p53 expression, K-ras gene mutation and microsatellite instability in gastric B-cell lymphomas.
OBJECTIVE
Genetic mechanisms involved in the development of gastric B-cell lymphomas remain unclear. The aim of the present study was to clarify the roles of mutations of the p53 and K-ras genes, and microsatellite instability (MSI) in the development of gastric B-cell lymphomas.


METHODS
We investigated p53 immunoreactivity, mutations of the K-ras gene, and MSI in 27 gastric marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue type (MZBCL) and 24 diffuse large B-cell lymphomas (DLBCL). p53 immunoreactivity was examined using a monoclonal antibody, DO-7. Mutation of the K-ras gene was detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. MSI was examined at five microsatellite loci with a microsatellite assay. Cases were classified as having high-frequency MSI (MSI-H) (>/= 2 loci showing instability), low-frequency MSI (MSI-L) (only one locus showing instability), or as microsatellite stable.


RESULTS
p53 immunoreactivity was detected in 1 of 16 (6%) MZBCL and 8 of 19 (42%) DLBCL. Frequency of p53 immunoreactivity in DLBCL was significantly higher than that in MZBCL (P = 0.018). MSI-H was detected only in 1 of 20 (5%) DLBCL. None of the cases examined showed mutation of the K-ras gene.


CONCLUSIONS
These data suggest that mutations of the p53 gene may play an important role in the development of gastric DLBCL, and that mutations of the K-ras gene and MSI may be involved in little part of the development of gastric B-cell lymphomas.
Hiyama
Toru
T
Health Service Center, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima 739-8521, Japan. tohiyama@hiroshima-u.ac.jp
Tanaka
Shinji
S
Masuda
Hiroshi
H
Shima
Hideyuki
H
Kose
Kazuhiro
K
Tuncel
Handan
H
Ito
Masanori
M
Kitadai
Yasuhiko
Y
Sumii
Masaharu
M
Uemura
Naomi
N
Yoshihara
Masaharu
M
Shimamoto
Fumio
F
Haruma
Ken
K
Chayama
Kazuaki
K
D043171:Chromosomal Instability / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53 / Q000235:genetics*; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D016393:Lymphoma, B-Cell / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics*