However, we should care that the tumour volume was smaller for HIF1α- or HIF2α-KO individual cells in the vivo study, but there was no difference in cell proliferation compared with the control in the in vitro study, which may be due to the short detection time in vitro and the different microenvironments between the in vitro and in vivo studies. This evidence concerns the gene EPAS1 and neoplasm.