Implications of Gene and p53 Protein Alterations in Determining Progression of Chronic Myeloid Leukemia Phases.

Abstract

TP53 gene and p53 protein play an important role in the control of the cell cycle and DNA repair. Alterations in the TP53 gene and in the p53 protein expression have been considered an unfavorable prognostic factor for certain forms of human cancer. Mutations in the TP53 gene in patients with chronic myeloid leukemia (CML) were found in up to 30 %, specially among those in blastic crisis. At present, the only widely available technology that reliable detects and defines all mutations is DNA sequencing. However, the routine of sequencing the entire TP53 gene, in all suggestive cases of mutation, in the laboratorial routine is prohibitively costly, complex, and time consuming. To screening of those genetic alterations for p53 protein expression and TP53 gene abnormalities, in CML patients, flow cytometry (FC) and single strand conformation polymorphism of polymerase chain reaction products (PCR-SSCP) techniques are proposed. We report the results of an analysis of 72 blood samples from CML patients: 54 in chronic phase (33 in initial chronic phase (ICP) and 21 in late chronic phase (LCP)), 7 in accelerated phase (AP) and 11 in blastic crisis (BC). DNA structure for exons 5, 6, 7, 8 and 8–9 of the TP53 gene and p53 protein expression using the monoclonal antibody DO7 by FC was performed. By PCR-SSCP analysis, shift in eletrophoretic mobility of the TP53 gene, were detected in 11 patients and p53 protein were expressed in 17 out of 72 CML patients. The abnormal PCR-SSCP pattern were showed in one case of ICP (exon 7), five cases of LCP (two in the exon 7, one in the exon 8 and two in the exons 8–9), one in AP (exon 8) and four in BC (two in the exon 5, one in the exon 6 and one in the exon 8–9). In these cases, the p53 protein were expressed in seven cases (in all cases of CB and AC and 2 out of 5 LCP samples of CML patients). The statistic analysis by qui-square test showed significance between the results of the two methods (p= 0,002). These results suggest that the two concomitant methods can increase the sensibility for screening the p53 protein expression and TP53 gene abnormalities in CML patients. The presence of abnormal profile of PCR-SSCP associated to the p53 protein expression, in advanced phases of this disease, might be considered an important indicator of the phase progression of CML.