To define metastasis‐specific CAF profiles by scRNA sequencing, we applied the MT‐ret melanoma fragment transplantation model (Gengenbacher et al. 2021) (MT‐ret–derived model) and combined it with mT/mG mice (Gt (ROSA)26Sortm4(ACTB‐tdTomato,‐EGFP)Luo/J) (Muzumdar et al. 2007), generating MM primary tumor samples and corresponding lung metastases, in which engrafted tumor cells are unlabeled while host TME cells constitutively express tdTomato (Figure S1a). This evidence concerns the gene ACTB and melanoma.