Analysis of surface antigen expression per cell of human osteogenic sarcoma cells by fluorescence-labelled monoclonal antibodies

The relationship between total surface antigen expression per cell (means) - measured by fluorescence-labelled monoclonal antibodies (fluorescence-histograms) and the distribution of cells in the cell cycle (DNA-histograms) and size-scattergrams (cell sorter FACS-IV) were analysed in drug treated unsynchronized and synchronized osteogenic sarcoma cells (2OS) in vitro. Drugs with various sites of action in the cell cycle were used. Adriamycin, Vindesine, in concentrations applied accumulate cells in G2 + M phase. Methotrexate arrests cells in the boundary of G1/S phase. Size-scattergram and DNA-histogram analysis have shown that the entrance of cells to the cell cycle is usually accompanied by an increase in the cells size and amount of their DNA. The size of the cells influenced antigenic expression much more than the distribution of the cells in the various cell cycle phases: in the bigger cells the expression per cell was more pronounced. The increase of antigen expression was the highest for Adriamycin and for Methotrexate treated cells. However, this increase was limited and never exceeded plus 50% in relation to the control. This relatively low difference resulted from the fact, that a given phase of the cell cycle included cells markedly heterogenic in respect of size and antigenic content. It was also shown that lower concentration of serum in culture medium and confluent growth of older cultures decrease surface antigen expression per cell.