Frequent Glycine‐to‐Aspartic Acid Mutations at Codon 12 of c‐Ki‐ras Gene in Human Pancreatic Cancer in Japanese

Point mutations at codons 12 and 13 of c‐Ki‐ras gene were analyzed in human pancreatic cancer. DNAs obtained from sample tissues were amplified by means of polymerase chain reaction and were analyzed by dot blot hybridization assays with oligonucleotide probes appropriate for detecting mutations at these codons. Out of 38 evaluated cases, point mutations at codon 12 were found in 35 cases; these mutations resulted in changes of the coded amino acid to aspartic acid in 24 cases, to valine in 9 cases, to arginine in 2 cases and to cysteine in one case. In one case, a glycine‐to‐aspartic acid mutation was found at codon 13. In two cases, two distinct mutations were simultaneously present. The frequency pattern of mutations at codon 12 was somewhat different from those given in two previous reports on the similar analysis of pancreatic cancers in European countries. This may indicate the presence of possible genetic or non‐genetic factors in determining preferential mutational patterns at these particular codons.