Based on the in vivo imaging result, in the mice that were intravenously injected with CEA‐positive HT‐29‐RFP, AsPC‐1‐RFP, or MGC803‐RFP cells and thereafter CEA‐CAR‐T cells 7 days later, the in vivo tumor generating fluorescence signal significantly decreased at 21 day after tumor cell inoculation, and the fluorescence signal decreased further at day 28. The gene discussed is CEACAM5; the disease is neoplasm.