Context Dependency of Epithelial-to-Mesenchymal Transition for Metastasis

We questioned whether EMT is required for metastasis, and we have analyzed metastasis formation in two distinct SCC models, different in terms of SCC ability to undergo EMT. We demonstrated that in spontaneous mouse model in which tumors presented a wide range of EMT (from well differentiated to fully EMT-like) presented high metastatic incidence: 49% (20/70) of mice presented LN metastasis and 28% (34/70) of mice presented lung metastases. Importantly, metastatic incidence was always associated with EMT-like tumors. However, in the second mouse model, that develops mostly well-differentiated tumors, the metastatic incidence was very low: 12% (5/42) of mice developed lung metastases and 10% (4/42) developed lymph node metastases. Importantly, the rare metastases were associated with tumors presenting some degree of EMT, supporting that EMT is needed for metastases arising from skin SCC.To understand whether EMT can occur at the intermediate step between primary tumor and distant metastasis, we analyzed blood from mice based on YFP reporter. We uncovered that most CTCs were EMT-like: 80% of CTCs were EpCAM-negative. This finding suggests that EpCAM marker, a gold standard used to detect CTCs, is not optimal as it doesn’t detect CTCs of EMT phenotype thus underestimating the real number of CTCs. Importantly, we noticed that the presence of CTCs was always associated with lung metastases and indeed can be used to predict prognosis of oncologic disease. Our immunofluorescent analysis of lung and lymph nodes showed that the majority of metastases were of differentiated phenotype. For the lung metastases, 71% (36/51) of them presented epithelial phenotype YFP+/K14+/Vim-, 14% (7/51) presented differentiated epithelial features but did not express K14 or Vimentin, 12% (6/51) presented an EMT hybrid epithelial phenotype YFP+/K14+/Vim+, whereas only 4% (2/51) were purely mesenchymal YFP+/K14-/Vim+. Histological analyses were confirmed by FACS analysis showing that lung metast
Doctorat en Sciences biomédicales et pharmaceutiques (Médecine)
info:eu-repo/semantics/nonPublished