Radiosensitizing Effect Of Gefitinib And Pemetrexed To Irradiation In The Non-small-cell Lungcancer Cell Line PC9

Objective Gefitinib (Gefitinib, Iressa), pemetrexed (pemetrexed) plays an important role in the treatment of lung adenocarcinoma. The research program of this vitro experiments is to compare the growth inhibition and induction of apoptosis of gefitinib and pemetrexed in lung adenocarcinoma cell line PC9 of EGFR 19 mutation in exon, And compare the two radiosensitizing effect when combined with radiotherapy, provide certain experimental basis for the treatment of the locally advanced lung cancer with EGFR 19 exon mutation.Method MTT assays were performed to measure the cytotoxicity effects of gefitinib and pemetrexed. caculating the IC20 Clonogenic survival assays were performed following standard methods in duplicate wells using six-well plates divided into 6 groups: control, radiation, gefitinib, pemetrexed, gefitinib combine irradiation, pemetrexed combine irradiation, they were treated with a single dose of 0 (control), 2, 4, 6, or 8 Gy. The survival curve and sensitizing enhancement ratio (SER) were caculated from the single-hit multi-target model formula: y=1-(1-exp(-k*x))^N. Alteration in apoptosis and cell cycle were measured to after gefitinib and pemetrexed combined treatment with radiation using flow cytometry. Western blots for CDC20 protein (the cell division cycle 20 homolog) were conducted after treatment with gefitinib or pemetrexed with or without radiation.Results1.Gefitinib and pemetrexed showed cell profiferation inhibition effect to PC9 cell line in a time-dose-dependent manner.The IC20 of gefitinib and pemetrexed was respectively 0.014?mol/L and 0.084?mol/L.2. The Dq? Do?SF2 of (P+R) group and (G+R) group were lower than those in R group.The SER (sensitization enhancement ratio) of (G+R) group was 1.1,the SER of (P+R) group was 1.4.The radiation-enhancing effects of pemetrexed was better than gefitinib.3.Gefitinib, pemetrexed and radiotherapy could enhance apoptosis rate,when drugs combine with radiotherapy, they enhanced radiation-inducedapoptosis. The apotosis was higher in (P+R) group than other groups. Cell cycleshowed that gefitinib could induce G1/G0 phase arrest, and pemetrexed induce S phase arrest, and the G2/M phase arrest and S phase reduced when combined treatment with radiation, especially in the (P+R) group. (P<0.05 ).4. The expression of CDC20 protein were higher after treated with drugs combine radiotherapy, especially in (P+R) group, but it had no difference in C, P,and R groups.Conclusions Both gefitinib, pemetrexed were radiosensitizers for PC9 radiotherapy, and pemetrexed was effective than gefitinib. And it indicated that the radiosensitizing effects of both drugs could be related to CDC20 induced G2/M phase increasd.