A comparative study of some growth characteristics and cell-surface properties of neoplastic cells

Tumour cells from a polyoma-induced ascitic tumour were fractionated on the basis of the electrical charge on the cell surface by free-flow electrophoresis. Several characteristics of tumour cells have been investigated: (1) differences in the proliferation and antigenicity within the tumour at any point in time; (2) variation in proliferative potential with the ageing of the tumour. In early ascitic tumours, electrophoretically fractionated cells exhibit very similar proliferative characteristics. However, most DNA synthesis was found in slow-moving cells. The behaviour of older tumours was different. Proliferative potential and DNA synthesis were weaker and restricted to slow-moving cells, suggesting that fast-moving cells in older tumours were resting cells. An enrichment in immunoglobulin-bearing cells was also found in slow-moving cell fractions, supporting the hypothesis of variability in expression of tumour-specific antigens. The role of cell-surface properties and cell kinetics is discussed in relation to electrical surface charge, which might be involved in cell dissemination and metastasis. Thus, free-flow electrophoresis represents a satisfactory approach to isolate tumour cell subpopulations with characteristics such as high proliferative potential or increased expression of tumour antigens.