Epithelial cancers consist in heterogeneous populations of cells characterized by different phenotypic and biological features. Neoplastic progression is driven by a subpopulation of cells within the tumor bulk defined as “cancer initiating cells”(CICs) with stemness features. Modulation of cancer initiating properties is a consequence of genetic and epigenetic changes in cancer cells combined with their interaction with the surrounding microenvironment.
To investigate how microenvironmental signals could influence the stemness properties and how these signals are integrated in tumors with different phenotypic features, eight non-small cell lung cancer cell lines were exposed to external stimuli such as TGFβ.
The frequency of CD133, previously identified as a marker of stemness in lung cancer, was evaluated by flow cytometry and the expression of epithelial and mesenchymal genes was analyzed by Real-Time PCR and immunofluorescence (IF) or immunohystochemistry (IHC).
TGFβ treatment resulted in heterogeneous increased of CD133+ cells and the extent of response was strictly dependent on the ratio between epithelial and mesenchymal features, estimated by the expression of E-cadherin and SNAI2 genes. Only cells that reached a critical threshold in the balance between epithelial and mesenchymal traits were able to generate CICs, acquiring increased in vivo tumorigenic properties in response to external stimuli. Consistently, in cell lines that reached the critical threshold by modulating the epithelial-mesenchymal balance through over expression of miR-200c or demethylation of E-cadherin promoter, the ability to acquire stemness phenotype under microenvironmental stimuli was restored. Single-cell analysis showed the presence of a sub-population of cells expressing both epithelial and mesenchymal markers that could be responsible of the phenotypic plasticity within different cell lines. Moreover, the evaluation of 60 primary lung tumors by IHC discovered a specific pattern of E-cadherin a SNAI2 that identify patients with worst prognosis.
Together these findings provided new insight to understand how dynamic modulation of epithelial and mesenchymal properties determines the plasticity of lung cancer cells through the generation of cancer initiating cells in response to microenviromental stimuli.
Citation Format: Francesca Andriani, Giulia Bertolini, Federica Facchinetti, Erika Baldoli, Massimo Moro, Patrizia Casalini, Roberto Caserini, Ugo Pastorino, Gabriella Sozzi, Luca Roz. Conversion to stem cell state in response to microenvironmental cues is regulated by balance between epithelial and mesenchymal features in lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1395. doi:10.1158/1538-7445.AM2015-1395