ALDH1A1 immunostaining of original ESCC cell lines and curcumin-surviving lines. The histograms summarize cell counts according to staining intensity as shown in Figure. 4. The maxima of the high-staining subpopulations in the original cell lines are shown by the asterisk. Curcumin-surviving cell lines, indicated with “S”, showed a significant loss of the high-staining subpopulation. The mean intensity of ALDH1A1 expression was significantly different among the original lines (F=307.047, p<0.0001). KY-5 staining was significantly higher than all other lines. YES-2 was significantly higher than YES-1, TE-8, TE-1, and KY-10. Also, TE-8 was significantly higher than YES-1, TE-1 and KY-10. The mean intensity of ALDH1A1 expression levels was also significantly different among the surviving lines (F=611.440, p<0.0001). KY-5S staining was significantly higher than all other surviving lines. YES-2S was significantly higher than TE-8S, KY-10S, TE-1S and YES-1S. TE-8S was higher than KY-10S, YES-1S and TE-1S. Also, KY-10S was significantly higher than YES-1S and TE-1S. The mean intensity of high-staining cells in the original cell lines was 477.80 ± 93.82, 243.77 ± 33.54, 222.23 ± 42.02, 199.70 ± 39.31, 180.88 ± 28.31, and 149.67 ± 16.29 for KY-5, YES-2, TE-8, KY-10, YES-1, and TE-1, respectively. The mean intensity of high-staining cells in the surviving cell lines was 496.93 ±108.38, 234.95 ±28.23, 206.67 ±26.77, and 145.55 ± 24.52 for KY-5S, YES-2S, KY-10S, and YES-1S.