CBX4 and hepatocellular carcinoma: To address this, two HCC cell lines, SMMC-7721 and MHCC97L, were stably infected with retrovirus carrying Flag alone or Flag-tagged Cbx4 (Figures 4a and b), followed by the treatment with increasing concentrations (from 0.1 to 20 μM for SMMC-7721 (Shanghai, China) and from 0.1 to 40 μM for MHCC97L (Shanghai, China)) of doxorubicin, a commonly used drug in TACE intervention.