Figure 3. Reduced melanoma colonization in lungs from Mcpt5-Cre⁺ vs. Mcpt5-Cre⁻ mice.

Melanoma cells (B16.F10) were intravenously injected into Mcpt5-Cre⁻ or Mcpt5-Cre⁺ mice. After 11 days, lungs were excised. A. Representative images of lungs from Mcpt5-Cre⁻ and Mcpt5-Cre⁺ mice. Note the abundance of melanoma nodules in lungs from Mcpt5-Cre⁻ mice and the lower content of nodules in lungs from Mcpt5-Cre⁺ mice. B. Quantification of melanoma nodules; n = 8-9, ** p < 0.01. C. Representative image of lungs from Mcpt5-Cre⁻ animals after melanoma administration. Melanoma areas are marked by arrowheads. D. Representative image of lungs from Mcpt5-Cre⁺ animals after melanoma administration. Melanoma accumulations are marked by arrowheads. E. Image showing the presence of mast cells (arrows; toluidine blue staining) in areas at a distance from the melanoma tumors (arrowhead). (C-E): Original magnification = 100 x; Bar = 100 μm. F. Representative image showing that mast cells occasionally are found in the immediate vicinity to melanoma tumors. G. Representative image showing a higher magnification of a lung tissue section from an Mcpt5-Cre⁻ animal. Note the presence of highly granulated, toluidine blue-positive mast cells (arrows). H. Representative image showing a higher magnification of a lung tissue section from an Mcpt5-Cre⁺ animal. Note the presence of toluidine blue-positive mast cells (arrow). (F-H): Original magnification = 400 x; Bar = 50 μm. I. mRNA was extracted from lungs of melanoma-treated Mcpt5-Cre⁻ or Mcpt5-Cre⁺ mice (+B16). As a control, mRNA was extracted from naïve animals (PBS). mRNA was analyzed by qPCR for the levels of transcripts for Dct2 and Gp100; mean values ± SEM; n = 4-6; * p < 0.05, ** p < 0.01. J. Correlation between the expression of Gp100 and Dct2. Regression analysis: R-sq (adj) = 98.7; p < 0.001; n = 10. K. Correlation between expression of Gp100 and number of melanoma nodules in lungs. Regression analysis: R-sq (adj) = 82.9; p < 0.001; n =10.