HSP90AB1 and cancer: For example, ER-resident HSP90 chaperone glucose-regulated protein 94 (GRP94, also known as Gp96) plays critical role in unfolded protein response (UPR) while mitochondria-resident HSP90 chaperone tumor necrosis factor receptor-associated protein 1 (TRAP1) is involved in mitochondrial bioenergetics, contributing to apoptosis resistance, cancer cell stemness and Warburg phenotype (47–50).