CD26− NFs primarily express collagens (Col15a1, Col18a1, Col4a1, Col4a2 and Col5a3) and proteins involved in collagen fibril formation, which have been previously linked to inhibition of angiogenesis, metastasis and tumor suppression (Dcn, Lum, Sparcl1 and Anxa5)38–40. This evidence concerns the gene COL15A1 and neoplasm.