FISH analysis of translocations involving the short arm of chromosome 9 in lymphoid malignancies

Deletion of the short arm of chromosome 9 (9p), resulting in the loss of the p16^INK4a/MTS1 gene, now called CDKN2, has been found to occur frequently in acute lymphoblastic leukemia, even in the absence of a microscopically visible deletion. In this study, we have used YAC probes encompassing the CDKN2 locus to analyze by fluorescence in situ hybridization patients with leukemia and lymphoma and translocations involving 9p in order to establish the CDKN2 status in relation to the karyotype. We found that, in leukemic cells exhibiting loss of heterozygosity at the CDKN2 locus, the deleted allele was from the cytogenetically normal chromosome 9, whereas the other allele was located on a rearranged chromosome. This finding suggests that CDKN2 gene loss is nonrandomly associated with 9p translocation in lymphoid proliferations. Genes Chromosom. Cancer 19:273–277, 1997. © 1997 Wiley-Liss, Inc.     

dic(4; 17)(p11;p11): A new recurrent chromosomal abnormality in chronic b-lymphoid disorders

We describe a new nonrandom rearrangement, dic(4;17)(p11;p11), which identified in three patients with small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). All three cases had in common atypical morphological features with a significant component of prolymphocytes, an unusual clinical outcome, and were refractory to chemotherapy. To further define the cytogenetic breakpoints, we investigated the cases by whole chromosome painting and fluorescence in situ hybridization (FISH) with centromeric probes. FISH analysis detected the same cytogenetic rearrangement in all patients, suggesting that the dic(4;17)(p11;pll) is a recurrent translocation in SLL/CLL. Moreover, FISH analysis showed a monoallelic deletion of the TP53 gene in all cases, suggesting a correlation with the aggressive course of the disease and the clinical outcome observed in these patients. Genes Chromosom Cancer 17:185–190 (1996). © 1996 Wiley-Liss, Inc.     

A translocation involving a specific breakpoint (q35) on chromosome 5 is characteristic of anaplastic large cell lymphoma (''Ki-1 lymphoma'')

Two cases of non-Hodgkin's lymphoma are reported in which a chromosomal translocation was observed involving the same site (q35) on the long arm of chromosome 5. The other breakpoint involved in the translocation was chromosome 2 (p23) in one case and chromosome 3 (q12) in the other. Both cases were large cell lymphomas expressing CD30 antigen ('Ki-1 lymphoma'). One was clearly of T lymphoid origin, the other probably B cell derived. One other case of a Ki-1 lymphoma with 2;5 translocation (involving the same breakpoint on chromosome 5) has been reported previously, and it is suggested that this cytogenetic abnormality may be specifically associated with Ki-1 lymphoma. The literature contains a further eight cases of lymphoid neoplasms with a translocation involving a breakpoint at q35 on chromosome 5. They have all been described as cases of 'malignant histiocytosis', but the present findings make it likely that these cases were in reality also examples of Ki-1 lymphoma. The breakpoint at the q35 region on chromosome 5 is close to the position of the fms proto-oncogene, suggesting that an abnormality affecting this gene might possibly play a causal role in 'Ki-1 lymphoma'. However, DNA restriction fragment analysis of the present cases showed no evidence that the breakpoint on chromosome 5 involves the fms gene or its immediate vicinity.     

t(2; 18) and t(18;22) Variant Chromosomal Translocations in B Cell Malignancies

Variant translocations (2;18 and 18;22) are described in this review. The chromosomal and molecular findings of these translocations of BCL2 and their effect on possible BCL2 gene activation is discussed. Unanswered questions still remain and these include why this is so rare compared to the 25% incidence recorded for translocations in Burkitt's lymphoma. Further studies are obviously still needed in order to determine the true frequency of these findings and their distribution in the various B-cell disorders.     

CDK1 is a marker of proliferation in human lymphoid cells

To better understand the relationship between the proliferation of human lymphoid cells and the expression of cdk1, a catalytic subunit of the histone HI kinase (HIK), we examined its mRNA and protein content in 3 B-cell lines: Ramos, Reh-6 and IARC 963. Cells were elutriated according to their position in the cell cycle. Cell fractions were analyzed for cdk1 mRNA and protein cellular content by Northern blot and immunoblot, respectively, as well as for H1K activity. Both mRNA and protein amounts and H1K activity varied according to cell cycle phase, the lowest values being observed in G₁-enriched fractions. For comparison, elutriated fractions were also tested for the expression of cdk2 and cdk4 proteins. Both showed some variations among fractions, but they were less clear than those of cdk1. We also tested 29 samples of lymphoid neoplastic and non-neoplastic tissues for proliferative activity (percentage of S and G₂/M cells estimated by flow cytometry) and expression of cdk1, cdk2 and cdk4 proteins. We found a significant correlation between the percentage of cells in S or S + G₂/M phases and cdk1 protein content but not cdk2 or cdk4 content. We conclude that cdk1 expression in human lymphoid cells varies during the cell cycle at both mRNA and protein levels. © 1995 Wiley-Liss, Inc.     

Hypermethylation of calcitonin gene in adult acute leukemia at diagnosis and during complete remission

Hypermethylation of the calcitonin gene has been described in various hematologic malignancies. In order to assess its frequency and potential usefulness as a marker for leukemic cells and to detect potential clinical correlations, 180 adult patients (aged > 15 years) with newly diagnosed acute leukemia including 133 cases of acute myeloid leukemia (AML) and 47 cases of acute lymphoblastic leukemia (ALL) were tested for its presence in leukemic blasts at diagnosis by Southern blot technique and polymerase chain reaction (PCR) using 3 sets of primers (P550, P566, P1400), amplifying the most frequent sites of hypermethylation upstream or within the gene. In AML, 92 patients (69%) had hypermethylation detected by Southern blot at diagnosis. This hypermethylation could be confirmed by PCR in 18 of 36 tested cases (50%). Hypermethylation was not significantly associated to any clinical or hematological characteristic of the disease. In ALL, 44 patients (94%) had hypermethylation detected by Southern blot at diagnosis. This hypermethylation could be confirmed by PCR in 33 of the 43 tested cases (77%). Sensitivity of PCR assessed by dilution was 1 to 0.1%. Hypermethylation was not either significantly related to any clinical or hematologic characteristics of the disease. Seven ALL cases which were positive by PCR at diagnosis and achieved cytological CR could be tested during CR. Five cases were negative and did not relapse after 3 to 27 months in CR. One case was positive at the beginning of CR and became negative after autologous transplant. However, he relapsed after 9 months in CR, 3 months after the last negative test. PCR for Bcr/Abl was also negative at this time. We conclude that hypermethylation of the calcitonine gene is frequent at diagnosis in adult acute leukemia, particularly in ALL.