Mouse and MDA-MB-231 Xenograft Model

Six- to nine-week-old immunodeficient NOD.Cg-Prkdc^scidIL2rg^tm1Wjl/SzJ (NSG) mice (Jackson Laboratory, Bar Harbor, ME, USA) were used in this study. The mice were maintained under sterile conditions in an animal lab at the Chonnam National University Hwasun Hospital (South Korea). All animals were fed with free alfalfa feed 72 h before optical imaging. The human breast cancer MDA-MB-231 xenograft models were made to investigate NK cell trafficking in vivo. The MDA-MB-231 cancer cells were harvested by centrifugation at 1,300 rpm and washed two times with phosphate buffered saline (PBS). The MDA-MB-231 cancer cells (1 × 10⁷ cells) were then mixed with Matrigel on ice at a ratio of 1:1. The mixture was then subcutaneously injected into the right-back leg of the NSG mice. All MDA-MB-231 tumor-bearing mice were maintained for at least 30 days before use in further experiments. The use of animals for this study was approved by the Institutional Animal Care and Use Committee of Chonnam National University.