Tecomin enhances natural killer cell effector activity with associated changes in cytolytic molecules and intracellular signaling pathways

Natural killer (NK) cells are critical effectors of innate antitumor immunity; however, their therapeutic potential is limited by insufficient expansion, functional exhaustion, and variable cytotoxic activity. Plant-derived small molecules have emerged as attractive immunomodulators capable of enhancing NK-cell function. In this study, we employed the human NK leukemia cell line KHYG-1 and the cancer cell lines K562, NPC-039, and FaDu to investigate whether tecomin enhances NK cells' antitumor activity. Tecomin did not reduce KHYG-1 cells' viability but significantly increased KHYG-1-mediated cytolysis of K562 cells. Tecomin also increased interferon-gamma secretion and increased the expression of granzyme A, granzyme B, and granulysin. Tecomin treatment was associated with increased phosphorylation or expression of STAT4, STAT1, STAT3, ERK, JNK, PI3K/AKT/mTOR, Ras/Raf/MEK, IL-9R/JAK1/JAK3, NK receptor-related signaling molecules, and increased histone H3 acetylation. Under Transwell coculture conditions, target cancer cells exposed to tecomin-treated KHYG-1 cells exhibited mitochondrial membrane depolarization, annexin V/PI-positive apoptosis, increased Bim and Bak expression, caspase-3, caspase-9, and PARP cleavage, and reduced expression of the DNA repair-associated proteins SET, HMGB2, and Ape1, indicating soluble factor-mediated apoptosis-associated effects. Pharmacological inhibition of ERK or JNK partially reduced tecomin-induced granzyme B expression, supporting the involvement of MAPK signaling in this response. Similar immune-enhancing effects were discovered in NK cells isolated from adult donors with head and neck squamous cell carcinoma. Together, these findings indicate that tecomin enhances NK-cell effector functions under in vitro and ex vivo experimental conditions, accompanied by increased cytolytic effector expression, cytokine secretion, NK receptor expression, and associated intracellular signaling changes.