Cytotoxic Anticancer Drug Enhances Nk Cell-Mediated Cytotoxicity Via the Dna Stress Induced Nkg2D Ligands in Non-Small-Cell Lung Cancer Cells

Abstract

ABSTRACT Aim: The role of immune escape of tumor cells is poorly understood. We investigated anticancer drugs induced NK group 2 member D (NKG2D) ligand expression in NSCLC, since immunosurveillance is maintained by mainly NK cells via the NKG2D-NKG2D ligand interaction. Here we demonstrate cytotoxic regents enhance NKG2D ligand MHC class I-related chain A and B (MICA/B) and UL16 binding protein (ULBP), resulting in enhancement of NK cell-mediated cytotoxicity in NSCLC cells in vitro, while contrasting effects are seen in clinical samples from NSCLC patients who received induction chemotherapy. Methods: A possible influence of anticancer drugs (gemcitabine, pemetrexed, docetaxel and vinorelbine) on the expressions of NKG2D ligands MICA/B and ULBP1-3 in 5 NSCLC cell lines was investigated by flow cytometry. To access the influence of DNA stress-induced ATM-ATR signaling, A549 cells were pretreated with ATM-ATR inhibitor KU55399 or caffeine then treated with gemcitabine, then the expressions of NKG2D ligands were assessed. NK cell-mediated cytotoxicity against A549 cells treated with gemcitabine was assessed by LDH release assay or CD107a degranulation assay. Formaldehyde-fixed, paraffin-embedded NSCLC specimens before and after chemotherapy were collected from 3 patients, then both MICA/B and ULBP-2 expressions were analyzed by immunohistochemical reaction (IHC). Results: Both gemcitabine and docetaxel promoted NKG2D ligands in NSCLC cell lines. Gemcitabine-induced NKG2D ligands expression was blocked by ATM-ATR inhibitors, and, as expected, gemcitabine enhanced NKG2D ligands induced NK cell-mediated cytotoxicity, and anti-NKG2D blocking antibody attenuated gemcitabine-induced NK killing in A549 cells. On the other hand, IHC data showed the expression of MICA/B and ULBP2 were regressed upon gemcitabine treatment in tumors from NSCLC patients. Conclusions: Cytotoxic anticancer drugs induce NKG2D ligands in cancer cell lines, while regressing them in clinical samples, suggesting that the cells expressing low level of NKG2D ligands can escape from NK cells in a host. Keeping the expression of NKG2D ligands in tumor around chemotherapy may be a good strategy for NSCLC treatment. Disclosure: M. Nakata: The author have received research grant from AstraZeneca. All other authors have declared no conflicts of interest.