Early diagnosis of metastatic colorectal cancer (mCRC) is extremely critical to improve treatment and extend survival. W3 is an aptamer that can specifically bind to mCRC cells with high affinity. Graphene oxide (GO) is a two-dimensional graphitic carbon nanomaterial, which has widely used in constructing biosensors. In this study, we have developed a no-wash fluorescent aptasensor for one-step and sensitive detection of mCRC LoVo cells. It is based on fluorescence resonance energy transfer (FRET) between GO and the W3 aptamer labeled with 5-carboxyfluorescein (FAM). GO can quench the green fluorescence of the FAM-labeled W3 (FAM-W3). In the presence of the target cells, FAM-W3 preferentially binds the target cells and detaches from the surface of GO, leading to the fluorescence of FAM recovery. It was demonstrated that the fluorescence recovery increases linearly in a wide range of 0~10⁷ cells/mL (R² = 0.99). The GO-based FAM-labeled W3 aptasensor (denoted as FAM-W3-GO) not only specifically recognizes mCRC cell lines (LoVo and HCT116), but also sensitively differentiates the target cells from mixed cells, even in the presence of only 5% of the target cells. Furthermore, FAM-W3-GO was applied to detect LoVo cells in human whole blood, which showed good reproducibility with an RSD range of 1.49% to 1.80%. Therefore, FAM-W3-GO may have great potential for early diagnosis of mCRC. This strategy of GO-based fluorescent aptasensor provides a simple, one-step, and highly sensitive approach for the detection of mCRC cells.

Colorectal cancer is the third leading cause of cancer death, and its incidence is continuing to increase rapidly in developing countries. Thus, it is clinically important to achieve an early diagnosis and early treatment for colorectal cancer. Aptamers, also known as chemical antibodies, are short, single-stranded oligonucleotide ligands selected by systematic evolution of ligands by exponential enrichment (SELEX). Because of their excellent chemical properties, such as easy synthesis, controllable modifications, long-term stability, low immunogenicity, and fast tissue penetration, aptamers have good application prospects in cancer diagnosis as well as therapy, and some are in clinical trials. In this review, we discuss aptamers that have been developed for colorectal cancer, and then briefly highlight applications of aptamers in colorectal cancer diagnosis and therapy.

The heterogeneity of tumor cells facilitates their dynamic adaptation to tumor microenvironmental pressures throughout progression. Nevertheless, the mechanisms underlying intercellular communication and transformation among heterogeneous tumor cells remain inadequately understood. In this study, we indicate that Ephrin type-A receptor 2 (EphA2) is heterogeneously expressed in gastric cancer (GC) tumor cells, with those exhibiting elevated EphA2 (EphA2^High) expression demonstrating enhanced migratory and invasive capabilities. EphA2^High cells facilitate the transfer of EphA2 via exosomes, which subsequently localize on the membrane of EphA2^Low cells, thereby activating the ERK signaling pathway in a ligand-independent manner. This process promotes the transformation of EphA2^Low cells and contributes to the progression of GC. An investigation into the correlation between serum levels and tumor metastasis in patients with GC revealed that those with lymph node metastasis exhibited higher levels of serum exosomal EphA2. This study elucidates the process of dominant group formation within heterogeneous tumor cells and suggests the viability of exosomal EphA2 as a potential biomarker for further clinical investigation.