Objective To observe the effect of somatostatin-14 peptide (SST-14) combined with 5-fluorouracil (5-FU) by intraperitoneal injection on human gastric cancer BGC-823 xenografts in nude mice and to explore its mechanism. Methods We constructed 28 human gastric cancer cell line BGC-823 transplantation tumor models of nude mice, and randomly divided them into the control group, 5-Fu group, SST group and the combination group with 7 mice in each group. The combination group was treated with SST-14 and 5-FU, in which SST-14 was injected intraperitoneally 1 mg/kg for four days a week, stopped for three days; 5-FU was injected intraperitoneally 20 mg/kg one time per week. SST group was injected intraperitoneally with SST-14 (1 mg/kg) for four days a week, stopped for three days. 5-FU group was injected intraperitoneally with 5-FU (20 mg/kg) one time per week. The control group was given the same volume of sterile saline. Each group was treated for 21 d. The nude mice were killed by cervical dislocation at 24 h after the last medication. The tumor tissue was stripped completely.The tumor volume was measured and the tumor inhibition rate was calculated. TUNEL method was used to detect the apoptosis rate in the tumor tissues. The expression of Bcl-2 and Bax in tumor tissues was detected by immunohistochemical SP method, and pERK and ERK was detected by Western blotting. Results The tumor volume of 5-FU group, SST group and the combination group was less than that of the control group after treatment, and the tumor volume of the combination group was less than that of 5-FU group and SST group (all P<0.05). The inhibition rate of tumor volume was 26.243％ in the 5-Fu group, 25.447％ in the SST group, and 44.433％ in the combination group. The apoptosis rate in the 5-FU group, SST group and the combination group was higher than that of the control group, and the apoptosis rate in the combination group was higher than that in the 5-FU group and SST group (all P<0.05). Compared with the control group, Bcl-2 protein expression and Bcl-2/Bax in transplanted tumor tissues decreased, Bax protein expression increased in the 5-FU group, SST group and the combination group (all P<0.05). Compared with 5-FU group and SST group, the relative expression level of Bcl-2 protein and Bcl-2/Bax decreased, but the relative expression level of Bax protein increased in the combination group (all P<0.05). The expression of pERK protein of the SST group and the combination group was lower than that of the control group (P<0.05). Conclusions SST-14 combined with 5-FU by intraperitoneal injection can inhibit the growth of human gastric cancer BGC-823 xenografts in nude mice, promote apoptosis of gastric cancer cells, and the effect is better than that of SST-14 or 5-FU alone. The mechanism may be related to the down-regulation of pERK expression in gastric cancer cells by SST-14.%目的 观察生长抑素14肽(SST-14)联合5-氟尿嘧啶(5-FU)腹腔注射治疗人胃癌细胞BGC-823裸鼠移植瘤的效果,并探讨其作用机制.方法 构建人胃癌细胞BGC-823裸鼠移植瘤模型28只,随机分为对照组、5-FU组、SST组、联合组各7只.联合组联合应用SST-14和5-FU,其中SST-14 1 mg/kg腹腔注射,用4 d、停3 d;5-FU 20 mg/kg腹腔注射,1次/周.SST组以SST-14 1 mg/kg腹腔注射,用4 d、停3 d.5-FU组用5-FU 20 mg/kg腹腔注射,1次/周.对照组给予同体积无菌生理盐水.各组连续用药21 d.末次用药24 h后经颈椎脱臼处死荷瘤裸鼠,完整剥离肿瘤组织,测量瘤体积,计算抑瘤率.TUNEL法测算移植瘤组织内细胞凋亡率.采用免疫组化SP法检测移植瘤组织中的Bcl-2、Bax蛋白;采用Western blotting法检测移植瘤组织中的pERK、ERK.结果 5-FU组、SST组、联合组治疗后瘤体体积小于对照组,联合组瘤体体积小于5-FU组、SST组(P均<0.05);5-FU组、SST组、联合组抑瘤率分别为26.24％、25.45％、44.43％.5-FU组、SST组、联合组肿瘤组织内细胞凋亡率高于对照组,且联合组高于5-FU组、SST组(P均<0.05).与对照组相比,5-FU组、SST组、联合组移植瘤组织中Bcl-2蛋白相对表达量、Bcl-2/Bax降低,Bax蛋白相对表达量增高(P均<0.05);与5-FU组、SST组相比,联合组Bcl-2蛋白相对表达量、Bcl-2/Bax降低,Bax蛋白相对表达量增高(P均<0.05).SST组、联合组移植瘤组织中pERK蛋白相对表达量低于对照组(P均<0.05).结论 SST-14联合5-FU腹腔注射可抑制BGC-823裸鼠移植瘤增长、促进胃癌细胞凋亡,效果优于SST-14或5-FU单独用药,其机制可能与SST-14下调胃癌细胞中pERK的表达有关.
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