Comprehensive Genetic Analysis by Integration of Conventional Karyotyping and Interphase FISH Helps Refinement of Biological Subclasses with Clinical Impact in Chronic Lymphocytic Leukemia

Abstract

Background: Various genetic technologies have been employed in the identification of genomic complexity and refinement of prognostic classification of clinically heterogeneous disease of chronic lymphocytic leukemia (CLL). Objective: The present study of interphase cytogenetics and conventional karyotyping was undertaken to perform comprehensive analysis of CLL genetics with an approach to refine early prognostication of disease. Material & Methods: Retrospective analysis by fluorescence in situ hybridization (FISH) was carried out on total 671 patients of CLL at diagnosis between 2008 and 2015. Conventional cytogenetics studies were performed in 50 of 671 patients using CPG Oligonucleotide + IL-2 and TPA (12-O-Tetradecanyl Phorbol 13-acetate) for stimulation of lymphocytes cultures. Results: Interphase cytogenetics could detect recurrent abnormalities such as del(13q14), +12, del(17p13), del(11q22), del(6q23) in 71% of cases. The incidence of del(13q) was higher in Rai stage 0, I, II (p = 0.0005); whereas patients with ≥2 aberrations were more common in advance stage III, IV (p = 0.001). Frequency of IgH translocation was 7%. Morphology and immunophenotypic analysis revealed atypical CLL with higher frequency of t(14;19) than t(14;18). Conventional karyotype could detect abnormal karyotype in 97% of cases which displayed targeted FISH abnormalities along with additional non-targeted chromosomal abnormalities. Patients with negative FISH markers showed clonal non-recurrent numerical and structural changes. The complex karyotype was identified in 24% cases which included targeted FISH aberrations as well as non-targeted numerical and structural abnormalities like deletions, and unbalanced translocations. A significant association was observed between complex karyotype and coexistence of ≥2 FISH markers (p = 0.009) and del(11q22) &/or del(17p) (p = 0.03). Conclusion: Our data of interphase FISH with integration of conventional karyotyping revealed genomic complexity that helped identification of biological subclasses with clinical impact at diagnosis. Further, these cytogenetic subclasses along with molecular markers are likely to evolve more refined prognostic groups, which will help design risk-adapted therapies in B-CLL.