LC treatment selectively induces expression of p21^cip1 gene, mRNA and protein in cancer cells.

(a) LC induces p21^cip1 gene expression but not p27 and GAPDH. HepG2 cells were treated with LC (2.5, 5.0, 10 mM) for 24 h; cells were collected for gene expression profile analysis. In the gene chip, there are 2 probes for p21^cip1 and 1 probe for p27^kip1. All the fold increases of p21^cip1 and p27^kip1 gene expression versus control were shown. (b) LC dose-dependently induces p21^cip1 mRNA expression but not p27^kip1 in HepG2 cells. HepG2 cells were incubated with different concentrations of LC (2.5, 5, 10 mM) for either 12 h or 24 h; the cells were collected for mRNA assay of p21^cip1 and p27^kip1 by real-time PCR. Fold increase of the LC-treated versus control was shown. Mean+SD (n = 3). *P<0.01, **P<0.05, compared with control. (c) LC dose-dependently and time-dependently induces p21^cip1 protein accumulation in HepG2 cancer cells. HepG2 and SMMC7721 cells were treated with various doses of LC for 48 h or HepG2 cells were exposed to 5 mM of LC for 12, 24, 36, 48 h; p21 and p27 proteins were detected by Western blot. (d) LC dose-dependently decreases Rb phosphorylation. HepG2 cells were treated with LC for 48 h; Rb and phosphorylated Rb were dectected by Western blot. Typical Western images were shown (left) and band intensity was quantified (right).