Introduction. MicroRNAs (miRNAs) are small non-coding single-stranded RNA molecules that regulate gene expression at the post-transcriptional level. In the pathogenesis of chronic lymphocytic leukemia (CLL), miR-15a and miR-16-1 play an important role. These miRNAs are located on chromosome 13 in the 13q14.3 region, which is deleted in more than 55% of CLL patients. This aberration affects expression of miRNAs. Objectives. The study aimed at performing a molecular genetic analysis of miR-15a and miR-16-1 expression in a group of 39 patients diagnosed with CLL and determining the association between the expression of the two miRNAs and types of deletions in the 13q14 region. Methods. We used fluorescence in situ hybridiziation (FISH) for determination of mono-or biallelic deletion 13q and quantitative polymerase chain reaction (Q-RT-PCR) to revealed expression miR-15a and miR-16-1 in 39 patients suffering from CLL. Results. The analysis comprised 19 patients with monoallelic 13q14 deletion, 3 patients with biallelic deletion, 9 patients with both monoallelic and biallelic deletions, and 8 patients without 13q14 deletion serving as controls. The results showed different levels of miRNA expression in individual patients. Significantly higher normalized levels of miR-15a expression were found in the control group and patients with monoallelic 13q14 expression compared with patients with biallelic deletion. There was a significantly decreased expression of both miRNAs in patients with biallelic deletion of the 13q14 region but only when deletions were present in 77% or more of cells, as detected by fluorescent in situ hybridization (FISH).

This study aimed at mapping the frequency of IGHV3-21 and IGHV1-69 in a group of 417 patients newly diagnosed with chronic lymphocytic leukemia (CLL) and described basic characteristics, cytogenetic abnormalities and prognosis of these patient subgroups. IGHV3-21 was found in 29 patients (7%) and IGHV1-69 in 51 patients (12.4%). The median overall survival (OS) rates were 97 months and 85 months in the IGHV3-21 and IGHV1-69 groups, respectively. In this small group of patients, the study failed to show a difference in OS of IGHV3-21 patients with mutated and unmutated IGHV status (p<0.597). There was also no difference in OS between IGHV3-21 patients with mutated IGHV status and all patients in the group having unmutated IGHV status (p<0.245). On the other hand, patients with IGHV3-21 and the presence of some other adverse prognostic factors (age ≥ 65 years, lymphocyte count ≥ 50×109/L, serum thymidine kinase ≥ 9U/L, deletion of 17p) had statistically significantly worse OS than IGHV3-21 patients without the presence of these prognostic factors. The multivariate analysis of an entire group of Binet clinical stage A patients proved that the presence of IGHV3-21 is as an independent adverse prognostic factor even though there was no statistical difference in OS between patients with IGHV3-21 and those without IGHV3-21 in the entire group (p<0.769). Patients with IGHV1-69 had the same probablility of OS irrespective of the presence of other adverse prognostic factors; their OS was significantly shorter as compared with the other patients from the entire group (p<0.03).The study mapped the occurrence of recurrent cytogenetic changes detected by FISH in IGHV3-21 (subset #2 and non-subset #2) and IGHV1-69 and compared it with the occurrence of recurrent changes in the entire group of patients. In IGHV1-69 and in subset #2 IGHV3-21, higher proportions of deletion of 11q were found (30% and 31%, respectively), with the deletion being present in 19.2% of the entire group of patients. None of the 3 patients with IGHV3-21 and deletion of 17p had subset #2. Patients with subset #2 IGHV3-21 had higher proportions of deletion of 13 (69%) as compared with non-subset #2 IGHV3-21 patients (27%).