In summary, CRISPR–Cas9‐mediated genome‐wide GOF screening identified that EZH2 rendered ESCC cells resistant to the PI3Kα inhibitor CYH33, which was associated with EZH2‐mediated cell cycle progression via the p21‐RB axis. The gene discussed is CDKN1A; the disease is esophageal squamous cell carcinoma.