ATF4 and neoplasm: Interestingly, the induction of PSAT1 and PHGDH was equivalent or even more pronounced in the double-treated tumours compared to the tumours from mice fed a -SG diet only, showing that, in vivo, the combination treatment did not reduce available serine sufficiently to compromise the ability of tumour cells to induce an ATF-4 response (Supplementary Figure 7f, g).