ATF4 and neoplasm: It is noteworthy to mention that unlike previous reports indicating ATF4 as an inducible transcription factor, our data strongly suggested that ATF4 protein was highly expressed in both normal tissue and tumor in the liver; however, the ratio of ATF4 in nucleus vs. cytosol, which indicated its transcriptionally active form, was increased both in hepatocytes with Tm treatment and in Ki67-positive tumor cells (Fig. 7).