First name
Irene
Last name
Schiano Lomoriello
Year of Study
Research Center
Thesis Title
Investigation of the role of the endocytic protein Epsin3 in EMT and mammary stem cell regulation in breast cancer
Thesis Abstract
Endocytosis is a critical regulator of many cellular processes, including proliferation, migration, epithelial-to-mesenchymal transition (EMT) and maintenance of the stem cell (SC) compartment. Subversion of endocytic routes plays an important role in cancer development, including breast cancer (BC). We recently uncovered an oncogenic role for the endocytic protein Epsin3 (Epn3) in BC. By screening a large cohort of BC patients, we found that the EPN3 gene is amplified in ∼10% of cases, while Epn3 protein is overexpressed in ∼50% of BCs and correlates with poor prognosis and distant metastasis.
To uncover the mechanisms through which Epn3 exerts oncogenic properties in BC we overexpressed Epn3 in non-tumorigenic mammary epithelial cells, MCF10A. We show that Epn3 overexpression causes a TGFβ-dependent EMT and expansion of the SC-like compartment, two events that are causally linked. Mechanistically, Epn3 overexpression enhances E-Cadherin endocytosis, resulting in destabilization of cell-cell junctions and translocation of β-catenin in the nucleus. The β-catenin/TCF-LEF pathway leads to the activation of the EMT transcriptional program and of the transcription of TGFβ receptors and ligands. Secretion of TGFβ ligands is a key event in the establishment of an autocrine TGFβ-positive-feedback loop, which is able to self-sustain EMT.
BC cells MCF10DCIS.com and HCC1569 partially recapitulate Epn3-dependent phenotypes observed in MCF10A-Epn3 cells and Epn3 overexpression in HCC1569 cells was able to increase their in vivo tumorigenic potential upon orthotopic transplantation in NSG mice.
In conclusion, our results identify new oncogenic properties for Epn3 and suggest an endocytic-based mechanism of how it contributes to EMT and BC.
To uncover the mechanisms through which Epn3 exerts oncogenic properties in BC we overexpressed Epn3 in non-tumorigenic mammary epithelial cells, MCF10A. We show that Epn3 overexpression causes a TGFβ-dependent EMT and expansion of the SC-like compartment, two events that are causally linked. Mechanistically, Epn3 overexpression enhances E-Cadherin endocytosis, resulting in destabilization of cell-cell junctions and translocation of β-catenin in the nucleus. The β-catenin/TCF-LEF pathway leads to the activation of the EMT transcriptional program and of the transcription of TGFβ receptors and ligands. Secretion of TGFβ ligands is a key event in the establishment of an autocrine TGFβ-positive-feedback loop, which is able to self-sustain EMT.
BC cells MCF10DCIS.com and HCC1569 partially recapitulate Epn3-dependent phenotypes observed in MCF10A-Epn3 cells and Epn3 overexpression in HCC1569 cells was able to increase their in vivo tumorigenic potential upon orthotopic transplantation in NSG mice.
In conclusion, our results identify new oncogenic properties for Epn3 and suggest an endocytic-based mechanism of how it contributes to EMT and BC.
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