Fig. 1: Cell–cell communication between radiosensitive and radioresistant esophageal cancer cells.

A Survival analysis of KYSE-150R, COLO680N, TE15, KYSE30, OE21, and KYSE-150 cells based on clonogenic assays after 4 Gy of irradiation. B DNA breaks in different esophageal squamous cancer cell lines were measured using comet assays 1 h after 4 Gy of irradiation. C The radiosensitive KYSE-150 cells alone, the radioresistant KYSE-150R cells alone, the KYSE-150 cells co-cultured with KYSE-150R cells for 48 h, and the KYSE-150R cells co-cultured with KYSE-150 cells for 48 h were exposed to different doses of radiation. Subsequent cell survival was determined using clonogenic assays. Data (A-C) are expressed as the mean ± SD of the values from three independent experiments. D Schematic displaying the establishment of the radioresistant (KYSE-150R/KYSE-150R) tumor xenograft mouse model (left), the radioresistant/radiosensitive (KYSE-150R/KYSE-150) xenograft mouse model (middle), and the radiosensitive (KYSE-150/KYSE-150) xenograft mouse model (right). E KYSE-150 xenografts on the right flank of the KYSE-150/KYSE-150 mouse model and the KYSE-150R/KYSE-150 mouse model were either exposed to 10 Gy of irradiation or left unirradiated. Xenograft tumors were photographed (left), the average volume was determined (middle), and the volumes of irradiated xenografts relative to those of unirradiated xenografts were calculated (right). F KYSE-150R xenografts on the left flank of the KYSE-150R/KYSE-150R mouse model and the KYSE-150R/KYSE-150 mouse model were either exposed to 10 Gy of radiation or left unirradiated. Xenograft tumors were photographed (left), the average volume was determined (middle), and the volumes of irradiated xenografts relative to those of unirradiated xenografts were calculated (right). Data (E and F) are expressed as the mean ± SD of the values obtained from five xenografts. **P < 0.01, *P < 0.05 (two-sided Student’s t test).