Fig. 5: IL-6 secreted by KYSE-150R cells decreases the sensitivity of KYSE-150 cells to radiotherapy.

A IL-6 protein levels in let-7a mimic-transfected human esophageal squamous cancer cell lines (KYSE-150R, COLO680N, TE15, OE21, KYSE30, and KYSE-150) were determined using western blotting. B ELISA-based quantification of IL-6 protein levels in the cell culture medium of different esophageal squamous cancer cell lines. C, D KYSE-150 cells were incubated in either basal medium or KYSE-150R-conditioned medium (culture medium collected from KYSE-150R cells) along with either an anti-IL-6 or IgG control antibody (10 ng/mL) and exposed to different doses of radiation. Cell survival was determined using clonogenic assays (C), and DNA breaks were measured using comet assays (D). E, F KYSE-150 cells were co-cultured with KYSE-150R cells in the presence of either the anti-IL-6 or IgG control (10 ng/mL) antibody and exposed to different doses of radiation. KYSE-150 cell survival was determined using clonogenic assays (E), and DNA breaks were measured using comet assays (F). Data (B-F) are expressed as the mean ± SD of the values from three independent experiments. *P < 0.05, **P < 0.01 (two-sided Student’s t test). G–I KYSE-150/KYSE-150 model mice were intravenously co-injected with either KYSE-150R serum (serum from mice bearing KYSE-150R xenografts) or KYSE-150 serum (serum from mice bearing KYSE-150 xenografts) and either the anti-IL-6 or IgG control antibody, as indicated, and exposed to 10 Gy of radiation. Xenograft tumors were photographed (G), the average volume was determined (H), and the volumes of irradiated xenografts relative to those of unirradiated xenografts were calculated (I). Data (H, I) are expressed as the mean ± SD of the values obtained from five xenografts. *P < 0.05, **P < 0.01 (two-sided Student’s t test).