Mouse melanoma types with various genotypes

Only a subset of melanoma patients has evidence for spontaneous T cell infiltration into tumor sites, previously associated with clinical responses. However, the molecular mechanisms explaining absence of a T cell response are not yet defined. Analyses of human melanoma metastases have revealed that T cell signature low tumors show alterations in the Wnt/b-catenin signaling pathway. We utilized an inducible mouse model driven by inducible BrafV600E and PTEN-deletion, with or without active b-catenin (CAT-STA) to test if tumor intrinsic active b-catenin can block anti-tumor immunity. While Braf/PTEN melanomas showed presence of a T cell infiltrate, T cells were nearly completely eliminated in tumors expressing active b-catenin. Adoptive transfer experiments revealed defective T cell priming when tumors expressed active b-catenin. Analysis of the antigen-presenting cell compartment revealed a selective decrease in the CD103+ DC subset within the tumor microenvironment, which could be associated with b-catenin depended inhibition of expression of the chemokine CCL4 within tumor cells. Here we used 3 mice of each genotype BrafV600E/PTEN-/- and BrafV600E/PTEN-/-/Cat-STA and compared their gene-expression profiles.