Abstract 962: A hybrid epithelial-mesenchymal phenotype identifies lung cancer cells with high metastatic potential due to increased stemness properties and escape from NK immunosurveillance

Abstract

Abstract Introduction: Epithelial to mesenchymal transition (EMT) is essential for cancer dissemination but its role in overt metastasis establishment remains an open issue. Multiple EMT states and great phenotypic plasticity have also been described, indicating the need for in-depth characterization of biological properties associated with different EMT phenotypes. The so-called hybrid phenotype, characterized by presence of both mesenchymal and epithelial markers, might in fact identify cancer cells with enhanced metastatic propensity. Materials and Methods: To assess the metastatic potential of different EMT phenotypes, we exploited two lung cancer cell lines with different properties (A549/epithelial and LT73/hybrid) and generated their respective sublines through four sequential rounds of in vitro migration assay (named M4). TGFβ treatment was also used to induce EMT. With a previously validated score based on the ratio between expression of epithelial (CDH1) or mesenchymal genes (SNAI2), cells were classified as: epithelial (A549)>hybrid (A549-M4, LT73)>mesenchymal (LT73-M4, A549-TGFβ). The disseminating/metastatic properties of the different lines were tested in vivo by subcutaneous and tail-vein injections in SCID mice. Interaction with NK cells (NKs), known to specifically target EMT cancer cells, was also assessed. Results and Discussion: Compared to parental cells, M4 cells showed up-regulation of EMT-associated genes, expansion of the subset of CD133+ lung cancer stem cells (CSC) and displayed in vivo higher ability to disseminate from primary tumors to murine lungs (2-fold change, p=0.004). However, hybrid cells (LT73 and A549-M4) showed an increased ability to generate overt lung metastases in experimental metastasis assays compared to either epithelial (A549) or mesenchymal cells (LT73-M4 and A549-TGFβ). The higher metastatic ability of hybrid cells was correlated with CSCs expansion and reduced NKs infiltration to the metastatic lungs. Expression of IL-8, a cytokine involved in NKs recruitment, was decreased in hybrid cells and they were less prone to chemoattract NKs in vitro compared to both epithelial and mesenchymal cells. Finally, in vivo prevention of NKs recruitment to the lungs using a neutralizing antibody, massively increased metastasis formation and expansion of CSCs in mice injected i.v. with mesenchymal A549-TGFβ (p=0.0006), but had limited effects in groups injected with both epithelial A549 and hybrid A549-M4. Conclusions: Our data indicate that the hybrid phenotype correlates with the highest metastatic potential related to efficient cancer cell dissemination, increased induction of stemness features and ability to avoid NKs recruitment. Conversely, fully mesenchymal cells show limited metastatic potential, possibly due the control exerted by NKs on their CSC subsets. Citation Format: Giulia Bertolini, Monica Parodi, Massimo Milione, Fabio Murianni, Giovanni Centonze, Giulia Taiè, Gabriella Sozzi, Massimo Vitale, Luca Roz. A hybrid epithelial-mesenchymal phenotype identifies lung cancer cells with high metastatic potential due to increased stemness properties and escape from NK immunosurveillance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 962.