奥曲肽致裸鼠肝癌原位移植瘤坏死的实验研究

Effects of octreotide on necrosis of hepatocellular carcinoma xenografts in nude mice

背景与目的:生长抑素类似物奥曲肽可抑制肝癌的生长,但能否使其坏死、获得更好的抗肿瘤效果呢?本研究旨在观察奥曲肽在体内、外对肝癌细胞株HepG2的作用,探讨其致肿瘤坏死的机制。方法:采用四甲基偶氮唑蓝法检测体外HepG2细胞的增殖,建立裸鼠肝癌HepG2细胞原位移植瘤模型,奥曲肽组裸鼠皮下注射奥曲肽100μg/(kg·d);对照组皮下注射相同体积的生理盐水,连续用药8周。组织学评估肿瘤坏死程度,免疫组化检测移植瘤中血管内皮生长因子(VEGF)的表达,Westernblot和免疫组化检测生长抑素受体2(SSTR2)的表达。结果:奥曲肽(0.1～1000nmol/L)作用24h,不影响HepG2细胞增殖。奥曲肽组裸鼠肝癌移植瘤重[(7.15±2.96)g]高于对照组[(4.21±3.11)g],移植瘤坏死体积[(81.86%±0.05)%]大于对照组[(43.75±0.06)%],两组相比差异均有统计学意义(P<0.05)。与对照组明显不同的是,奥曲肽组移植瘤中未见VEGF表达。两组移植瘤组织血窦中SSTR2表达无显著性差异(P>0.05)。结论:在肝癌细胞活跃增殖条件下,奥曲肽通过移植瘤血窦中SSTR2介导,仅仅抑制肿瘤血管生成,可致裸鼠肝癌显著坏死的良好效应。

Background and Objective. Octreotide, a kind of somatostatin analogue, may inhibit the growth of hepatocellular carcinoma （HCC）. This study was to investigate the mechanism of inducing necrosis of HCC xenografts in nude mice by octreotide. Methods. The proliferation of HepG2 cells was determined by MTT assay. Nude mice bearing HepG2 xenografts were treated with octreotide [100 μg ·（kg·d）^-1] or normal saline （as control） for eight weeks. The necrosis of HCC was estimated by histology. Vascular endothelial growth factor （VEGF） was detected by immunohistochemistry. Somatostatin receptor 2 （SSTR2） was quantified by Western blot and located with immunohistochemistry. Results： The proliferation of HepG2 cells was not obviously affected by 24-hour treatment of octreotide （0.1-1000 nmol/L） in vitro. The tumor weight was significantly heavier in octreotide group than in control group [（7.15±2.96） g vs. （4.21±3.11） g, P〈0.05], while the proportion of necrotic volume was significantly higher in octreotide group than in control group [ （81.86±0.05）% vs. （43.75±0.06）%, P〈0.05]. In contrast with control group, VEGF was undetected in the xenografts in octreotide group. SSTR2 expression in xenograft sinusoids was similar in both groups. Conclusion. With active proliferation of HCC cells, octreotide can induce necrosis in HCC xenografts only through the inhibition of angiogenesis mediated by SSTR2 in the tumor.