RUNX3 inactivation by point mutations and aberrant DNA methylation in bladder tumors.
RUNX3 is inactivated at high frequency in many tumors. However, in most cases, inactivation is caused by silencing of the gene due to promoter hypermethylation. Because epigenetic silencing is known to affect many major tumor suppressor genes in cancer cells, it is not clear whether RUNX3 is primarily responsible for the induction of carcinogenesis in these cases, except for the gastric cancer cases that we reported previously. We investigated genetic and epigenetic alterations of RUNX3 in 124 bladder tumor cases and seven bladder tumor-derived cell lines. Here we show that RUNX3 is inactivated by aberrant DNA methylation in 73% (90 of 124) of primary bladder tumor specimens and 86% (six of seven) of bladder tumor cell lines. In contrast, the promoter regions of 20 normal bladder mucosae were unmethylated. Importantly, one patient bore missense mutations, each of which resulted in amino acid substitutions in the highly conserved Runt domain. The mutations abolished the DNA-binding ability of RUNX3. A second patient had a single nucleotide deletion within the Runt domain coding region that resulted in truncation of the protein. RUNX3 methylation was a significant risk factor for bladder tumor development, superficial bladder tumor recurrence, and subsequent tumor progression. These results strongly suggest that inactivation of RUNX3 may contribute to bladder tumor development and that promoter methylation and silencing of RUNX3 could be useful prognostic markers for both bladder tumor recurrence and progression.
Kim
Wun-Jae
WJ
Department of Urology , College of Medicine, Institute for Tumor Research, Chungbuk National University, Cheongju, South Korea. wjkim@chungbuk.ac.kr
Kim
Eun-Jung
EJ
Jeong
Pildu
P
Quan
Changyi
C
Kim
Jiyeon
J
Li
Qing-Lin
QL
Yang
Jeong-Ook
JO
Ito
Yoshiaki
Y
Bae
Suk-Chul
SC
D001483:Base Sequence; D045744:Cell Line, Tumor; D050677:Core Binding Factor Alpha 3 Subunit / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000378:metabolism; D018450:Disease Progression; D005091:Exons; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D008969:Molecular Sequence Data; D009364:Neoplasm Recurrence, Local / Q000235:genetics; D009367:Neoplasm Staging; D017354:Point Mutation; D011379:Prognosis; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology
D050677:Core Binding Factor Alpha 3 Subunit; D004273:DNA, Neoplasm; C493729:Runx3 protein, human