Fig. 3: sNK cells induced a significant level of killing in both stem-like and differentiated tumors.

OSCSCs (A, C), OSCCs (D, F), MP2 (G, I), and PL12 (J, L) were cultured on eSight plates for 20–24 h before primary untreated, primary activated, and sNK cells were added at 2.5:1 E:T ratio, and co-cultures were continued to 70–80 h. The graphs for normalized cell index were assessed by the eSight RTCA and RTCA pro software (A, D, G, J). Microscopic images of tumor and NK cell interactions, as shown in the figures, were captured by eSight after 24 h of incubation (scale: 0–200 µm) (C, F, I, L). sNK cells were generated as described in Fig. 1, on day 15 of sNK cell cultures, another set of NK cells was isolated from the same healthy individuals and were treated with IL-2 (5000 U/ml) and with a combination of IL-2 (5000 U/ml) and anti-CD16 mAb (3 µg/ml) for 18 h. Primary activated NK cells and sNK cells were used as effectors against OSCSCs (B), OSCCs (E), MP2 (H), and PL12 (K) to measure NK cell-mediated cytotoxicity using a standard 4-h ⁵¹Cr release assay against tumor cells. The lytic units (LU) 30/10⁶ cells were determined using the inverse number of NK cells required to lyse 30% of target cells × 100.