COL1A1 and neoplasm: IL-6 has also been shown to regulate collagen expression42, however, Col1a1 (Fig. 5h) as well as other ECM proteins expressed in 4T1 tumours (Supplementary Figure 5b) Col3a1, Tnc and Fn1, were unaffected by the loss of IL-6 (Supplementary Figure 6g–i).