Balanced and unbalanced translocations in a multicentric series of 2843 patients with chronic lymphocytic leukemia

Chromosomal translocations in chronic lymphocytic leukemia (CLL) are very rare, and therefore systematic analysis of large series of cases is needed to allow the identification of recurrent rearrangements, breakpoints involved, and target genes. The aims of the present study were to identify new translocations and their clinical impact and to establish their frequency in a large cohort of 2843 CLL patients. By conventional cytogenetics 250 translocations were identified in 215 (7.5%) patients, 186 (74%) were apparently balanced and 64 (26%) were unbalanced. All chromosomes were involved in translocations, except Y chromosome. The chromosomes more frequently translocated were in decreasing frequency chromosomes 14, 18, 13, 17, 1, 6, 2, 3, 8, and 11. Translocations were found in the karyotypes either as the unique chromosomal abnormality (27%), associated with another alteration (24%), or as a part of a complex karyotype (CK, 48%). A large proportion of rearranged breakpoints involved genes related to CLL such as IGH (14q32), RB1, MIR15A, MIR16-1 (13q14), BCL2 (18q21), IGL (22q11.2), TP53 (17p13), IRF4 (6p25-p23), ATM (11q22), and CDK6 (7q21). Overall, 76 novel CLL translocations were identified, including a recurrent t(8;11)(p21;q21-23). Whole-genome sequencing and/or copy-number microarray data of 24 cases with translocations confirmed all rearrangements, enabled refinement of 3 karyotypes and all breakpoints at gene level. The projected survival and time to first treatment significantly decreased linearly with the number of translocations. In summary, this study allowed to establish the frequency of translocations (7.5%) and to identify new translocations in a cohort of 2843 CLL patients.

Extramedullary multiple myeloma patient-derived orthotopic xenograft with a highly altered genome: combined molecular and therapeutic studies

Extramedullary multiple myeloma (EMM) has an overall survival of 6 months and occurs in 20% of multiple myeloma (MM) patients. Genetic and epigenetic mechanisms involved in EMM and the therapeutic role of new agents for MM are not well established. Besides, well-characterized preclinical models for EMM are not available. Herein, a patient-derived orthotopic xenograft (PDOX) was generated from a patient with an aggressive EMM to study in-depth genetic and epigenetic events, and drug responses related to extramedullary disease. A fresh punch of an extramedullary cutaneous lesion was orthotopically implanted in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ(NSG) mouse. The PDOX mimicked histologic and phenotypic features of the tumor of the patient. Cytogenetic studies revealed a hyperploid genome with multiple genetic poor-prognosis alterations. Copy number alterations (CNAs) were detected in all chromosomes. The IGH translocation t(14;16)(q32;q23)IGH/MAF was already observed at the medullary stage and a new one, t(10;14)(p?11-12;q32), was observed only with extramedullary disease and could be eventually related to EMM progression in this case. Exome sequencing showed 24 high impact single nucleotide variants and 180 indels. From the genes involved, only TP53 was previously described as a driver in MM. A rather balanced proportion of hyper/hypomethylated sites different to previously reported widespread hypomethylation in MM was also observed. Treatment with lenalidomide, dexamethasone and carfilzomib showed a tumor weight reduction of 90% versus non-treated tumors, whereas treatment with the anti-CD38 antibody daratumumab showed a reduction of 46%. The generation of PDOX from a small EMM biopsy allowed us to investigate in depth the molecular events associated with extramedullary disease in combination with drug testing.

FMOD expression in whole blood aids in distinguishing between chronic lymphocytic leukemia and other leukemic lymphoproliferative disorders. A pilot study

BACKGROUND

Within the hematopoietic compartment, fibromodulin (FMOD) is almost exclusively expressed in chronic lymphocytic leukemia (CLL) lymphocytes. We set out to determine whether FMOD could be of help in diagnosing borderline lymphoproliferative disorders (LPD).

METHODS

We established 3 flow cytometry-defined groups (CLL [n = 65], borderline LPD [n = 28], broadly defined as those with CLLflow score between 35 and -20 or discordant CD43 and CLLflow, and non-CLL LPD [n = 40]). FMOD expression levels were determined by standard RT-PCR in whole-blood samples. Patients were included regardless of lymphocyte count but with tumor burden ≥40%.

RESULTS

FMOD expression levels distinguished between CLL (median 98.5, interquartile range [IQR] 37.8-195.1) and non-CLL LPD (median 0.012, IQR 0.003-0.033) with a sensitivity and specificity of 1. Most borderline LPDs were CD5/CD23/CD200-positive with no loss of B-cell antigens and negative or partial expression of CD43. 16/22 patients with available cytogenetic analysis showed trisomy 12. In 25/28 (89%) of these patients, FMOD expression levels fell between CLL and non-CLL (median 3.58, IQR 1.06-6.21).

DISCUSSION

This study could suggest that borderline LPDs may constitute a distinct group laying in the biological spectrum of chronic leukemic LPDs. Future studies will have to confirm these results with other biological data. Quantification of FMOD can potentially be of help in the diagnosis of phenotypically complex LPDs.

Characterizing patients with multiple chromosomal aberrations detected by FISH in chronic lymphocytic leukemia

We analyzed the features of chronic lymphocytic leukemia (CLL) with multiple abnormalities (MA) detected by FISH. A local database including 2095 CLL cases was used and 323 with MA (15.4%) were selected. MA was defined by the presence of two or more alterations (deletions of 13q14 (13q-), 11q22 (11q-), 17p13 (17p-) or trisomy 12 (+12)). The combination of 13q- with 11q- and 13q- with 17p-, accounted for 58.2% of the series, in contrast to 11q- with 17p- (3.7%). Patients carrying MA since diagnosis presented a short time to first therapy(TTFT) (27 months) and overall survival (OS) (76 months). The combinations including 17p- had a shorter OS (58 months) than the ones without 17p- (not reached, p = .002). Patients with a complex-FISH were the ones with worse OS (34 months). MA imply poor prognosis when they emerge at diagnosis, probably due to the high incidence of bad prognosis markers, which may be a reflection of a more complex karyotype.

Patients with chronic lymphocytic leukemia and complex karyotype show an adverse outcome even in absence of TP53/ATM FISH deletions

Genomic complexity identified by chromosome banding analysis (CBA) predicts a worse clinical outcome in CLL patients treated either with standard or new treatments. Herein, we analyzed the clinical impact of complex karyotypes (CK) with or without high-risk FISH deletions (ATM and/or TP53, HR-FISH) in a cohort of 1045 untreated MBL/CLL patients. In all, 99/1045 (9.5%) patients displayed a CK. Despite ATM and TP53 deletions were more common in CK (25% vs 7%; P < 0.001; 40% vs 5%; P < 0.001, respectively), only 44% (40/90) patients with TP53 deletions showed a CK. CK group showed a significant higher two-year cumulative incidence of treatment (48% vs 20%; P < 0.001), as well as a shorter overall survival (OS) (79 mo vs not reached; P < 0.001). When patients were categorized regarding CK and HR-FISH, those with both characteristics showed the worst median OS (52 mo) being clearly distinct from those non-CK and non-HR-FISH (median not reached), but no significant differences were detected between cases with only CK or HR-FISH. Both CK and TP53 deletion remained statistically significant in the multivariate analysis for OS. In conclusion, CK group is globally associated with advanced disease and poor prognostic markers. Further investigation in larger cohorts with CK lacking HR-FISH is needed to elucidate which mechanisms underlie the poor outcome of this subgroup.

Development Refractoriness of MLL-Rearranged Human B Cell Acute Leukemias to Reprogramming into Pluripotency

Induced pluripotent stem cells (iPSCs) are a powerful tool for disease modeling. They are routinely generated from healthy donors and patients from multiple cell types at different developmental stages. However, reprogramming leukemias is an extremely inefficient process. Few studies generated iPSCs from primary chronic myeloid leukemias, but iPSC generation from acute myeloid or lymphoid leukemias (ALL) has not been achieved. We attempted to generate iPSCs from different subtypes of B-ALL to address the developmental impact of leukemic fusion genes. OKSM(L)-expressing mono/polycistronic-, retroviral/lentiviral/episomal-, and Sendai virus vector-based reprogramming strategies failed to render iPSCs in vitro and in vivo. Addition of transcriptomic-epigenetic reprogramming “boosters” also failed to generate iPSCs from B cell blasts and B-ALL lines, and when iPSCs emerged they lacked leukemic fusion genes, demonstrating non-leukemic myeloid origin. Conversely, MLL-AF4-overexpressing hematopoietic stem cells/B progenitors were successfully reprogrammed, indicating that B cell origin and leukemic fusion gene were not reprogramming barriers. Global transcriptome/DNA methylome profiling suggested a developmental/differentiation refractoriness of MLL-rearranged B-ALL to reprogramming into pluripotency.

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Neither primary B-ALL blasts nor leukemic B cell lines can be reprogrammed to iPSCs

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Global transcriptome and DNA methylome suggest a developmental refractoriness

Interstitial 13q14 deletions detected in the karyotype and translocations with concomitant deletion at 13q14 in chronic lymphocytic leukemia: different genetic mechanisms but equivalent poorer clinical outcome

Deletion of 13q14 as the sole abnormality is a good prognostic marker in chronic lymphocytic leukemia (CLL). Nonetheless, the prognostic value of reciprocal 13q14 translocations [t(13q)] with related 13q losses has not been fully elucidated. We described clinical and biological characteristics of 25 CLL patients with t(13q), and compared with 62 patients carrying interstitial del(13q) by conventional G-banding cytogenetics (CGC) [i-del(13q)] and 295 patients with del(13q) only detected by fluorescence in situ hybridization (FISH) [F-del(13q)]. Besides from the CLL FISH panel (D13S319, CEP12, ATM, TP53), we studied RB1 deletions in all t(13q) cases and a representative group of i-del(13q) and F-del(13q). We analyzed NOTCH1, SF3B1, and MYD88 mutations in t(13q) cases by Sanger sequencing. In all, 25 distinct t(13q) were described. All these cases showed D13S319 deletion while 32% also lost RB1. The median percentage of 13q-deleted nuclei did not differ from i-del(13q) patients (73% vs. 64%), but both were significantly higher than F-del(13q) (52%, P < 0.001). Moreover, t(13q) patients showed an increased incidence of biallelic del(13q) (52% vs. 11.3% and 14.9%, P < 0.001) and higher rates of concomitant 17p deletion (37.5% vs. 8.6% and 7.2%, P < 0.001). RB1 involvement was significantly higher in the i-del(13q) group (79%, P < 0.001). Two t(13q) patients (11.8%) carried NOTCH1 mutations. Time to first treatment in t(13q) and i-del(13q) was shorter than F-del(13q) (67, 44, and 137 months, P = 0.029), and preserved significance in the multivariate analysis. In conclusion, t(13q) and del(13q) patients detected by CGC constitute a subgroup within the 13q-deleted CLL patients associated with a worse clinical outcome.

Scoring systems in mantle cell lymphoma: a critical point of view

A proposal for a scoring system in the diagnosis of chronic lymphoproliferative diseases other than CLL has been recently published in Cytometry Part B. The authors apply this score for deciding whether or not FISH evaluation for the detection of IGH/CCND1 rearrangements must be performed to exclude Mantle Cell Lymphoma (MCL). In their validation series, no MCL scored <3. We have applied their system to our cases of MCL and also to a small series of Marginal Zone lymphomas. In our hands, the scoring system as has been published does not discriminate adequately between both entities. We propose using the negativity of a marker, CD11c, instead of the platelet count to improve the results. However, we believe that given the clinical and prognostic implications of the diagnosis of MCL, scoring systems should be greatly ameliorated prior to their generalized use.

Incidence and prognostic impact of secondary cytogenetic aberrations in a series of 145 patients with mantle cell lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm with an aggressive behavior, characterized by the t(11;14)(q13;q32). Several secondary genetic abnormalities with a potential role in the oncogenic process have been described. Studies of large MCL series using conventional cytogenetics, and correlating with proliferation and survival, are scarce. We selected 145 MCL cases at diagnosis, displaying an aberrant karyotype, from centers belonging to the Spanish Cooperative Group for Hematological Cytogenetics. Histological subtype, proliferative index and survival data were ascertained. Combined cytogenetic and molecular analyses detected CCND1 translocations in all cases, mostly t(11;14)(q13;q32). Secondary aberrations were present in 58% of patients, the most frequent being deletions of 1p, 13q and 17p, 10p alterations and 3q gains. The most recurrent breakpoints were identified at 1p31-32, 1p21-22, 17p13, and 1p36. Aggressive blastoid/pleomorphic variants displayed a higher karyotypic complexity, a higher frequency of 1p and 17p deletions and 10p alterations, a higher proliferation index and poor survival. Gains of 3q and 13q and 17p13 losses were associated with reduced survival times. Interestingly, gains of 3q and 17p losses added prognostic significance to the morphology in a multivariate analysis. Our findings confirm previous observations indicating that proliferation index, morphology and several secondary genetic alterations (3q gains and 13q and 17p losses) have prognostic value in patients with MCL. Additionally, we observed that 3q gains and 17p losses detected by conventional cytogenetics are proliferation-independent prognostic markers indicating poor outcome.