After the inoculation of mice with MC38 mouse colon cancer cells that expressed sPD-L1 and membrane-type PD-L1 at a cell number of 1:99 followed by anti-PD-L1 antibody treatment, the whole tumor showed resistance to PD-L1 treatment despite 1% of tumor cells expressing sPD-L1. This evidence concerns the gene SPDL1 and malignant colon neoplasm.