To further investigate the role of cyclin D1 on cell cycle progression in KIT‐mutant GIST cells, we utilised CRISPR/Cas9 to delete the CCND1 gene, resulting in reduced cyclin D1 protein level, decreased p‐Rb level and impaired cell proliferation (Figure 5A, B). Here, RB1 is linked to gastrointestinal stromal tumor.