ART4 and neoplasm: Surprisingly, circulating tumour cells (CTCs) in the blood upregulate expression of common stroma-derived ECM proteins, such as collagens (Col1a2, Col3a1), TIMP-2, the proteoglycan decorin (Dcn), the glycoprotein osteonectin (Sparc), and fibronectin, as revealed by single-cell RNA-sequencing of pancreatic CTCs (Fig. 4a)202,203.