Figure 4. B16 cells were stably transfected with pIRES-neo3 and pIRES-neo3-HPV16 E6/E7+pGL3-luc. (A, B) E6 and E7 levels in B16 cells transfected with pIRES-neo3-HPV16 E6/E7 or pIRES-neo3 were verified by qRT-PCR. (C, D) E6 and E7 levels in B16 cells transfected with pIRES-neo3-HPV16 E6/E7-pGL3-luc were verified by qRT-PCR. (E) B16 cells were treated with G418 at concentrations of 0, 400, 500, 600, 700 and 800 μg/mL, and their proliferation was measured with an MTT assay at 24, 48, 72 and 96 h, respectively. **P < 0.01 compared to the NC group.