甘薯sporamin蛋白调控IGFs/VEGF信号传导通路对结直肠癌的抑制作用及机制研究

The insulin like growth factors (IGFs)/vascular endothelial growth factor (VEGF) pathway is associated with the risk of the obesity-related colorectal cancer (CRC). Our previous study found that the storage protein of the sweet potato, sporamin, significantly inhibited the differentiation and proliferation of the 3T3 preadipocyte and suppressed the growth and metastasis of the xenografted cancer cells as well as the expression of the VEGF in CRC cell lines, but its impact on the IGFs/VEGF pathway remains unclear. The current study plans to investigate the absorption of the sporamin protein after oral consumption and examine its inhibitory effect on the growth, metastasis and angiogenesis of the xenografted and carcinogen-induced tumors as well as its impact on the serum and tissue levels of the biomarkers related to the IGFs/VEGF pathway such as IGF1, IGF2, IGF1R, IGFBP3, VEGFA and VEGFC in obese mice models. Adipocytes and CRC cells will be cultured independently or co-cultured together in Transwell inserts and treated by the sporamin protein to examine its inhibitory effect on the IGFs/VEGF signal transduction pathway. The underlying signal transduction mechanisms will be explored by using the gene transfection, gene silence and other molecular biological techniques. Then, on the basis of the animal and the cell based studies, sensitive biomarkers to the sporamin treatment will be screen out and used in a dietary intervention clinical trial aimed to investigate the efficacy of the supplementation of the sporamin protein on the status of the disease in obese CRC patients. The results of the present study will provide scientific evidence for the revelation of the effects of the sporamin protein on the chemoprevention of the obesity-related CRC.

胰岛素样生长因子（IGFs）/血管内皮生长因子（VEGF）通路与肥胖相关性结直肠癌（CRC）的发生有关。课题组前期研究发现甘薯sporamin蛋白显著抑制3T3前脂肪细胞分化、增殖及CRC细胞VEGF表达，但对IGFs/VEGF通路的作用不详。本研究拟通过肥胖小鼠CRC移植瘤和化学致癌模型观察sporamin蛋白的吸收利用情况、对肿瘤生长、转移和新血管生成的抑制作用及对IGFs/VEGF轴的IGF1、IGF2、IGF1R、IGFBP3、VEGFA、VEGFC等相关标志物的影响；通过脂肪细胞、CRC细胞单独培养和共培养体系，采用基因转染、沉默等技术探索sporamin蛋白调控IGFs/VEGF通路的作用机制。在此基础上，筛选出对sporamin蛋白干预敏感的指标，通过临床试验观察补充sporamin蛋白对肥胖CRC患者发病的作用，为揭示其在化学预防肥胖相关性CRC中的作用提供科学依据。

Sporamin蛋白是甘薯块根中特有的一种具有丝氨酸蛋白质抑制剂活性、抗氧化活性、及抗癌活性的生物活性成分。本研究发现：实验动物经口摄入sporamin蛋白可预防1,2-二甲肼（DMH）单独诱导的小鼠结肠癌及DMH与葡聚糖硫酸钠（DSS）联合诱导的炎症相关性结肠癌的发生，对腹腔移植瘤模型动物也有类似作用，主要表现为降低肿瘤负荷，改善贫血，改善荷瘤鼠体内氨基酸代谢失衡状态和肠道微生态失衡状态、降低肠道炎症反应水平，减少血管生成、提高肠粘膜稳定性等。体内、外实验表明其作用机制与IGF1/HIF-1α/VEGF轴及Wnt/β-Catenin轴信号通路密切相关。Sporamin蛋白可显著降低体内IGF-1，IGF-2，IGF-1R的表达量，提高IGF-2R及IGFBP1-7的表达量。转录组学检测发现sporamin蛋白干预可显著下调多种促癌基因的表达，上调抑癌基因的表达；主要影响细胞对遗传信息和环境刺激的处理，调节相关的免疫反应和代谢过程，影响体内各种酶的活性，提高机体的解毒功能。在肥胖动物中还可以调节脂代谢，对免疫系统和炎症反应有更显著的调节作用。其在高脂膳食诱导的肥胖小鼠体内对肿瘤发生发展的抑制作用可能与其对肥胖导致的体内病理反应的抑制有关。结论：甘薯sporamin蛋白在体内外对结直肠癌均有显著的抑制作用，对肥胖相关性结肠癌作用更明显，其作用机制与减轻炎症反应，调控IGF/VEGF轴信号通路、抑制血管新生、调控癌症相关基因表达、及改善肠道微生态等多重作用有关，是一种值得进一步研究的食物天然活性物质。