Contributions
Abstract: EP607
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
Chronic lymphocytic leukemia (CLL) is a prevalent lymphoproliferative disease characterized by a high heterogeneity of the course. The variability of CLL is directly related to the immunobiological characteristics of cell clones in each patient, differences in the survival of leukemia cells, their activation, proliferation and interaction with the microenvironment. Telomeres, which are located at the ends of chromosomes and represent nucleoprotein structures, serve as protection against 'replicative aging' of cells during division. In tumor cells, genomic instability is associated with pronounced telomere dysfunction, at the same time critical telomere contraction and, ultimately, chromosome degradation with loss of cell viability are prevented by the activation of cellular telomerase.
Aims
To evaluate the influence of the length of telomeric fragments (LTF) of lymphocytes and telomerase activity in CLL on the nature of the disease course.
Methods
We examined 95 patients at the onset of CLL and 22 healthy individuals (comparison group), comparable in age and gender. The length of telomeric fragments in CD19-positive peripheral blood lymphocytes was determined using the multi-color flow cytometry method with the stage of fluorescent in situ hybridization ('FACS Canto II', Becton Dickinson). The activity of cellular telomerase was evaluated by the level of expression of the matrix RNA gene of the catalytic unit of the human telomerase reverse transcriptase (hTERT) enzyme, for which the content of complementary DNA in the reactions of reverse transcription and quantitative polymerase chain reaction was determined in the peripheral blood in real time («DT-96», DNA Technology). The significance of the differences in the parameters was determined using the Mann-Whitney test. The time from the diagnosis of CLL to the start of specific treatment was calculated by the Kaplan-Meyer method.
Results
LTF in peripheral blood B-lymphocytes in patients was significantly shorter than in donors (3,7 [2,8; 4,6] kb vs. 6,8 [5,6; 8,7] kb, p < 0,01). In all patients with CLL, cellular hTERT was in an activated state. Reduction of LTF below 5,0 kb, corresponding to less than 1,5 standard deviations from the mean value in the comparison group, was found in 35,7 % of cases, moderate activation of hTERT (up to 15,2 copies per µl) - in 74,7 %, high activation (more than 15,2 copies per µl) - in 25,3 %. There were 4 groups of patients, depending on the levels of LTF and the degree of hTERT activation. Group I included 9 patients with shortened LTF and high hTERT activation, group II - with shortened LTF and moderate hTERT activation (n=25), group III - without a decrease in LTF with high hTERT activation (n=15), and group IV - without a decrease in LTF with moderate hTERT activation (n=46). The median duration of the time period from the diagnosis of CLL to the start of specific therapy in groups I, II, III and IV of patients was 4,0; 22,0; 30,0 and 36,0 months, respectively. The time interval before the start of therapy in patients of group I was significantly shorter than in other groups (p≤ 0,001). No statistical differences were found between groups II, III, and IV.
Conclusion
A significant influence of the state of the 'telomer-telomerase' system on the nature of the CLL course was established. A decrease of LTF in B-lymphocytes, combined with a high activation of cellular telomerase, correlates with earlier initiation of therapy.
Keyword(s): Chronic lymphocytic leukemia, Telomerase, Telomere length
Abstract: EP607
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
Chronic lymphocytic leukemia (CLL) is a prevalent lymphoproliferative disease characterized by a high heterogeneity of the course. The variability of CLL is directly related to the immunobiological characteristics of cell clones in each patient, differences in the survival of leukemia cells, their activation, proliferation and interaction with the microenvironment. Telomeres, which are located at the ends of chromosomes and represent nucleoprotein structures, serve as protection against 'replicative aging' of cells during division. In tumor cells, genomic instability is associated with pronounced telomere dysfunction, at the same time critical telomere contraction and, ultimately, chromosome degradation with loss of cell viability are prevented by the activation of cellular telomerase.
Aims
To evaluate the influence of the length of telomeric fragments (LTF) of lymphocytes and telomerase activity in CLL on the nature of the disease course.
Methods
We examined 95 patients at the onset of CLL and 22 healthy individuals (comparison group), comparable in age and gender. The length of telomeric fragments in CD19-positive peripheral blood lymphocytes was determined using the multi-color flow cytometry method with the stage of fluorescent in situ hybridization ('FACS Canto II', Becton Dickinson). The activity of cellular telomerase was evaluated by the level of expression of the matrix RNA gene of the catalytic unit of the human telomerase reverse transcriptase (hTERT) enzyme, for which the content of complementary DNA in the reactions of reverse transcription and quantitative polymerase chain reaction was determined in the peripheral blood in real time («DT-96», DNA Technology). The significance of the differences in the parameters was determined using the Mann-Whitney test. The time from the diagnosis of CLL to the start of specific treatment was calculated by the Kaplan-Meyer method.
Results
LTF in peripheral blood B-lymphocytes in patients was significantly shorter than in donors (3,7 [2,8; 4,6] kb vs. 6,8 [5,6; 8,7] kb, p < 0,01). In all patients with CLL, cellular hTERT was in an activated state. Reduction of LTF below 5,0 kb, corresponding to less than 1,5 standard deviations from the mean value in the comparison group, was found in 35,7 % of cases, moderate activation of hTERT (up to 15,2 copies per µl) - in 74,7 %, high activation (more than 15,2 copies per µl) - in 25,3 %. There were 4 groups of patients, depending on the levels of LTF and the degree of hTERT activation. Group I included 9 patients with shortened LTF and high hTERT activation, group II - with shortened LTF and moderate hTERT activation (n=25), group III - without a decrease in LTF with high hTERT activation (n=15), and group IV - without a decrease in LTF with moderate hTERT activation (n=46). The median duration of the time period from the diagnosis of CLL to the start of specific therapy in groups I, II, III and IV of patients was 4,0; 22,0; 30,0 and 36,0 months, respectively. The time interval before the start of therapy in patients of group I was significantly shorter than in other groups (p≤ 0,001). No statistical differences were found between groups II, III, and IV.
Conclusion
A significant influence of the state of the 'telomer-telomerase' system on the nature of the CLL course was established. A decrease of LTF in B-lymphocytes, combined with a high activation of cellular telomerase, correlates with earlier initiation of therapy.
Keyword(s): Chronic lymphocytic leukemia, Telomerase, Telomere length