S1PR1 and hepatocellular carcinoma: Another unfavorable marker mediated by the PERK ER-stress branch, ER resident oxidase 1-alpha (ERO1-α), has been found to play a key role in HCC invasion, metastasis, and angiogenesis by triggering the S1PR1/STAT3/VEGF-A signaling pathway, both in vitro and in vivo [41].