PECAM1 and neoplasm: However, staining of B16F10 tumours from Atf4WT/WT and Atf4Δ/Δ mice for VEGF and CD31 and CXCL12 and CD31 showed that although there was no difference in the total signal of areas positive for VEGF and CXCL12 (Extended Data Fig. 8d,e), the levels of both angiogenic factors were lower in the perivascular areas of tumours grown in Atf4Δ/Δ mice (Fig. 5h–k).