Tumor-derived exosomes containing circ_0008039 promote the stemness of colorectal cancer cells by inhibiting ferroptosis

This study was to investigate the impact of exosomes-derived circ_0008039 on ferroptosis and stemness in colorectal cancer cells, as well as its associated molecular mechanisms. The cell colony formation ability was evaluated using the MTT assay and colony formation assay, respectively. Additionally, the sphere formation assay was employed to examine the cells' ability to aggregate into spheres. The targeting relationship between circ_0008039, miR-302e, and SLC7A11 was verified through dual luciferase assay. Furthermore, RNA immunoprecipitation (RIP) analysis of circ_0008039 and miR-302e was conducted. Western blotting was utilized to detect the protein expression of exosome surface antigens (TSG101 and CD63), stem cell markers (CD133, Nanog, and SOX-2), as well as SLC7A11 in both exosomes and cell lysates. The levels of glutathione (GSH), malondialdehyde (MDA), reactive oxygen species (ROS), and Fe²⁺ were determined using corresponding kits. Circ_0008039 exhibited significant downregulation in cancer tissues and cells. Furthermore, exosome-derived circ_0008039 played a crucial role in promoting cell viability, clone formation, and resistance to ferroptosis by inhibiting MDA, ROS, and Fe²⁺ levels. Additionally, circ_0008039 acted as a miR-302e sponge to regulate SLC7A11 expression. In colorectal cancer (CRC) tissues, miR-302e was negatively correlated with SLC7A11 expression while circ_0008039 was negatively correlated with miR-302e expression. Mechanistic validation demonstrated that circ_0008039 regulated CRC cell proliferation, stemness maintenance and ferroptosis through the modulation of the miR-302e/SLC7A11 axis. The Circ_0008039/miR-302e/SLC7A11 axis plays a pivotal role in facilitating the proliferation and maintenance of stemness in CRC cells, while enhancing resistance to ferroptosis.