A near-infrared dye DiD (1,1-dioctadecyl-3,3,3,3-tetramethylindodicarbocyanine) was used to label NK-92 cells and NK-92-scFv(MOC31)-zeta cells functionalized to target the epithelial cell adhesion molecule (EpCAM) antigen on prostate cancer cells. Here, EPCAM is linked to prostate cancer.