5-Bromodeoxyuridine induces expression of a tumour-specific surface antigen on normal avian cells

Third Gordon Hamilton-Fairley Memorial Lecture. Tumour markers--where do we go from here?

An overview of the application of markers for solid tumours is presented. Some of the potential problems with general cancer tests are considered as well as the ways in which the more specific markers have been applied. The limited specificities of markers defined so far remain a serious limitation but they have found useful clinical application. Their use in radioimmunolocalisation provides an interesting challenge to the physical methods of tumour localisation and the possibilities of drug targeting by antibodies are as exciting as the difficulties are formidable. It is, I suggest, a field that will continue to evolve and be productive.

Dissection of the antigenic determinants expressed on the cell surface of RSV-transformed fibroblasts by monoclonal antibodies

Fusion of P3/X63-Ag8 mouse myeloma cells with splenocytes obtained from mice hyperimmunized with a BHK hamster fibroblast line transformed by an env-strain of Rous sarcoma virus (RSV) resulted in the production of antibody-secreting hybridomas. Seven hybrid clones secreted antibodies binding to RSV-transformed BHK fibroblasts but not to the parental control non-transformed line. The antibodies produced by three of these clones did identify antigenic determinants expressed also on BHK cells transformed by SV 40. The antibodies produced by four other clones reacted specifically with cells transformed by RSV but not with cells productively infected by the transformation-defective Rous-associated virus-1; one of these reacted with RSV-transformed hamster cells only, three others identified antigenic determinants common to RSV-transformed cells of different animal species. These data give further support to the idea that RSV-transformed cells express a cell-surface antigen, specific for transformation, the expression of which is controlled by the transforming src gene, and that the specificities carried on it follow a complex pattern, arising from the interaction between antigenic determinants of cellular and viral origin.

Interaction between cellular and viral genes in the expression of the RSV-induced transformation-specific cell-surface antigen VCSA

Transformation of BHK hamster fibroblasts by an env- strain of Rous sarcoma virus (RSV) leads to the appearance at the cell surface of a virus-induced nonvirion antigen (VCSA), specific for transformation, whose expression is controlled by the transforming src gene. Previous work has shown that a rabbit anti-VCSA serum lyses specifically, in the presence of complement, 51Cr-labelled RSV-transformed cells from different animal species. Now, by competition experiments with a panel of different unlabelled cells we show that the VCSA expressed on RSV-transformed hamster fibroblasts is a complex of at least three distinct antigenic specificities: (1) one expressed on all RSV-transformed fibroblasts, regardless their species and the subgroup or strain of the transforming virus; (2) one cross-reacting with a cell-surface antigen (CSA) expressed at various degrees on untransformed avian fibroblasts, but not on mammalian fibroblasts; (3) one species-specific, present only on RSV-transformed hamster fibroblasts. It is concluded that VCSA is a complex of several antigenic determinants, and that some of these differ in different cells transformed by RSV. This observation indicates that VCSA expression at the cell surface is likely to be the result of the interaction between the viral src gene product pp60src with host cell gene(s) or gene product(s), rather than the simple expression of this molecule at the cell surface.

The effect of avian retroviruses on limb bud chondrogenesis in vitro

Mesenchymal cells isolated from stage 24 embryonic chicken limb buds were infected with the temperature-sensitive transformation mutants of Rous sarcoma virus tsNY68, tsNY10 and tsLA25 at the nonpermissive temperature for transformation (41 degrees C). Virus infection greatly inhibited subsequent limb bud chondrogenesis under nontransforming conditions, as indicated by a reduction in the rate of 35SO4 incorporation into cell-associated proteoglycans. The inhibition of chondrogenesis was directly related to the percentage of cells infected with tsNY68 at 41 degrees C. The observed inhibition of chondrogenesis was independent of src gene expression since this effect was also caused by many viruses which lack the src gene, including the leukosis viruses RAV-1, RAV-2 and MAV-2(0); the src deletion mutant RSVtd107; and the reticuloendotheliosis viruses REV-T and SNV. Infection of mesenchymal cells with tsNY68 under nontransforming conditions did not cause changes in parameters such as the rate of thymidine incorporation, total cell DNA and total cell protein. Infection with tsNY68 at 41 degrees C resulted in altered kinetics of 35SO4 incorporation into cell-associated proteoglycans and a corresponding reduction in 35SO4-labeled proteoglycans extracted from the cell layer. There were no apparent quantitative effects on the rate of accumulation of proteoglycans in the culture medium. The proteoglycans extracted from the cells and the collected medium of tsNY68-infected cultures were smaller than those of uninfected cultures, as shown by agarose gel chromatography.