Reovirus activated NK cells show enhanced cetuximab mediated antibody-dependent cellular cytotoxicity against colorectal cancer cells

Methods Here we investigated the direct effect of reovirus on NK cell mediated ADCC against the EGFR (Epidermal Growth Factor) positive colorectal cancer cell line: DLD-1 (KRAS mut). NK cells isolated from human PBMCs were cultured with 1pfu of reovirus for 12 hrs. These reovirus treated NK cells were co-cultured with DLD-1 cells coated with increasing concentrations anti-EGFR antibody cetuximab. ADCC was measured after 4hrs using a lactate dehydrogenase (LDH) based cytotoxicity assay. We observed that the reovirus treated NK cells (Reo-NK cells) exhibited a ~16-fold increase in cytotoxicity against DLD-1 (16.3% ±1.5, n=3) compared to untreated NK cells (NK cells), even in the absence of any cetuximab antibody. In the presence of cetuximab antibody, NK cells showed a dose dependent increase in ADCC, with maximum ADCC, observed at 0.1 μg/ml of cetuximab (DLD-NK: 33.4%± 7.1, n=3). Interestingly, Reo-NK cells showed maximum ADCC even at 0.01 μg/ml of cetuximab (DLD1-Reo-NK: 39.1±7.4, DLD1-NK: 26.7±2.4%, n=3).