Fig. 1

HDAC4 is highly expressed in radioresistant EC tissues and cells. A HDAC4 mRNA level in radioresistant (n = 46) and radiosensitive ESCC (n = 36) tissues was determined using RT-qPCR, normalized to GAPDH. B HDAC4 expression in radioresistant (n = 46) and radiosensitive ESCC (n = 36) tissues was determined using immunohistochemistry. C HDAC4 protein level in radioresistant (n = 46) and radiosensitive ESCC (n = 36) tissues was determined using Western blot analysis, normalized to GAPDH. D The Kaplan–Meier curve was used to plot the OS of patients according to median value of HDAC4 mRNA expression (> 1.218, high HDAC4 expression; < 1.218, low HDAC4 expression); low censored indicates missing data points of patients with low HDAC4 expression due to personal factors, while high censored indicates missing data points of patients with high HDAC4 expression due to personal factors. E HDAC4 mRNA level in normal esophageal epithelial cell line and EC cell lines was determined using RT-qPCR, normalized to GAPDH. F The survival of radioresistant KYSE30 cells and parental cells under X-ray irradiation of 2, 4, 6, and 8 Gy was detected by colony formation assay. G Colony-formation ability of radioresistant KYSE30 (KYSE30R) cells and parental cells under 0 or 8 Gy X-ray irradiation was detected by colony formation assay and statics of colonies. H HDAC4 expression in radioresistant KYSE30 (KYSE30R) cells and parental cells was determined using Western blot analysis. Values obtained from three independent experiments in triplicate are expressed as mean ± standard deviation and analyzed by Mann–Whitney t test. Values between two groups were analyzed by unpaired t-test, values among three or more groups by one-way ANOVA followed by Tukey's post hoc test, and effects as a function of irradiation dose were analyzed by two-way ANOVA followed by Bonferroni post hoc test. * p < 0.05 compared with radiosensitive ESCC tissues, NE1, or KYSE30 cells. ^#p < 0.05 compared with KYSE140, KYSE150, and KYSE180 cells