Cytotoxic Tissue-Resident NK Cells Show Potent Antitumor Activity in Solid Tumors : Science Translational Medicine | May 2026
Introduction
Natural killer (NK) cell–based immunotherapy has emerged as a promising strategy in cancer treatment because of its ability to mediate tumor killing without prior antigen sensitization. However, clinical efficacy in solid tumors has remained limited, largely due to poor tumor infiltration, immune suppression within the tumor microenvironment and uncertainty regarding the most therapeutically effective NK-cell subsets.
Problem Statement
Conventional ex vivo expanded NK cells often fail to adequately infiltrate and persist within solid epithelial tumors, reducing their therapeutic effectiveness. At the same time, tissue-resident NK (trNK) cells represent a biologically diverse population, with some subsets demonstrating immunosuppressive properties while others appear highly cytotoxic. Identifying and selectively expanding the most effective antitumor trNK population remains a major challenge in adoptive NK-cell therapy.
Summary
This translational study identifies a distinct population of highly cytotoxic tissue-resident NK cells characterized by coexpression of CD39, CD49a and CD103, termed cytotoxic trNK (ctrNK) cells, with potent activity against solid epithelial tumors. Using multiomic characterization, the investigators demonstrated that these ctrNK cells possess enhanced tumor-killing capacity, superior migration into tumor organoids and markedly improved control of solid tumors in vivo compared with conventionally activated peripheral NK cells. Importantly, the enhanced antitumor activity appeared linked not only to cytolytic function but also to improved tissue infiltration and retention within the tumor microenvironment, partly mediated through CD103-associated epithelial adhesion mechanisms. A particularly significant finding was that exposure to epithelial tumor cells during ex vivo expansion could drive differentiation toward this highly cytotoxic tissue-resident phenotype, creating a potentially scalable platform for adoptive immunotherapy. These findings directly address one of the major barriers in solid tumor immunotherapy—the inability of transferred immune cells to effectively penetrate and function within immunosuppressive tumor environments. The study positions ctrNK cells as a promising next-generation cellular therapy platform for solid malignancies and provides an important biologic framework for refining NK-cell engineering and expansion strategies in cancer immunotherapy.
