NF-κB and ALDH1A1 levels in original ESCC cell lines and curcumin-surviving lines measured using ELISA. (A) ALDH1A1 expression levels varied between the six original ESCC lines. ALDH1A1 expression was significantly higher in KY-5 than in all other lines (asterisk). YES-2 had higher expression than the other four lines (filled square). (B) NF-κB levels also varied between the cell lines. KY-5 showed significantly higher NF-κB levels than the other four lines (asterisk). YES-2 also had higher NF-κB levels than the other three cell lines (filled square). YES-1 was higher than one line (filled circle). All significant differences were based on one-way ANOVA (F=152.71, p<0.0001 for ALDH1A1 and F=55.73, p<0.0001 for NF-κB). (C) ALDH1A1 and NF-κB levels in the original cell lines showed a strong correlation (R=0.903, linear regression, p=0.0134). (D) This relationship was absent in the surviving lines (R=−0.004, p=0.994). (E) All cell lines but one (TE-1) had lower ALDH1A1 levels in the surviving lines than in the original lines. This decline was not a function of ALDH1A1 levels in the original lines (R=−0.285, p=0.583). (F) In contrast, the change in NF-κB levels between original and surviving lines was inversely correlated with NF-κB levels in the original lines (R=−0.901, p=0.0139). The average optical density at 410 nm of three wells (±SD) is shown. Curcumin-surviving cell lines were derived from cells that survived 60 μM curcumin treatment, except YES-2S, which survived 40 but not 60 μM curcumin.