CD56dim/CD56bright NK cell subpopulations and CD16/CD57 expression correlated with tumor development stages

BACKGROUND: NK cells are characterized by cytotoxic activity against tumor cells and CD3-CD16+CD56+ phenotype. Two distinct subpopulations of NK cells were characterized in the peripheral blood: NK-CD56dim representing over 95% of NK cells and involved in antitumor cytotoxicity, and NK-CD56bright representing approximately 10% of NK cells and involved in secretion of cytokines.AIM: The aim of the study was to compare the presence of NK-CD56dim/NK-CD56bright subpopulations and their CD16/CD57 expression in peripheral blood NK cells during the particular development stages of malignancy: primary tumor (PT), lymph node invasion (LNI) and distant sites metastases (Mt). MATERIAL AND METHODS: We have analyzed by flow-cytometry peripheral blood samples from total 36 cancer patients: 24 patients with PT, 6 patients with LNI and 6 patients with Mt.RESULTS: The presence of the overall NK cells showed no significant variation between patients in different stages of tumor development. The phenotype analysis showed that CD16+ and/or CD57+ cells were lower in LNI patients compared to PT or Mt patients. Double-positive CD16+CD57+ cells were found decreased in patients with Mt, compared to patients with PT. During the stages of tumor development, NK-CD56bright subpopulation increased progressively (7% in PT patients, 13% in LNI patients, 65% in Mt patients), whereas NK-CD56dim subpopulation gradually decreased (92%, 86%, and 35% respectively). CD16/CD57 expression decreased in NK-CD56dim and increased in NK-CD56bright cells over the three studied stages.CONCLUSION: Our results show changes in NK cells characteristics during tumor development: reversal of NK-CD56dim/NK-CD56brightdistribution and modification of CD16/CD57 expression. Both types of changes can concur in reducing the efficiency of NK cell activity in patients with progressive tumors.