Disrupting ATF4 expression mechanisms provides an effective strategy for BRAF-targeted melanoma therapy (Knockdown Series)

BRAF V600 mutation influences cellular signaling pathways for melanoma development. Here, we show that mutated BRAF plays an essential role in the adaptive stress response following activation of general control non-derepressible 2 (GCN2) kinase. In parallel with GCN2, BRAF ensures ATF4 induction by utilizing mTOR and eIF4B as downstream regulators during nutrient stress and BRAF-targeted, therapeutic stress. Upon pharmacological BRAF inhibition, this signaling pathway exhibits temporal resistance, compared with the MEK-ERK pathway, thereby enabling transient induction of ATF4 under GCN2 activation. Notably, the prevention of GCN2 activation, using a chemical inhibitor that we identified, produces synergistic cell killing with BRAF inhibition. Thus, oncogenic BRAF can collaborate with the GCN2–ATF4 pathway, promoting stress adaptation for cell survival. We examined the gene expression change in BRAF-mutated melanoma A375 cells transfected with siRNA specific for BRAF and cultured in glutamine-free medium for 18 h, or A375 cells transfected with siRNA specific for ATF4 and then treated with vemurafenib for 4 h.