Selection and identification of a novel DNA aptamer for recognizing colorectal cancer stem cells

Metastasis is one of the main causes of cancer-related deaths. Cancer stem cells (CSCs) have the ability to initiate metastasis; however, there is a lack of effective biomarkers to characterize CSC. In this study, subtractive cell-SELEX was performed using colorectal cancer (CRC) HCT116 cells with high stemness characteristics and CL187 cells with low stemness characteristics as the target and negative cells, respectively, for stemness-specific aptamers selection. Two aptamers were obtained, among which aptamer L33 had good specificity for CRC cells with stemness characteristics. Besides, aptamer L33 had excellent affinity with a Kd of 16.6 ± 2.1 nM and good temperature stability. Subsequently, we obtained two cell subpopulations by L33-based cell sorting and confirmed that the L33-positive cell subpopulation had higher expression of stemness-associated markers, stronger tumor sphere-forming capacity, chemotherapy drug tolerance, migration and invasion ability, and in vivo tumorigenicity. After confirming that aptamer L33 is closely associated with tumor stemness, we used L33 as a stem circulating tumor cell (CTC) capture probe and found a higher detection rate of L33-positive CTCs in the peripheral blood of patients with metastatic CRC, suggesting that CTC capture analysis based on L33 has a stronger ability to predict metastasis. Therefore, aptamer L33 developed in this study may provide a potential target for the diagnosis of metastatic CRC and CSC based therapy.