基于肿瘤细胞异质性构建多功能纳米靶向胶束及其抗肿瘤研究

Cancer cells heterogeneity,co-existing of cancer cells and cancer stem cells(CSCs),have a profound influence on the tumorigenic process and partially contribute to metastasis, relapse, and inherent or acquired drug resistance. Thus, it is significantly important to design a novel anti-cancer strategy to inhibiting both CSCs and cancer cells. Salinomycin (Sal) has recently been shown to potently and selectively kill human breast CSCs and to inhibit breast cancer growth and metastasis in mice. And Sal could sensitize breast cancer cells to the effects of Doxorubicin (Dox), which associated with an increase in DNA damage and a decrease in anti-apoptotic protein p21 levels. But toxicity of Sal and Dox affecting skeletal muscle and cardiac muscle hampered their clinical use. To overcome the problem, we have synthesized a pH-responsive di-block polymer, PGA-b-PLA, that has been used to constitute multi-functional polymeric micelles (m-PMs) for targeting delivery of Sal and Dox. m-PMs take advantage of several characters for drugs loading and killing both breast CSCs and breast cancer cells. The results of prelimimary study shown that PGA-b-PLA could de-shield/shield Tat peptide conjugated to surface of m-PMs at different pH value, which could protect Tat peptide from enzymatic cleavage and targetingly enhance cellular uptake of bioactive molecules. The results also indicated that with enhanced penetrating retention effect and Tat peptide, m-PMs could play a vital role in targeting delivery of Sal and Dox,facilitating accumulation and endocytosis of Sal and Dox by cancer cells, changing biodistribution, and lowering toxicity of Sal and Dox. Many of the current works focus on investigating(a)decomposition stability of PGA-b-PLA,(b)releasing profile and mechanism of m-PMs, (c)the mechanism of de-shielding/shielding Tat peptide, (d)intracellular tracking of m-PMs, (e)subcellular location of m-PMs, and (f)the mechanism of m-PMs inducing apoptosis of breast cancer stem cells and breast cancer cells. In future, we will pay more attention to compare m-PMs with free drug(s) in some respects, such as pharmacokinetic parameters, toxicity, ability of inhibit tumor growth and metastasis.

肿瘤细胞异质性（即肿瘤干细胞和肿瘤细胞的同时存在）是导致肿瘤耐药、复发和转移的重要原因。因此，应同时针对肿瘤干细胞和肿瘤细胞设计治疗策略。盐霉素是乳腺癌干细胞特异性强效抑制剂；与阿霉素联合应用可显著逆转乳腺癌耐药细胞耐药性。但两种药物的心肌和骨骼肌毒性限制了临床联合应用。 基于以上问题，本课题应用新型环境响应型高分子材料构建了多功能纳米靶向胶束。胶束利用其多元载药驱动力同步递送盐霉素和阿霉素，可同时抑制乳腺癌干细胞和乳腺癌细胞。初步研究证实，新型高分子可选择性暴露非选择性的细胞穿膜肽，靶向性发挥其强穿膜能力，增加药物吸收；已有研究提示，多功能载药胶束具有pH敏感释药特点，可实现靶向递送的目的，改变药物体内分布，降低药物毒性；未来，本课题将重点研究多功能载药胶束的细胞摄取机制，诱导乳腺癌细胞和乳腺癌干细胞凋亡、逆转耐药的机制，评价安全性，抑制肿瘤生长及预防转移的能力。

本项目较好的完成了研究目标，首先合成新型环境响应型高分子嵌段共聚物PGA-b-PLA，并对其进行了详细表征，研究结果显示安全性好，无细胞毒性。其次，应用这种材料构建一种同时运载两种药物的多功能纳米靶向胶束，实现了同步抑制乳腺癌细胞和乳腺癌干细胞目的。研究结果显示，胶束粒径179nm，载药量大于8%，包封率大于85%。释药机理研究发现靶向胶束构象随环境pH值改变而变化。这种改变对于胶束的靶向性释药行为发挥了关键作用。体外药效学评价结果显示靶向胶束对乳腺癌细胞均有较强的抑制作用，同时对ALDH1+的干细胞亚群也有较强的抑制作用。细胞摄取研究发现胶束表面的聚谷氨酸构象在不同条件下的变化开启释药通道，促进药物释放；同时选择性的暴露（或保护）肽，促进药物载体的跨膜吸收。体内药效学研究结果显示靶向胶束对乳腺癌干细胞模型鼠瘤体生长均具有较强的抑制作用，但是这种作用的体内外相关性差。我们认为可能与胶束粒子偏大有关。但是这种关联性仍不确定，建议首先应继续制备不同大小的粒子进行评价，明确粒子大小与体内作用的相关性。在此基础上，应通过优化设计调整处方中药物/高分子材料比例，优化制备条件来减少粒子大小，增进其体内抗肿瘤作用。此外，靶向胶束中两种药物的比例也是值得进一步考察的研究点。项目组也将继续推进上述研究工作。第三，研究成果在国际生物医学刊物上发表SCI收录论文10余篇，其中包括了发表在《Advanced Drug Delivery Reviews》，《Theranostics》和《Biomaterials》等高影响因子杂志上的文章。研究成果申请专利1项，已进入实质审查阶段。培养博士生5名，硕士生4名。项目的研究工作实现了申请书中设计的学术价值，下一步将逐步推进项目的成果转化工作，实现其社会价值和经济价值。