Comparative transcriptomic analysis reveals distinct ER stress responses in tunicamycin sensitive and resistant CHO cells

Tunicamycin (TM), an inhibitor of N-linked glycosylation, induces endoplasmic reticulum (ER) stress by causing the accumulation of misfolded proteins, thereby activating the unfolded protein response (UPR) to restore homeostasis. Although TM-induced UPR and ER stress responses have been investigated in CHO cells, the transcriptional adaptations underlying stable ER stress tolerance remain poorly understood. To distinguish transient stress responses from long-term adaptive mechanisms, we performed comparative transcriptomic analysis of parental TM-sensitive CHOK1 suspension cells and a TM-resistant derivative following TM treatment. TM treatment of parental CHOK1 suspension cells induced ER stress and activated the UPR pathway. In contrast, TM treatment of the TM-resistant cells failed to induce UPR or other stress-associated pathways, suggesting a reprogrammed, stress-tolerant state. Comparative transcriptomic analysis revealed gene categories associated with TM resistance and responsiveness. Notably, TM-resistant cells exhibited elevated basal expression of stress regulators, including PERK pathway effectors Gadd34 and Chop, indicative of a pre-adapted transcriptional state. Conversely, TM-responsive genes involved in protein processing, cell cycle, and metabolism were selectively activated only in sensitive CHO_C cells upon exposure. Together, these findings demonstrate that while TM triggers an acute stress response in naïve cells, long-term adaptation drives transcriptional reprogramming underlying enhanced ER stress tolerance and sustained cell survival.