty-two cases were of sporadic tumours whereas four patients had a hereditary form of the disease. Four tumours were malignant. We perf ormed a semiquantitative multiplex PCR in which the p16 gene was coamp lified with an unrelated sequence as an internal control, Standards we re constructed by mixing DNA from cell lines with a known p16 status t o simulate various degrees of p16 loss, Deletion of the p16 gene was d etermined by densitometry, measuring the ratio of intensity of the two resulting bands as an indication of the relative abundance of the two templates in the sample. RESULTS No homozygous deletion of the pie tu mour suppressor gene was found in any of the phaeochromocytoma samples . CONCLUSIONS We have demonstrated that the p16 gene is not deleted in sporadic, hereditary, malignant or benign forms of phaeochromocytomas , and therefore probably does not play a role in the pathogenesis of t his tumour, However, because of the small number of malignant cases an alysed, we cannot exclude a low frequency of p16 deletions in this sub set of tumours.