PROLIFERATION AND OXYGENATION STATUS OF WIDR SPHEROIDS IN DIFFERENT LACTATE AND OXYGEN ENVIRONMENTS

Human colon adenocarcinoma cells WiDr were cultured as monolayers or m ulticellular spheroids in 5% or 20% (v/v) oxygen and in various extern al lactate concentrations of 0-20 mM. Doubling times and H-3-thymidine labeling indices of exponential monolayer cells indicated that there was no difference in growth behavior between the two oxygen environmen ts, yet these parameters reflected a growth retardation upon elevation of lactate. Growth of WiDr spheroids was retarded in both low oxygen and high lactate concentrations. There was a tendency towards a decrea se in the thickness of the viable cell rim with increasing lactate in 20% O-2, whereas the width of the viable rim increased significantly a s a function of external lactate in 5% O-2. Intraspheroidal oxygen ten sions (Po-2) measured with microelectrodes were less in 5% O-2 than in 20% O-2, yet did not vary systematically as a function of external la ctate. Po-2 values in the spheroid center dropped to 0 mm Hg prior to the emergence of central necrosis under all conditions investigated. U nlike numerous other spheroid types investigated up to now, WiDr spher oids mimic tumor microregions with hypoxia-induced necrosis and with n onproliferating cells at very low oxygen pressure.