Contribution of acidic melanoma cells undergoing epithelial-to-mesenchymal transition to aggressiveness of non-acidic melanoma cells
- 514 Downloads
Tumor cell plasticity largely depends on epithelial-to-mesenchymal transition (EMT) and its reversion. It was ascertained that EMT characterizes disease progression, including melanoma malignancy. As most solid tumors, melanoma shows extracellular acidosis, we analyse the impact of acidic environment on the EMT development in human melanoma cells. Melanoma cells were exposed to an acidic extracellular environment (pH 6.7) and tested for EMT markers. We found that acidic cells express a significant up-regulation of mesenchymal markers (N-cadherin, Vimentin), transcription factors (Twist, NF-κB) and a significant, although modest, reduction of E-cadherin expression. Acidic cell also express an increased invasiveness through Matrigel associated with an up-regulation of MMP-9 activity. When we injected acidic cells intravenously into immunodeficient animals, we found a number of lung micrometastases not different from non-acidic cells. Indeed, they show a partial G1 cell cycle arrest, which might interfere with the growth of lung colonies. When we investigated the in vitro invasiveness and lung colonization of a mixed population of acidic and non acidic melanoma cells, we found that acidic cells promote in vitro invasiveness of non-acidic cells and this cooperation leads to an higher migration rate than acidic cells. Moreover, acidic cells cooperate for a better lung colonization of non-acidic cells, that represent the greater part of cells participating to lung micrometastases. We found evidence that acidity triggers in melanoma cells an EMT program, which although “incomplete”, potentiates migration rate and development of lung colonies into immunodeficient host of cells grown in standard pH.
KeywordsExtracellular acidity Epithelial-to-mesenchymal transition NF-κB Invasiveness Tumor cell dissemination Human melanoma
This study was financially supported by grants from Istituto Toscano Tumori and Ente Cassa di Risparmio di Firenze.
Conflict of interest
The authors declare that they have no conflict of interest.
- 1.Alonso SR, Tracey L, Ortiz P, Pérez-Gómez B, Palacios J, Pollán M, Linares J, Serrano S, Sáez-Castillo AI, Sánchez L, Pajares R, Sánchez-Aguilera A, Artiga MJ, Piris MA, Rodríguez-Peralto JL (2007) A high-throughput study in melanoma identifies epithelial–mesenchymal transition as a major determinant of metastasis. Cancer Res 67:3450–3460PubMedCrossRefGoogle Scholar
- 4.Mani SA, Guo W, Liao MJ, Eaton EN, Ayyanan A, Zhou AY, Brooks M, Reinhard F, Zhang CC, Shipitsin M, Campbell LL, Polyak K, Brisken C, Yang J, Weinberg RA (2008) The epithelial–mesenchymal transition generates cells with properties of stem cells. Cell 133:704–715PubMedCentralPubMedCrossRefGoogle Scholar
- 23.Fischer K, Hoffmann P, Voelkl S, Meidenbauer N, Ammer J, Edinger M, Gottfried E, Schwarz S, Rothe G, Hoves S, Renner K, Timischl B, Mackensen A, Kunz-Schughart L, Andreesen R, Krause SW, Kreutz M (2007) Inhibitory effect of tumor cell-derived lactic acid on human T cells. Blood 109:3812–3819PubMedCrossRefGoogle Scholar
- 35.Kato Y, Lambert CA, Colige AC, Mineur P, Noël A, Frankenne F, Foidart JM, Baba M, Hata R, Miyazaki K, Tsukuda M (2005) Acidic extracellular pH induces matrix metalloproteinase-9 expression in mouse metastatic melanoma cells through the phospholipase D-mitogen-activated protein kinase signaling. J Biol Chem 280:10938–10944PubMedCrossRefGoogle Scholar
- 38.Celià-Terrassa T, Meca-Cortés O, Mateo F, de Paz AM, Rubio N, Arnal-Estapé A, Ell BJ, Bermudo R, Díaz A, Guerra-Rebollo M, Lozano JJ, Estarás C, Ulloa C, Álvarez-Simón D, Milà J, Vilella R, Paciucci R, Martínez-Balbás M, de Herreros AG, Gomis RR, Kang Y, Blanco J, Fernández PL, Thomson TM (2012) Epithelial–mesenchymal transition can suppress major attributes of human epithelial tumor-initiating cells. J Clin Invest 122:1849–1868PubMedCentralPubMedCrossRefGoogle Scholar