MIR21 and neoplasm: Supporting the MIR21-mediated regulation of JAM-A mRNA translation observed in CRC cell lines, overexpression of MIR21 in a metastatic CRC PDO line (Supplementary Fig. S6B) also resulted in reduced JAM-A protein levels both ex vivo and in vivo and, despite the small sample size (n = 2 per condition), was associated with increased tumour proliferation (Fig. 5F, G and Supplementary Fig. S6C).