ATF6 and squamous cell carcinoma: Furthermore, activation of ATF6α and PERK have been shown to be essential for the long-term survival of dormant HEp-3 cells (Human Epidermoid carcinoma) derived from a cervical lymph node (metastatic site) from a buccal mucosa squamous cell carcinoma (primary site) in vitro and in vivo [52,53].