Modulating cell-cell communication with a high-throughput label-free cell assay

A high-throughput label-free cell assay for modulating cell-cell communication is demonstrated with the Epic® system, a resonant waveguide grating sensor platform. Natural killer (NK) cells are known to be able to recognize abnormal cells (e.g., cancer cells and cells presenting intercellular adhesion molecule 1 [ICAM1] through cell surface receptors) and kill them. In this study, the effect of effecter cells NK92MI on two kinds of target cells, cervical cancer cells (HeLa) and Chinese hamster ovarian cells overexpressing ICAM1 (CHO-ICAM1), was examined. Living target cells' response to NK92MI cells was monitored in real time and measured as wavelength shift in picometers. The authors showed that the detectability of target cell response is affected by multiple factors: the ratio of effecter cells to target cells (E/T), the interaction time of the two types of cells, and the target cell type. For example, with the effecter cells NK92MI and the same incubation time of 16 h, a minimal E/T ratio of 1 is required to detect HeLa cell response, whereas an E/T of 0.5 is sufficient to detect CHO-ICAM1 cell response. The authors confirmed that NK92MI cell-mediated target cell cytotoxicity results in negative optical signals and is associated with apoptosis mainly through caspase pathways. Distinct optical signals could be generated with the pretreatment of the target cells with various known pharmaceutical reagents, making the assay useful for discovering new chemicals that may affect cell-cell communications.