High frequency of dicentric chromosomes detected by multi-centromeric FISH in patients with acute myeloid leukemia and complex karyotype

Dicentric chromosomes (DCs) are considered markers of cancer in various malignancies. However, they can be overlooked when conventional analysis or multicolor fluorescence in situ hybridization (mFISH) is used to detect complex karyotypes. We analyzed the karyotypes of 114 patients with acute myeloid leukemia (AML) and complex karyotypes and verified the presence of monosomies by FISH using multi-centromeric probes. Monosomy was detected in 63% of patients by G-banding/mFISH and confirmed in 55% of patients by centromeric FISH. FISH analysis indicated a high frequency of DCs that were previously considered monosomies. In some cases, it was apparent that the derivative monocentric chromosome was a primary DC. DCs were formed mostly by chromosomes 17 and 20. In conclusion, chromosome loss and unbalanced translocation suggest the presence of a hidden DC or its previous existence. DCs undergo several stabilizing changes and can induce other chromosomal aberrations and/or the formation of new DCs. This can result in the clonal evolution of abnormal cells, which is considered an independent prognostic marker of an unfavorable disease course and short survival.

Role of rituximab in treatment of patients with primary central nervous system lymphoma: a retrospective analysis of the Czech lymphoma study group registry

We have investigated whether the addition of rituximab to methotrexate, procarbazine, vincristine, radiotherapy and cytarabine was associated with improved outcome of primary central nervous system lymphomas (PCNSL). Of 164 patients, 49 received rituximab. Median age was 63 years, median Karnofsky performance score (KPS) was 60 and median follow-up of living patients was 59.5 months. 1- and 2-year PFS were 49.7 and 37.9%, 1- and 2-year OS were 57.0 and 45.3%. Median progression-free survival (PFS), but not overall survival (OS) was significantly better for patients treated with rituximab (22.9 vs. 10.9 months, p = 0.037). In multivariate analysis, age ≤70 years and KPS ≥90 were predictive for PFS and OS, rituximab was an independent prognostic factor for PFS only. In landmark analyses, rituximab was not found beneficial for long-term survivors and no group particularly benefited from rituximab. In conclusion, addition of rituximab was associated with improved PFS, but not OS in this unselected cohort of PCNSL patients.

Molecular cytogenetic analysis of dicentric chromosomes in acute myeloid leukemia

Dicentric chromosomes (DCs) have been described in many hematological diseases, including acute myeloid leukemia (AML). They are markers of cancer and induce chromosomal instability, leading to the formation of other chromosomal aberrations and the clonal evolution of pathological cells. Our knowledge of the roles and behavior of human DCs is often derived from studies of induced DCs and cell lines. It is difficult to identify all the DCs in the karyotypes of patients because of the limitations of metaphase cytogenetic methods. The aim of this study was to revise the karyotypes of 20 AML patients in whom DCs were found with conventional G-banding or multicolor fluorescence in situ hybridization (mFISH) with (multi)centromeric probes and to characterize the DCs at the molecular cytogenetic level. FISH analyses confirmed 23 of the 29 expected DCs in 18 of 20 patients and identified 13 others that had not been detected cytogenetically. Fourteen DCs were altered by other chromosomal changes. In conclusion, karyotypes with DCs are usually very complex, and we have shown that they often contain more than one DC, which can be missed with conventional or mFISH methods. Our study indicates an association between number of DCs in karyotype and very short survival of patients.

Jumping-like translocation-a rare chromosomal rearrangement in a patient with Burkitt lymphoma/leukemia

Chromosomal translocations are acquired genetic rearrangements in human cancers. Jumping translocations are rare nonreciprocal rearrangements involving the same donor chromosome segment translocated to two or more recipient chromosomes. In this report, we describe a patient with Burkitt lymphoma/leukemia (BL) and a complex karyotype including a t(2;8)(p12;q24), copy-neutral loss of heterozygosity at 17p13.1-p13.3 and 19q13.1-q13.2, trisomy 20, and two uncommon chromosomal aberrations. The first uncommon aberration was a complex rearrangement of chromosome 15 (probably the consequence of chromothripsis) masked by an apparently balanced reciprocal translocation, t(11;15)(p11.2;q21). The second one was a special type of unbalanced "vice versa" jumping translocation, which involved the same acceptor chromosome arm (13q) and various donor chromosome segments. It is unclear whether both atypical rearrangements are the consequence of the TP53 alteration or whether assumed chromothripsis influenced the development of the jumping-like translocation. However, the presence of the t(11;15)(p11.2;q21) in all pathological cells suggests that it occurred in the early stage of the disease, whereas the jumping-like translocation, as an additional change, subsequently accelerated the progression of the disease.

Telomere length, molecular cytogenetic findings, and immunophenotypic features in previously untreated patients with B-chronic lymphocytic leukemia

Telomere length was evaluated by terminal repeat fragment method in 66 previously untreated patients with B-chronic lymphocytic leukemia (B-CLL) to ascertain whether telomere shortening was associated with genomic aberrations, immunoglobulin variable heavy chain (IgVH) mutational status, CD38 and ZAP-70 expression, and telomerase activity. Chromosomal aberrations were present in peripheral blood cells of 73% patients (48/66), no difference in telomere length between patients with good and intermediate prognosis according to cytogenetics was found. Association between telomere length and IgVH mutational status, ZAP-70 and CD38 expression was proved as significantly shorter telomeres in patients with unmutated IgVH status (p=0.01) and ZAP-70 positivity (p=0.01) and CD38 positivity (p=0.05) were detected. Telomerase activity was positive in 11 patients out of 21 examined, correlation between telomere length and telomerase activity was found (p=0.05). Telomere length and telomerase activity in combination with other prognostic parameters complete the risk profile of B-CLL patients and might serve for an easy decision on optimal treatment strategy.

KEYWORDS

B-chronic lymphocytic leukemia, telomere length, telomerase activity, chromosomal aberrations, prognosis.

Combined molecular biological and molecular cytogenetic analysis of genomic changes in 146 patients with B-cell chronic lymphocytic leukemia

Interphase fluorescence in situ hybridization was used to detect common deletions in B-CLL patients as well as trisomy 12 and aberrations of IgH gene complex at 14q32.33 where we evaluated not only translocation-like signal pattern but also deletions. 120 (82%) patients showed genetic changes - del(13)(q14) 95 (62%), deletion of ATM gene 22 (15%), deletion of p53 gene 25 (17%) and trisomy 12 was proved in 18 (12%) cases. IgH rearrangements were detected in 45 (31%), split of the signals in 11 (8%), deletion of 3' segment flanking IgH gene in 5 (3%) and deletions of variable segment in 29 (20%) patients. Although deletions of 3' segment flanking IgH gene complex are supposed to have an adverse prognostic impact and the genetic background of variable segment deletions is believed to be most probably physiological, we assumed a detailed mapping of the 14q32.33 region will be needed to unravel these mysteries.