Surface Engineering of NK Cells with Poly-L-Glutamic Acid Enhances Tumor-Selective Immunotherapy Against Ovarian Cancer.

Natural killer (NK) cells are promising effectors for cancer immunotherapy, as they can recognize and eliminate tumor cells without prior antigen sensitization. However, insufficient tumor recognition remains a critical limitation that reduces the anticancer efficacy of NK cells against solid tumors. To address this limitation, we developed a lipid-mediated cell membrane engineering strategy to enhance the targeting and cytotoxic efficacy of NK cells toward solid tumors, particularly ovarian cancer cells. In this strategy, poly-L-glutamic acid (PLE) was employed as an ovarian cancer-targeting module due to the specific affinity of PLE for cholesterol-rich membrane domains. To display PLE on NK cells, a lipid moiety is incorporated to anchor PLE onto the NK cell membrane via hydrophobic insertion, enabling rapid and non-genetic surface modification. As a result, the surface-engineered NK cells with PLE-Lipid (i.e., PLE-NK) displayed PLE on the NK cell surface, allowing direct recognition of ovarian cancer cells without compromising the intrinsic properties of NK cells. This enhanced recognition subsequently increased NK-cancer cluster formation by promoting interactions between membrane-presented PLE on NK cells and cholesterol on ovarian cancer cells. Consequently, PLE-NK cells exhibited enhanced cytotoxicity against ovarian cancer cells (i.e., OVCAR-3 cells) and effectively disrupted 3D tumoroids, while PLE-NK cells showed no off-target effects on normal fibroblasts. Collectively, these findings demonstrate that PLE-Lipid-mediated NK surface engineering provides a simple and effective strategy to improve the tumor targeting ability of NK cells and offers a promising platform for NK cell-based immunotherapy against ovarian cancer.