Integrative NGS testing reveals clonal dynamics of adverse genomic defects contributing to a natural progression in treatment-naïve CLL patients.

Large-scale next-generation sequencing (NGS) studies revealed extensive genetic heterogeneity, driving a highly variable clinical course of chronic lymphocytic leukaemia (CLL). The evolution of subclonal populations contributes to diverse therapy responses and disease refractoriness. Besides, the dynamics and impact of subpopulations before therapy initiation are not well understood. We examined changes in genomic defects in serial samples of 100 untreated CLL patients, spanning from indolent to aggressive disease. A comprehensive NGS panel LYNX, which provides targeted mutational analysis and genome-wide chromosomal defect assessment, was employed. We observed dynamic changes in the composition and/or proportion of genomic aberrations in most patients (62%). Clonal evolution of gene variants prevailed over the chromosomal alterations. Unsupervised clustering based on aberration dynamics revealed four groups of patients with different clinical behaviour. An adverse cluster was associated with fast progression and early therapy need, characterized by the expansion of TP53 defects, ATM mutations, and 18p- alongside dynamic SF3B1 mutations. Our results show that clonal evolution is active even without therapy pressure and that repeated genetic testing can be clinically relevant during long-term patient monitoring. Moreover, integrative NGS testing contributes to the consolidated evaluation of results and accurate assessment of individual patient prognosis.

Low-burden TP53 mutations in CLL: clinical impact and clonal evolution within the context of different treatment options.

Patients with chronic lymphocytic leukemia (CLL) bearing TP53 mutations experience chemorefractory disease and are therefore candidates for targeted therapy. However, the significance of low-burden TP53 mutations with <10% variant allele frequency (VAF) remains a matter for debate. Herein, we describe clonal evolution scenarios of low-burden TP53 mutations, the clinical impact of which we analyzed in a "real-world" CLL cohort. TP53 status was assessed by targeted next-generation sequencing (NGS) in 511 patients entering first-line treatment with chemo- and/or immunotherapy and 159 patients in relapse before treatment with targeted agents. Within the pretherapy cohort, 16% of patients carried low-burden TP53 mutations (0.1% to 10% VAF). Although their presence did not significantly shorten event-free survival after first-line therapy, it affected overall survival (OS). In a subgroup with TP53 mutations of 1% to 10% VAF, the impact on OS was observed only in patients with unmutated IGHV who had not received targeted therapy, as patients benefited from switching to targeted agents, regardless of initial TP53 mutational status. Analysis of the clonal evolution of low-burden TP53 mutations showed that the highest expansion rates were associated with fludarabine, cyclophosphamide, and rituximab regimen in both first- and second-line treatments (median VAF increase, 14.8× and 11.8×, respectively) in contrast to treatment with less intense treatment regimens (1.6×) and no treatment (0.8×). In the relapse cohort, 33% of patients carried low-burden TP53 mutations, which did not expand significantly upon targeted treatment (median VAF change, 1×). Sporadic cases of TP53 mutations' clonal shifts were connected with the development of resistance-associated mutations. Altogether, our data support the incorporation of low-burden TP53 variants in clinical decision making.

Evolution of TP53 abnormalities during CLL disease course is associated with telomere length changes.

BACKGROUND: Telomeres are protective structures at chromosome ends which shorten gradually with increasing age. In chronic lymphocytic leukemia (CLL), short telomeres have been associated with unfavorable disease outcome, but the link between clonal evolution and telomere shortening remains unresolved. METHODS: We investigated relative telomere length (RTL) in a well-characterized cohort of 198 CLL patients by qPCR and focused in detail on a subgroup 26 patients who underwent clonal evolution of TP53 mutations (evolTP53). In the evolTP53 subgroup we explored factors influencing clonal evolution and corresponding changes in telomere length through measurements of telomerase expression, lymphocyte doubling time, and BCR signaling activity. RESULTS: At baseline, RTL of the evolTP53 patients was scattered across the entire RTL spectrum observed in our CLL cohort. RTL changed in the follow-up samples of 16/26 (62%) evolTP53 cases, inclining to reach intermediate RTL values, i.e., longer telomeres shortened compared to baseline while shorter ones prolonged. For the first time we show that TP53 clonal shifts are linked to RTL change, including unexpected RTL prolongation. We further investigated parameters associated with RTL changes. Unstable telomeres were significantly more frequent among younger patients (P = 0.032). Shorter telomeres were associated with decreased activity of the B-cell receptor signaling components p-ERK1/2, p-ZAP-70/SYK, and p-NFκB (P = 0.04, P = 0.01, and P = 0.02, respectively). CONCLUSIONS: Our study revealed that changes of telomere length reflect evolution in leukemic subclone proportion, and are associated with specific clinico-biological features of the explored cohort.

Transcription factor YY1 can control AID-mediated mutagenesis in mice.

Activation-induced cytidine deminase (AID) is crucial for controlling the immunoglobulin (Ig) diversification processes of somatic hypermutation (SHM) and class switch recombination (CSR). AID initiates these processes by deamination of cytosine, ultimately resulting in mutations or double strand DNA breaks needed for SHM and CSR. Levels of AID control mutation rates, and off-target non-Ig gene mutations can contribute to lymphomagenesis. Therefore, factors that control AID levels in the nucleus can regulate SHM and CSR, and may contribute to disease. We previously showed that transcription factor YY1 can regulate the level of AID in the nucleus and Ig CSR. Therefore, we hypothesized that conditional knock-out of YY1 would lead to reduction in AID localization at the Ig locus, and reduced AID-mediated mutations. Using mice that overexpress AID (IgκAID yy1f/f ) or that express normal AID levels (yy1f/f ), we found that conditional knock-out of YY1 results in reduced AID nuclear levels, reduced localization of AID to the Sµ switch region, and reduced AID-mediated mutations. We find that the mechanism of YY1 control of AID nuclear accumulation is likely due to YY1-AID physical interaction which blocks AID ubiquitination.

Activation-induced deaminase and its splice variants associate with trisomy 12 in chronic lymphocytic leukemia.

Activation-induced cytidine deaminase (AID) is a mutator enzyme essential for somatic hypermutation (SHM) and class switch recombination (CSR) during effective adaptive immune responses. Its aberrant expression and activity have been detected in lymphomas, leukemias, and solid tumors. In chronic lymphocytic leukemia (CLL) increased expression of alternatively spliced AID variants has been documented. We used real-time RT-PCR to quantify the expression of AID and its alternatively spliced transcripts (AIDΔE4a, AIDΔE4, AIDivs3, and AIDΔE3E4) in 149 CLL patients and correlated this expression to prognostic markers including recurrent chromosomal aberrations, the presence of complex karyotype, mutation status of the immunoglobulin heavy chain variable gene, and recurrent mutations. We report a previously unappreciated association between higher AID transcript levels and trisomy of chromosome 12. Functional analysis of AID splice variants revealed loss of their activity with respect to SHM, CSR, and induction of double-strand DNA breaks. In silico modeling provided insight into the molecular interactions and structural dynamics of wild-type AID and a shortened AID variant closely resembling AIDΔE4, confirming its loss-of-function phenotype.

ToTem: a tool for variant calling pipeline optimization.

BACKGROUND: High-throughput bioinformatics analyses of next generation sequencing (NGS) data often require challenging pipeline optimization. The key problem is choosing appropriate tools and selecting the best parameters for optimal precision and recall. RESULTS: Here we introduce ToTem, a tool for automated pipeline optimization. ToTem is a stand-alone web application with a comprehensive graphical user interface (GUI). ToTem is written in Java and PHP with an underlying connection to a MySQL database. Its primary role is to automatically generate, execute and benchmark different variant calling pipeline settings. Our tool allows an analysis to be started from any level of the process and with the possibility of plugging almost any tool or code. To prevent an over-fitting of pipeline parameters, ToTem ensures the reproducibility of these by using cross validation techniques that penalize the final precision, recall and F-measure. The results are interpreted as interactive graphs and tables allowing an optimal pipeline to be selected, based on the user's priorities. Using ToTem, we were able to optimize somatic variant calling from ultra-deep targeted gene sequencing (TGS) data and germline variant detection in whole genome sequencing (WGS) data. CONCLUSIONS: ToTem is a tool for automated pipeline optimization which is freely available as a web application at https://totem.software .

Seshat: A Web service for accurate annotation, validation, and analysis of TP53 variants generated by conventional and next-generation sequencing.

Accurate annotation of genomic variants in human diseases is essential to allow personalized medicine. Assessment of somatic and germline TP53 alterations has now reached the clinic and is required in several circumstances such as the identification of the most effective cancer therapy for patients with chronic lymphocytic leukemia (CLL). Here, we present Seshat, a Web service for annotating TP53 information derived from sequencing data. A flexible framework allows the use of standard file formats such as Mutation Annotation Format (MAF) or Variant Call Format (VCF), as well as common TXT files. Seshat performs accurate variant annotations using the Human Genome Variation Society (HGVS) nomenclature and the stable TP53 genomic reference provided by the Locus Reference Genomic (LRG). In addition, using the 2017 release of the UMD_TP53 database, Seshat provides multiple statistical information for each TP53 variant including database frequency, functional activity, or pathogenicity. The information is delivered in standardized output tables that minimize errors and facilitate comparison of mutational data across studies. Seshat is a beneficial tool to interpret the ever-growing TP53 sequencing data generated by multiple sequencing platforms and it is freely available via the TP53 Website, http://p53.fr or directly at http://vps338341.ovh.net/.

GLASS: assisted and standardized assessment of gene variations from Sanger sequence trace data.

MOTIVATION: Sanger sequencing is still being employed for sequence variant detection by many laboratories, especially in a clinical setting. However, chromatogram interpretation often requires manual inspection and in some cases, considerable expertise. RESULTS: We present GLASS, a web-based Sanger sequence trace viewer, editor, aligner and variant caller, built to assist with the assessment of variations in 'curated' or user-provided genes. Critically, it produces a standardized variant output as recommended by the Human Genome Variation Society. AVAILABILITY AND IMPLEMENTATION: GLASS is freely available at http://bat.infspire.org/genomepd/glass/ with source code at https://github.com/infspiredBAT/GLASS. CONTACT: nikos.darzentas@gmail.com or malcikova.jitka@fnbrno.cz. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Different spectra of recurrent gene mutations in subsets of chronic lymphocytic leukemia harboring stereotyped B-cell receptors.

We report on markedly different frequencies of genetic lesions within subsets of chronic lymphocytic leukemia patients carrying mutated or unmutated stereotyped B-cell receptor immunoglobulins in the largest cohort (n=565) studied for this purpose. By combining data on recurrent gene mutations (BIRC3, MYD88, NOTCH1, SF3B1 and TP53) and cytogenetic aberrations, we reveal a subset-biased acquisition of gene mutations. More specifically, the frequency of NOTCH1 mutations was found to be enriched in subsets expressing unmutated immunoglobulin genes, i.e. #1, #6, #8 and #59 (22-34%), often in association with trisomy 12, and was significantly different (P<0.001) to the frequency observed in subset #2 (4%, aggressive disease, variable somatic hypermutation status) and subset #4 (1%, indolent disease, mutated immunoglobulin genes). Interestingly, subsets harboring a high frequency of NOTCH1 mutations were found to carry few (if any) SF3B1 mutations. This starkly contrasts with subsets #2 and #3 where, despite their immunogenetic differences, SF3B1 mutations occurred in 45% and 46% of cases, respectively. In addition, mutations within TP53, whilst enriched in subset #1 (16%), were rare in subsets #2 and #8 (both 2%), despite all being clinically aggressive. All subsets were negative for MYD88 mutations, whereas BIRC3 mutations were infrequent. Collectively, this striking bias and skewed distribution of mutations and cytogenetic aberrations within specific chronic lymphocytic leukemia subsets implies that the mechanisms underlying clinical aggressiveness are not uniform, but rather support the existence of distinct genetic pathways of clonal evolution governed by a particular stereotyped B-cell receptor selecting a certain molecular lesion(s).

TP53 mutation analysis in chronic lymphocytic leukemia: comparison of different detection methods.

TP53 gene defects represent a strong adverse prognostic factor for patient survival and treatment resistance in chronic lymphocytic leukemia (CLL). Although various methods for TP53 mutation analysis have been reported, none of them allow the identification of all occurring sequence variants, and the most suitable methodology is still being discussed. The aim of this study was to determine the limitations of commonly used methods for TP53 mutation examination in CLL and propose an optimal approach for their detection. We examined 182 CLL patients enriched for high-risk cases using denaturing high-performance liquid chromatography (DHPLC), functional analysis of separated alleles in yeast (FASAY), and the AmpliChip p53 Research Test in parallel. The presence of T53 gene mutations was also evaluated using ultra-deep next generation sequencing (NGS) in 69 patients. In total, 79 TP53 mutations in 57 (31 %) patients were found; among them, missense substitutions predominated (68 % of detected mutations). Comparing the efficacy of the methods used, DHPLC and FASAY both combined with direct Sanger sequencing achieved the best results, identifying 95 % and 93 % of TP53-mutated patients. Nevertheless, we showed that in CLL patients carrying low-proportion TP53 mutation, the more sensitive approach, e.g., ultra-deep NGS, might be more appropriate. TP53 gene analysis using DHPLC or FASAY is a suitable approach for mutation detection. Ultra-deep NGS has the potential to overcome shortcomings of methods currently used, allows the detection of minor proportion mutations, and represents thus a promising methodology for near future.

Targeted next-generation sequencing in chronic lymphocytic leukemia: a high-throughput yet tailored approach will facilitate implementation in a clinical setting.

Next-generation sequencing has revealed novel recurrent mutations in chronic lymphocytic leukemia, particularly in patients with aggressive disease. Here, we explored targeted re-sequencing as a novel strategy to assess the mutation status of genes with prognostic potential. To this end, we utilized HaloPlex targeted enrichment technology and designed a panel including nine genes: ATM, BIRC3, MYD88, NOTCH1, SF3B1 and TP53, which have been linked to the prognosis of chronic lymphocytic leukemia, and KLHL6, POT1 and XPO1, which are less characterized but were found to be recurrently mutated in various sequencing studies. A total of 188 chronic lymphocytic leukemia patients with poor prognostic features (unmutated IGHV, n=137; IGHV3-21 subset #2, n=51) were sequenced on the HiSeq 2000 and data were analyzed using well-established bioinformatics tools. Using a conservative cutoff of 10% for the mutant allele, we found that 114/180 (63%) patients carried at least one mutation, with mutations in ATM, BIRC3, NOTCH1, SF3B1 and TP53 accounting for 149/177 (84%) of all mutations. We selected 155 mutations for Sanger validation (variant allele frequency, 10-99%) and 93% (144/155) of mutations were confirmed; notably, all 11 discordant variants had a variant allele frequency between 11-27%, hence at the detection limit of conventional Sanger sequencing. Technical precision was assessed by repeating the entire HaloPlex procedure for 63 patients; concordance was found for 77/82 (94%) mutations. In summary, this study demonstrates that targeted next-generation sequencing is an accurate and reproducible technique potentially suitable for routine screening, eventually as a stand-alone test without the need for confirmation by Sanger sequencing.

Ofatumumab added to dexamethasone in patients with relapsed or refractory chronic lymphocytic leukemia: Results from a phase II study.

The treatment of relapsed/refractory chronic lymphocytic leukemia (CLL) remains a challenging clinical issue. An important treatment option is the use of high-dose corticosteroids. The purpose of this clinical trial was to determine the efficacy and toxicity of an ofatumumab-dexamethasone (O-Dex) combination in relapsed or refractory CLL. The trial was an open-label, multicenter, nonrandomized, Phase II study. The O-Dex regimen consisted of intravenous ofatumumab (Cycle 1: 300 mg on day 1, 2,000 mg on days 8, 15, and 22; Cycles 2-6: 1,000 mg on days 1, 8, 15, and 22) and oral dexamethasone (40 mg on days 1-4 and 15-18; Cycles 1-6). The O-Dex regimen was given until best response, or a maximum of six cycles. Thirty-three patients (pts) were recruited. Twenty-four (73%) pts completed at least three cycles of therapy. The remaining nine pts were prematurely discontinued owing to Grade 3/4 infections (seven pts), disease progression (one pt), or uncontrollable diabetes mellitus (one pt). Overall response rates/complete remissions (ORR/CR) were achieved in 22/5 pts (67/15%). The median progression-free survival (PFS) was 10 months. In pts with p53 defects (n = 8), ORR/CR were achieved in 5/2 pts (63/25%) with a median PFS of 10.5 months. The median overall survival (OS) was 34 months. The Grades 3-5 infectious toxicity in 33% of pts represented the most frequent side effect during the treatment period. In conclusion, the O-Dex regimen shows a relatively high ORR and CR with promising findings for PFS and OS. The study was registered at www.clinicaltrials.gov (NCT01310101).

TP53 mutation analysis in clinical practice: lessons from chronic lymphocytic leukemia.

In leukemia, TP53 mutations are not frequent but clearly associate with impaired survival and therapy response. Here, we describe the biological and clinical consequences of TP53 dysfunction as well as the methodical aspects of TP53 analysis in chronic lymphocytic leukemia (CLL). In CLL, TP53 defects are routinely analyzed as part of disease prognostication. Deletions of TP53 locus (17p) have been uniformly detected using I-FISH for several years. Since monoallelic mutations have also been shown to have negative prognostic impact, it is recommended to examine both TP53 mutations and deletions. Several methods are used to detect TP53 mutations, and next-generation sequencing (NGS) is becoming a convenient option for routine analysis. Besides this, ultradeep NGS permits the detection of minor clones carrying TP53 mutations, even below 1%. The prognostic impact of minor TP53-defective subclones is currently unknown, nevertheless they unequivocally bear the risk of being selected by therapy. Prospective studies assessing the consequences of carrying such clones are in progress.

Identification of novel sequence variations in microRNAs in chronic lymphocytic leukemia.

MicroRNA (miRNA) expression is deregulated in many tumors including chronic lymphocytic leukemia (CLL). Although the particular mechanism(s) responsible for their aberrant expression is not well characterized, the presence of mutations and single-nucleotide polymorphisms (SNPs) in miRNA genes, possibly affecting their secondary structure and expression, has been described. In CLL; however, the impact and frequency of such variations have yet to be elucidated. Using a custom resequencing microarray, we screened sequence variations in 109 cancer-related pre-miRNAs in 98 CLL patients. Additionally, the primary regions of miR-29b-2/29c and miR-16-1 were analyzed by Sanger sequencing in another cohort of 213 and 193 CLL patients, respectively. Altogether, we describe six novel miR-sequence variations and the presence of SNPs (n = 27), most of which changed the miR-secondary structure. Moreover, some of the identified SNPs have a significantly different frequency in CLL when compared with a control population. Additionally, we identified a novel variation in miR-16-1 that had not been described previously in CLL patients. We show that this variation affects the expression of mature miR-16-1. We also show that the expression of another miRNA with pathogenetic relevance for CLL, namely miR-29b-2, is influenced by the presence of a polymorphic insertion, which is more frequent in CLL than in a control population. Altogether, these data suggest that sequence variations may occur during CLL development and/or progression.

Multiple productive immunoglobulin heavy chain gene rearrangements in chronic lymphocytic leukemia are mostly derived from independent clones.

In chronic lymphocytic leukemia, usually a monoclonal disease, multiple productive immunoglobulin heavy chain gene rearrangements are identified sporadically. Prognostication of such cases based on immunoglobulin heavy variable gene mutational status can be problematic, especially if the different rearrangements have discordant mutational status. To gain insight into the possible biological mechanisms underlying the origin of the multiple rearrangements, we performed a comprehensive immunogenetic and immunophenotypic characterization of 31 cases with the multiple rearrangements identified in a cohort of 1147 patients with chronic lymphocytic leukemia. For the majority of cases (25/31), we provide evidence of the co-existence of at least two B lymphocyte clones with a chronic lymphocytic leukemia phenotype. We also identified clonal drifts in serial samples, likely driven by selection forces. More specifically, higher immunoglobulin variable gene identity to germline and longer complementarity determining region 3 were preferred in persistent or newly appearing clones, a phenomenon more pronounced in patients with stereotyped B-cell receptors. Finally, we report that other factors, such as TP53 gene defects and therapy administration, influence clonal selection. Our findings are relevant to clonal evolution in the context of antigen stimulation and transition of monoclonal B-cell lymphocytosis to chronic lymphocytic leukemia.

Chromosomal translocations and karyotype complexity in chronic lymphocytic leukemia: a systematic reappraisal of classic cytogenetic data.

The significance of chromosomal translocations (CTRAs) and karyotype complexity (KC) in chronic lymphocytic leukemia (CLL) remains uncertain. To gain insight into these issues, we evaluated a series of 1001 CLL cases with reliable classic cytogenetic data obtained within 6 months from diagnosis before any treatment. Overall, 320 cases were found to carry ≥ 1 CTRAs. The most frequent chromosome breakpoints were 13q, followed by 14q, 18q, 17q, and 17p; notably, CTRAs involving chromosome 13q showed a wide spectrum of translocation partners. KC (≥ 3 aberrations) was detected in 157 cases and significantly (P < 0.005) associated with unmutated IGHV genes and aberrations of chromosome 17p. Furthermore, it was identified as an independent prognostic factor for shorter time-to-first-treatment. CTRAs were assigned to two categories (i) CTRAs present in the context of KC, often with involvement of chromosome 17p aberrations, occurring mostly in CLL with unmutated IGHV genes; in such cases, we found that KC rather than the presence of CTRAs per se negatively impacts on survival; (ii) CTRAs in cases without KC, having limited if any impact on survival. On this evidence, we propose that all CTRAs in CLL are not equivalent but rather develop by different processes and are associated with distinct clonal behavior.

ERIC recommendations for TP53 mutation analysis in chronic lymphocytic leukemia-2024 update.

In chronic lymphocytic leukemia (CLL), analysis of TP53 aberrations (deletion and/or mutation) is a crucial part of treatment decision-making algorithms. Technological and treatment advances have resulted in the need for an update of the last recommendations for TP53 analysis in CLL, published by ERIC, the European Research Initiative on CLL, in 2018. Based on the current knowledge of the relevance of low-burden TP53-mutated clones, a specific variant allele frequency (VAF) cut-off for reporting TP53 mutations is no longer recommended, but instead, the need for thorough method validation by the reporting laboratory is emphasized. The result of TP53 analyses should always be interpreted within the context of available laboratory and clinical information, treatment indication, and therapeutic options. Methodological aspects of introducing next-generation sequencing (NGS) in routine practice are discussed with a focus on reliable detection of low-burden clones. Furthermore, potential interpretation challenges are presented, and a simplified algorithm for the classification of TP53 variants in CLL is provided, representing a consensus based on previously published guidelines. Finally, the reporting requirements are highlighted, including a template for clinical reports of TP53 aberrations. These recommendations are intended to assist diagnosticians in the correct assessment of TP53 mutation status, but also physicians in the appropriate understanding of the lab reports, thus decreasing the risk of misinterpretation and incorrect management of patients in routine practice whilst also leading to improved stratification of patients with CLL in clinical trials.

Unveiling the dynamics and molecular landscape of a rare chronic lymphocytic leukemia subpopulation driving refractoriness: insights from single-cell RNA sequencing.

Early identification of resistant cancer cells is currently a major challenge, as their expansion leads to refractoriness. To capture the dynamics of these cells, we made a comprehensive analysis of disease progression and treatment response in a chronic lymphocytic leukemia (CLL) patient using a combination of single-cell and bulk genomic methods. At diagnosis, the patient presented with unfavorable genetic markers, including notch receptor 1 (NOTCH1) mutation and loss(11q). The initial and subsequent treatment lines did not lead to a durable response and the patient developed refractory disease. Refractory CLL cells featured substantial dysregulation in B-cell phenotypic markers such as human leukocyte antigen (HLA) genes, immunoglobulin (IG) genes, CD19 molecule (CD19), membrane spanning 4-domains A1 (MS4A1; previously known as CD20), CD79a molecule (CD79A) and paired box 5 (PAX5), indicating B-cell de-differentiation and disease transformation. We described the clonal evolution and characterized in detail two cell populations that emerged during the refractory disease phase, differing in the presence of high genomic complexity. In addition, we successfully tracked the cells with high genomic complexity back to the time before treatment, where they formed a rare subpopulation. We have confirmed that single-cell RNA sequencing enables the characterization of refractory cells and the monitoring of their development over time.

ATM mutations uniformly lead to ATM dysfunction in chronic lymphocytic leukemia: application of functional test using doxorubicin.

ATM abnormalities are frequent in chronic lymphocytic leukemia and represent an important prognostic factor. Sole 11q deletion does not result in ATM inactivation by contrast to biallelic defects involving mutations. Therefore, the analysis of ATM mutations and their functional impact is crucial. In this study, we analyzed ATM mutations in predominantly high-risk patients using: i) resequencing microarray and direct sequencing; ii) Western blot for total ATM level; iii) functional test based on p21 gene induction after parallel treatment of leukemic cells with fludarabine and doxorubicin. ATM dysfunction leads to impaired p21 induction after doxorubicin exposure. We detected ATM mutation in 16% (22 of 140) of patients, and all mutated samples manifested demonstrable ATM defect (impaired p21 upregulation after doxorubicin and/or null protein level). Loss of ATM function in mutated samples was also evidenced through defective p53 pathway activation after ionizing radiation exposure. ATM mutation frequency was 34% in patients with 11q deletion, 4% in the TP53-defected group, and 8% in wild-type patients. Our functional test, convenient for routine use, showed high sensitivity (80%) and specificity (97%) for ATM mutations prediction. Only cells with ATM mutation, but not those with sole 11q deletion, were resistant to doxorubicin. As far as fludarabine is concerned, this difference was not observed. Interestingly, patients from both these groups experienced nearly identical time to first treatment. In conclusion, ATM mutations either alone or in combination with 11q deletion uniformly led to demonstrable ATM dysfunction in patients with chronic lymphocytic leukemia and mutation presence can be predicted by the functional test using doxorubicin.

The outcome of chronic lymphocytic leukemia patients who relapsed after fludarabine, cyclophosphamide, and rituximab.

BACKGROUND: There are minimal data about the efficacy of subsequent therapy in patients with relapse after FCR (fludarabine, cyclophosphamide, and rituximab) chemoimmunotherapy. METHODS: We retrospectively analyzed the outcomes of 119 patients who relapsed after standard-dose FCR. The patient cohort consisted of patients who relapsed after FCR administered as first-line therapy (Group 1, n = 63) and patients relapsing after FCR administered in second/subsequent line; (Group 2, n = 56). RESULTS: Basic parameters (age, clinical stage, cytogenetics, molecular genetics) did not differ significantly between these subgroups. Likewise, median progression-free survival (PFS) was not considerably different after FCR (18.6 vs. 14.7 months). Subsequent therapy for relapsed disease included FCR retreatment, R-CHOP, alemtuzumab, or rituximab plus high-dose dexamethasone. Overall response rates for the two groups did not significantly differ (59% vs. 44%). Although PFS after subsequent therapy was relatively short, longer PFS was observed in Group 1 (13.3 vs. 5.9 months; P = 0.01), in patients with response duration ≥ 24 months after previous FCR (13 vs. 6.1 months; P < 0.01), and in patients who achieved complete remission after FCR (10.8 vs. 7.9 months in partial remission; P = 0.01). Newly detected 17p deletions were observed in 5/62 patients, and new p53 mutations in 6/34 FCR-treated patients. CONCLUSION: Our data indicate that the prognosis of patients who relapse after FCR remains poor regardless of the subsequent treatment regimen.