Figure 5. The dose and time dependency of the HSV-tk/GCV system to affect cell viability detected using CCK-8. Different concentrations of GCV were added to the HLECs infected by Lenti-IRES-EGFP, LTKCRE, the enhanced specific lentiviral vector combination, or Lenti-hPGK-EGFP-HSVtk for 24 h (A) or 96 h (B). The cell viability of the group treated with the enhanced specific lentiviral vector combination was significantly suppressed compared with that treated with LTKCRE.