Genetics Of Chronic Lymphocytic Leukemia Research Articles

Distinct molecular genetics of chronic lymphocytic leukemia in Taiwan: clinical and pathogenetic implications.

Differences in chronic lymphocytic leukemia between the Asian and the Western population are widely known. To further clarify these ethnic differences, we profiled the molecular genetics in a cohort of 83 newly diagnosed patients from Taiwan. In detail, we assessed: (i) the usage and the mutational status of the clonotypic immunoglobulin heavy-chain variable region (IgHV) genes, (ii) the presence of VH CDR3 stereotypes, and (iii) TP53, NOTCH1, SF3B1, BIRC3, and MYD88 mutations. The IgHV gene repertoire was biased and distinct from that observed in the West with the most common IgHV genes being IgHV3-23, IgHV3-7, and IgHV3-48. In terms of IgHV gene mutational status, 63.8% of patients carried mutated rearrangements, whereas 22.4% of patients were assigned to stereotyped subsets (6.9% to major subsets and 15.5% to minor ones). The frequencies of NOTCH1, SF3B1, BIRC3 and MYD88 mutations were 9.6%, 7.2%, 1.2%, and 2.4%, respectively; however, the frequency of TP53 mutations was significantly higher (20.5%). Patients with TP53 mutations or del(17p), SF3B1 mutations and unmutated IgHV had a worse outcome compared to the other patients. In conclusion, the differences observed in IgHV properties suggest different pathogenetic factors implicated in the development of chronic lymphocytic leukemia, while the high frequency of TP53 mutations could in part explain the dismal outcome of these patients in Taiwan

Deciphering the molecular landscape in chronic lymphocytic leukemia: time frame of disease evolution.

Dramatic advances in next generation sequencing technologies have provided a novel opportunity to understand the molecular genetics of chronic lymphocytic leukemia through the comprehensive detection of genetic lesions. While progress is being made in elucidating the clinical significance of recurrently mutated genes, layers of complexity have been added to our understanding of chronic lymphocytic leukemia pathogenesis in the guise of the molecular evolution and (sub)clonal architecture of the disease. As we prepare for an era of tailored therapy, we need to appreciate not only the effect mutations have on drug response but also the impact subclones containing specific mutations have at initial presentation, during therapy and upon relapse. Therefore, although the wealth of emerging genetic data has great potential in helping us devise strategies to improve the therapy and prognosis of patients, focused efforts will be required to follow disease evolution, particularly in the context of novel therapies, in order to translate this knowledge into clinical settings.

New Strategies in Chronic Lymphocytic Leukemia: Shifting Treatment Paradigms

Over the past two decades, slow but deliberate progress has been made in understanding the genetics of chronic lymphocytic leukemia (CLL) and how the surrounding microenvironment influences leukemia cell survival. The complexity of CLL with respect to different chromosomal aberrations, lack of a common aberrant signaling pathway activation, and associated immune suppression of the disease has been seen a major stumbling block for developing a single targeted therapy similar to imatinib used in chronic myeloid leukemia. The upcoming therapeutic era we are entering with the B-cell receptor (BCR) tyrosine kinase inhibitors ibrutinib and idelalisib appears to be overcoming this obstacle. Indeed, for the large majority of patients, it appears that application of BCR kinase inhibitors can promote durable remissions without the need for chemotherapy. Where other very active targeted agents such as ABT-199, therapeutic antibodies, and chimeric antigen receptor-modified T-cells will be used in CLL also represents a major question that future clinical trials will answer.

Clinical implications of the molecular genetics of chronic lymphocytic leukemia.

Genetics and molecular genetics have contributed to clarify the biological bases of the clinical heterogeneity of chronic lymphocytic leukemia. In recent years, our knowledge of the molecular genetics of chronic lymphocytic leukemia has significantly broadened, offering potential new clinical implications. Mutations of TP53 and ATM add prognostic information independently of fluorescence in situ hybridization cytogenetic stratification. In addition, next generation sequencing technologies have allowed previously unknown genomic alterations in chronic lymphocytic leukemia to be identified. Mutations of NOTCH1, SF3B1 and BIRC3 have been associated with short time to progression and survival. Each of these lesions recognizes a different distribution across different clinical phases and biological subgroups of the disease. The clinical implications of these molecular lesions are in some instances well established, such as in the case of patients with TP53 disruption, who should be considered for alternative therapies/allogeneic stem cell transplant upfront, or in patients with ATM disruption, who are candidates to rituximab-based immunochemotherapy. On the contrary, NOTCH1, SF3B1 and BIRC3 mutations appear to have a specific significance, the clinical value of which is currently being validated, i.e. association to Richter syndrome transformation for NOTCH1 mutations, and short progression-free survival after treatment for SF3B1 mutations. Certainly, these new lesions have helped clarify the molecular bases of chronic lymphocytic leukemia aggressiveness beside TP53 disruption. This review covers the recent advancements in our understanding of the molecular genetics of chronic lymphocytic leukemia and discusses how they are going to translate into clinical implications for patient management.

Incidence and Clinical Significance of SF3B1 Somatic Mutation in Chronic Lymphocytic Leukemia.

Abstract 2881Our understanding of the genetics of chronic lymphocytic leukemia (CLL) has advanced significantly in the last few years. Recently, somatic mutations in SF3B1, a gene encoding a core component of the RNA splicing machinery, have been detected in tumor samples from variable proportions of CLL patients. Interestingly, mutations of SF3B1 are also found in patients with myelodysplastic syndrome, where they represent founding mutations, are specifically associated with phenotype with ring sideroblasts, and have a favorable prognostic significance.In this study, we analyzed incidence and clinical significance of SF3B1 mutation in 335 consecutive unselected CLL patients followed between 2000 and 2011. We analyzed 359 tumor samples from 335 patients: 191 were collected at diagnosis, 75 during follow up in untreated patients with stable disease (median time from diagnosis to sampling 24 months, range 8–110), 31 at first progression and before first line therapy (median time from diagnosis to sampling 37 months, range 5–110), and 62 in previously treated patients with active disease (median time from diagnosis to sampling 51 months, range 7–171). The overall median follow-up was 57 months (range 10–225). SF3B1 exons 14, 15 and 16 were screened for mutation by using denaturing high-performance liquid chromatography (DHPLC), and positive samples were then analyzed by Sanger sequencing.We detected 30 heterozygous missense mutations in 29 patients, with an overall incidence of 8.7% (29/335). Most of mutations were single base substitutions, and the most frequent mutation was K700E in exon 15, found in 40% of mutated patients, followed by G742D in exon 16 (27% of mutants). While SF3B1 (K700E) is the most frequent mutation also in myelodysplastic syndromes, SF3B1 (G742D) is rarely found in these latter disorders.Mutations frequency was low at diagnosis (6.3%) and in untreated patients with stable disease (5.3%), whereas it increased significantly at progression (9.7%) and in previously treated patients with active disease (16.1%) (P=.027). Of 268 patients evaluated at diagnosis and before progression or treatment, 87% were in Binet stage A and 13% in Binet stage B or C, 40% had unmutated IGHV status, 14% carried del11q or del17p detected by I-FISH, 15% were CD38+ and 25% were ZAP70+. Within this group, SF3B1 mutations were detected in 16/268 (6%) patients, and were associated with advanced Binet stage (B or C) (15% vs 5%, P=.037); there was also a trend for association with unmutated IGHV pattern (P=.053) and CD38 expression (P= .068). Interestingly, of 9 patients carrying IGHV3–21, four were SF3B1 mutated and had a stereotyped HCDR3.In order to evaluate the impact of SF3B1 mutation on overall survival (OS) and time to first treatment (TTFT), we analyzed 234 untreated patients in Binet stage A (161 evaluated at diagnosis and 73 during follow-up). Also in this subset, SF3B1 mutation (11/234 or 5%) was associated with CD38 expression (P=.007) and unmutated IGHV status (P=.05). Median OS was not reached (9 events so far). In univariate analysis, SF3B1 mutation had no impact on OS, whereas unmutated IGHV, CD38 expression and ZAP70 positivity were associated with worse OS (P=.002, P=.002 and P=.003, respectively).Seventy-six patients were treated and median TTFT was 40 months (range 1–154). Univariate analysis showed an adverse impact of SF3B1 mutation on TTFT (median TTFT 26 months in mutated vs 109 months in unmutated patients, P=.0009). Unmutated IGHV, CD38 expression and presence of del17p or del11q had a crude association with shorter TTFT as well (P<.0001, P=.0002 and P=.0009, respectively). However, in a Cox multivariable analysis, SF3B1 mutation status lost significance and only IGHV status maintained an independent adverse impact on TTFT.In 37 CLL patients, serial samples were available for mutation analysis. We identified three SF3B1 mutations that were acquired at follow up, and this occurred in patients who were refractory to or relapsed after at least one line of therapy.In conclusion, the findings of this study indicate that SF3B1 mutations have a low incidence in early stages of CLL, whereas they occur more frequently in advanced stages. At variance with myelodysplastic syndromes, SF3B1 mutations are unlikely to represent founding or driver mutations in CLL patients. More likely, they occur during clonal evolution of the disease, and may therefore be considered as a molecular marker of disease progression. Disclosures:No relevant conflicts of interest to declare.

Analysis of a large multi‐generational family provides insight into the genetics of chronic lymphocytic leukemia

We report the genetic analysis of a large multi-generational family composed of 144 individuals in which 11 members have been diagnosed with chronic lymphocytic leukaemia (CLL). The observation of a significant over-representation of monoclonal B-cell lymphocytosis (MBL) in unaffected family members strongly supports MBL being a surrogate marker of carrier status. A genome-wide linkage scan of the family using high-density 10K single nucleotide polymorphisms provided no significant evidence for a single gene model of disease susceptibility, inviting speculation that susceptibility to CLL has a more complex basis. The absence of a correlation in IGHV usage between affected family members does however argue strongly against exposure to a single super-antigen in disease development.

Genetics of chronic lymphocytic leukemia: genomic aberrations and V(H) gene mutation status in pathogenesis and clinical course.

The genetic characterization of chronic lymphocytic leukemia (CLL) has made significant progress over the past few years. While conventional cytogenetic analyses only detected chromosome aberrations in 40-50% of cases, new molecular cytogenetic methods, such as fluorescence in situ hybridization (FISH), have greatly enhanced our ability to detect chromosomal abnormalities in CLL. Today, genomic aberrations are detected in over 80% of CLL cases. Genes potentially involved in the pathogenesis were identified with ATM in a subset of cases with 11q deletion and p53 in cases with 17p13 deletion. For the most frequent aberration, the deletion 13q14, candidate genes have been isolated. Genetic subgroups with distinct clinical features have been identified. 11q deletion is associated with marked lymphadenopathy and rapid disease progression. 17p deletion predicts for treatment failure with alkylating agents, as well as fludarabine and short survival times. In multivariate analysis 11q and 17p deletions provided independent prognostic information. Recently, another important issue of genetic risk classification in CLL was identified with the mutation status of the immunoglobulin variable heavy chain genes (V(H)). CLL cases with unmutated V(H) show more rapid disease progression and shorter survival times. Whether CD38 expression can serve as a surrogate marker for V(H) mutation status is currently discussed controversially. V(H) mutation status and genomic abnormalities, such as 17p and 11q deletion, have recently been shown to be related to each other, but were of independent prognostic information in multivariate analysis. Moreover, genomic aberrations and V(H) mutation status appear to give prognostic information irrespective of the clinical stage and may therefore allow a risk assessment for individual patients early in the course of their disease.