ATF4 and non-small cell lung carcinoma: Pterostilbene enhances endoplasmic reticulum stress (ERS) signalling Phosphorylated protein kinase R – like endoplasmic reticulum kinase (p‐PERK), Inositol‐Requiring Enzyme 1 Alpha (IRE1), ATF4, CHOP → decreases cell viability and induces apoptosis in A549 & PC9 NSCLC cells