N-ras and p53 gene mutations are very rare events in multiple myeloma.

The frequencies of p53 and N-ras gene mutations were examined in multiple myeloma. DNA samples of 45 cases of multiple myeloma were obtained from stored bone marrow smears. All samples were analyzed for the N-ras gene at codon 12 by the allele specific restriction analysis method and at codon 61 by direct sequencing. DNA was screened for mutations by single-strand conformation polymorphism analysis for the p53 gene in exons 5 to 8. DNA fragments showing an altered electrophoretic pattern were further studied by direct sequencing to confirm the mutations. Ras mutations were found in two cases at codon 61 (4.4%). A point mutation of the p53 gene was detected in one of 45 cases (2.2%). These 3 cases with mutations were in an advanced stage. In conclusion, N-ras and p53 gene mutations may occur at a late stage of multiple myeloma, but the frequencies of the mutations are very low.