To examine the effects of Id4 on the biological characteristics of CRC, HCT116 cells with stable Id4 expression (HCT116-Id4 cells) were established, and the Id4 expression was confirmed by Western blotting and real-time RT-PCR (Figures 1(b) and 1(c), P < 0.05). The gene discussed is ID4; the disease is colorectal carcinoma.