乳腺癌拮抗肽SA-12的抗肿瘤活性与分子机制研究

Breast cancer is considered to be the most common malignancy in women. With deeply research in the molecular targeted therapy, treatment of breast cancer has made considerable progression. However, the clinical efficacy is still not satisfactory. Exploration of strategies or drugs with high treatment efficiency, specificity, and low side effects is still a difficult problem in this field. Anticancer peptides specifically target to oncoproteins are assigned to be with high efficiency, specificity, low side effects and other advantages. In previous studies, the applicant has constructed mRNA-peptide display technology series platform successfully, put total protein of SKBr-3 cells as bait, and screened 8 binding peptides. Preliminary research on the capture peptides indicated that SA-12 has a significant role in the inhibition of proliferation and induction of apoptosis on SKBr-3 cells, and the mechanism by which maybe closely related with bioactivity change of the targeted protein MECP2 and mitochondrial apoptosis pathway. This project to be carried out will investigate the in vitro and in vivo anti-tumor activity of SA-12 deeply, and reveal its role in the targeted protein MECP2 and PI3K/PTEN/Akt/mTOR signaling pathway, further, elucidate the molecular mechanisms and signal transduction pathway depended by its tumor suppression activity. Finally, provide novel theoretical basis for the high efficiency, specificity, and low side effects strategies in targeted therapy of breast cancer.

乳腺癌是女性首发的恶性肿瘤，随着分子靶向治疗研究的深入，乳腺癌治疗已取得了长足进步，但临床疗效依然不尽理想。治疗效率高、特异性强、副作用小的策略或药物的探索依然是该领域的难题。针对肿瘤蛋白的特异性多肽类抗肿瘤药物具有高效性、特异性、低副作用等优势。前期研究中，申请者成功构建了mRNA-多肽展示技术研究平台，以乳腺癌细胞系SKBr-3总蛋白为诱饵筛选得到8条结合肽，发现其中SA-12具有明显的抑制SKBr-3增殖并诱导凋亡的作用，其抑瘤机制可能涉及靶蛋白MECP2生物功能的变化，并且与线粒体凋亡途径密切相关。本课题拟对拮抗肽SA-12在乳腺癌治疗中的抗肿瘤活性进行深入的体外及体内水平研究与探讨，并揭示其在靶蛋白MECP2及PI3K/PTEN/Akt/mTOR信号通路中的作用，阐明其抑瘤活性所依赖的具体分子机制及信号转导途径，为高效性、特异性、低副作用的乳腺癌分子靶向治疗策略提供新的理论依据。

随着恶性肿瘤分子靶向治疗技术的不断进步，乳腺癌治疗取得了长足进步，然而临床上还是有很大一部分乳腺癌患者因肿瘤复发及转移而死亡，新型抗乳腺癌药物及其作用机制的研究依然迫在眉睫。针对肿瘤蛋白的多肽类抗肿瘤药物具有高效性、特异性、低副作用等优势。前期研究中，成功构建了mRNA-多肽展示技术研究体系，并以乳腺癌细胞系SKBr-3总蛋白为诱饵筛选得到1条新型乳腺癌拮抗肽SA-12。初步的细胞生物学研究发现，SA-12具有明显的抑制SKBr-3增殖并诱导凋亡的作用。本项目对拮抗肽SA-12在乳腺癌治疗中的抗肿瘤活性进行了细胞生物学水平与分子生物学水平的深入研究与探讨。揭示了SA-12对3种典型乳腺癌细胞系SKBr-3、MDA-MB-231与MCF-7的增殖抑制、促凋亡活性、周期阻滞以及对肿瘤细胞迁移能力的抑制作用，明确了SA-12与靶蛋白MECP2间的相互作用特征，并探讨了SA-12在凋亡、周期与转移相关信号通路中的作用，明确了其抑瘤效应与肿瘤细胞凋亡、周期及转移相关信号通路变化间的确切关系。细胞生物学水平的研究发现，SA-12对乳腺癌细胞SKBr-3、MDA-MB-231与MCF-7的增殖具有明显抑制作用，对SKBr-3细胞具有凋亡诱导作用，对MDA-MB-231与MCF-7细胞具有周期阻滞作用，对SKBr-3、MDA-MB-231与MCF-7细胞的迁移能力具有抑制作用。并进一步分子生物学水平探讨了SA-12抗肿瘤作用的分子机制，明确了SA-12的抗肿瘤作用与肿瘤相关蛋白CDC20B和MECP2有关；SA-12诱导的SKBr-3细胞凋亡是通过线粒体途径实现，涉及到Bcl-2家族和相关的caspases家族成员；SA-12能够阻滞MDA-MB-231和MCF-7细胞周期于G0/G1期，其中细胞周期相关基因cyclin D1、CDK4与p16参与此过程；SA-12的抑制作用可能是通过阻断MECP2来降低cyclin D1和CDK4基因的表达而增强p16基因的表达；此外，SA-12能够增加MDA-MB-231与MCF-7细胞肿瘤转移抑制基因E-Cadherin、NM23和TIMP1的表达水平，这可能与SA-12诱导的乳腺癌细胞转能力移抑制有关。本项目揭示了拮抗肽SA-12在乳腺癌细胞中的抗肿瘤活性，并初步阐明了其所介导的抑瘤效应所依赖的分子机制。