title: Mesenchymal to amoeboid transition is associated with stem-like features of melanoma cells.
abstract: BACKGROUND
  Cellular plasticity confers cancer cells the ability to adapt to microenvironmental changes, a fundamental requirement for tumour progression and metastasis. The epithelial to mesenchymal transition (EMT) is a transcriptional programme associated with increased cell motility and stemness. Besides EMT, the mesenchymal to amoeboid transition (MAT) has been described during tumour progression but to date, little is known about its transcriptional control and involvement in stemness. The aim of this manuscript is to investigate (i) the transcriptional profile associated with the MAT programme and (ii) to study whether MAT acquisition in melanoma cancer cells correlates with clonogenic potential to promote tumour growth.
  
  
  RESULTS
  By using a multidisciplinary approach, we identified four different treatments able to induce MAT in melanoma cells: EphA2 overexpression, Rac1 functional inhibition using its RacN17 dominant negative mutant, stimulation with Ilomastat or treatment with the RhoA activator Calpeptin. First, gene expression profiling identified the transcriptional pathways associated with MAT, independently of the stimulus that induces the MAT programme. Notably, gene sets associated with the repression of mesenchymal traits, decrease in the secretion of extracellular matrix components as well as increase of cellular stemness positively correlate with MAT. Second, the link between MAT and stemness has been investigated in vitro by analysing stemness markers and clonogenic potential of melanoma cells undergoing MAT. Finally, the link between MAT inducing treatments and tumour initiating capability has been validated in vivo.
  
  
  CONCLUSIONS
  Taken together, our results demonstrate that MAT programme in melanoma is characterised by increased stemness and clonogenic features of cancer cells, thus sustaining tumour progression. Furthermore, these data suggest that stemness is not an exclusive feature of cells undergoing EMT, but more generally is associated with an increase in cellular plasticity of cancer cells.
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Taddei
authors.forename: Elisa
authors.initials: E
authors.lastname: Giannoni
authors.forename: Andrea
authors.initials: A
authors.lastname: Morandi
authors.forename: Luigi
authors.initials: L
authors.lastname: Ippolito
authors.forename: Matteo
authors.initials: M
authors.lastname: Ramazzotti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Callari
authors.forename: Paolo
authors.initials: P
authors.lastname: Gandellini
authors.affiliation: Department of Experimental and Clinical Biomedical Sciences, Tuscany Tumor Institute, University of Florence, viale Morgagni 50, Florence 50134, Italy. paola.chiarugi@unifi.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Chiarugi
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement; D004151:Dipeptides / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000502:physiology; D036104:Receptor, EphA2 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000819:agonists / Q000235:genetics / Q000378:metabolism
chemical_list: D004151:Dipeptides; C071482:calpeptin; D036104:Receptor, EphA2; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein