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  • 1
    In: Blood, American Society of Hematology, Vol. 117, No. 24 ( 2011-06-16), p. 6650-6659
    Abstract: Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed a thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples. We find that MYC expression is highly variable, and that high MYC expression levels can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. Furthermore, we show that posttranscriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1m might play a dual transcriptional and posttranscriptional role in this process. Altogether, our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in GSI-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2011
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  • 2
  • 3
    In: DNA Repair, Elsevier BV, Vol. 5, No. 9-10 ( 2006-9), p. 1246-1258
    Type of Medium: Online Resource
    ISSN: 1568-7864
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2006
    detail.hit.zdb_id: 2082770-2
    SSG: 12
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  • 4
    In: Blood, American Society of Hematology, Vol. 116, No. 21 ( 2010-11-19), p. 4188-4188
    Abstract: Abstract 4188 Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed the first thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples (n=163). RQ-PCR analysis first revealed that levels of MYC transcript are highly variable, and that high MYC expression can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. MYC protein levels were next assessed by western blot in a subpanel of 29 primary T-ALL samples. Although a large spectrum of protein expression was also observed, no direct correlation was apparent between transcript level and protein abundance. This discrepancy is in line with the frequent deregulation of factors controlling MYC protein turn-over in cancer cells. In Burkitt Lymphoma (BL) for example, mutations in the MYC-box (in and around the critical T58 phosphorylation site) impede efficient addressing to the proteasome, and results in oncogenic MYC protein stabilization. We sequenced the MYC-box region of 116 T-ALL samples and found no such mutations, suggesting that BL and T-ALL use different routes to achieve oncogenic MYC levels. An alternative candidate is the E3 ubiquitin ligase FBXW7 which has been shown to target both NOTCH1 and MYC for proteosomal degradation, and the loss-of-function mutations of which were previously shown to impair MYC protein stability. Although T-ALL harboring inactivating FBXW7 mutations were associated with high MYC protein level as expected, such mutants represented only 10% of the cases, and could thus not account for the numerous cases showing MYC protein accumulation in our series. This implied the frequent occurrence of other, alternative mechanisms of MYC stabilization in T-ALL. To identify these processes, we performed a detailed pan-genomic analysis of a T-ALL case showing high MYC protein levels at relapse but low MYC at diagnosis, despite identical transcript levels. Among a total of ten genomic aberrations found in this patient, only one difference was found between diagnosis and relapse, namely the progression of mono-allelic to bi-allelic deletion of a 10q23 region including the PTEN tumor suppressor gene. PTEN is considered the main negative regulator of the PI3K-AKT signaling. As AKT inactivates GSK3β, the serine-threonine kinase involved in MYC phosphorylation at T58, PTEN inactivation constitutes a likely candidate of MYC protein accumulation. To further test this hypothesis, we probed by western blot PTEN and MYC proteins in the previous subpanel of 29 T-ALL, and observed an inverse inter-relationship between PTEN and MYC protein levels. This anti-correlation was particularly clear in cases with abundant PTEN protein levels, where only faint MYC could be found despite relatively high transcription levels. Conversely, high MYC protein levels were in most cases associated with rather low PTEN protein levels. Finally, we functionally demonstrate that in T-ALL cell lines, the PI3K chemical inhibitor LY294002 which antagonizes AKT signaling and mimics PTEN function, is able to downmodulate MYC levels and activity. Altogether, our data reveals that post-transcriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1 mutations might play a dual transcriptional and post-transcriptional role in this process. Our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in γ-secretase inhibitor-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2010
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  • 5
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    Rockefeller University Press ; 2006
    In:  The Journal of Experimental Medicine Vol. 203, No. 11 ( 2006-10-30), p. 2563-2563
    In: The Journal of Experimental Medicine, Rockefeller University Press, Vol. 203, No. 11 ( 2006-10-30), p. 2563-2563
    Type of Medium: Online Resource
    ISSN: 1540-9538 , 0022-1007
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    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 2006
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  • 6
    In: The Journal of Experimental Medicine, Rockefeller University Press, Vol. 203, No. 11 ( 2006-10-30), p. 2425-2431
    Abstract: Follicular lymphoma is one of the most common adult lymphoma, and remains virtually incurable despite its relatively indolent nature. t(14;18)(q32;q21) translocation, the genetic hallmark and early initiating event of follicular lymphoma (FL) pathogenesis, is also present at low frequency in the peripheral blood of healthy individuals. It has long been assumed that in healthy individuals t(14;18) is carried by circulating quiescent naive B cells, where its oncogenic potential would be restrained. Here, we question this current view and demonstrate that in healthy individuals, t(14;18) is actually carried by an expanding population of atypical B cells issued from germinal centers, displaying genotypic and phenotypic features of FL, and prone to constitute potent premalignant FL niches. These findings strongly impact both on the current understanding of disease progression and on the proper handling of t(14;18) frequency in blood as a potential early biomarker for lymphoma.
    Type of Medium: Online Resource
    ISSN: 1540-9538 , 0022-1007
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    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 2006
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  • 7
    In: Blood, American Society of Hematology, Vol. 108, No. 11 ( 2006-11-16), p. 821-821
    Abstract: Follicular lymphoma (FL) is one of the most common B-cell lymphoma, and remains virtually incurable despite its relatively indolent nature. T(14;18)(q32;q21), the genetic hallmark and early initiating event of FL pathogenesis, is also present at low frequency (10−5–10−7) in blood from healthy individuals (HI), indicating that t(14;18) and the ensuing BCL2 overexpression is necessary but not sufficient for malignant transformation. It has long been assumed that in HI, t(14;18) is carried by circulating quiescent naïve B-cells, where its oncogenic potential would be restrained. Yet, several reports, including long-term persistence and immunomodulation of t(14;18)+ cells in lymphoma-free individuals, led us to question this model and investigate the status of circulating t(14;18)+ cells in HI. We first determined if t(14;18)+ cells are naïve B-cells by assessing class-switch recombination (CSR) on the translocated allele. Using 2 long-range PCR assays designed to amplify unswitched BCL2/Sμ and switched BCL2/Sg regions, DNA samples from 6 HI with t(14;18) were tested. Contrary to previous assumptions, our data clearly show that most peripheral t(14;18)+ cells already underwent CSR (n=5/6) and therefore that most t(14;18)+ cells are not naïve B-cells. Are they then memory B cells? Naïve and memory B cell subsets from 9 HI were isolated by cell sorting according to IgD and CD27 markers, and the rate of t(14;18) analyzed in each subset relatively to that of the total B cells. Strikingly, while the level of naïve t(14;18)+ cells remained at baseline for all individuals, memory B-cells tightly accounted for the wide modulation of t(14;18) frequencies observed between individuals. In addition, sequence analysis of t(14;18) clones revealed that this wide modulation was not due to the accumulation of clonally unrelated t(14;18) naïve B-cells, but rather to the clonal expansion of t(14;18)-bearing memory B-cells. To further define the t(14;18)+ cells, we next examined the repartition of the translocation in the IgD−/CD27+ and IgD+/CD27+ memory B-cell subsets. Unexpectedly, we found that the IgD+/CD27+ subset contained significantly higher rates of translocation than the IgD−/CD27+, both in terms of prevalence and frequency. Thus, while CSR is found in the majority of translocated alleles (~75%), most t(14;18)+ memory B cells have not switched their productive allele (~70%) and express an IgM/D. Most importantly, although atypical among physiological peripheral B-cells, this “allelic paradox” is a specific hallmark of FL, and suggests the presence of the same selective pressure in favor of sIgM expression on a B-cell population that is at the same time permanently driven to switch. In line with B-cell hyperplasia in BCL2 transgenic mice slowly progressing to low grade lymphoma, it is likely that “FL-like” cells in HI are rescued by BCL2 from apoptosis, and “frozen” at a differentiation stage in which constitutive AID expression drives continuous somatic hypermutation and CSR activity, two mechanisms conferring a high propensity for genomic instability. Altogether, our findings identify a novel intermediate step in early lymphomagenesis, and strongly impact both on the current understanding of disease progression from potent pre-malignant niches, and on the proper handling of t(14;18) frequency in blood as a potential early biomarker for lymphoma.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2006
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  • 8
    In: Blood, American Society of Hematology, Vol. 134, No. Supplement_1 ( 2019-11-13), p. 2775-2775
    Abstract: Introduction: The risk of developing a follicular lymphoma (FL) begins to be better understood with the identification in large epidemiological studies of familial predisposition, some occupational exposures and genetic factors. Genome wide-association studies (GWAS) identified constitutional single nucleotide polymorphisms (SNPs) at risk of FL in HLA region (rs12195582), in 11q23.3 (near CXCR5), in 11q24.3 (near ETS1), in 3q28 (near LPP), in 18q21.33 (near BCL2), and 8q24 (near PVT1); three suggestive loci are localized at 17q25.3 (near CYBC1), 3q13.33 (CD86), 18q12.3 (SLC14A2) (Skibola, Am J Hum Genet. 2014). High t(14;18) frequency in blood years before diagnosis from healthy individuals was also defined as a predictive biomarker for FL (Roulland, J Clin Oncol 2014). It is currently unknown whether any relationship exists between inherited genetic variants associated with FL susceptibility and t(14;18) frequency and if the combination of the two biomarkers could be useful for a better stratification of risk of FL development in healthy individuals. Methods: We used quantitative PCR assays to estimate t(14;18) frequency in prediagnostic blood samples from 105 individuals that were obtained on average 6.4 years before FL diagnosis (pre-FL group) together with 236 age and gender-matched individuals (control group) that were issued from the participants in the EPIC cohort ( European Prospective Investigation Into Cancer and Nutrition). Constitutional DNA was analyzed for the genotyping of the nine SNPs associated with FL risk (HLA, rs12195582; CXCR5, rs4938573; ETS1, rs4937362; LPP, rs6444305; BCL2, rs17749561; PVT1, rs13254990; CYBC1, rs3751913; CD86, rs2681416; SLC14A2, rs11082438). Genotyping were performed in duplicate using TaqMan® assays on Fluidigm platform. The nine SNPs were analyzed individually and combined in a polygenic risk score (PRS). PRS is a weighted average of the number of risk alleles with the weights being the log of the odds-ratio (OR) reported in the FL GWAS (Skibola, Am J Hum Genet. 2014). A model for FL risk was developed using multivariable logistic regression. Predictive ability was assessed by area under Receiver Operating Characteristic (ROC) curve, with 10-fold cross-validation. This work is supported by the French NCI (INCA, PRT-K16-167). Results: t(14;18) frequency as a log-transformed continuous variable is predictive of FL risk (OR: 1.50; 95%CI: 1.29-1.78, P 〈 0.001); PRS is also strongly associated with FL risk (OR: 3.31; 95%CI: 2.01-5.62, P 〈 0.001). Age at screening (OR: 0.98; 95%CI: 0.95-1.01, P=0.24) did not influence FL risk. A weak but statistically significant correlation between t(14; 18) frequency and PRS was observed (Pearson correlation=0.18, P=0.002). In multivariable analysis, both PRS (OR: 2.84, 95%CI: 1.66-4.99, P 〈 0.001) and t(14;18) frequency (OR: 1.45, 95%CI: 1.18-1.84, P 〈 0.001) remained statistically significant. No departure from log-linear effect was observed in the modeling nor statistical interaction between PRS and log-transformed t(14;18), confirming that t(14; 18) frequency and genetic markers (PRS) were two independent factors of FL risk. Sensitivity analyses showed that these results were not influenced by the delay between the date of the screening and the FL diagnosis. Combining t(14;18) frequency and the PRS in a prediction model allowed the identification of some individuals at very high risk of developing FL and a shiny web application was developed to provide an easy-to-use tool to obtain individualized risk predictions for new patients (Figure). Area under ROC curve (AUC) showed that the model that integrated t(14;18) frequency and PRS (AUC: 0.69, 95%CI: 0.62-0.76) had a better prediction of FL risk than t(14;18) frequency (AUC: 0.62, 95%CI: 0.55-0.70) and PRS alone (AUC: 0.68, 95%CI: 0.61-0.75). Conclusions: Genetic variants combined in PRS and t(14;18) frequency allowed the identification of individuals at high-risk of FL development and provided a better way, when these two biomarkers were combined, to discriminate healthy individuals from pre-FL cases many years before malignant transformation. These findings could be used for screening test of populations with some environmental exposures positively associated with FL development in epidemiological studies and may contribute in the future to monitoring or early intervention. Figure Disclosures Salles: Roche, Janssen, Gilead, Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Amgen: Honoraria, Other: Educational events; Novartis, Servier, AbbVie, Karyopharm, Kite, MorphoSys: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Epizyme: Consultancy, Honoraria.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    RVK:
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2019
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  • 9
    In: Blood, American Society of Hematology, Vol. 120, No. 21 ( 2012-11-16), p. 150-150
    Abstract: Abstract 150 The recent demonstration that memory B-cells can re-enter germinal centers (GCs) and participate to new rounds of GC reactions has opened the possibility that multi-hit B-cell lymphomagenesis could be a much more dynamic process than initially anticipated, gradually progressing throughout the successive passages of memory B-cells in GCs during a lifetime of successive immunological challenges. Here, we provide evidence for this scenario in follicular lymphoma (FL), a GC derived B-cell malignancy initiated in the bone marrow by the hallmark t(14;18) BCL2/IGH translocation. To address this issue, we engineered an original sporadic BCL2tracer mouse model mimicking the rare occurrence of t(14;18) translocation in humans through V(D)J recombination errors (1 in a million B-cells) allowing to track the resultant BCL2-expressing clones; and underwent a molecular/immunofluorescent tracking of t(14;18)+ clones vs. normal memory B-cells in paired lymphoid tissue samples (spleen, lymph nodes, bone marrow) from healthy individuals. We first show that contrary to the current dogma, ectopic BCL2 expression is not sufficient to provoke the FL's characteristic differentiation arrest of activated B-cells as GC B-cells, thereby suggesting that differentiated BCL2+ memory B-cells must return to the GC to acquire additional oncogenic hits and “fix” in situ growth. Strikingly, we further find that in a small fraction of “healthy” humans, such differentiation arrest already operated, and that a clonally expanded population of t(14;18)+ cells with FL-like features have widely disseminated in blood and in multiple lymphoid organs (spleen, lymph nodes, bone marrow), with unprecedentedly reported frequencies (from 1/million to 1/500 cells in some individuals), shaping the systemic disease presentation observed in FL patients. Using molecular/immunofluorescent backtracking of such clones in various paired and remote lymphoid organs, we further demonstrate that t(14;18)+ clones systematically display an extensive history of AID (activation-induced cytidine deaminase)-mediated events compatible with iterative rounds of GC co-opting, in sharp contrast to single memory B-cell clones from the same individuals. We thus show that BCL2-expressing memory B-cells require multiple GC transits to acquire the distinctive FL-like maturation arrest as centrocyte/centroblasts and to progress to advanced FL precursor stages. Altogether, our data argue for a model of lymphomagenesis, in which progression from precursor stages to FL occurs asymptomatically over an extended period of time by subverting the dynamic and plastic attributes of memory B-cells. This understanding of the pre-clinical phases driving FL development in asymptomatic patients should help rationalize prospective approaches designed to identify biomarkers of risk, and innovative therapeutic targets present in early, potentially more curable phases of the disease. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
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  • 10
    In: Journal of Clinical Oncology, American Society of Clinical Oncology (ASCO), Vol. 32, No. 13 ( 2014-05-01), p. 1347-1355
    Abstract: The (14;18) translocation constitutes both a genetic hallmark and critical early event in the natural history of follicular lymphoma (FL). However, t(14;18) is also detectable in the blood of otherwise healthy persons, and its relationship with progression to disease remains unclear. Here we sought to determine whether t(14;18)-positive cells in healthy individuals represent tumor precursors and whether their detection could be used as an early predictor for FL. Participants and Methods Among 520,000 healthy participants enrolled onto the EPIC (European Prospective Investigation Into Cancer and Nutrition) cohort, we identified 100 who developed FL 2 to 161 months after enrollment. Prediagnostic blood from these and 218 controls were screened for t(14;18) using sensitive polymerase chain reaction–based assays. Results were subsequently validated in an independent cohort (65 case participants; 128 controls). Clonal relationships between t(14;18) cells and FL were also assessed by molecular backtracking of paired prediagnostic blood and tumor samples. Results Clonal analysis of t(14;18) junctions in paired prediagnostic blood versus tumor samples demonstrated that progression to FL occurred from t(14;18)-positive committed precursors. Furthermore, healthy participants at enrollment who developed FL up to 15 years later showed a markedly higher t(14;18) prevalence and frequency than controls (P 〈 .001). Altogether, we estimated a 23-fold higher risk of subsequent FL in blood samples associated with a frequency 〉 10 −4 (odds ratio, 23.17; 95% CI, 9.98 to 67.31; P 〈 .001). Remarkably, risk estimates remained high and significant up to 15 years before diagnosis. Conclusion High t(14;18) frequency in blood from healthy individuals defines the first predictive biomarker for FL, effective years before diagnosis.
    Type of Medium: Online Resource
    ISSN: 0732-183X , 1527-7755
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    Language: English
    Publisher: American Society of Clinical Oncology (ASCO)
    Publication Date: 2014
    detail.hit.zdb_id: 2005181-5
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