ABCB1 and ovarian carcinoma: We transiently transfected GCS in human OVCAR-8 ovarian carcinoma cells, which express low level of MDR1 [36], in order to explore putative mechanisms underlying GCS upregulation of MDR1. One week after the transfection, GCS protein levels were elevated by 10-fold, 20-fold and 25-fold in cells transfected with increasing amounts of GCS plasmid DNA (2, 4, and 8 μg/dish) (Figure 5A).