PPAR-β基因对人结肠癌细胞裸鼠成瘤的影响及机制研究

Effect of PPAR-β Gene on Human Colon Cancer Growth in Vivo and Molecular Mechanism

摘要: 目的：探讨过氧化物酶体增殖物激活受体-β (peroxisome proliferator-activated receptor-β, PPAR-β)对人结肠癌细胞裸鼠移植瘤生长的影响及机制。方法：分别将PPAR-β特异性沉默和野生型的人结肠癌细胞KM12C种植于裸鼠背部皮下，动态监测移植瘤体积，20天后取瘤体称重，免疫组化比较二者分化程度；荧光定量PCR(RT- PCR)、免疫组化、Western blot检测体内外人结肠癌细胞血管内皮生长因子(VEGF)表达；此外，用PPAR-β特异性激动剂GW501516处理离体细胞，检测VEGF与剂量的相关性。结果：PPAR-β沉默组的移植瘤生长速度明显快于对照组，并且低分化肿瘤的比例、VEGF表达水平显著高于对照组。特异性激活沉默组的PPAR-β并没有改变其VEGF的表达，在对照组中则观察到VEGF水平与激活程度呈剂量相关性降低。结论：PPAR-β沉默在移植瘤中发挥了促瘤作用，提示PPAR-β可能是结肠癌细胞的抑癌基因，并可伴有阻止VEGF表达的作用。To explore the effect of peroxisome proliferator-activated receptor-β (PPAR-β) gene on human colon cancer growth in vivo and the molecular mechanism. Methods: The models of colon cancer xenografts in nude mice were established by respectively subcutaneous injected human colon cancer cell line KM12C with PPAR β knockdown or untreated. The xenografts were measured daily and weighted 20 days later. The results of two groups were compared by immunohistochemisty (IHC). Vascular endothelial growth factor (VEGF) was detected by real-time reverse-transcription (RT-PCR), IHC, Western blot. Meanwhile, KM12C cell was treated in vitro by using PPAR-β ago- nist GW501516 and then the relativity of the dose and VEGF was analyzed. Result: The xenografts in PPAR β-knock- down group grew significantly earlier and larger and they were more frequently less-differentiated compared to those in control group. Meanwhile, the expression of VEGF, either in xenografts or in KM12C cell line, was significantly higher in PPAR β-knockdown group than that in control group. Moreover, specific activation of PPAR β didn’t change the expression of VEGF in the KM12C cells with PPAR β knockdown, while yielded a dose-dependent decrease of VEGF in those without PPAR β knockdown. Conclusion: These findings indicate that PPAR β may induce the differentiation and inhibit the growth of colon cancer, which may be associated with its inhibition effect on VEGF in colon cancer cells.