Figure 4.

Downregulation of p27^kip expression by hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) during apoptosis. Rabbit corneal primary epithelial (RCPE) cell cultures in Dulbecco’s Modified Eagle Medium with Ham’s F-12 (DMEM/F-12)/0.25% fetal calf serum (FCS) were pretreated with 20 ng/ml HGF or KGF for 30 min before staurosporine (STS) was added. Cultures were further incubated in the presence of STS (10 ng/ml) for 2 h. Then the medium was removed, and fresh medium containing HGF or KGF but no STS was added, and incubation continued for 8 h (A) to 22 h (B). Levels of p27^kip in cellular extracts at different time points were determined with western immunoblotting using monoclonal p27^kip antibody and quantified with densitometry (C and D). Similar results were obtained in two additional experiments. Data shown are mean±standard deviation (SD). *p<0.05, control versus HGF or KGF, #p<0.05 STS versus STS+HGF or STS+KGF.