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Genome-wide association studies (GWAS) of chronic lymphocytic leukemia (CLL) have shown that common genetic variation contributes to the heritable risk of CLL. To identify additional CLL susceptibility loci, we conducted a GWAS and performed a meta-analysis with a published GWAS totaling 1,739 individuals with CLL (cases) and 5,199 controls with validation in an additional 1,144 cases and 3,151 controls. A combined analysis identified new susceptibility loci mapping to 3q26.2 (rs10936599, P = 1.74 × 10−9), 4q26 (rs6858698, P = 3.07 × 10−9), 6q25.2 (IPCEF1, rs2236256, P = 1.50 × 10−10) and 7q31.33 (POT1, rs17246404, P = 3.40 × 10−8). Additionally, we identified a promising association at 5p15.33 (CLPTM1L, rs31490, P = 1.72 × 10−7) and validated recently reported putative associations at 5p15.33 (TERT, rs10069690, P = 1.12 × 10−10) and 8q22.3 (rs2511714, P = 2.90 × 10−9). These findings provide further insights into the genetic and biological basis of inherited genetic susceptibility to CLL. [ABSTRACT FROM AUTHOR]

Recent multi-stage genome-wide association studies ( GWAS) have identified single nucleotide polymorphisms ( SNPs) that are robustly associated with chronic lymphocytic leukaemia ( CLL) risk. Given that most of these SNPs map to non-coding regions of the genome, it suggests that the functional basis of many GWAS signals will be through differential gene expression. By referencing publically accessible expression quantitative trait loci ( eQTL) data on lymphoblastoid cells lines ( LCLs) we have globally demonstrated an association between GWAS P-values and eQTLs, consistent with much of the variation in CLL risk being defined by variants impacting on gene expression. To explore using eQTL data to select GWAS SNPs for replication, we genotyped rs2072135 ( GWAS P-value = 0·0024, eQTL P-value = 1·510−19) in five independent case-control series totalling 1968 cases and 3538 controls. While not attaining statistical significance (combined P-value = 1 × 10−4), rs2072135 defines a promising risk locus for CLL. Incorporating eQTL information offers an attractive strategy for selecting SNPs from GWAS for validation. [ABSTRACT FROM AUTHOR]

Background: NOTCH1 PEST domain mutations in chronic lymphocytic leukemia have recently been shown to be of prognostic relevance. Both NOTCH1 and NOTCH2 are constitutively activated in B-cell CLL but not expressed in normal B cells and may be involved in survival and resistance to apoptosis in CLL. We screened for mutations in different parts of both NOTCH1 and NOTCH2 genes and related the changes to survival and other known risk factors.Methods: In a cohort of 209 CLL patients, we used single strand conformation analysis to determine which of the samples carrying the NOTCH mutations and direct dideoxy sequencing was used to determine the exact nucleotide changes. Kaplan-Meier curves and log rank test were used to determine overall survival for NOTCH1 mutated cases and Cox regression analysis was used to calculate hazardous ratios.Results: In the present study, we found NOTCH1 PEST domain mutations in 6.7% of the cases. A shorter overall survival was found in patients with NOTCH1 mutations compared to wildtype (p = 0.049). Further, we also examined the extracellular and the heterodimerisation domains of the NOTCH1 gene and the PEST domain and heterodimerisation domain of the NOTCH2 gene, but no mutations were found in these regions. NOTCH1 mutations were most commonly observed in patients with unmutated IGHV gene (10/14), and associated with a more aggressive disease course. In addition, NOTCH1 mutations were almost mutually exclusive with TP53 mutations. In the combined group of NOTCH1 (6.7%) or TP53 (6.2%) mutations, a significant difference in overall survival compared to the wildtype NOTCH1 and TP53 was found (p = 0.002).Conclusions: Both NOTCH1 and TP53 mutations seem to be independent predictive markers for worse outcome in CLL-patients and this study emphasizes the contention that NOTCH1 mutations is a novel risk marker. [ABSTRACT FROM AUTHOR]

Thirty-eight adult patients with chronic lymphocytic leukemia (CLL) underwent reduced-intensity conditioning (RIC) allogeneic stem cell transplant (allo-SCT) in Sweden between 1999 and 2007. The cumulative incidences of acute graft-versus-host disease (GVHD) grades II-IV and chronic GVHD were 29% and 47%, respectively. Rates of non-relapse mortality, progression-free survival (PFS) and overall survival (OS) were 18%, 47% and 74% at 1 year, and 21%, 25% and 45% at 5 years, respectively. T-cell chimerism after transplant was measured in 31 out of 34 patients (91%) surviving beyond day +100. Seventeen patients achieved >90% donor T-cell engraftment at 3 months after allo-SCT and, compared with the 12 patients with ≤90% donor T-cell engraftment, they showed favorable PFS at 1 year (82% vs. 33%, p =0.002) and better long-term PFS and OS ( p =0.002 and 0.046, respectively). Donor T-cell engraftment of >90% at 3 months after RIC allo-SCT for CLL seems to predict favorable short-term and long-term outcome. [ABSTRACT FROM AUTHOR]

A recent genome wide association study of chronic lymphocytic leukaemia (CLL) provided evidence that common variation at 2q13 (rs17483466), 2q37.1 (rs13397985), 6p25.3 (rs872071), 11q24.1 (rs735665), 15q23 (rs7176508) and 19q13.32 (rs11083846) affects CLL risk. To verify and further explore the relationship between these variants and CLL risk we genotyped case-control datasets from Spain and Sweden (824 cases, 850 controls). Combined data provided statistically significant support for an association between genotypes at rs13397985, rs872071, rs735665, rs7176508 and rs11083846 and CLL risk. CLL risk increased with increasing numbers of risk alleles ( Ptrend = 1·40 × 10−15), consistent with a polygenic model of disease susceptibility. These data validate the relationship between common variation and risk of CLL. [ABSTRACT FROM AUTHOR]

To identify new risk variants for chronic lymphocytic leukemia (CLL), we conducted a genome-wide association study of 299,983 tagging SNPs, with validation in four additional series totaling 2,503 cases and 5,789 controls. We identified four new risk loci for CLL at 2q37.3 (rs757978, FARP2; odds ratio (OR) = 1.39; P = 2.11 × 10−9), 8q24.21 (rs2456449; OR = 1.26; P = 7.84 × 10−10), 15q21.3 (rs7169431; OR = 1.36; P = 4.74 × 10−7) and 16q24.1 (rs305061; OR = 1.22; P = 3.60 × 10−7). We also found evidence for risk loci at 15q25.2 (rs783540, CPEB1; OR = 1.18; P = 3.67 × 10−6) and 18q21.1 (rs1036935; OR = 1.22; P = 2.28 × 10−6). These data provide further evidence for genetic susceptibility to this B-cell hematological malignancy. [ABSTRACT FROM AUTHOR]

Fludarabine, cyclophosphamide, and rituximab (FCR) is first-line treatment of medically fit chronic lymphocytic leukemia (CLL) patients; however, despite good response rates, many patients eventually relapse. Although recent high-throughput studies have identified novel recurrent genetic lesions in adverse prognostic CLL, the mechanisms leading to relapse after FCR therapy are not completely understood. To gain insight into this issue, we performed whole-exome sequencing of sequential samples from 41 CLL patients who were uniformly treated with FCR but relapsed after a median of 2 years. In addition to mutations with known adverse-prognostic impact (TP53, NOTCH1, ATM, SF3B1, NFKBIE, and BIRC3), a large proportion of cases (19.5%) harbored mutations in RPS15, a gene encoding a component of the 40S ribosomal subunit. Extended screening, totaling 1119 patients, supported a role for RPS15 mutations in aggressive CLL, with one-third of RPS15-mutant cases also carrying TP53 aberrations. In most cases, selection of dominant, relapse-specific subclones was observed over time. However, RPS15 mutations were clonal before treatment and remained stable at relapse. Notably, all RPS15 mutations represented somatic missense variants and resided within a 7 amino-acid, evolutionarily conserved region. We confirmed the recently postulated direct interaction between RPS15 and MDM2/MDMX and transient expression of mutant RPS15 revealed defective regulation of endogenous p53 compared with wild-type RPS15. In summary, we provide novel insights into the heterogeneous genetic landscape of CLL relapsing after FCR treatment and highlight a novel mechanism underlying clinical aggressiveness involving a mutated ribosomal protein, potentially representing an early genetic lesion in CLL pathobiology. [ABSTRACT FROM AUTHOR]

Abstract: The 309T>G polymorphism in the promoter region of the MDM2 gene, known as SNP309, has recently been suggested as an unfavorable prognostic marker in chronic lymphocytic leukemia (CLL) although this has been questioned. To investigate this further, we analyzed the MDM2 SNP309 genotypes in 418 CLL patients and correlated the results with established CLL prognostic factors, time to treatment and overall survival. In this Swedish cohort, no association existed between any particular MDM2 SNP309 genotype, overall survival and time to treatment. Furthermore, no correlation was shown between the MDM2 SNP309 genotypes and Binet stage, IGHV mutational status and recurrent genomic aberrations. In summary, this study argues against the use of the MDM2 SNP309 as a prognostic marker in CLL. [Copyright &y& Elsevier]

Abstract: Deoxycytidine kinase (dCK) and deoxyguanosine kinase (dGK) catalyze the first step in the intracellular cascade of fludarabine (2-fluoroadenine-β-d-arabinofuranoside) and cladribine (2-chlorodeoxyadenosine) phosphorylation, which leads to activation of these prodrugs, commonly used for treatment of chronic lymphocytic leukemia (CLL). Thus, resistance to nucleoside analogues may primarily be due to low levels of deoxynucleoside kinase activity. The purpose of this study was to investigate the activity profiles of dCK and dGK and characterize the possible relationship between the levels of dCK enzymatic activities and mRNA levels in B-CLL cells from untreated patient samples in an attempt to determine the best approach for predicting sensitivity to nucleoside analogues and thereby optimizing treatment of CLL. For this purpose, dCK and dGK analyses were done in blood cells from 59 untreated symptomatic patients with CLL. The dGK activity towards 2-chlorodeoxyadenosine was significantly lower than of dCK (median 73pmol/mgprotein/min (85–121, 95% CI) versus 353pmol/mgprotein/min (331–421)). The median dCK mRNA level was 0.107 (0.096–0.120, 95% CI). There was a lack of correlation between the activities of dCK and dGK, which indicates that these proteins are regulated independently. We also found that the dCK and dGK activity measurement towards their endogenous substrates were comparable to the nucleoside analogues tested. Such variations in enzyme activities and mRNA levels may well explain differences in clinical responses to treatment. There was no correlation between the levels of dCK mRNAs and enzymatic activities using a quantitative real-time PCR procedure. Sequencing of dCK mRNA did not reveal alternate splicing or mutations in the coding region. The relation between activity and mRNA levels was studied by short interfering RNA (siRNA) method, which showed that in the siRNA treated cells the down-regulation of dCK expression, and activity followed each other. However, in control cells the mRNA levels remained stable but the protein activity markedly decreased. These data demonstrate that the dCK activity is not reflected by dCK mRNA expression that indicates a post-translational mechanism(s). [Copyright &y& Elsevier]

Abstract: TP53 mutations in the absence of 17p-deletion correlate with rapid disease progression and poor survival in chronic lymphocytic leukemia (CLL). Herein, we determined the TP53 mutation frequency in 268 newly diagnosed CLL patients from a population-based material. Overall, we detected TP53 mutations in 3.7% of patients (n =10), where 7/10 cases showed a concomitant 17p-deletion, confirming the high prevalence of TP53 mutation in 17p-deleted patients. Only 3 (1.1%) of the newly diagnosed patients in our cohort thereby carried TP53 mutations without 17p-deletion, a frequency that is much lower than previous reports on referral cohorts (3–6%). Our findings imply that TP53 mutations are rare at CLL onset and instead may arise during disease progression. [ABSTRACT FROM AUTHOR]