MKI67 and neoplasm: Staining with anti-Ki-67 demonstrated a high degree of cellular proliferation in control, anti-PD-1, and anti-PD-L1-treated mice, with a marked decrease in proliferation for PLX4720-containing groups, confirming PLX4720 anti-tumour effect.31 Flow cytometry with anti-PD-L1 antibody showed increased PD-L1 surface expression in anti-PD-1-treated groups (Fig. 2b).