Molecular genetics configuration of chronic myeloid leukemia

Abstract Background: Chronic myeloid leukemia (CML) represents roughly 20% of all leukemia cases in adults, being the most common chronic myeloproliferative malignancy, with a significant global disease budren and rate of disability-adjusted life years in the advanced phases. The diagnostic significance of BCR-ABL1 transcripts, T315I and K222R/665A resistance mutations remain under continuous research focusing on the improvement of therapeutic approaches and monitoring options. Objectives: The aim of the study was to assess the significance of BCR-ABL1 transcripts and mutational spectrum in CML patients. Material and methods: This prospective and cross-sectional study included 131 CML patients, which were treated and followed up at the Institute of Oncology from the Republic of Moldova between 2017–2024. The age range was 14–82 years (average age - 47.9 years). The male/female ratio was 1.4:1. The quantitative reverse transcription polymerase chain reaction (PCR) and next-generation sequencing in certain cases were performed in order to determine the expression of the BCR-ABL p210 and p190 transcripts. The quantitative and qualitative assessments of DNA and RNA extraction were performed by means of the NanoDrop Lite UV Spectrophotometer. Five transcription products (b2a2, b3a2, b2a3, b3a3 si e1a2) were analyzed by the usage of the PCR test. The immunophenotyping was performed in CML cases with the acute phase. The type of leukemia was asserted according to the 2022 Revision of WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues. Venous blood samples were collected for molecular-genetic detection of T315I and K222R/665A mutations of the BCR-ABL1 gene in order to assert their diagnostic and biological significance. The study design referred to the out-patient and hospitalized care. Results: The expression range of the BCR-ABL p210 transcript was 9.5-100% IS. In 91 (69.5%) of cases, the expression of the chimeric BCR-ABL gene transcripts exceeded 65%. In 7 (5.3%) patients the BCR-ABL p210 expression rate was less than 50% at diagnosis. The percentage of BCR-ABL1 fusion gene expression below 25% was recorded only in 11.3% of the patients, being especially revealed in cases with the chronic phase (94.1%) and not in the acute phase. The growth trend of the percentage of BCR-ABL1 transcripts-bearing cells was observed (p<0.05) during the CML transformation from the early chronic phase (48.15%) into the late chronic phase (56.963%) and accelerated phase (66.588%). The most frequent was the b3a2 transcript (68 cases or 56.7%) (p<0.001). The b3a3 transcript was detected only in 2 (1.7%) cases (p<0.001). It is worth noting that the b3a2 transcript prevailed at the time of diagnosis of the disease in cases with the early chronic phase (50.0%) and the late chronic phase (57.3%) (p<0.001). Patients with b3a2 transcript dominated (50.0%) in subgroup with the accelerated phase, and patients with b3a2 (66.7%) and b3a3 (33.3%) transcripts - in subgroup with the acute phase (p<0.001). The e1a2 (p190) transcript was detected at the onset of the disease in 12 (10.0%) cases, especially in patients with late chronic phase (10.7%) and acute phase (33.3%), which may identify it as the factor that accelerates the evolution of the disease. T315I mutation was revealed in 37.1% of cases, and the K222R/665A mutation – in 3.1% of cases. Relapses occurred in 6 (60%) of 10 patients with T315I mutation, and in one case with K222R/665A mutation. Survival of patients without resistance mutations from the disease onset to the last follow-up visit ranged from 62 to 287.3 months (M=154.7±3.62). The survival of patients with resistance mutations from the disease onset to the last monitoring visit ranged from 45.7 to 283.4 months (M=148.5±4.31). Conclusions: The BCR/ABL1 fusion gene expression growth matches the CML progression. The b3a2 transcription product proved to be the most frequent BCR-ABL1 transcript. The survival rates of CML patients depend on the presence of resistance mutations.