GPC3 and cancer: Its main functions in cancer progression are the GPC3-induced stimulation of Wnt signaling for tumor progression, the interaction of GPC3 with various growth factors, the stimulation of epithelial–mesenchymal transition (EMT), and the recruitment and polarization of macrophages towards a tumor-promoting M2-phenotype (Figure 1) [86,87,88,89,90,91,92,93,94,95].