EGFR and squamous cell carcinoma: Thereby viability of EGFR-overexpressing breast carcinoma and squamous cell carcinoma cells was reduced to about 50% at a concentration of 100 μg/mL of total granular proteins from activated NKL/GrB-T cells, which corresponds to approximately 5 to 10 ng/mL (125 to 250 pM) of GrB-T as estimated in cytotoxicity assays employing recombinant GrB-T expressed in yeast as a standard [15] (data not shown).