DHTKD1 and colorectal cancer: As shown in Fig. 3A, a cytopathic effect was observed in the CEA-positive colorectal cancer cells infected with either Ad·(ST13)·CEA·E1A(Δ24), Ad·(EGFP)·CEA·E1A(Δ24) or ONYX-015 compared with the CEA-negative HeLa cells.