Cloning of fresh lymphoma cells

A human B-cell lymphoma line with a de novo multidrug resistance phenotype

A human diffuse large cell lymphoma line (WSU-DLCL) expressing multidrug resistance (MDR) was established from a patient with primary chemotherapy-resistant disease. This cell line has the same phenotypic features as malignant cells from the patient. The established cell line has features of a mature B-cell neoplasm with no evidence for commitment to other lineages. WSU-DLCL grows in suspension forming relatively large clumps of cells with a doubling time of 20 hours. By light microscopic examination, the cells are very large with primitive lymphoid features, have a large amount of cytoplasm containing numerous vacuoles and an irregular outline. Immunophenotypic characterization by monoclonal antibodies and flow cytometric analysis showed a monoclonal IgM kappa B-cell phenotype with high expression of the multidrug-resistant P-glycoprotein compared with either normal peripheral blood lymphocytes or cells of the REH cell line. The cells were negative for T-cell and myeloid/monocyte antigens as well as Epstein-Barr virus nuclear antigen (EBNA). In addition, the cell line expressed high levels of MDR RNA. DNA histogram generated by flow cytometry indicated a DNA index of 1.83. Cytogenetic analysis confirmed hypertriploidy and showed complex chromosomal abnormalities including 14q+. This cell line should be a valuable tool to study the role of the MDR gene in the primary resistance of lymphomas to chemotherapy and to facilitate therapeutic investigations.

Establishment of a near-tetraploid B-cell lymphoma line with duplication of the 8;14 translocation

The neoplastic cells of a patient with diffuse histiocytic lymphoma were grown in three systems: Soft agar, liquid culture, and by heterotransplantation into the nude mouse. In each case, the growing cells were shown to bear the same immunoglobulin heavy and light chain type as the original neoplastic cells (IgM-lambda). In both the liquid culture and nude mouse heterotransplant tumors, karyotypic analysis revealed the presence of pseudodiploid and near-tetraploid metaphases bearing one and two copies of an 8;14 translocation, respectively. From the liquid culture separate clones of pseudodiploid and near-tetraploid cells were isolated in soft agar, and separate cell lines SK-DHL2A and SK-DHL2B were established. Studies comparing the proliferative characteristics of the two lines showed no difference in cell population doubling time or clonigenicity in soft agar. Hence, the presence of two copies of the translocated material did not confer a proliferative advantage on cells containing it. Theses lines may be valuable in future studies of cell proliferation and oncogenesis in the human immune system.

Induction of in vitro proliferation and maturation of human aneuploid myelogenous leukemic cells

Human leukemic cells were induced to proliferate and mature to macrophage-like cells in primary cultures supplemented with conditioned medium (CM) from phytohemagglutinin and alloantigen-stimulated normal T lymphocytes. Blast and promyelocyte-enriched preparations, isolated after depletion of adherent phagocytic cells and lymphoid cells from samples of myelogenous leukemia patients, were suspended in liquid cultures with 30% CM. Cell cycle analysis was performed throughout the course of induced cellular maturation. Within 24 h of exposure to CM, cells with macrophage-like morphology were identified among the developing adherent cells. Approximately 15-30% of the cells in culture suspensions also developed macrophage-like morphology and esterase reactivity with alpha-napthyl acetate after incubation for 2 d. The number of these nonproliferating cells increased and became predominant in the later culture period. Flow cytometric measurement of DNA content showed that these mature cells had the same aneuploid stemline as the undifferentiated leukemic cells, indicating that genetically abnormal leukemic cells can be induced to differentiate. Reduction in the total RNA content of the macrophage-like cells was also determined by flow cytometry. Reduction in RNA and development of adherent cells served as early markers of maturation, in addition to the later acquisition of complement receptors and phagocytic capacity. Cell cycle analysis showed that CM stimulated the proliferation of immature cells. This initial proliferation may precede intertwined events of proliferation and concurrent maturation of immature cells. Later in the culture period, cellular proliferation decreased, leading to termination of the cultures.