Study Of The Radiosensitization Of Esophageal Squamous Carcimoma Cell Lines By Docetaxel: Mechanisms Of Action

Objective:The aim of this study was to determine the works ofradiosensitizing of docetaxel in human esophageal squamous carcinomaECA109and TE-13cell lines and its mechanisms.Methods:1ECA109and TE-13cell lines were cultured in vitro. The effects ofdifferent doses of docetaxel(0,0.1,0.5,1,5,10,50,100nM)on theproliferation in ECA109and TE-13cell lines after24h,48h and72h weremeasured by MTT colorimetric method, then chose suitable doses.2The irradiated sensitivity of ECA109and TE-13cell lines with orwithout docetaxel were analysized with clonegentic assay.3Change of cell cycle and apoptosis index in ECA109and TE-13celllines with or without docetaxel were measured with flow cytometry at0h,12h,24h and48h after irradiated by4Gy.4The expression of p21, bax and bcl-2protein in ECA109with docetaxelwere checked by western blotting at24h after irradiated by4Gy.Results:1MTT colorimetric method showed that docetaxel could inhibit theproliferation in ECA109and TE-13cell lines.The OD values of docetaxelgroups were clearly decreased after treated with docetaxel for48h and72h,and there were statistically differences between control group and eachtreatment group(P<0.05); Moreover, we found docetaxel significantlyinhibited the proliferation in ECA109and TE-13cell lines with adose-dependent and time-dependent manner. According to the inhibitioncurves, we chose0.5nM and1nM in ECA109and TE-13cell lines forradiosensitization.2The cloning formation results of ECA109and TE-13showed the D0 value were3.00Gy and2.41Gy and SF2were0.95and0.93; the D0valuewere2.54Gy and2.31Gy and SF₂were0.88and0.90in ECA109withdocetaxel(0.5nM) and TE-13with docetaxel(1nM).3The percent of G₀/G₁were significantly decreased and G₂/M weresignificantly increased(P<0.05) in ECA109and TE-13cell lines treatedgroups.The distribution of cell cycle was taken place earlier in docetaxelgroup than radiation group, and the percent of G₀/G₁was the lowest after12hours by doctaxel, then recovred to normal after48hours. Moreover, at12h,24h,48h the lowest percent of G₀/G₁and the highest percent of G₂/M were indocetaxel with radiation group(P<0.05). There were not influenced onapoptosis after irradiated by4Gy at different time in ECA109and TE-13celllines(P>0.05). Apoptosis index were increased significantly in docetaxelgroup and docetaxel with radiation group(P<0.05),and in the later group theapoptosis index was the highest.4The expression of p21and bax protein in ECA109cell line weresignificantly increased (P<0.05) in each treated group compared with contorlgroup, and the expression of p21and bax protein were statistically higher indocetaxel with radiation group than the docetaxel group and the radiationgroup(P<0.05). The expression of bcl-2protein in ECA109cell line wassignificantly decreased (P<0.05) in each treated group compared with contorlgroup, and there was no statistical difference between each treated group.Theratio of bcl-2/bax,which reflect the radionsensitivity of cell lines wasstatistically higher in docetaxel with radiation group than the others(P<0.05).Conclusions:1Docetaxel could inhibit the proliferation in ECA109and TE-13celllines with a dose-dependent and time-dependent manner.2Docetaxel showed the radiosensitizing effect in ECA109and TE13cell lines.3The mechanism of radiosensitization by docetaxel probably does notinvolve modulating cell cycle and increasing apoptosis index, but also p21andbax protein were up-regulated and the ratio of bcl-2/bax was down-regulated may play a key role in this effect.