Author response image 1. qPCR shows that IFN target genes are down-regulated in TIE:EGFP^high melanoma cells compared to TIE:EGFP^- melanoma cells.

Two Tg(mitfa:BRAF^V600E);p53^-/-;mitfa^-/- tumors expressing TIE:EGFP, mitfa:BFP and mpeg:mCherry were dissociated for FACS. We sorted two populations of cells: TIE:EGFP^high mitfa:BFP⁺ mpeg:mCherry^-, and TIE:EGFP^- mitfa:BFP⁺ mpeg:mCherry^-. Here, we gated for mitfa:BFP⁺ melanoma cells, gating out the macrophage population which may contain mitfa:BFP due to tumor cell phagocytosis. We isolated RNA from these sorted populations, performed cDNA synthesis, and performed qPCR. We used housekeeping gene b-actin to normalize values according to loading differences. Here, we confirmed that 4 major IFN genes discussed in the manuscript are down-regulated: irf7, irf1b, stat1b, and b2m. We included 3 additional IFN genes here to further validate the IFN pathway trend: mxa, mxb, and isg15. Fold change of mitfa is included here as a negative control, as we do not expect its expression to change between the two conditions. N=2 tumors, 3 technical replicates each. 2-tailed, unpaired t-tests were performed.