吉非替尼对胃癌细胞株放射增敏的作用

背景与目的:表皮生长因子受体(epidermal growth factor receptor,EGFR)在绝大部分人类上皮肿瘤中都有表达,其表达高低与放疗抗拒有关.我们检测EGFR酪氨酸激酶抑制剂吉非替尼(gefitinib)对高表达胃癌细胞株放射增敏的作用,并初步探讨其机制.方法:Western blot法测定7株人胃癌细胞株(MKN45、SGC7901、SNU-1、N87、AGS、SNU-16、KATO-Ⅲ)中EGFR蛋白的表达,选取2株EGFR相对高表达的胃癌细胞用于后续实验.采用MTT法测定吉非替尼的半数抑制浓度(50%inhibition concentration,IC50),克隆形成实验计算细胞存活率,拟合生存曲线并计算放射生物学参数,流式细胞仪检测吉非替尼联合放疗的凋亡率及细胞周期分布.结果:选取7株胃癌细胞中EGFR表达最高的MKN45和SGC7901细胞,发现其存活率均随吉非替尼浓度或放射剂量的增加而明显下降(P＜0.05).MTT法检测吉非替尼对MKN45及SGC7901细胞的IC50分别为0.4mmol/L和0.8 mmol/L.MKN45细胞在0.1×IC50及0.2×IC50剂量下的增敏比(SER)分别为1.102和1.154,SGC7901则为1.092和1.176.吉非替尼或照射均可增加凋亡率,减少S期细胞比例及增加G2/M期细胞比例(P＜0.01).结论:吉非替尼序贯照射应用可提高EGFR高表达胃癌细胞的放射敏感性并阻碍细胞增殖、促进凋亡和干扰细胞周期分布.吉非替尼有望成为EGFR高表达胃癌的放射增敏剂.

Effect of gefitinib on radiosensitivity of gastric cancer cell lines

BACKGROUND & OBJECTIVE: Epidermal growth factor receptor (EGFR) is expressed in most human epithelial cancers and is involved in the development of cancer cell resistance to irradiation. We used gefitinib, a selective EGFR tyrosine kinase inhibitor (EGFR-TKI), to investigate its effects and mechanisms in enhancing the radiosensitivity of human gastric cancer cell lines in vitro. METHODS: The expression of EGFR protein in 7 human gastric cell lines (MKN45, SGC7901, SNU-1, N87, AGS, SNU-16, and KATO-III) was determined by Western blot, in which 2 cell lines with high expression of EGFR were selected for additional test. The inhibitory effect of gefitinib on cell proliferation was measured by MTT assay. Cell survival was determined by clonogenic assay, and then the radiosensitivity parameters were calculated. The effects of gefitinib in combination with radiation on cell apoptosis and cell cycle distribution were analyzed by flow cytometry. RESULTS: Of the 7 gastric cancer cell lines, the expression of EGFR in MKN45 and SGC7901 cells were the highest. The 50% inhibition concentrations (IC(50)) of gefitinib were 0.4 mmol/L for MKN45 cells and 0.8 mmol/L for SGC7901 cells. Cell survival was significantly decreased with the elevation of gefitinib concentration or radiation dose (P<0.05). When treated with 0.1x and 0.2 x IC(50) of gefitinib, the radiosensitization enhancement ratios (SER) of MKN45 cells were 1.102 and 1.154, and those of SGC7901 cells were 1.092 and 1.176, respectively. Either gefitinib or radiation induced cell apoptosis, reduced the percentage of cells at S phase and increased the percentage of cells at G(2)/M phase (P<0.01). CONCLUSIONS: Gefitinib followed by radiation could increase the radiosensitivity of MKN45 and SGC7901 cells with high expression of EGFR and inhibit cell proliferation, induce apoptosis, and alter cell phase distribution. Gefitinib could be a radiation sensitizer for gastric tumors with high expression of EGFR.