Fig. 6

CircRNAs mediate tumor survival and apoptosis by UPR. Circ_002117 induced ER stress by upregulating GRP78, IRE1, eIF2α, and CHOP, subsequently resulting in the apoptosis of gastric cancer cells. CircCDR1as induces ER stress by upregulating eIF2α under hypoxia conditions, increasing OSCC cell survival. Moreover, circCDR1as promoted hypoxia-induced autophagy in OSCC cells by sponging miR-671-5p. CircRNA_101036 induced the UPR pro-apoptosis pathway by increasing CHOP protein, which induces apoptosis