P53 ALTERATIONS IN GASTRIC-CARCINOMA - A STUDY OF 56 PRIMARY TUMORS AND 204 NODAL METASTASES

We have looked for LOH, mutation, and expression of p53 in a series of se primary gastric carcinomas, using Southern blotting, constant dena turant gel electrophoresis (CDGE), direct sequencing, and immunohistoc hemistry. Two hundred-four lymph node metastases from 36 of these case s were also studied by immunohistochemistry. Loss of constitutional he terozygosity for the p53 locus was detected in five of 16 informative cases; in four of these cases there was a concurrent point mutation at the retained allele. Immunoreactivity for p53 product and mutation of p53 were observed in nine and 10 of the 56 tumors, respectively. Ther e was no significant relationship between p53 immunoreactivity or muta tion and pathologic features. The overall prevalence of p53 mutations, as detected bq CDGE, was 18%. Direct sequencing confirmed p53 mutatio ns (all G:C-A:T transitions) in seven cases, six of which were missens e mutations; the remaining case was a silent mutation. In three of the cases with missense mutations, these occurred at CpG dinucleotides (c odons 175, 273, and 282). Three cases with immunoreactivity for p53 pr oduct in the primary tumor also showed positive staining in the metast ases. In two of these cases (with six and nine metastases, respectivel y) a positive staining was observed in all lymph node metastases, wher eas in the remaining case only two of four nodal metastases were posit ively stained. In no single case was a positive staining observed in a metastasis where the primary tumor gave a negative staining result. F ive of the six cases with p53 mutations and fresh material available f or cell culture were successfully grown in vitro and all had abnormal karyotypes.