SSCP detection of N-ras promoter mutations in AML patients.

Activation of the N-ras gene via coding region mutations has been previously documented in 25% of patients with acute myeloid leukemia (AML). Since overexpression of normal N-ras is also transforming in vitro, the N-ras promoter of AML patients was analyzed for the presence of promoter mutations that may affect expression of the N-ras gene. Single-stranded conformational polymorphism (SSCP) was used to analyze samples from 26 AML patients and 13 normal subjects. A novel polymorphism at position 390 within the N-ras promoter was observed in both AML patients and normal samples at an overall frequency of 26%. In addition, two of 26 patients had single-base substitutions within protein binding sites that altered the binding of transcription factors to the promoter. One patient had a T-->A mutation at position 520 within an AP-1 binding site; the other had an A-->G mutation at position 409 within a protein binding region adjacent to a Myb binding site. The data suggest that in addition to coding region mutations in the N-ras gene, mutations in the promoter region that could alter regulation of N-ras expression provide an alternative mechanism of involvement of N-ras in AML.