ATM and cancer: Specifically, genes involved in DDR, such as TP53, Ataxia Telangiectasia Mutated (ATM), and Ataxia Telangiectasia And Rad3‐Related Protein (ATR), are frequently mutated in both OSCC tissues and patient‐derived OSCC tumoroids.[3] Adjuvant chemoradiotherapy which triggers DDR is a routine treatment for OSCC patients.[4] It is well established that ER stress is closely related to cancer cell proliferation, apoptosis, angiogenesis, and metastasis.[1] However, little is known about the role of ER stress in DDR.