In vitro cell-based immunofluorescent staining was performed according to previously established protocols23 (link). The cells were incubated with primary antibodies at concentration recommended by the manufacturers: primary antibodies included mouse anti-SOX2 (catalog # 4900 S, Cell Signaling Technologies, Danvers, MA, USA) at 1:400 dilution, rat anti-SSEA3 (catalog # MAB-1434, R&D Systems, Minneapolis, MN, USA) at 10 µg/ml final concentration, goat anti-SOX17 (catalog # AF1924, R&D Systems) at 1:500 dilution, rabbit anti-AFP (catalog # SAB3500533, Sigma-Aldrich, St. Louis, MO, USA) at 1:200 dilution, mouse anti-NCAD (ab98952, Abcam, Cambridge, UK) at 1:500 dilution, and rabbit anti-ECAD (ab40772, Abcam) at 1:00 dilution. The applied secondary antibodies were all AlexaFlour (Thermo Fisher) at concentrations of 1 µg/ml: 568 goat anti-rabbit IgG (H + L) catalog # A11011, 647 goat anti-mouse IgG (H + L) catalog # A21235, 647 donkey anti-goat IgG (H + L) catalog # A21447, and 647 goat anti-rat (µ chain) catalog # A21248. Imaging was performed using either the Opera Phenix (PerkinElmer, Waltham, MA, USA; see Fig. 1B) or Olympus IX71 inverted fluorescence microscope (Olympus, Shinjuku City, Tokyo, Japan; see Figs. 2A, C and 4B).