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. The gene discussed is ATF4; the disease is neoplasm.