Jeanne-Marie Libouton

Improved detection of chromosomal abnormalities in chronic lymphocytic leukemia by conventional cytogenetics using CpG oligonucleotide and interleukin-2 stimulation: A Belgian multicentric study.

We performed a multicentric study to assess the impact of two different culture procedures on the detection of chromosomal abnormalities in 217 consecutive unselected cases with chronic lymphocytic leukemia (CLL) referred for routine analysis either at the time of diagnosis (n = 172) or during disease evolution (n = 45). Parallel cultures of peripheral blood or bone marrow were set up with the addition of either the conventional B‐cell mitogen 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA) or a combination of CpG oligonucleotide (CpG) and interleukin‐2 (IL‐2). Cytogenetic analyses were performed on both cultures. Clonal abnormalities were identified in 116 cases (53%). In 78 cases (36%), the aberrant clone was detected in both cultures. Among these, the percentages of aberrant metaphases were similar in both conditions in 17 cases, higher in the CpG/IL‐2 culture in 43 cases, and higher in the TPA culture in 18 cases. Clonal aberrations were detected in only one culture, either in CpG/IL‐2 or TPA in 33 (15%) and 5 (2%) cases, respectively. Taken together, abnormal karyotypes were observed in 51% with CpG/IL‐2 and 38% with TPA (P < 0.0001). Application of FISH (n = 201) allowed the detection of abnormalities not visible by conventional cytogenetic analysis in 80 cases: del(13q) (n = 71), del(11q) (n = 5), +12 (n = 2), del(14q) (n = 1), and del(17p) (n = 1). In conclusion, our results confirm that CpG/IL‐2 stimulation increases the detection rate of chromosomal abnormalities in CLL compared with TPA and that further improvement can be obtained by FISH. However, neither conventional cytogenetics nor FISH detected all aberrations, demonstrating the complementary nature of these techniques.

KANK1, a candidate tumor suppressor gene, is fused to PDGFRB in an imatinib-responsive myeloid neoplasm with severe thrombocythemia

KANK1 , a candidate tumor suppressor gene, is fused to PDGFRB in an imatinib-responsive myeloid neoplasm with severe thrombocythemia

The value of interphase fluorescence in situ hybridization for the detection of translocation t(12;21) in childhood acute lymphoblastic leukemia

ETV6/CBFA2 fusion by means of FISH, using two cosmid probes mapped on ETV6 and on CBFA2, respectively. The cut-off value (mean + three standard deviations) for positivity established on control patients was 9.3%. A comparison between FISH and molecular methods [reverse-transcriptase polymerase chain reaction/Southern blot (RT-PCR/SB)] was possible in 52 patients: 34 of 52 (65.4%) showed negative results with both approaches, and 13 of 52 (25%) were positive; 5 of 52 (9.6%) showed discrepancies: four patients who were positive using RT-PCR/SB were negative using FISH. Conversely, one patient negative when using RT-PCR/SB was positive with FISH. Further investigations on this patient, cytogenetically characterized by add(12p), showed an atypical breakpoint on ETV6, located 5′ to the common breakpoint. Compared with RT-PCR and SB, dual-color interphase FISH with the cosmid probe set proved to be highly specific but showed limited sensitivity.

Dicentric (1;15) in myeloid disorders

We report three cases of myeloid disorders with a dic(1;15)(p11;p11), resulting in trisomy of the long arm of chromosome 1. A review of the literature showed six cases, reported as t(1;15). We suggest that these cases have the same anomaly and should be reappraised as dic(1;15).

Refinement of 1p36 alterations not involving PRDM16 in myeloid and lymphoid malignancies

Fluorescence in situ hybridization was performed to characterize 81 cases of myeloid and lymphoid malignancies with cytogenetic 1p36 alterations not affecting the PRDM16 locus. In total, three subgroups were identified: balanced translocations (N = 27) and telomeric rearrangements (N = 15), both mainly observed in myeloid disorders; and unbalanced non-telomeric rearrangements (N = 39), mainly observed in lymphoid proliferations and frequently associated with a highly complex karyotype. The 1p36 rearrangement was isolated in 12 cases, mainly myeloid disorders. The breakpoints on 1p36 were more widely distributed than previously reported, but with identifiable rare breakpoint cluster regions, such as the TP73 locus. We also found novel partner loci on 1p36 for the known multi-partner genes HMGA2 and RUNX1. We precised the common terminal 1p36 deletion, which has been suggested to have an adverse prognosis, in B-cell lymphomas [follicular lymphomas and diffuse large B-cell lymphomas with t(14;18)(q32;q21) as well as follicular lymphomas without t(14;18)]. Intrachromosomal telomeric repetitive sequences were detected in at least half the cases of telomeric rearrangements. It is unclear how the latter rearrangements occurred and whether they represent oncogenic events or result from chromosomal instability during oncogenesis.

Patterns of genomic aberrations suggest that Burkitt lymphomas with complex karyotype are distinct from other aggressive B-cell lymphomas with MYC rearrangement.

We previously showed that complex karyotypes (CK) and chromosome 13q abnormalities have an adverse prognostic impact in childhood Burkitt lymphomas/leukemias (BL) and diffuse large B‐cell lymphomas (DLBCL). The aim of our study was to identify recurrent alterations associated with MYC rearrangements in aggressive B‐cell lymphomas with CK. Multicolor fluorescence in situ hybridization (M‐FISH) was performed in 84 patient samples (59 adults and 25 children), including 37 BL (13 lymphomas and 24 acute leukemias), 12 DLBCL, 28 B‐cell lymphomas with intermediate features (DLBCL/BL), 4 B‐cell precursor acute lymphoblastic leukemias (BCP‐ALL), and 3 unclassifiable B‐cell lymphomas. New (cytogenetically undetected) abnormalities were identified in 80% of patients. We also refined one‐third of the chromosomal aberrations detected by karyotyping. M‐FISH proved to be more useful in identifying chromosomal partners involved in unbalanced translocations and in revealing greater complexity of 13q rearrangements. Most of the newly identified or refined recurrent alterations involved 1q, 13q and 3q (gains/losses), 7q and 18q (gains), or 6q (losses), suggesting that these secondary aberrations may play a role in lymphomagenesis. Several patterns of genomic aberrations were identified: 1q gains in BL, trisomies 7 in DLBCL, and 18q‐translocations in adult non‐BL. BCP‐ALL usually displayed an 18q21 rearrangement. BL karyotypes were less complex and aneuploid than those of other MYC‐rearranged lymphomas. BCP‐ALL and DLBCL/BL were associated with a higher rate of early death than BL and DLBCL. These findings support the categorization of DLBCL/BL as a distinct entity and suggest that BL with CK are indeed different from other aggressive MYC‐rearranged lymphomas, which usually show greater genetic complexity.

Chronic Myeloid Leukemia with a Rare Variant Philadelphia Translocation: t(9;22;21)(q34;q11;q22)

A case of chronic myeloid leukemia displaying an uncommon t(21;22)(q22;q11) is reported. For the first time, this translocation has been characterized by fluorescence in situ hybridization (FISH) and the reverse transcriptase polymerase chain reaction (RT-PCR). FISH, with the use of whole-chromosome painting probes and probes specific for the BCR and ABL genes, showed a three-way variant Philadelphia translocation (9;22;21)(q34;q11;q22) with a BCR/ABL fusion residing on the der(22). In addition, RT-PCR demonstrated a b2a3 BCR/ABL fusion transcript. Underlying mechanisms and prognostic implications are discussed.