Chitosan修饰的低氧激活型光敏脂质体在三阴乳腺癌治疗中的实验研究

To achieve the efficient therapy of triple negative breast cancer is encouraging but still remains a big challenge worldwide, thus it would be of great clinical significance to discover specific molecular target and effective treatment for TNBC. There were a higher proportion of CD44+/CD24- breast cancer stem cells among TNBC cells as evidenced by numbers of previous trials. Fortunately, chitosan modified nano-liposomes could specifically target CD44+ breast cancer stem cells while circumventing normal stem cells. Besides, chitosan modified nano-liposomes were specifically distribute in tumor sites for a long period via tail vein injection. In this study, chitosan modified hypoxia activated photosensitive liposome drug delivery systems were constructed for specifically targeting TNBC stem cells based on targeting CD44v. HPPH in the drug delivery system were activated to achieve photodynamic therapy upon NIR excitation. TH302 loaded into the system were activated to kill breast cancer stem cells under hypoxia environment. Thus, a synergetic combination of PDT and hypoxia activated chemotherapy could be expected to achieve more effectively eliminate breast cancer cells and unexpected treatment efficiency. Drug delivery, targeting and therapeutic effects could be simultaneously monitored upon PET and PAI bimodal imaging in vitro and vivo.

三阴乳腺癌治疗瓶颈已属于世界性难题，寻找特异性分子靶点及有效治疗手段具有重要临床意义。在前期实验中发现：三阴乳腺癌细胞中存在着较高比例的CD44+/CD24-乳腺癌干细胞；壳聚糖偶联的纳米脂质体可特异性靶向CD44+乳腺癌干细胞，而不与正常干细胞结合；尾静脉注射的壳聚糖偶联的纳米脂质体可在肿瘤部位选择性分布并长时间停留。以此为基础，本课题以CD44v为靶点，构建壳聚糖修饰的低氧激活型光敏脂质体给药系统，特异性靶向三阴乳腺癌干细胞；在近红外激光照射下，光敏脂质体给药系统中的HPPH被激活而发挥光动力治疗效应；负载的TH302则可在乏氧环境下活化并杀伤乳腺癌干细胞，以弥补光动力学治疗的不足，更高效地清除乳腺癌干细胞，起到协同治疗作用。在体内外实验中，药物的运输、靶向、及治疗效果均可在PET和PAI双模态成像下实现实时观察。

三阴性乳腺癌由于其高侵袭、易复发、转移等恶性生物学行为及缺乏有效治疗靶点，其治疗瓶颈已属于世界性难题，因此寻找特异性分子靶点及有效治疗手段具有重要临床意义。肿瘤干细胞在肿瘤形成、转移中起着重要的作用，在本课题中，我们拟以乳腺癌干细胞标记物CD44为治疗靶点，构建壳聚糖（chitosan，CO）修饰的载低氧激活型化疗药物TH302的HPPH（pyro-acid）脂质体（CO-pyro-acid-TH302/Lipo），以此特异性的靶向杀伤三阴性乳腺癌干细胞。前期研究基础表明三阴乳腺癌细胞中存在着较高比例的CD44+乳腺癌干细胞亚群；小鼠尾静脉注射的壳聚糖（chitosan，CO）偶联的纳米脂质体可特异性的在肿瘤部位分布并长时间停留。以此为基础，本项目的研究内容包括：① 三阴性乳腺癌干细胞的富集及特性鉴定；② 制备和表征CO-pyro-acid-TH302/Lipo；③ 探讨CO-pyro-acid-TH302/Lipo对CD44+三阴性乳腺癌干细胞的靶向性及相关机制；④ 研究CO-pyro-acid-TH302/Lipo对CD44+三阴性乳腺癌干细胞的体内外杀伤效果。本项目证实了CD44是三阴性乳腺癌干细胞治疗的一个有效靶点，光学成像和核素成像均表明CO-pyro-acid-TH302/Lipo对CD44+三阴性乳腺癌干细胞具有特异性的靶向能力。分子动力学模拟揭示了CD44与CO结合的分子机制。体内外治疗实验表明，CO-pyro-acid-TH302/Lipo联合光动力治疗和乏氧激活药物治疗以及CO的特异性靶向能力，弥补三阴性乳腺癌杀伤缺乏特异性靶点的缺陷，使得更多的药物能够进入肿瘤区域实现杀伤，并且能特异性杀伤肿瘤干细胞，减弱肿瘤细胞的增殖能力和侵袭能力，由于两种治疗方式分别需要用乏氧环境和外源性的近红外光激活，故本身的治疗就具有一定的安全性，对非靶器官的副作用较低。研究成果为三阴性乳腺癌临床治疗提供了一种安全、高效的靶向杀伤策略，在三阴性乳腺癌治疗中具有一定应用前景。