ATF4 and hepatocellular carcinoma: Among hepatoma cell lines, cell viability data from both drug screening projects revealed a positive correlation between resistance to bortezomib and the expression level of TRIB3 (Figure 4A), a gene upregulated by bortezomib (Figure 1F and 2B) and known to be a negative regulator of the ATF4 pathway [12,15,30].