Glypican-3 (Gpc3) Induces A Mesenchymal-Epithelial Transition In Human Breast Cancer Cells Lines

Glypicans constitute a family of heparan sulphate proteoglycans which are linked to the extracellular surface of the plasma membrane through a glycosylphosphatidylinositol anchor. Since GPC3 has been linked to cancer, herein we generated and characterized a pre-clinical human breast cancer cell model to evaluate the role of GPC3 in human mammary tumor progression. GPC3 expression was blocked in MCF-7 cells (poorly-metastatic, GPC3 +) by siRNA (generating MCF-7-shGPC3 sublines), while it was overexpressed in MDA-MB231cells (metastatic, GPC3 -) by viral infection (producing MDA-MB231-GPC3 sublines). We performed in vitro and in vivo characterization of this model. GPC3 silenced MCF-7 cells acquired F-actin stress fibers, enhanced their clonogenic ability (Colony number 130 -shGPC3 vs. 37 -sh Negative Control (NC)) as well as their migration (Wound coverage (%): 15 -shGPC3 vs. 2 -shNC), were less susceptible to cell death induction (Cell death (%): 21.6 -shGPC3 vs. 34 -shNC), diminished the expression of the epithelial marker E-Cadherin while acquired the mesenchymal marker N-Cadherin, and were more invasive and metastatic in vivo. These cells exhibited an upregulation of the EMT-transcription factor ZEB1, and the canonical Wnt/beta-Catenin signaling pathway was activated. GPC3 overexpressing MDA-MB231 cells misplaced their fibroblast-like appearance as well as their F-actin stress fibers, repressed their clonogenicity (Colony number: 8 -GPC3 vs. 40 -vector) and migratory capacity (Wound coverage (%): 10 -GPC3 vs. 90 -vector), were more sensitive to death in starving condition (Cell death (%) 30 -GPC3 vs. 6.5 -vector), got the ability to form E-Cadherin dependent-spheroids, reexpressed E-Cadherin in cell-cell junctions and downregulated the mesenchymal markers N-Cadherin and vimentin, while were less invasive and metastatic in vivo. The expression of the E-Cadherin repressor ZEB1 was diminished, as well as the activity of the canonical Wnt/beta-Catenin signaling pathway. However, when canonical Wnt signaling was activated by LiCl, the expression of E-Cadherin did not change. In summary, we present in vitro and in vivo experimental evidence supporting the hypothesis that GPC3 has a protective role of human breast cancer progression by inducing mesenchymal-epithelial transition (MET). The canonical Wnt/beta-Catenin signaling inhibition would not be required for MET process induced by GPC3. Citation Format: Lilian F. Castillo, Rocio Tascon, Elisa Bal de Kier Joffe, Giselle Peters. Glypican-3 (GPC3) induces a mesenchymal-epithelial transition in human breast cancer cells lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1686.