Radiation‐induced senescence was also observed in HCT116 colon cancer cells, which displayed reduced proliferation, enlarged and flattened cell morphology with prominent nuclei persisting for at least 12 days, increased cell size, SA‐β‐Gal accumulation, and induction of p53 and p21 (Fig. S2). Here, CDKN1A is linked to colonic neoplasm.