Contributions
Abstract: PB1861
Type: Publication Only
Background
The mutational status of IGHV genes is a well-established prognostic biomarker in chronic lymphocytic leukemia (CLL). Patients with unmutated IGHV genes experience a more progressive course of the condition and their survival is significantly reduced with respect to patients with mutated IGHV genes. Increasingly, studies are reporting the type and composition of IGH-VDJ rearrangements and defining specific stereotyped CLL subsets.
Aims
Analyze the IGH-VDJ rearrangements in a series of patients with CLL, determine their distribution and compare to results from similar studies. Group the rearrangements according to stereotype subsets and evaluate if a relation exists between subsets and other common genetic alterations in CLL.
Methods
The cohort included 49 patients diagnosed with CLL at the Hospital Universitario de Gran Canaria Doctor Negrín between 2014 and 2017. The characterization of IGH-VDJ rearrangements was determined from cDNA obtained from peripheral blood samples by Sanger sequencing using a 3130 Genetic Analyzer (Life Technologies, Carlsbad, CA). Chromosomal alterations were determined using FISH as part of routine diagnosis procedures. The statistical analyses were performed using R software.
Results
Of the 49 patients, 30 (61%) presented mutated IGHV genes vs. 19 (39%) that were ummutated. With respect to the genetic alterations detected by FISH, 8% harbored del(11q), 10% del(17p), 18% +12, and 60% del(13q). There was a statistically significant association between del(11q) and unmutated IGHV genes (p=0.018, Fisher) and a marginally significant association between del(13q) and mutated IGHV genes ((p=0.075, Fisher), both in agreement with previously published results. The distribution of VH family usage and its association with the mutational status of IGHV was studied (Figure 1). The distribution of used VH families from highest to lowest incidence was IGHV3 (46.9%), IGHV4 (24.5%), IGHV1 (22.4%), IGHV5 (4.1%) and IGHV2 (2%), similar to that previously described in a series of Spanish CLL patients (González-Gascón et al, 2013). The frequency of mutated vs. unmutated for VH3 was 56.54% vs. 43.5%, 45.5% vs. 54.5% for VH1, and 75% vs. 25% for VH4, respectively. These frequencies were similar to those previously published with the exception of IGHV1 and VH3, for which the number of unmutated cases in IGHV1 was reported to be twice the number of mutated cases, with the opposite reported in VH3. With respect to the subfamily distribution (Figure 2), the highest incidence was VH3-30 (16%) followed by VH3-2, VH1-69 and VH4-59 (8% each). However, according to González-Gascón et al., the predominant subfamilies were VH1-69 and VH3-23 (18%) followed by VH4-34 (16%) and VH3-30 (12%). Table 1 shows the characteristics of the amino acids that constitute the HCDR3 region (quantity and proportion of hydrophilic/hydrophobic residues) and their relation with IGHV mutational status. We identified three cases that belonged to described stereotypes defined by Agathangelidis et al. (Blood, 2012): two were # 2 and one #202.
Conclusion
In general, our results are similar to those published on other Spanish CLL patients in terms of the IGHV family distributions, subfamilies and associations with other chromosomal alterations. The differences observed could be a result of the limited size of the patient series analyzed in this study. The different distribution of hydrophilic/hydrophobic amino acids among mutated and unmutated cases of CLL is a novel result and could possibly be associated with prognosis.
Session topic: 5. Chronic lymphocytic leukemia and related disorders – Biology & Translational Research
Keyword(s): Chronic Lymphocytic Leukemia, IGH, Mutation status
Abstract: PB1861
Type: Publication Only
Background
The mutational status of IGHV genes is a well-established prognostic biomarker in chronic lymphocytic leukemia (CLL). Patients with unmutated IGHV genes experience a more progressive course of the condition and their survival is significantly reduced with respect to patients with mutated IGHV genes. Increasingly, studies are reporting the type and composition of IGH-VDJ rearrangements and defining specific stereotyped CLL subsets.
Aims
Analyze the IGH-VDJ rearrangements in a series of patients with CLL, determine their distribution and compare to results from similar studies. Group the rearrangements according to stereotype subsets and evaluate if a relation exists between subsets and other common genetic alterations in CLL.
Methods
The cohort included 49 patients diagnosed with CLL at the Hospital Universitario de Gran Canaria Doctor Negrín between 2014 and 2017. The characterization of IGH-VDJ rearrangements was determined from cDNA obtained from peripheral blood samples by Sanger sequencing using a 3130 Genetic Analyzer (Life Technologies, Carlsbad, CA). Chromosomal alterations were determined using FISH as part of routine diagnosis procedures. The statistical analyses were performed using R software.
Results
Of the 49 patients, 30 (61%) presented mutated IGHV genes vs. 19 (39%) that were ummutated. With respect to the genetic alterations detected by FISH, 8% harbored del(11q), 10% del(17p), 18% +12, and 60% del(13q). There was a statistically significant association between del(11q) and unmutated IGHV genes (p=0.018, Fisher) and a marginally significant association between del(13q) and mutated IGHV genes ((p=0.075, Fisher), both in agreement with previously published results. The distribution of VH family usage and its association with the mutational status of IGHV was studied (Figure 1). The distribution of used VH families from highest to lowest incidence was IGHV3 (46.9%), IGHV4 (24.5%), IGHV1 (22.4%), IGHV5 (4.1%) and IGHV2 (2%), similar to that previously described in a series of Spanish CLL patients (González-Gascón et al, 2013). The frequency of mutated vs. unmutated for VH3 was 56.54% vs. 43.5%, 45.5% vs. 54.5% for VH1, and 75% vs. 25% for VH4, respectively. These frequencies were similar to those previously published with the exception of IGHV1 and VH3, for which the number of unmutated cases in IGHV1 was reported to be twice the number of mutated cases, with the opposite reported in VH3. With respect to the subfamily distribution (Figure 2), the highest incidence was VH3-30 (16%) followed by VH3-2, VH1-69 and VH4-59 (8% each). However, according to González-Gascón et al., the predominant subfamilies were VH1-69 and VH3-23 (18%) followed by VH4-34 (16%) and VH3-30 (12%). Table 1 shows the characteristics of the amino acids that constitute the HCDR3 region (quantity and proportion of hydrophilic/hydrophobic residues) and their relation with IGHV mutational status. We identified three cases that belonged to described stereotypes defined by Agathangelidis et al. (Blood, 2012): two were # 2 and one #202.
Conclusion
In general, our results are similar to those published on other Spanish CLL patients in terms of the IGHV family distributions, subfamilies and associations with other chromosomal alterations. The differences observed could be a result of the limited size of the patient series analyzed in this study. The different distribution of hydrophilic/hydrophobic amino acids among mutated and unmutated cases of CLL is a novel result and could possibly be associated with prognosis.
Session topic: 5. Chronic lymphocytic leukemia and related disorders – Biology & Translational Research
Keyword(s): Chronic Lymphocytic Leukemia, IGH, Mutation status