Contributions
Abstract: EP623
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
The mutational status of the variable region of the immunoglobulin heavy chain (IGHV) genes remains the most significant prognostic factor in chronic lymphocytic leukemia (CLL) patients. Numerous studies confirmed an improved progression-free and overall survival (OS) for mutated (M) IGHV patients compared to unmutated (UM) patients. However, the groups of M and UM patients are also heterogeneous, and additional markers are used for a more accurate prognosis. There are some evidences that CLL is antigen-driven disease: gene-expression profile indicating activation of signaling pathways through the B-cell receptors (BCR), expression of similar BCRs (stereotyped cases), efficacy of drugs inhibiting BCR signaling, etc.
Aims
The aim of this work was to determine the prognostic value of the signs of antigen selection in IGHV sequences of CLL patients.
Methods
The study included 127 M IGHV CLL patients (88 men and 39 women aged 58.6±0.91 years). All patients gave written informed consent. The IGHV gene mutational status was assessed by a direct sequencing. BASELINe statistics was used to determine if antigen selection occurred (Uduman et al., 2011, 2014). Major stereotyped subsets were assigned using the ARResT/AssignSubsets tool. All analyzed sequences were presented in Genbank database. Mutations of TP53 gene were analyzed in 88 patients by a direct sequencing and were revealed in three patients. OS was analyzed by Kaplan-Meier statistic.
Results
The distributions of replacement (R) and silent (S) mutations in the CDR (complementary determining region) and the FR (framework region) regions of M sequences were 75.7:24.3 and 61.1:38.9, correspondingly, and were in agreement with data of Rene et al. (2014). Using BASELINe statistics, we found that two sequences (1.6%) had signs of positive selection and 15 sequences (11.8%) had signs of negative selection in CDRs (p<0.05). The FR regions had signs of negative selection (p<0.05) in 37 (29.1%) cases. In other cases, the Σ statistic values were borderline (p<0.1) or insignificant (p>0.1). No associations of OS with signs of selection in CDRs were found. At the same time, OS was worse in CLL patients with signs of negative selection in FRs (group I, median of OS 111 months) compared to other M IGHV patients (group II, median of OS 202 months), p=0.027. Observed CLL patients of both groups were comparably by age (p=0.287), gender (p=0.488), Binet stage (p=0.37), TP53 mutational status (p=0.781), and the expression of stereotyped BCRs (p=0.488). In comparison to group II, sequences of group I had higher numbers of S mutations in CDRs (1.94±0.23 vs 0.96±0.2; p=0.001) and in FRs (5.97±0.34 vs 2.73±0.19; p=0.001), slightly lower numbers of R mutations in FRs (4.7±0.39 vs 6.04±0.31; p=0.05), and significantly lower R to S ratio in FRs (41.1:58.8 vs 69.4:30.6; p=0.00001). Besides, the number of amino acid substitutions in codons 24-26, 80, 83, and 96 was significantly reduced (or absent) (p=0.00041, when comparing the total number). In multivariate analysis, which was carried out considering the recommendations of International CLL-IPI working group (2016), the following factors were predictive for OS of M CLL patients: clinical stage (Binet A vs Binet B-C), age (≤65 years vs >65 years), and negative selection in FRs (data of serum β2-microglobulin concentration were missing; TP53 mutations were detected in a small number of cases and had no prognostic value in our M IGHV group).
Conclusion
The obtained data suggest of possible impact of features of somatic hypermutation processes in CDRs and FRs of IGHV for CLL prognosis.
Keyword(s): Chronic lymphocytic leukemia, IGH
Abstract: EP623
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
The mutational status of the variable region of the immunoglobulin heavy chain (IGHV) genes remains the most significant prognostic factor in chronic lymphocytic leukemia (CLL) patients. Numerous studies confirmed an improved progression-free and overall survival (OS) for mutated (M) IGHV patients compared to unmutated (UM) patients. However, the groups of M and UM patients are also heterogeneous, and additional markers are used for a more accurate prognosis. There are some evidences that CLL is antigen-driven disease: gene-expression profile indicating activation of signaling pathways through the B-cell receptors (BCR), expression of similar BCRs (stereotyped cases), efficacy of drugs inhibiting BCR signaling, etc.
Aims
The aim of this work was to determine the prognostic value of the signs of antigen selection in IGHV sequences of CLL patients.
Methods
The study included 127 M IGHV CLL patients (88 men and 39 women aged 58.6±0.91 years). All patients gave written informed consent. The IGHV gene mutational status was assessed by a direct sequencing. BASELINe statistics was used to determine if antigen selection occurred (Uduman et al., 2011, 2014). Major stereotyped subsets were assigned using the ARResT/AssignSubsets tool. All analyzed sequences were presented in Genbank database. Mutations of TP53 gene were analyzed in 88 patients by a direct sequencing and were revealed in three patients. OS was analyzed by Kaplan-Meier statistic.
Results
The distributions of replacement (R) and silent (S) mutations in the CDR (complementary determining region) and the FR (framework region) regions of M sequences were 75.7:24.3 and 61.1:38.9, correspondingly, and were in agreement with data of Rene et al. (2014). Using BASELINe statistics, we found that two sequences (1.6%) had signs of positive selection and 15 sequences (11.8%) had signs of negative selection in CDRs (p<0.05). The FR regions had signs of negative selection (p<0.05) in 37 (29.1%) cases. In other cases, the Σ statistic values were borderline (p<0.1) or insignificant (p>0.1). No associations of OS with signs of selection in CDRs were found. At the same time, OS was worse in CLL patients with signs of negative selection in FRs (group I, median of OS 111 months) compared to other M IGHV patients (group II, median of OS 202 months), p=0.027. Observed CLL patients of both groups were comparably by age (p=0.287), gender (p=0.488), Binet stage (p=0.37), TP53 mutational status (p=0.781), and the expression of stereotyped BCRs (p=0.488). In comparison to group II, sequences of group I had higher numbers of S mutations in CDRs (1.94±0.23 vs 0.96±0.2; p=0.001) and in FRs (5.97±0.34 vs 2.73±0.19; p=0.001), slightly lower numbers of R mutations in FRs (4.7±0.39 vs 6.04±0.31; p=0.05), and significantly lower R to S ratio in FRs (41.1:58.8 vs 69.4:30.6; p=0.00001). Besides, the number of amino acid substitutions in codons 24-26, 80, 83, and 96 was significantly reduced (or absent) (p=0.00041, when comparing the total number). In multivariate analysis, which was carried out considering the recommendations of International CLL-IPI working group (2016), the following factors were predictive for OS of M CLL patients: clinical stage (Binet A vs Binet B-C), age (≤65 years vs >65 years), and negative selection in FRs (data of serum β2-microglobulin concentration were missing; TP53 mutations were detected in a small number of cases and had no prognostic value in our M IGHV group).
Conclusion
The obtained data suggest of possible impact of features of somatic hypermutation processes in CDRs and FRs of IGHV for CLL prognosis.
Keyword(s): Chronic lymphocytic leukemia, IGH