EFFECT OF MEDIUM EXCHANGE-RATE ON COLONY GROWTH OF THE HUMAN TUMOR-CELL LINE MDA-231 CLONED WITHIN THE PERFUSED CAPILLARY CLONING SYSTEM

The conventional human tumor stem cell assay is limited by the lack of flexibility for drug scheduling with single agents and its inability to test drug combinations. Recently, we described the cloning of tumor cell lines within porous glass capillary tubes which allow free excha nge of substances. The present study describes the influence of variou s perfusion modalities on the colony growth of the human tumor cell li ne MDA-231 cloned within the perfused capillary cloning system (PCCS). Colony growth of tumor cells within the PCCS is strongly dependent on perfusion tube volume, flow rate and duration of perfusion with growt h medium. Best colony growth was achieved using a perfusion tube volum e of 12 ml resulting in a cloning efficiency of 36.3%. Continuous perf usion with fresh medium did not improve the cloning efficiency; in fac t, colony growth was hampered compared to colony growth within unperfu sed porous capillaries. However, cloning efficiency was acceptable whe n continuous perfusion was started at day 6 (26.4%) instead of day 0 ( 17.2%), or when a short perfusion with high volume (12 ml/h) was disco ntinued after 1 h at day 0. In contrast to the conventional capillary cloning system the PCCS has the potential for investigating secretion and kinetics of tumor-specific factors and the effect of growth-stimul ating or growth-inhibiting drugs.