结肠癌细胞对吉非替尼的敏感性与Akt、MAPK表达的关系

Relationship between the sensitivity of human colon carcinoma cells to gefitinib and the expressions of Akt and MAPK

目的检测结肠癌细胞表皮生长因子受体(EGFR)下游信号蛋白与细胞对EGFR抑制剂吉非替尼敏感性的关系。方法采用免疫细胞化学染色法检测6种结肠癌细胞系(Lovo、HCT116、HT29、LS174T、SW480、SW620)中EGFR蛋白的表达;MTT法观察吉非替尼对细胞生长的抑制作用;Western blotting法检测EGFR的下游信号蛋白Akt、丝裂原活化蛋白激酶(MAPK)及其磷酸化蛋白的表达水平。结果EGFR蛋白在SW620细胞中无明显表达,而在其他5种细胞中均有表达,尤以Lovo细胞中表达最强。Lovo细胞对吉非替尼的敏感性最高,HT29和SW480敏感性居中,其他3种细胞的敏感性均较差。各细胞系在胎牛血清中和EGF刺激状态下的生长抑制率和IC50值无显著差异。Akt蛋白在各细胞系均有表达且无显著差异;磷酸化Akt(p-Akt)在Lovo和SW620细胞中表达最低(P<0.05),在LS174T细胞中表达最强(P<0.05)。MAPK蛋白在Lovo细胞中表达最低(P<0.05),在LS174T和SW480细胞中表达较强(P<0.05);磷酸化MAPK(p-MAPK)在LS174T细胞中表达最弱(P<0.05)。结论Akt、MAPK及其磷酸化蛋白的表达水平与结肠癌细胞对吉非替尼的敏感性不一致,提示结肠癌对吉非替尼的反应性不能完全由EGFR表达和活性决定,也与其下游信号蛋白Akt、MAPK无关。

Objective To investigate the relationship between the sensitivity of colon carcinoma cells to epidermal growth factor receptor （EGFR） inhibitor, gefitinib, and the downstream proteins of EGFR. Methods The expressions of EGFR proteins of 6 colon carcinoma cell lines （Lovo, HCT116, HT29, LS174T, SW480 and SW620） were determined with immunocytochemistry staining. The inhibitory effects of gefitinib on the growth of colon carcinoma cells were assessed by MTT, and the expression levels of Akt and MAPK as well as their phosphorylated forms （p-Akt and p-MAPK） were assessed by Western blotting. Results EGFR protein expressed in all the Lovo, HCT116, HT29, LS174T and SW480 cells, and the highest expression was found in Lovo cells, but not in SW620 cells. Lovo cells showed the highest, HT29 and SW480 cells showed moderate, sensitivity to gefitinib, while the others showed more or less resistance to gefitinib. No significant difference was found between the growth inhibition and IC50 values among the 6 cell lines despite of being treated with fetal bovine serum or EGF. Akt protein existed in all the cell lines without notable difference. Lovo and SW620 cells showed the least of p-Akt expression （P〈0. 05）, and LS174T showed the highest （P〈0. 05）; Lovo cells showed the least of MAPK expression （P〈0. 05）, while LS174T and SW480 cells showed the highest （P〈0.05）; and LS174T showed the least of p-MAPK expression （P〈 0.05）. Conclusion The basic expressions of Akt, MAPK, p-Akt and p-MAPK are not parallel with the responses of colon carcinoma cells to gefitinib, implying that the sensitivity of colon carcinoma cells to gefitinib is neither entirely dependent on the expression and activity of EGFR, nor on its downstream proteins, akt and MAPK.