Single-Molecule Localization Microscopy allows for the analysis of cancer metastasis-specific miRNA distribution on the nanoscale
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Olga Oleksiuk1,2,*, Mohammed Abba1,2,*, Kerem Can Tezcan1,2, Wladimir Schaufler3,4, Felix Bestvater3, Nitin Patil1,2, Udo Birk5, Mathias Hafner6, Peter Altevogt7, Christoph Cremer5,8, Heike Allgayer1,2
1Department of Experimental Surgery, Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
2Centre for Biomedicine and Medical Technology Mannheim, University of Heidelberg, Heidelberg, Germany
3Light Microscopy Facility, German Cancer Research Centre (DKFZ), Heidelberg, Germany
4Karlsruhe Institute of Technology, Karlsruhe University, Karlsruhe, Germany
5Institute of Molecular Biology (IMB), Mainz, Germany
6Institute for Molecular and Cellular Biology, Mannheim University of Applied Sciences, Mannheim, Germany
7Skin Cancer Unit, German Cancer Research Center (DKFZ), Heidelberg and Dept. of Dermatology, Venereology and Allergology, UMM, University of Heidelberg, Heidelberg, Germany
8Institute of Pharmacy and Molecular Biotechnology (IPMB), Heidelberg, Germany
*These authors have contributed equally to this work
Heike Allgayer, e-mail: firstname.lastname@example.org
Christoph Cremer, e-mail: email@example.com
Keywords: microRNAs, miR-31, super-resolution, localization microscopy, metastasis
Received: May 19, 2015 Accepted: October 23, 2015 Published: November 05, 2015
We describe a novel approach for the detection of small non-coding RNAs in single cells by Single-Molecule Localization Microscopy (SMLM). We used a modified SMLM–setup and applied this instrument in a first proof-of-principle concept to human cancer cell lines. Our method is able to visualize single microRNA (miR)-molecules in fixed cells with a localization accuracy of 10–15 nm, and is able to quantify and analyse clustering and localization in particular subcellular sites, including exosomes. We compared the metastasis-site derived (SW620) and primary site derived (SW480) human colorectal cancer (CRC) cell lines, and (as a proof of principle) evaluated the metastasis relevant miR-31 as a first example. We observed that the subcellular distribution of miR-31 molecules in both cell lines was very heterogeneous with the largest subpopulation of optically acquired weakly metastatic cells characterized by a low number of miR-31 molecules, as opposed to a significantly higher number in the majority of the highly metastatic cells.
Furthermore, the highly metastatic cells had significantly more miR-31-molecules in the extracellular space, which were visualized to co-localize with exosomes in significantly higher numbers. From this study, we conclude that miRs are not only aberrantly expressed and regulated, but also differentially compartmentalized in cells with different metastatic potential. Taken together, this novel approach, by providing single molecule images of miRNAs in cellulo can be used as a powerful supplementary tool in the analysis of miRNA function and behaviour and has far reaching potential in defining metastasis-critical subpopulations within a given heterogeneous cancer cell population.
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