Metformin upregulated p-eIF2α, CRT and CHOP, whereas miR-708-5p transfection increased the levels of GRP78, p-eIF2α, ATP2A1 and CHOP, indicating that both metformin and miR-708-5p can cause ER stress in prostate cancer cells (Figure 3a). This evidence concerns the gene ATP2A1 and prostate cancer.