Nectin4 as a Promising Target for CAR-NK Cell Therapy in Breast Cancer Treatment

Background: Breast cancer continues to be a major global health burden, with a significant proportion of patients developing metastatic or treatment-resistant disease. Novel therapeutic strategies are urgently needed. Nectin cell adhesion molecule 4 (Nectin4), an adhesion molecule overexpressed in aggressive breast cancer subtypes, represents a promising target for immunotherapy due to its restricted expression in normal tissues. This study investigated the therapeutic potential of Nectin4-directed chimeric antigen receptor natural killer (CAR-NK) cell therapy against triple-negative breast cancer (TNBC) at the preclinical stage. Methods: Human natural killer (NK) cells obtained from peripheral blood from healthy donors were engineered to express an anti-Nectin4 chimeric antigen receptor (CAR) via lentiviral transduction, expanded ex vivo, and then used for functional studies. Cytotoxic activity was assessed in vitro against Nectin4-high-expressing breast cancer cells using luciferase-based killing assays at various effector-to-target ratios. In vivo efficacy was evaluated in NOD/SCID/IL2rγnull (NSG) mice bearing subcutaneous breast cancer tumors treated with CAR-NK cells, compared to untransduced NK cells and phosphate-buffered saline controls. Tumor growth was monitored using bioluminescence imaging and harvested tumors were subsequently analyzed for Nectin4 expression using immunohistochemistry. Results: CAR-NK cells potently and specifically lysed Nectin4-positive breast cancer cells in vitro, with up to 95% target cell lysis at an effector-to-target ratio of 5:1. In vivo, CAR-NK treatment reduced tumor burden and prolonged survival compared with controls. Immunohistochemical analysis revealed a marked reduction in Nectin4 expression within tumors from the CAR-NK-treated group, consistent with targeted tumor cell elimination. Conclusions: CAR-NK cells targeting Nectin4 demonstrated potent cytotoxic activity in vitro and effectively suppressed tumor growth in vivo, supporting the further evaluation of Nectin4 as a therapeutic target for CAR-NK-based immunotherapy in TNBC, particularly for aggressive subtypes with limited treatment options.