SPDL1 and neoplasm: Furthermore, a mixture of only 1% MC38 cells with sPD-L1 variants (MC38/mPD-L1v242) and 99% of cells that overexpressed wild-type PD-L1 (MC38/mPD-L1) were found to cause resistance to PD-L1 blockade therapy by accumulation of soluble PD-L1 in the tumor and plasma.