DLL3 and neoplasm: Together with the increased antitumor TIL response in the ELISpot assay and delayed tumor outgrowth after rechallenge with DLL3KO mSCLC tumors, this suggests that IL-18 stimulates tumor-reactive TILs, which is in line with earlier findings in a CD19+ lymphoma model (20) and may be important for elimination of DLL3– tumor cells in tumors with heterogeneous DLL3 expression.