Sg. Chi et al., Elevated and biallelic expression of p73 is associated with progression ofhuman bladder cancer, CANCER RES, 59(12), 1999, pp. 2791-2793
p73, a member of the p53 family at 1p36.3, has been demonstrated to be expr
essed monoallelically and induce apoptosis or G(1) arrest of the cell cycle
, To explore the candidacy of p73 as a suppressor in bladder tumorigenesis,
we examined expression level, allelic origin, and mutation of p73 mRNA in
45 primary bladder carcinomas. Quantitative PCR analysis showed no allelic
loss of the gene but showed various levels of mRNA expression in both carci
noma and noncancerous tissues. Elevated expression of p73 was frequently ob
served in carcinoma tissues [18 (40.0 %) of 45] and showed a strong correla
tion with tumor stage or grade. Allotyping analysis using a StyI polymorphi
sm detected biallelic expression in 12 (52.2%) of 23 heterozygous carcinoma
s but none in 4 noncancerous tissues. Tumor-specific biallelic expression w
as also identified from one matched set. In addition, 8 (66.7%) of these 12
expressed high levels of p73 mRNA, whereas only 2 (18.2%) of 11 monoalleli
c expressors showed high expression, which suggests that the increased expr
ession of p73 might be caused by the transcriptional activation of a silent
allele in carcinomas. Single-strand conformational polymorphism analysis o
f the entire coding region of p73 revealed no mutation, whereas 12 (26.7%)
of the same set showed p53 alterations, No relationship between expression
of p73 and p53 mutation or expression of p21(Waf1) or MDM2 was identified.
Taken together, our data argue that p73 does not play a role as a tumor sup
pressor in bladder carcinogenesis and suggest that the activation of a sile
nt allele may contribute to the progression of bladder tumors.