Genetic alterations in the p53 gene in the blast crisis of chronic myelogenous leukemia: analysis by polymerase chain reaction based techniques.

Rearrangements of the c-abl protooncogene and the bcr-gene are found in > 90% of patients in chronic phase of chronic myelogenous leukemia (CML). The molecular events leading to blast crisis, however, have not been well characterized. Gross alterations of the p53 gene have been detected in 30% of patients with blast crisis. Since point mutations in the p53 gene appear to be important in the process of transformation in many epithelial tumors, we looked for these mutations in the critical regions of the p53 gene (exons 4, 5, 6, 7, and 8). We used the polymerase chain reaction (PCR), direct sequencing, differential PCR, and single strand conformation polymorphism (SSCP) analysis to detect mutations of the p53 gene in samples from 21 patients with CML blast crisis. Two of 21 patients exhibited an intragenic deletion or rearrangement in p53. In addition, these patients were homozygous for the mutant p53 allele. No mutations were found in the p53 gene of the remaining 19 patients. However, sequencing of the CML blast crisis cell line, K562, revealed an insertion of a C at base position 956 within the fifth exon, causing a frame shift mutation and an early translational stop at codon 148. We conclude that, in contrast to solid tumors, mutations in exons 4-8 of p53 are not frequently seen in primary samples from CML blast crisis. However, deletions and/or rearrangements within the p53 gene do occur and may contribute to the progression from chronic phase to blast crisis in a limited number of patients with CML.