Mast cells promote melanoma colonization of lungs
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Helena Öhrvik1, Mirjana Grujic1, Ida Waern2, Ann-Marie Gustafson1, Nancy Ernst4, Axel Roers3, Karin Hartmann4, Gunnar Pejler1,2
1Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
2Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
3Institute for Immunology, University of Technology Dresden, Dresden, Germany
4Department of Dermatology, University of Luebeck, Luebeck, Germany
Karin Hartmann, email: email@example.com
Gunnar Pejler, email: Gunnar.Pejler@imbim.uu.se
Keywords: mast cells, Mcpt5, melanoma, inflammation, EMT
Received: June 30, 2016 Accepted: August 26, 2016 Published: September 02, 2016
Mast cells have been implicated in malignant processes, mainly through clinical correlative studies and by experiments performed using animals lacking mast cells due to defective c-kit signaling. However, mast cell-deficient mouse models based on c-kit defects have recently been questioned for their relevance. Here we addressed the effect of mast cells in a tumor setting by using transgenic Mcpt5-Cre+ R-DTA+ mice, in which the deficiency of mast cells is independent of c-kit defects. Melanoma cells (B16.F10) were administered either subcutaneously or intravenously into Mcpt5-Cre+ R-DTA+ mice or Mcpt5-Cre- R-DTA+ littermate controls, followed by the assessment of formed tumors. In the subcutaneous model, mast cells were abundant in the tumor stroma of control mice but were absent in Mcpt5-Cre+ R-DTA+ mice. However, the absence of mast cells did not affect tumor size. In contrast, after intravenous administration of B16.F10 cells, melanoma colonization of the lungs was markedly reduced in Mcpt5-Cre+ R-DTA+ vs. Mcpt5-Cre- R-DTA+ animals. Decreased melanoma colonization of the lungs in Mcpt5-Cre+ R-DTA+ animals was accompanied by increased inflammatory cell recruitment into the bronchoalveolar lavage fluid, suggesting that mast cells suppress inflammation in this setting. Further, qPCR analysis revealed significant alterations in the expression of Twist and E-cadherin in lungs of Mcpt5-Cre+ R-DTA+ vs. control Mcpt5-Cre- R-DTA+ animals, suggesting an impact of mast cells on epithelial-mesenchymal transition. In conclusion, this study reveals that mast cells promote melanoma colonization of the lung.
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