![]() The same areas from 300 nm sections were imaged by fluorescence microscopy (GFP) and EM. b Correlative light and electron microscopy (CLEM) of SkMel2 cells expressing ezrin-GFP. Further PH domains are shown in Supplementary Fig. a SkMel2 cells in suspension transfected with the indicated plasmids (PLCδ-PH, Akt-PH: RFP-labelled PIP 2-binding PH domains of PLCδ and Akt/PKB), stained with phalloidin or DiI and DAPI and the indicated antibodies (P-ERM: phosphorylated ezrin/radixin/moesin, podocal: podocalyxin). Furthermore, in suspension the ezrin pole was not aligned with the nuclear–centrosomal axis, distinguishing it from uropod-like structures of amoeboid migrating cells 12, 13 (Supplementary Fig. 1a), demonstrating that sc polarity is distinct from apical–basal polarity. Interestingly, the apical marker podocalyxin was polarised in detached cells, however, independently of the ezrin pole, localising to a PM area located distal to the nucleus (Fig. 1a) while the polarity regulator Protein Kinase C ζ did not co-localize with the ezrin pole (Fig. The PM itself was accumulated at the pole and enriched with phosphatidylinositol 4,5-bisphosphate (PIP 2, Fig. Additionally, polar accumulation of F-actin and the plasma membrane (PM) receptors CD44, β1-Integrin, melanoma cell adhesion molecule (MCAM) and intercellular adhesion molecule-1 (ICAM-1) was observed (Fig. Ezrin-green fluorescent protein (GFP) as well as endogenous ezrin, moesin, Radixin-GFP and phosphorylated ezrin/radixin/moesin proteins accumulated at one pole of single cells in suspension (Fig. ![]() To investigate sc polarity in tumour cells in liquid phase, polarity markers of different polar structures of single cells 9, 10, 11, 12, 13 were imaged in human SkMel2 melanoma cells in suspension (Fig. Tumour cells maintain their polarity in liquid phase We find that sc polarity affects attachment, adhesion, transmigration and metastasis. ![]() ![]() We characterise sc polarity in tumour cell lines and human tumour specimens from biopsies collected in liquid phase and investigate the role of sc polarity in human tumour cells, mouse models of metastasis and ex vivo. Sc polarity is defined by the intrinsic presence of an ezrin- and actin-rich pole in absence of an extracellular stimulus in non-adhering, non-migrating cells. Here we identify a distinct type of polarity termed single-cell (sc) polarity that tumour cells maintain in liquid phase. However, the polarisation of cells during liquid or detached phases and the relevance of such polarisation for metastasis have remained unclear. The metastatic cascade thus involves dynamic depolarisation and repolarisation of metastasising cells, reflecting their high plasticity. Throughout the metastatic process, solid tumour cells establish distinct types of polarity, such as apical–basal polarity in the tissue context of established primary or metastatic tumours or front–back polarity during migratory phases 7, 8. Metastasis is a multistep process comprising dedifferentiation, dissociation and local invasion of primary tumour cells, intravasation into blood or lymph vessels, survival and transport in circulation, arrest in microvessels of distant organs and extravasation and metastatic outgrowth 6. Despite novel promising targeted cancer therapies, patients diagnosed with systemic metastatic disease are no longer eligible for curative treatment options in many cancer subtypes 3, 4, 5 necessitating research on additional, broadly applicable strategies for metastasis intervention. ![]() Metastases are the major cause of cancer-related deaths 1, 2. Nature Communications volume 9, Article number: 887 ( 2018) Single cell polarity in liquid phase facilitates tumour metastasis ![]()
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