RESUMEN
Neoplastic cells within individual carcinomas often exhibit considerable phenotypic heterogeneity in their epithelial versus mesenchymal-like cell states. Because carcinoma cells with mesenchymal features are often more resistant to therapy and may serve as a source of relapse, we sought to determine whether such cells could be further stratified into functionally distinct subtypes. Indeed, we find that a basal epithelial marker, integrin-ß4 (ITGB4), can be used to enable stratification of mesenchymal-like triple-negative breast cancer (TNBC) cells that differ from one another in their relative tumorigenic abilities. Notably, we demonstrate that ITGB4+ cancer stem cell (CSC)-enriched mesenchymal cells reside in an intermediate epithelial/mesenchymal phenotypic state. Among patients with TNBC who received chemotherapy, elevated ITGB4 expression was associated with a worse 5-year probability of relapse-free survival. Mechanistically, we find that the ZEB1 (zinc finger E-box binding homeobox 1) transcription factor activity in highly mesenchymal SUM159 TNBC cells can repress expression of the epithelial transcription factor TAp63α (tumor protein 63 isoform 1), a protein that promotes ITGB4 expression. In addition, we demonstrate that ZEB1 and ITGB4 are important in modulating the histopathological phenotypes of tumors derived from mesenchymal TNBC cells. Hence, mesenchymal carcinoma cell populations are internally heterogeneous, and ITGB4 is a mechanistically driven prognostic biomarker that can be used to identify the more aggressive subtypes of mesenchymal carcinoma cells in TNBC. The ability to rapidly isolate and mechanistically interrogate the CSC-enriched, partially mesenchymal carcinoma cells should further enable identification of novel therapeutic opportunities to improve the prognosis for high-risk patients with TNBC.
Asunto(s)
Carcinoma/metabolismo , Integrina beta4/metabolismo , Mesodermo/metabolismo , Células Madre Neoplásicas/metabolismo , Neoplasias de la Mama Triple Negativas/metabolismo , Carcinoma/genética , Carcinoma/mortalidad , Línea Celular Tumoral , Transición Epitelial-Mesenquimal , Femenino , Humanos , Integrina beta4/genética , Mesodermo/citología , Pronóstico , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Neoplasias de la Mama Triple Negativas/genética , Neoplasias de la Mama Triple Negativas/mortalidad , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismo , Homeobox 1 de Unión a la E-Box con Dedos de Zinc/genética , Homeobox 1 de Unión a la E-Box con Dedos de Zinc/metabolismoRESUMEN
Keratin intermediate filament proteins form the major cytoskeleton in all embryonic and adult epithelia. Increasing evidence suggests that keratins, besides their primary cytoskeletal function, can act as scaffolds which locally regulate cell growth and survival in epithelial cells. Many of these functions, however, are not understood in full, owing to keratin redundancy. We have recently created mice which lack all keratins and found that keratins act upstream of mTOR signaling to regulate protein biosynthesis via GLUT localization. Here, we report that keratins are necessary to maintain adhesion between endodermal and mesodermal cell layers of the yolk sac. As a consequence, keratin(-/-) embryos suffer from reduced yolk sac hematopoiesis and vasculogenesis. Pathway analysis revealed a reduction of the hedgehog target Foxf1 in yolk sac mesoderm of keratin(-/-) embryos, and subsequent reduction of BMP-4 and P-p38 MAPK. These defects may be caused by the overall reduction in protein biosynthesis and diminished adhesion. Our data show for the first time that keratins are necessary for the differentiation of a non-epithelial cell lineage through a combination of mechanical and signaling mechanisms.