FLVCR2 and cancer: Indeed, CCs and CCTs could only be detected after we observed the generation of the second membrane outside the cell membrane in CC/CCT culture kits, managed to separate the second membranes from cancer cells, obtained the CC proteome, and compared the relative abundances of the marker from ~10,000 clinically annotated cancer/normal specimens (Fig. 1 and SI Appendix, Figs. S3 and S4).