新型ASCT2靶向抑制剂的发现及其抑制MYCN扩增神经母细胞瘤的作用机理研究

Abnormal glutamine metabolism is one of the hallmarks of cancer cells. Cancer cells rely on increased glutamine uptake, which provides an unlimited growth advantage for cancer cells. ASCT2, a Na+-dependent glutamine transporter, which belongs to the amino acid transport system ASC family, is aberrantly over-expressed in many cancer cells. Our previous study found RNAi-mediated silencing of ASCT2 gene significantly inhibited the growth and survival of MYCN-amplified neuroblastoma cells and delayed the tumorigenesis in nude mice, indicating that ASCT2 is a potential therapeutic target of MYCN-amplified neuroblastoma. So far there is no high-specific ASCT2 targeted inhibitors reported. Basing on the technology of high throughput screening, two ASCT2 targeted inhibitors have been screened from the library of small molecules targeting the metabolic pathways. By using the research methods of multi-disciplines, for instance, cell molecular biological techniques, biochemical methods, model animals, and so on, we will verify the specificity and effectiveness of these two candidate inhibitors, as well as assess pre-clinical efficiency, latent side effects and the mechanism of these two candidate compounds. In a word, all of these results will provide the experimental basis for the development and application of ASCT2 targeted inhibitors of anticancer drugs.

异常谷氨酰胺代谢是肿瘤细胞的标志性特征，肿瘤细胞高度依赖谷氨酰胺转运系统吸收大量谷氨酰胺维持其无限增殖。ASCT2是Na+依赖性的谷氨酰胺转运蛋白，属于氨基酸转运系统system ASC家族成员之一，在肿瘤细胞中异常高表达。我们前期研究发现，通过RNAi介导ASCT2基因沉默，显著抑制MYCN扩增神经母细胞瘤的细胞生长及裸鼠移植瘤的发生，表明ASCT2是其治疗的潜在靶点。迄今为止，国内外尚未见高特异性ASCT2靶向抑制剂的报道。本课题建立了ASCT2靶向抑制剂的高通量筛选模型，从靶向代谢通路的小分子化合物库中，已筛出ASCT2靶向抑制作用相对专一和有效的两个候选化合物，拟采用分子细胞生物学、生物化学、模式动物等学科交叉的研究方法，验证高通量筛选的候选化合物靶向ASCT2的特异性和有效性，并探讨其临床前疗效、作用机理及潜在毒副作用，为ASCT2靶向抑制剂类抗肿瘤药物的开发和应用提供实验依据。

异常谷氨酰胺代谢是肿瘤细胞的标志性特征，ASCT2是Na+依赖性的谷氨酰胺转运蛋白，在许多肿瘤细胞中异常高表达。迄今为止，国内外尚未见高特异性ASCT2靶向抑制剂的报道。我们通过酮与伯胺结构化学物反应获得目标化合物，并采用核磁共振鉴定其化学结构；进而利用目标化合物在MYCN扩增神经母细胞瘤、胰腺癌、结肠癌细胞进行体外抗肿瘤活性的评价，结果显示其对胰腺癌和结肠癌的抗肿瘤活性比对MYCN神经母细胞瘤的作用明显；我们进一步在细胞水平上证实由RNAi介导的ASCT2基因的沉默或者ASCT2抑制剂均能显著抑制胰腺癌细胞的谷氨酰胺代谢，有效抑制其生长，并通过PI3K/Akt/mTOR信号通路阻滞细胞周期，促进其凋亡；在动物体内证实ASCT2沉默后促使细胞凋亡从而抑制胰腺癌细胞的体内成瘤，最后我们通过揭示miR137在结直肠癌中沉默的调控机制进一步证明ASCT2在结肠癌细胞中过表达的机制。本研究揭示了ASCT2在胰腺癌、结肠癌发生发展中的重要作用，为胰腺癌或结肠癌的治疗提供新靶点。