Objective The aim of the study was to investigate whether colon cancer stem cells induced by epidermalgrowth factor （EGF）to enter the cell cycle enhan.ced the chemosensitivity of colon cancer.Methods . In vitro, EGF was used to stimulate the entry of human colon cancer HCT116 cells into the cellcycle. Before and after treatment with EGF, CD133＋ HCT116 cells were collected and flow cytometry wasconducted to determine the apoptosis rate based on the 5-Fu and Ki-67 expression rates. The cell cycledistribution of the two groups was also determined. In vivo, a subcutaneous xenograft model of HCT116human colon cancer cell lines in nude mice was established. The nude mice were divided into two groupsand treated with EGF and 5-Fu, respectively. Differences in the growth of implanted tumors revealed theefficiency of cycle-induction combined chemotherapy.Results （1） After EGF stimulation, the S-G2/M proportion of CD133＋ HCT116 cells and Ki67 expressionWere increased, indicating that more cancer stem cells entered the cell cycle and promoted proliferation; （2）After EGF stimulation, CD133＋ HCT116 cells showed a higher apoptosis rate induced by 5-Fu. （3） Animalexperiments showed that the group subjected to combined treatment with EGF and 5-Fu had smaller tumorsizes compared to the group treated with 5-Fu alone.Conclusion EGF enhanced tumor sensitivity to chemotherapeutic drugs, likely by promoting tumor stemcells to enter the cell cycle.
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