Western Blot Analysis of Cellular Proteins

Western blots were performed as described (Yang et al., 2019 (link); Yang et al., 2022 (link)) using the following antibodies against IDO1 (ab211017, Abcam), Flag (ab205606, Abcam), CD63 (ab217345, Abcam), CD81 (ab109201, Abcam), RUNX2 (ab23981, Abcam), Calnexin (#2433, CST) and GAPDH (AF2823, Beyotime). The whole protein was extracted by RIPA Lysis Buffer (Beyotime Biotechnology, China), and the concentration was detected by a BCA protein assay kit (Beyotime Biotechnology, China). Cell lysates were kept on ice for 30 min and centrifuged at 16,000 g for 3–5 min at 4°C. Supernatants were collected and boiled in SDS loading buffer, and the same amounts of protein were separated by 10% SDS-PAGE and blotted onto polyvinylidene fluoride membranes (Millipore, United States of America). Bands were visualized using chemiluminescence.