Cytogenetics of chronic T cell leukemia, including two patients with a 14q+ translocation

Molecular analysis of the t(14;18) chromosomal translocation in malignant lymphomas

One of the most common karyotypic abnormalities is the t(14;18) translocation, which is found in many lymphomas that have a characteristic follicular morphology. Recent molecular studies have shown that this chromosomal translocation results in the juxtaposition of the candidate proto-oncogene bcl-2 (B-cell leukemia-lymphoma) on chromosome 18 with the immunoglobulin heavy-chain locus on chromosome 14. However, because performing accurate cytogenetic studies in solid hematolymphoid neoplasms is difficult, knowledge of the prevalence of the t(14;18) translocation and, by association, the extent of bcl-2 involvement in human lymphomas is limited. We used a number of chromosome-18 DNA probes to analyze various subtypes of Hodgkin's and non-Hodgkin's lymphomas and test for structural abnormalities near or within the bcl-2 gene. Molecular features of the t(14;18) translocation were found in virtually all follicular neoplasms and about 28 percent of diffuse large-cell lymphomas. No changes in bcl-2 were found in several other subtypes of Hodgkin's and non-Hodgkin's lymphomas, including those previously suggested to originate from follicular-center cells and those about which cytogenetic data have been difficult to obtain. Our findings suggest a close pathogenetic relation between bcl-2 and a large group of non-Hodgkin's lymphomas, both with and without a follicular morphology. The methods employed in this study may be useful in improving the accuracy of diagnosis and subclassification of malignant lymphomas.

Chromosome abnormalities, sister chromatid exchanges, and cell cycle analysis in phytohemagglutinin-stimulated adult T cell leukemia lymphocytes

Chromosome abnormalities, sister chromatid exchanges (SCE), and cell cycle kinetics were studied in phytohemagglutinin-stimulated lymphocytes from 8 adult T cell leukemia (ATL) patients. In all these cases, chromosome abnormalities were observed in 5-day PHA-stimulated cultures. Four cases had characteristic marker chromosomes; two were due to a balanced translocation, t(9;21), and two to a simple deletion, 5p-. The other four cases, however, had rather complicated chromosome abnormalities, e.g., 1q+, 2q+, 5q+, 6q-, 14q+, 10p-. When chromosome abnormalities were analyzed in previously reported cases, the abnormalities were mostly distributed among chromosomes #1, #2, #5, #6, #14, and #21. These findings suggest that the abnormalities involving #1, #2, #5, #6, #14, and #21 are intimately related to ATL. The SCE frequency was in the normal range in ATL cells. Cell cycle analysis revealed that the duration of two cell cycles in cells labeled with bromodeoxyuridine (BrdU) required approximately 80 hr in ATL cells, whereas the time of two cell cycles in normal cells is 40 hr. These findings indicate that the ATL cell cycle time is about 40 hr, about double that of normal cells (20 hr), in PHA-stimulated cultures. ATL has been known to be a mature T cell leukemia and to respond poorly to chemotherapy. The latter may be due to the elongated cell cycle or to the mature characteristics of the leukemic cells. The association of ATL with cutaneous T cell lymphoma is also discussed.

The biology of tumor growth in the non-Hodgkin's lymphomas. A dual parameter flow cytometry study of 220 cases

Dual parameter flow cytometry studies (cell DNA content and electronic cell volume) were performed in 220 cases of non-Hodgkin's lymphoma. All cases were characterized as B or T cell malignancies, based on immunologic surface marker characteristics. Aneuploidy by flow cytometry was more common among the B cell lymphomas than among the T cell lymphomas, and was most common among the large B cell lymphomas and B cell lymphomas of intermediate size. Ploidy index distributions showed a prominent hyperdiploid peak, as well as tumor cell populations with near-tetraploid DNA contents. In serial studies, a decrease in ploidy index was observed in association with clinical and histologic transformation in one case. The highest S fractions were observed among the large and intermediate B cell lymphomas and among the aggressive T cell lymphomas. In clinical samples consisting of mixtures of diploid and aneuploid populations, the data on the aneuploid components could often be separated from other components of the mixture in multiparameter studies on the basis of the larger electronic cell volumes of the aneuploid cells. In each case, the aneuploid large cell component almost invariably had a higher S fraction than the residual component(s) of the mixture. Overall, the data are consistent with a model of clonal selection and clonal evolution in the lymphomas in which early cytogenetic abnormalities that involve little or no change in total cell DNA content are followed by cell tetraploidization that is associated with cytogenetic instability and chromosome loss over the course of time.

Chromosome 14q+ in adult T-cell leukemia

Cytogenetic studies were performed on leukemic cells from two patients with adult T-cell leukemia. A 14q+ marker chromosome was found in the peripheral blood leukocytes from patient No. 1 and in a leukemic T-cell line (MT-1) derived from the peripheral blood of patient No. 2. The 14q+ resulted from a t(12;14) in patient No. 1 and from a t(Y;14) in patient No. 2 with a break point at 14q32 in each case. In addition, the leukemic cells from patient No. 1 showed a t(1;7) and a 9q-, while the MT-1 line had numerous structural abnormalities. Thus, it is clear that a 14q+ translocation is not restricted to B-cell neoplasms but occurs in T-cell neoplasms as well.