The Radiation-sensitizing Effect Of Flavopiridol In Esophageal Cancer Cell Lines Eca109and Its Mechanism

Flavopiridol is a small molecule cyclin-dependent protein kinases （CDKs）inhibitors. The chemical structure of Flavonoids, originally came from an Indian plant,is the first clinical trials confirmed CDKs inhibitors on a variety of tumors. There is asignificantly possible anti-tumor mechanism of inhibition of CDKs activity, especiallyin cdk-1,2,4. Because of this it can make cell cycle arrest. We conjecture that thismechanism will play a role in Eca109radiozensitivity. By previous experimentaldetermination of Flavopiridol on Eca109cell line IC₅₀193.3nmol/L, and prove that theEca109cell lines with radiation to read sensitive role,38.66nmol/L(that is1/5IC₅₀) theFlavopiridol the SER （radiation to read sensitive ratio） of1.194. But the molecularmechanisms of radiationsensitization in esophageal Eca109cell lines is still unclear.The study found that cyclinD1proteins in the people a variety of tumor cells haveabnormal expression. In this study, by the combined effect of flavopiridol and radiationin the Eca109cell lines, and the Eca109cell cycle changes of esophageal cancer beforeand after the experiment, as well as cyclinD1protein expression level, to analyse thesensitivity radiation mechanism of flavopiridol with Eca109cells of esophagealcancer,which provide the basis of the therapy of esophageal cancer in clinicalapplication.Purpose: To investigate the radiosensitizing effect of flavopiridol on Eca109cellline and its mechanism.Methods: Assayed the growth inhibitory rate of flavopiridol by MTT assay and theradiosensitizing rate by clonogenic survival.Using flow cytometry observed cycledistribution and the rate of apoptosis.Tested proteins cyclinD1, ERK/pERK, caspase-3,Bax and Bcl-2in western blotting to analyze the mechanism of the radiosensitizingeffect. Result:1. MTT assay showed flavopiridol could inhibit the survival rate ofEca109and the effect was dose dependent. Its IC₅₀was193.3nmol/L.2. Flavopiridol enhanced the radiosensitivity of Eca109and sensitizationenhancement ratio（SER） were1.194at0.2×IC₅₀.3. The cells treated with flavorpiridol were G₂/M arrest and the apoptosis causedby radiation was increasing in them.4. The proteins caspase-3and Bax in cells treated with flavopiridol were increasingwhile cyclinD1and Bcl-2were decreasing.Conclusion:1. Flavopiridol can enhance the radiosensitivity of Eca109.It canincrease the cell apoptosis induced by radiation.2. The radiosensitizing effect of flavopiridol may be brought about by decreasingthe level of proein cyclinD1thus increasing the percentage of G₂/M phage.