Fractionated irradiation induced radio-resistant esophageal cancer EC109 cells seem to be more sensitive to chemotherapeutic drugs

Background: Chemo-radiotherapy, a combination of chemotherapy and radiotherapy, is the most frequent treatment for patients with esophageal cancer. In the process of radiotherapy, the radiosensitive cancer will become a radio-resistant one. Methods: In order to detect the chemotherapeutic drug sensitivity in radio-resistant cancer cells and improve the therapy efficiency, we firstly established a radio-resistant esophageal cancer cell model (referred to as EC109/R) from the human esophageal squamous cell carcinoma cell line EC109 through fractionated irradiation using X-rays. The radio-sensitivity of EC109/R cells was measured by clonogenic assay. To detect the drug sensitivity for EC109/R compared to its parent cells, we employed MTT method to screen the effectiveness of five different drugs commonly used in clinical therapy. The ratio of apoptosis was examined by flow cytometry. Results: EC109/R cells were more sensitive to 5-fluorouracil, doxorubicin, paclitaxel and etoposide, but tolerant to cisplatin compared to its original cells. Conclusion: Our study implies that fractionated irradiation induced radio-resistant esophageal cancer cell is more sensitive to certain kind of chemotherapeutic drugs. It provides evidence for choosing the sequence of radiotherapy and chemotherapy in esophageal cancer.