Collective cell migration of thyroid carcinoma cells: a beneficial ability to override unfavourable substrates.
OBJECTIVE
Tumor cell invasion and metastasis are life threatening events. Invasive tumor cells tend to migrate as collective sheets. In the present in vitro study we aimed to (i) assess whether collective tumor cells gain benefits in their migratory potential compared to single cells and (ii) to identify its putative underlying molecular mechanisms.


METHODS
The migratory potential of single and collective carcinoma cells was assessed using video time lapse microscopy and cell migration assays in the absence and presence of seven potential gap junction inhibitors or the Rac1 inhibitor Z62954982. The perturbation of gap junctions was assessed using a dye diffusion assay. In addition, LDH-based cytotoxicity and RT-PCR-based expression analyses were performed.


RESULTS
Whereas single breast, cervix and thyroid carcinoma cells were virtually immobile on unfavourable plastic surfaces, we found that they gained pronounced migratory capacities as collectives under comparable conditions. Thyroid carcinoma cells, that were studied in more detail, were found to express specific subsets of connexins and to form active gap junctions as revealed by dye diffusion analysis. Although all potential gap junction blockers suppressed intercellular dye diffusion in at least one of the cell lines tested, only two of them were found to inhibit collective cell migration and none of them to inhibit single cell migration. In the presence of the Rac1 inhibitor Z62954982 collective migration, but not single cell migration, was found to be reduced up to 20 %.


CONCLUSIONS
Our data indicate that collective migration enables tumor cells to cross otherwise unfavourable substrate areas. This capacity seems to be independent of intercellular communication via gap junctions, whereas Rac1-dependent intracellular signalling seems to be essential.
Neuro- and Tumor Cell Biology Group, Department of Nuclear Medicine, University Hospital Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany.
Liudmila
L
Lobastova
Department of Prosthodontics, Preclinical Education, and Material Science, University of Bonn, Bonn, Germany.
Dominik
D
Kraus
Life Science Inkubator, Bonn, Germany.
Alexander
A
Glassmann
Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany.
Dilaware
D
Khan
Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany.
Christian
C
Steinhäuser
Neuro- and Tumor Cell Biology Group, Department of Nuclear Medicine, University Hospital Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany.
Christina
C
Wolff
Neuro- and Tumor Cell Biology Group, Department of Nuclear Medicine, University Hospital Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany.
Nadine
N
Veit
Oral Cell Biology Group, Department of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany.
Jochen
J
Winter
Neuro- and Tumor Cell Biology Group, Department of Nuclear Medicine, University Hospital Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany. r.probstmeier@uni-bonn.de.
Rainer
http://orcid.org/0000-0001-7671-0373
R
Probstmeier
D001943:Breast Neoplasms / Q000473:pathology; D002450:Cell Communication / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D006801:Humans; D009361:Neoplasm Invasiveness / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013964:Thyroid Neoplasms / Q000473:pathology*; D002583:Uterine Cervical Neoplasms / Q000473:pathology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
C107953:RAC1 protein, human; D020830:rac1 GTP-Binding Protein
Collective cell migration; Gap junction; Rac; Single cell migration; Thyroid carcinoma