Fig. 3

NK cell-derived supernatant (SN) promotes the differentiation of cancer stem-like cells and increases their sensitivity to cisplatin. a Representative flow cytometry analysis of ALDH enzymatic activity in spheres after 4 h with NK-derived SN. The ALDH inhibitor DEAB was used as a negative control to establish the baseline fluorescence of the cells. Bar graph shows the percentage of ALDH⁺ cells (mean ± SEM, n = 3). b Fold-change mRNA expression levels of stemness-related markers in spheres treated with NK-SN relative to untreated spheres set as 1 (mean ± SEM, n = 5). c Cytotoxic effects of cisplatin in spheres cultured in DMEM/F12 (black bars) and upon culture with NK-SN (gray bars) for 4 h determined by the MTT assay. The percentage of viable cells was normalized respective to untreated cells (mean ± SEM, n = 3). d Representative histograms illustrating the expression of specific ligands on the surface of spheres cultured in DMEM/F12 medium (gray histograms) or previously incubated with NK-SN for 4 h (black histograms). *P < 0.05, **P < 0.01, and ***P < 0.001 represents spheres in NK-SN vs. spheres in regular DMEM/F12