COL1A1 and neoplasm: In contrast to the small tumours, no difference was observed in the expression levels of Col1a1 and Col1a2 between the Atf4WT/WT and Atf4Δ/Δ cohorts (Extended Data Fig. 2i), which suggests that there is activation of an alternative mechanism of Col1 gene expression to compensate for ATF4 loss during tumour progression.