Background/Aims: Phosphatidylcholine reduces chemically-induced hepatocarcinogenesis in rats and the growth of hepatic cancer cells. We planned to determine whether apoptosis pathways via death ligands were induced by phosphatidylcholine.
Methodology: Growth inhibition of hepatic cancer cell lines (HepG2, Hep3B, Alexander, and HuH-7) was examined by MTT assay. On apoptosis induction, flow cytometry analyses were performed after Fas or TNF-alpha ligand stimulation followed by phosphatidylchohne. Expressions of caspase-8, -3 and PARP after phosphatidylcholine stimulation were examined by immunoblotting. TUNEL staining was also performed after phosphatidylcholine stimulation.
Results: MTT assays showed growth inhibitions by phosphatidylcholine dose-dependently. Ratios of sub-G(1) phase cell population by FACScan significantly increased on 48h phosphatidylcholine stimulation in comparison to the control group (p<0.05). Fas or TNF-alpha ligand followed by phosphatidylcholine stimulation significantly increased apoptotic cells more than by phosphatidylcholine alone (p<0.05). Enhanced appearances of cleaved caspase-8, -3 and fragmented PARP were shown on immunoblotting and apoptotic cells on TUNEL staining after phosphatidylcholine stimulation. Phosphatidylcholine was assumed to reduce hepatic carcinogenesis by apoptosis induction via the death ligands (Fas and/or TNF-alpha) pathway followed by caspase-8 and -3 inductions.
Conclusions: Phosphatidylcholine intake may well inhibit carcinogenesis in patients at high risk for hepatocellular carcinoma by apoptosis induction.