COL1A1 and neoplasm: Notably, the vCAFs were substantially reduced in Atf4Δ/Δ mice (Fig. 2g and Extended Data Fig. 3e), and Col1a1 and Col1a2 were significantly downregulated only in the vCAF subcluster in the small tumours in Atf4Δ/Δ mice (Fig. 2h).