Further analysis of the effect of AZD9291 on the proliferation and apoptosis of GBM cells in vivo by immunofluorescence staining of the GBM sections with antibodies against Ki67 and cleaved caspase-3 (an apoptotic marker) showed that the numbers of the Ki67-positive cells and the cleaved caspase-3-positive cells in the GBM sections in the AZD9291 treatment group were significantly higher than those in the control group (Fig. 4e and f), suggesting that AZD9291 inhibited the proliferation and promoted apoptosis of the GBM cells in vivo. The gene discussed is MKI67; the disease is glioblastoma.