title: Radiobiological characteristics of cancer stem cells from esophageal cancer cell lines.
abstract: OBJECTIVE
  To study the cancer stem cell population in esophageal cancer cell lines KYSE-150 and TE-1 and identify whether the resulting stem-like spheroid cells display cancer stem cells and radiation resistance characteristics.
  
  
  METHODS
  A serum-free medium (SFM) suspension was used to culture esophageal cancer stem cell lines and enrich the esophageal stem-like spheres. A reverse transcription polymerase chain reaction assay was used to detect stem cell gene expression in the spheroid cells. Radiosensitivity of stem-like spheres and parental cells were evaluated by clonogenic assays. Furthermore, different cells after different doses of irradiation were tested to evaluate the change in sphere formation, cell cycle and CD44(+)CD271(+) expression of tumor stem-like spheroid cells using flow cytometry before and after irradiation.
  
  
  RESULTS
  The cells were observed to generate an increased number of spheres in SFM with increasing cell passage. Radiation increased the rate of generation of stem-like spheres in both types of cells. The average survival fraction (SF2) of the cultured KYSE-150 compared with TE-1 stem-like spheres after 2 Gy of radiation was 0.81 ± 0.03 vs 0.87 ± 0.01 (P < 0.05), while the average SF2 of KYSE-150 compared with TE-1 parental cells was 0.69 ± 0.04 vs 0.80 ± 0.03, P < 0.05. In the esophageal parental cells, irradiation dose-dependently induced G2 arrest. Stem-like esophageal spheres were resistant to irradiation-induced G2 arrest without significant changes in the percentage population of irradiated stem-like cells. Under irradiation at 0, 4, and 8 Gy, the CD44(+)CD271(+) cell percentage for KYSE150 parental cells was 1.08% ± 0.03% vs 1.29% ± 0.07% vs 1.11% ± 0.09%, respectively; the CD44(+)CD271(+) cell percentage for TE1 parental cells was 1.16% ± 0.11% vs 0.97% ± 0.08% vs 1.45% ± 0.35%, respectively. The differences were not statistically significant. Under irradiation at 0, 4, and 8 Gy, the CD44(+)CD271(+) cell percentage for KYSE-150 stem-like spheres was 35.83% ± 1.23% vs 44.9% ± 1.67% vs 57.77% ± 1.88%, respectively; the CD44(+)CD271(+) cell percentage for TE1 stem-like spheres was 16.07% ± 0.91% vs 22.67% ± 1.12%, 16.07% ± 0.91% vs 33.27% ± 1.07%, respectively. The 4 and 8 Gy irradiated KYSE-150 and TE-1 stem-like spheres were compared with the 0 Gy irradiated group, and the differences were statistically significant (P < 0.05).
  
  
  CONCLUSIONS
  The KYSE-150 and TE-1 stem-like spheres are more radioresistant than their parental cells which may suggest that cancer stem cells are related to radioresistance.
authors.affiliation: Jian-Lin Wang, Jing-Ping Yu, Zhi-Qiang Sun, Su-Ping Sun, Department of Radiation Oncology, Changzhou Second People's Hospital Affiliated to Nanjing Medical University, Changzhou 213003, Jiangsu Province, China.
authors.forename: Jian-Lin
authors.initials: JL
authors.lastname: Wang
authors.affiliation: Jian-Lin Wang, Jing-Ping Yu, Zhi-Qiang Sun, Su-Ping Sun, Department of Radiation Oncology, Changzhou Second People's Hospital Affiliated to Nanjing Medical University, Changzhou 213003, Jiangsu Province, China.
authors.forename: Jing-Ping
authors.initials: JP
authors.lastname: Yu
authors.affiliation: Jian-Lin Wang, Jing-Ping Yu, Zhi-Qiang Sun, Su-Ping Sun, Department of Radiation Oncology, Changzhou Second People's Hospital Affiliated to Nanjing Medical University, Changzhou 213003, Jiangsu Province, China.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Sun
authors.affiliation: Jian-Lin Wang, Jing-Ping Yu, Zhi-Qiang Sun, Su-Ping Sun, Department of Radiation Oncology, Changzhou Second People's Hospital Affiliated to Nanjing Medical University, Changzhou 213003, Jiangsu Province, China.
authors.forename: Su-Ping
authors.initials: SP
authors.lastname: Sun
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints / Q000528:radiation effects; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D006801:Humans; D014411:Neoplastic Stem Cells / Q000473:pathology / Q000528:radiation effects*; D011836:Radiation Tolerance; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018874:Spheroids, Cellular; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor
keywords: Cell cycle; Cell spheres; Esophageal neoplasms; Neoplastic stem cell; Radiation resistance