CONICET | Buscador de Institutos y Recursos Humanos

Glypican-3(GPC3) is a heparan sulfate proteoglycan related to cancer. Previously, weoverexpressed GPC3 in MDA-MB231 human breast cancer cells (metastatic andGPC3-). We showed that GPC3 inhibits clonogenic and migratory capacities, whileincreases homotypic adhesion and apoptotic susceptibility. Moreover, GPC3induced the reexpression of the epithelial marker E-Cadherin. Our resultssuggest that GPC3 would act as a metastatic suppressor by regulating epithelial-mesenchymaltransition (EMT). In this work we observed that GPC3 overexpression induces a changein the MDA-MB231 cell morphology, from a fibroblastic to a more epithelial phenotype,as well as prevents the F-actin stress fibers formation. In vivo assays showed that GPC3 overexpression inhibits tumorigenicity(64% -vector vs 20% -GPC3; p<0.05), local invasion (75% -vector vs 0% -GPC3;p<0.05) and spontaneous metastasis incidence (50% -vector vs 0% -GPC3;p<0.001). To elucidate the molecular mechanisms involved in these effects,we evaluated the canonical Wnt pathway activity. Although GPC3 induced aninhibition of this pathway, no changes in the E-Cadherin expression levels wereobserved when we reverse the effect of GPC3 on Wnt signaling. So, we studiedthe expression of the E-Cadherin transcriptional suppressors: SNAIL, SLUG andZEB1. GPC3 leaded a decrease in the ZEB1 mRNA and protein levels. When weoverexpress ZEB1 in MDA-MB231-GPC3 cells, the increase of E-Cadherin expressioninduced by GPC3 was reversed. To test this invivo, we performed IHC for E-Cadherin and ZEB1, in MDA-MB231-GPC3 tumors.ZEB1 staining was detected in 73±15% of -vector tumor cells vs 33±3% of -GPC3tumor ones (p<0.01). While the most of control tumor cells was negative for E-Cadherin,this signal was positive in the 95±5% of -GPC3 tumor cells (p<0.001). Ourresults show that GPC3 expression reverted EMT by downregulating ZEB1expression in human breast cancer cells. This effect would be independent ofthe canonical Wnt pathway.