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Background. Most patients with chronic myeloid leukemia (CML) treated with tyrosine kinase inhibitors achieve durable optimal responses. Loss of the achieved molecular response is observed in 15–30 % of patients. Mutations in the BCR::ABL kinase domain are one of the most common mechanisms for the development of resistance to tyrosine kinase inhibitors.Aim. To conduct a retrospective analysis of the BCR::ABL kinase domain mutational profile in patients with CML observed at the Russian Research Institute of Hematology and Transfusiology from 2012 to 2023. To assess the impact of mutations type and number on the rate of achieving a major molecular response (MMR). To study the risk of MMR loss depending on the therapy line and existing mutational status.Materials and methods. 1831 patients with CML were examined at different times. The mutational status of the BCR::ABL kinase domain was analyzed by direct Sanger sequencing. A standard cytogenetic study was carried out using GTG banding technology with the analysis of at least 20 metaphase plates.Results. Mutations in the BCR::ABL kinase domain were identified in 27.6 % of the total studied patients. The most common mutation, 6.3 % in the overall group or 22.7 % among patients with mutations, was the T315I mutation. Additional chromosomal aberrations (ACAs) were detected in Ph-positive cells in 20.5 % of patients, in Ph-negative clones in 3.9 % of cases (p = 0.0001). The frequency of ACAs detection did not statistically significantly differ (p = 0.25) between patients with BCR::ABL mutations (23.5 %) and with a negative mutation status (17.7 %), and the presence of mutations in the kinase domain did not correlate with ACAs in Ph-positive clones (p = 0.73). However, the frequency of T315I mutation detection in Ph-positive cells had significant differences: 40.9 % in combination with ACAs and 21 % without ACAs (p = 0.032). Patients with the T315I mutation had significantly worse MMR than patients with mutations in other BCR::ABL regions (p = 0.04) and patients without mutations (p = 0.02). The probability of MMR achieving did not differ significantly between patients with different numbers of BCR::ABL mutations (p = 0.14). Loss of MMR occurred more often in patients with mutations (p = 0.04) and not depend on the line of therapy (p = 0.03).Conclusion. For complete monitoring and optimal choice of therapy, CML patients require not only monitoring of BCR::ABL relative expression level, but also standard cytogenetic and analysis of the mutational status.

Aim. To study the prognostic significance of gene mutations and intracellular signaling pathways involved in lymphomagenesis in patients with follicular lymphoma using next generation sequencing (NGS).Materials and methods. The prospective study included 26 patients with a median age of 51.5 years. Mutational screening was performed for cohort using custom NGS Panel of 118 genes. Gene set enrichment analysis (GSEA) was performed using Metascape. The data was analyzed in SPSS Statistics 26 and R 4.2.2.Results. The highest mutation frequency was noted in the genes: KMT2C – 50 %, KMT2D – 50 %, CREBBP – 31 %, NOTCH2 – 31 %, GNAS – 23 %. Missense mutations occurred with a frequency of 84.3 %. ARID1A gene mutation is an unfavorable prognostic factor according to progressive-free (p = 0.014) and event-free (p = 0.029) survival analysis. Tumor mutation burden (TMB) was defined as the number of mutations per megabase (Mb) of the coding sequence, the median TMB was 5.0 (3.3–8.3) mutations/Mb. The TMB threshold of 6 mutations/Mb divided patients into groups with high (44 %) and low (56 %) TMB. In the high TMB group, 2-year event-free survival was 27.3 % (95 % confidence interval 6.0–61.0), which was significantly lower than in low TMB group – 72.7 % (95 % confidence interval 41.9–91.6; p = 0.037). The most enriched cellular pathways according to GSEA results were regulation of cell activation (–log10(q-value) = 6.357), chromatin remodeling (–log10(q-value) = 5.707), histone modification (–log10(q-value) = 4.569). We have also demonstrated other possibilities of GSEA using follicular lymphoma as an example.Conclusion. TMB is a significant prognostic factor in patients with follicular lymphoma. We have shown that mutations in the MYC, CREBBP, EZH2, KMT2D genes lead to dysregulation in several intracellular processes, mediating complex molecular changes. The most enriched intracellular pathways in follicular lymphoma are those of chromatin remodeling, regulation of cell activation and histone modification.