Novel complex t(V;9;22) rearrangements in three cases with chronic myeloid leukemia and a rare translocation in a case with classical Philadelphia chromosome.

The fusion gene BCR/ABL arises in connection with a complex translocation event in 2-10% of cases with chronic myeloid leukemia (CML). Due to causative treatment with Imatinib most cases with variant rearrangements show no specific prognostic significance, though the events of therapy resistance remain to be studied. Herein we report on three CML cases with complex chromosomal aberrations not observed before, involving chromosomal regions such as 1p32, 2q11 and 6q12. Additionally we report on one case with the rare translocation t(3;8)(p22;q22) along with the classic Philadelphia (Ph) chromosome. In two cases, two different breakpoints on chromosome 22 were found. Moreover, in one of them two breakpoints on chromosome 9 were observed. The following chromosomal studies, during therapy by Imatinib, have revealed different cytogenetic responses.

Novel cryptic chromosomal rearrangements detected in acute lymphoblastic leukemia detected by application of new multicolor fluorescent in situ hybridization approaches.

Routine cytogenetic analysis provides important information on diagnostic and prognostic relevance for hematological malignancies. However, it is often difficult to obtain good karyotypes, especially of cells from cases with acute lymphoblastic leukemia (ALL) because of poor morphology and spreading. Thus, detailed karyotyping can be hampered and even in case of a 'normal karyotype' according to banding cytogenetics doubts remain if the result is reliable. In order to address this problem a series of 37 ALL cases without any detectable numerical or structural chromosomal defects was selected and studied by two recently developed multicolor fluorescence in situ hybridization (FISH) approaches: 1) multitude multicolor banding (mMCB) is a FISH-banding technique, which allows the analyses of inter- and intra-chromosomal rearrangements of the whole human karyotype in one single experiment; 2) chromosome-specific subcentromere/subtelomere-specific multicolor (subCTM-)FISH applies locus-specific subtelomeric and subcentromic probes and enables the characterization of the subtelomeric and peri-centric regions of the chromosomes, not analyzable by other FISH-approaches. Thus, we detected the following recurrent cryptic chromosomal aberrations: del(12)(pter) [8 cases], del(9)(qter) [3 cases], and del(11)(pter) [2 cases]. Moreover, cryptic changes in additional nine subtelomeric and in two subcentromeric regions were observed one time, each. In summary, mMCB and subCTM were proven to be powerful methods in the screening for new cryptic chromosomal aberrations, which considerably increased the accuracy of cytogenetic diagnosis.

Molecular cytogenetic characterization of the mouse cell line WMP2 by spectral karyotyping and multicolor banding applying murine probes.

The Moloney murine leukemia virus-transformed suspension cell line WMP2 is derived from wild mice (Mus musculus) of the WMP/WMP strain. These mice carry nine pairs of metacentric Robertsonian translocation chromosomes. As the chromosomes of the wild-type mouse are all acrocentric, metaphase spreads of the WMP2 cells seam to be highly suited for physical gene mapping. Here we studied the WMP2 line using spectral karyotyping (SKY) combined with new established mouse specific multicolor banding (mcb) probes for the chromosomes X, 3, 4, 6 and 18. SKY revealed that the WMP2 cell line developed further four derivative chromosomes. After application of mcb five previously unrecognizable intrachromosomal rearrangements with 9 breakpoints were detected for the studied chromosomes.

Microdissection-derived murine mcb probes from somatic cell hybrids.

The multicolor-banding (mcb) technique is a fluorescence in situ hybridization (FISH)-banding approach, which is based on region-specific microdissection libraries producing changing fluorescence intensity ratios along the chromosomes. The latter are used to assign different pseudocolors to specific chromosomal regions. Here we present the first three available mcb-probe sets for the Mus musculus chromosomes 3, 6, and 18. In the present work, the creation of the microdissection libraries was done for the first time on mouse/human somatic cell hybrids. During creation of the mcb-probes, the latter enabled an unambiguous identification of the, otherwise in GTG-banding, hardly distinguishable murine chromosomes.

Detection of cryptic chromosomal aberrations in the in vitro non-proliferating cells of acute myeloid leukemia.

A total of 22 acute myeloid leukemia (AML) cases were analyzed by cell-specific comparative genomic hybridization (micro-CGH). Conventional banding analysis identified a monosomy 7 in six (group I), a trisomy 8 in eight (group II) and a normal karyotype in eight cases (group III). A total of 32 additional chromosomal imbalances was detected and confirmed in two independent micro-CGH experiments. However, only in 9 of the 22 cases (group I: 4 cases; group II: 1 case; group III: 4 cases) the existence of 11 of the 32 (34.5%) detected copy number alterations could be confirmed by other fluorescence in situ hybridization (FISH) approaches. These results lead to two conclusions: i) in the in vitro non-proliferating population of AML tumor cells one can detect cryptic chromosomal aberrations, which might constitute tumor markers of diagnostic and prognostic value; ii) The results of CGH need to be checked by other approaches.