Pathogenetic value of TP53 point mutations in adult acute myeloid leukemia patients

The aim of the study was to assess pathogenetic significance of TP53 gene mutations in adult acute myeloid leukemia (AML) patients. Clinical observation was carried out on 114 AML patients at the Sverdlovsk Regional Clinical Hospital No. 1 (Ekaterinburg), including 56 males and 58 females. The average age of subjects was 53.3±2.8 years.
Morphologically, AML was previously verified in all cases at specialized laboratories by using standard cytological, cytochemical, immunophenotypic, histological and immunohistochemical methods. The study included the following variants of AML: M0 – 5, M1 – 9, M2 – 47, M2baso – 3, M2eo – 2, M3 – 8, M4 – 25, M4eo – 3, M5 – 3, M6 – 4, M7 – 1, acute myelofibrosis – 1, blastic plasmacytoid dendritic cell neoplasm – 2. Samples of peripheral blood and bone marrow aspirates from patients were examined. Exons 4-11 within the TP53 gene were tested for molecular damage by using sequencing method. In addition, 81 samples, including 22 AML with normal and 23 with an unspecified karyotype were examined for gene mutations by using molecular genetic and immunohistochemical methods. cDNA sequencing was carried out on automatic genetic analyzer in forward and reverse sequences. The sequencing results were processed by using the MEGA X software and statistical hypothesis that they may be described by a binomial distribution. The statistical hypothesis was tested by using Fisher’s exact test and χ² test.
According to the results of cytogenetic and PCR studies, a favorable prognosis was determined in 25 cases (21.9%), intermediate – 24 (21.1%) and unfavorable – in 33 (28.9%). No genetic abnormalities could be detected in 32 samples (28.1%) with standard cytogenetics and real-time PCR, and prognosis option for such patients was not specified.
TP53 missense mutations were revealed as C292T, A377G, A659G, C817T transitions (4 cases) and C569G, G733T, G841C transversions (3 cases); synonymous A639G substitutions were also determined (1.8% ) and C891T (0.9%), in codon position 3, providing no pathogenetic significance. In one sample (0.9%), a deletion of thymidine at position 645 of the coding sequence was determined, leading to produced shortened mutant protein. All the above mutations were localized in the region of the DNA-binding domain. Also, in one case (0.9%), a tandem duplication of 19 nucleotides at position 960 of the coding sequence of the NLS domain protein located in acetylation site. Non-synonymous C215G transversion, which is a polymorphic gene variant, was determined in 94 samples (82.5%). Clinically, all TP53-positive AML were characterized by unfavorable prognosis and primary resistance to standard chemotherapy. The average age of such patients was 63.0±5.4 years, with average follow-up reaching up to 3.1±0.9 months.