Biological characteristics in bladder cancer depend on the type of genetic instability.
OBJECTIVE
Malignant tumors show an inherent genetic instability that can be classified as microsatellite instability (MSI) or chromosomal instability (CIN). To elucidate the differences in biological characteristics of bladder cancer between the two types of genetic instability, the expression of the mismatch repair (MMR) proteins, Aurora-A and p53 proteins, the number of centrosomes, numerical aberrations of chromosomes and 20q13, and DNA ploidy were examined in 100 human urothelial carcinomas of the bladder.


METHODS
Expressions of the MLH1, MSH2, Aurora-A, and p53 proteins and the numbers of centrosomes were immunohistochemically assessed. Numerical aberrations of chromosomes 7, 9, 17, and 20q13 spots were evaluated by fluorescence in situ hybridization, and DNA ploidy was assessed by laser scanning cytometry.


RESULTS
The expression levels of the MMR related-proteins decreased in 9 of 100 tumors. Tumors with low MLH1 or MSH2 expression (designated as MSI cancers) were not linked with centrosome amplification, Aurora-A overexpression, increased p53 immunoreactivity, 20q13 gain, DNA aneuploidy, and disease progression. MSI cancers showed a favorable prognosis. CIN cancers (49 cases), defined as tumors with a large intercellular variation in centromere copy numbers, were associated more frequently with centrosome amplification, Aurora-A overexpression, increased p53 immunoreactivity, and 20q13 gain than the others (51 cases). Tumors with disease progression were included in the CIN cancer group.


CONCLUSIONS
The present observations suggest that there are differences in the biological characteristics of the two types of genetic instability.
Yamamoto
Yoshiaki
Y
Department of Urology, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan.
Matsuyama
Hideyasu
H
Kawauchi
Shigeto
S
Furuya
Tomoko
T
Liu
Xiu Ping
XP
Ikemoto
Kenzo
K
Oga
Atsunori
A
Naito
Katsusuke
K
Sasaki
Kohsuke
K