Differential cytotoxicity of cis-platinum and blenoxane against human carcinoma kbe cells in multicellular spheroids of different ages: Response at different temperatures

Abstract

Human KBE epidermoid carcinoma cells were reproducibly grown in suspension as multicellular spheroids (MCS). Initial aggregation at 48 hours is followed by a rapid diameter increase until day 10. The size increase then continues with daily refeedings, under the growth conditions used, but at a slower rate. When cells are treated in MCS with either blenoxane (bleomycin) or cis-diamminedichloroplatinum (II) (cis-platinum), the survival of cells (by cloning efficiency (CE) essay) varied from that of surface attached (SA) cells. The survival was dependent on the age of the MCS as well as their size; the age response was significantly different for cis-platinum and blenoxane. Hyperthermic incubation of KBE cells in MCS at different ages for 1 hour (40–43°C) resulted in cell killing similar to that observed after hyperthermic incubation of surface attached cells. In combined byperthermia/chemotherapy experiments, simultaneous treatment with blenoxane resulted in little or no increase in MCS cell toxicity at 40°C; at 42.5°C, there was increased toxicity. The increase in toxicity was similar for MCS of different ages. Upon simultaneous cis-platinum treatment, an increase in toxicity was observed at 40°C, but only in older MCS. At 42.5°C, an increased toxicity (relative to treatment at 37°C) was observed in MCS of all ages. These results are, in general, similar to those described for other in vitro and in vivo systems, but emphasize the differences in the survival response which can result for treatment of human cancer cells in MCS of different ages over even a small size range (up to 1 mm diameter). This is much smaller than clinically detectable tumors. This reproducible human cancer cell multicellular spheroid model has great potential for representing the variability likely to be present in micrometastases of different sizes, and in small regions of solid tumors, and therefore for assisting in preliminary evaluation of combined modality protocols.