rLZ-8 enhances G1 arrest, expression of p53 and p53
transactivational activity
The signal pathway involved in antigrowth effect of rLZ-8 on A549
cells was assessed by first examining cell cycle distribution in the rLZ-
8-treated cells. When the cells were treated with rLZ-8 for 24 h, the
percent of G1 arrest cells was increased from 64.9% in the control cells
to 80.5% in the cells treated with rLZ-8 (15 lg/ml); whereas, the subG1
population was increased only slightly from 1 to 6% under similar
circumstances (Figure 2A). The expression of three proteins, p53, p21/
Cip1 and p27/Kip1, was increased after rLZ-8 treatment (Figure 2B).
Both p21 and p27 are cyclin-dependent kinase inhibitors that are associated
with the G1 checkpoint; furthermore, p21 is directly regulated by
p53 (37). When a p53 reporter system was transiently transfected into
A549 cells, the transactivational activity of p53, measured in terms of