The p16 gene has been identified as a candidate tumour suppressor gene
at 9p21, a region commonly deleted in bladder cancer. We screened 140
bladder tumours and 16 cell lines for deletions and sequence variants
of p16. Eight cell lines showed homozygous deletion of p16 and two ha
d small sequence variations. All 13 tumours with small defined deletio
ns of 9p21, 18/31 (58%) of tumours with monosomy 9 and 9/91 (10%) of t
umours with no chromosome 9 loss of heterozygosity had homozygous dele
tion of p16. No tumour-specific sequence variants were identified. Del
etion mapping revealed a nested set of deletions focused on p16. Six d
eletions involved p16 but not the related and adjacent gene p15 and on
e tumour had an intragenic deletion of p16. All other deletions involv
ed both p16 and p15. We conclude that p16 represents the major target
for deletion at 9p21 in bladder cancer.