ATF4 and hepatocellular carcinoma: To further confirm the sensitizer role of LBP in 125I-mediated apoptosis and anti-proliferative effect in HCC cells, the PERK-eIF2α-ATF4-CHOP pathway-related proteins were detected after SMMC7721 cells were treated with 125I or a combination of 125I and LBP (Fig. 4a).