Figure 6.

Antiadhesion effect of PC expression on cell aggregation. (A) Aggregation assay of parental CHO-K1 cells and CHO-PC5 and CHO-PC13 cells stably expressing PC. CHO-PC13 cells, the highest PC expression clone, showed complete inhibition of aggregation in both the presence and absence of Ca²⁺. CHO-PC5 cells, expressing the lowest level of PC, showed a 35% reduction in aggregation after 180 min of incubation in both the presence and absence of Ca²⁺. However, aggregation was slower in the absence of Ca²⁺, because it was reduced at 60 and 120 min compared with parental CHO cells. (B) Aggregation assay of parental MDCK cells and MDCK-PC6 and MDCK-PC8 cells stably overexpressing PC. Aggregation in MDCK-PC6 and MDCK-PC8 cells was reduced 60 and 80%, respectively, compared with parental cells. Cell suspensions were seeded and allowed to aggregate for 0 to 180 min in the presence of 1 mM CaCl₂ or 1 mM EGTA (in the case of CHO cells) at 37°C as described in MATERIALS AND METHODS. Aggregation was estimated by the following formula: % aggregation = (N₀ − N_t)/N₀ × 100, where N_t is the total number of particles at the incubation time t and N₀ is the total number of cells. Results (means ± SD) represent the average of values obtained in three independent experiments.