Additional study revealed that saikosaponin A induced apoptosis by upregulating the levels of GRP78, p-PERK, p-eIF2α, ATF4, and CHOP in AGS and MKN-74, and overcome radio resistance in GC cells thus, a process that could be blocked by GRP78 or PERK knockdown. The gene discussed is DDIT3; the disease is gastric cancer.