TPA-induced growth arrest in HepG2 is PKCα-dependent. (A) 1 × 105 of parental HepG2 and PKCα knockdown HepG2 cells were seeded in 24 well plates. After culturing in serum-free medium for 24 hrs, cells were treated with TPA 100 nM in serum-free medium for indicated time before MTT analysis. The cell proliferation rate were analyzed using Day6 as 100%. Results shown are averages of three independent experiments performed in triplicates. (B) The expression profile of different PKC isoforms in parental HepG2 and HepG2 PKCα knockdown stable lines were examined by Western blot analysis.