Clonal derivatives 8 and 11 of the T47D human breast carcinoma cell line release particles that have the biochemical characteristics of a retrovirus. Particles recovered from cultures of [3H]uridine-labeled clone 11 had a density of 1.18 g/ml and contained 60-70S and 35S RNAs associated with reverse transcriptase activity. The production of these particles was steroid-dependent. Clone 8 particles had a higher density, 1.195 g/ml, and their production was independent of steroid hormone. By RIA, antigens crossreactive with the 52,000-dalton envelope glycoprotein gp52, the major external protein of mouse mammary tumor virus, were found associated with these particles and in the media. Most of the gp52-related antigen was in soluble form, but it was enriched in the particle preparation. A lesser amount of antigen was distributed within the cultured cells. Absorption of rabbit antibody to gp52 with clone 11 particle preparations eliminated the ability of this antibody to detect immunocytochemically a crossreactive antigen previously localized in tissue sections of human breast carcinoma. These results indicate that the particle isolates from T47D contain the same gp52-related antigen found in human breast carcinomas and constitute an excellent source for the purification and characterization of this antigen.
We examined by Southern blotting the state of the cellular oncogene c-myc in the dog transmissible venereal tumor. The tumor DNA contains a 16.8-kilobase pair (kbp) rearranged c-myc fragment in addition to the normal 15-kbp and 7.5-kbp fragments. We compared the structure of the cloned rearranged c-myc (re-myc) with that of a cloned normal c-myc and found that the rearrangement was due to the insertion of a 1.8-kbp DNA upstream to the first exon of c-myc. The inserted DNA is flanked by 10-base-pair direct repeats and contains a dA-rich tail, suggesting its origin from mRNA. Partial sequence of the inserted element showed 62% homology with the primate interdispersed Kpn I repetitive element. These results provide an example for the behavior of repetitive DNA sequences like the Kpn I family, as movable elements that can transpose nearby to oncogenes or other structural genes and perhaps affect their activity.
Adenosine deaminase (ADA) activity was determined in peripheral blood T cells, thymocytes and blasts of 42 acute leukemia patients. Thymocytes had higher ADA activity than mature peripheral blood T cells. B ALL (acute lymphoblastic leukemia) cells had significantly lower activity compared with T ALL and non-B, non-T cells. The latter had a wide range of enzymatic activities but mostly in the T cell range. Based on these results, as well as on assays of B and T cell lines, it seems that thymus-derived cells--and especially prethymic and immature T cells--have high ADA activity. This finding could be useful in subtyping the heterogeneous group of non-B, non-T ALL.
We examined by Southern blotting the state of the cellular oncogene c-myc in the dog transmissible venere- al tumor. The tumor DNA contains a 16.8-kilobase pair (kbp) rearranged c-myc fragment in addition to the normal 15-kbp and 7.5-kbp fragments. We compared the structure of the cloned rearranged c-myc (rc-myc) with that of a cloned normal c-myc and found that the rearrangement was due to the inser- tion of a 1.8-kbp DNA upstream to the first exon of c-myc. The inserted DNA is flanked by 10-base-pair direct repeats and contains a dA-rich tail, suggesting its origin from mRNA. Par- tial sequence of the inserted element showed 62% homology with the primate interdispersed Kpn I repetitive element. These results provide an example for the behavior of repetitive DNA sequences like the Kpn I family, as movable elements that can transpose nearby to oncogenes or other structural genes and perhaps affect their activity.
It has been suggested that the malignant transformation, in some of the acute leukemias, may involve totipotent stem cells resulting in a biphenotypic leukemia expressing both myeloid, and lymphoid characteristics. We describe here a hybrid cell acute leukemia, in a 16-day-old infant, in whom leukemic cells coexpressed myeloid and lymphoid B cell antigens. Blast cells in the bone marrow showed L2 morphology according to the French American British (FAB) classification, with positive periodic-acid Schiff, and nonspecific esterase staining. Sudan black, and specific esterase were negative. Terminal deoxynucleotidyl transferase, was strongly positive in 5% of blasts, and faintly reactive with the rest. Karyotypic analysis demonstrated a translocation of t(11:17);(q23;p13). Immunoglobulin gene analysis revealed rearrangement of the heavy chain genes. The blasts' phenotype was HLA/DR+ B4+ My7+ My9+ common acute lymphoblastic leukemia antigen (CALLA) B1- T11-. Dual immunofluorescence staining using anti My7, and My9 fluorescein isothiocyanate, and anti B4 pycoerythrin conjugated monoclonal antibodies, and flow cytofluorometry, revealed a labeling pattern of 25% B4+; 10% to 15% My7+; 17% My9+; and 50% of cells coexpressing B4 My7, and My9 antigens. These results provide evidence for a hybrid leukemia with lymphomyeloblasts being part of a single clone, which may indicate the origin of this leukemic clone from a pluripotent (lymphoid/myeloid) stem cell.
