SIRT1 and hepatocellular carcinoma: HepG2, PLC/PRF/5, and MHCC97H hepatocellular carcinoma cells were transiently transfected with SIRT1-overexpressing plasmids, treated with 1.25 μM 1-P for 4 h, exposed to 625 nm light irradiation (1 h), and further incubated for 20 h.