Bioinformatics database-based results demonstrated that CBX7 was closely related to the progression and prognosis of gliomas and participated in cell cycle regulation. However, this in silico evidence was insufficient to elucidate the role of CBX7 reliably. Therefore, we constructed siRNAs targeting CBX7 and a lentivirus vector expressing CBX7. We then assessed the CBX7 protein levels in four GBM cell lines (Figure 3A). Other typical PRC1 elements in U251, U87 and LN229 cells were also tested (Supplementary Figure 2A). U251 cells containing high concentrations of CBX7 were used in knockdown experiments of CBX7 expression via the transient transfection of siRNA targeting CBX7 (si-CBX7) as well as a control vector (si-ctrl). The efficiency of three different sequences si-CBX7 was tested in U251 cells and the optimal si-CBX7 sequences was chosen for the subsequent experiments (Supplementary Figure 2B). We further constructed two stable CBX7 expressing cell lines, U87 and LN229, using a lentiviral CBX7-expression vector (Lenti-CBX7) and control cell lines using a control lentiviral vector (Lenti-ctrl) in the parental cells. The efficiency of up/downregulation of CBX7 is shown in Figure 3A.