三阴性乳腺癌（TNBC）是一类特殊乳腺癌亚型，具有高转移率和死亡率。由于缺乏ER、PR和HER-2的表达，内分泌及靶向治疗对其无效，常规化疗具有毒副作用，因此亟需发展针对TNBC的特异性治疗方法。核酸适配子是通过Cell-SELEX技术从核酸文库中筛选到的能与靶细胞特异结合的寡核苷酸，可有效用于肿瘤的靶向治疗，但目前未见针对TNBC的研究报道。本研究将在前期建立的Cell-SELEX筛选平台基础上，根据三阴性乳腺癌细胞的复杂分子特性，创建基于序贯式消减Cell-SELEX的适配子筛选新策略，即选择三阴性乳腺癌细胞作为靶细胞，选择分子表达模式差异程度不同的多个非三阴性乳腺癌细胞作为消减细胞，通过逐级序贯式筛选获得TNBC特异性核酸适配子。从多角度探讨所获适配子用于TNBC特异性治疗的可能性：将适配子作为分子靶向药物；将适配子作为化疗药物载体；将适配子用于患者循环肿瘤细胞捕获，特异性监控治疗。

Triple-negative breast cancer (TNBC) is a special kind of breast cancer subtypes, with a high metastasis rate and mortality. The absence of ER, PR and HER-2 expression renders TNBC insensitive to some of the most effective therapies available for breast cancer treatment including HER2-directed therapy and endocrine therapy. The lack of known specific therapeutic targets results in a limited arsenal to attack TNBC, primarily consisting of standard cytotoxic chemotherapy. Therefore, it needs to find new therapeutic targets to achieve effective treatment of TNBC. Aptamers are generated from randomly synthesized nucleic acid libraries via an evolutionary process known as cell-based systematic evolution of ligands by exponential enrichment (Cell-SELEX). Aptamers are single-stranded DNA or RNA oligonucleotides that could be useful in targeted cancer therapy, but no studies have reported for TNBC. In this study, according to the complexity of the molecular characteristics of TNBC cells, we create a new screening strategy, named Sequential Cell-SELEX, for aptamers screening in the establishment of the Cell-SELEX screening platform. Choose TNBC cells as the target cell and choose multiple non-TNBC cells with different molecular expression patterns as the subtractive cell, to acquire TNBC-specific aptamers by stepwise sequential screening. We explore the possibility of the specific treatment of TNBC from many angles: the aptamers as molecular targeted drugs; the aptamers as chemotherapeutic drug carriers; the aptamers as probes for capturing circulating tumor cells in patients and monitoring treatment.