Effect of early-stage autophagy inhibition in BRAFV600E autophagy-dependent brain tumor cells

Background: Autophagy is a multi-step process, with recent advances enabling the development of inhibitors targeting both its early (initiation) and late (fusion) stages. The specific point of inhibition may influence therapeutic outcomes in cancer. We previously demonstrated that BRAFV600E-mutant central nervous system (CNS) tumors rely on autophagy, and that blocking late-stage autophagy enhances the efficacy of BRAF inhibitors (BRAFi), even in resistant cells.

Objective: While early-stage autophagy inhibition has been shown to reduce tumor cell survival in some cancers, its role in CNS tumors remains unexplored. We assessed the impact of early-stage inhibition in autophagy-dependent CNS tumor models.

Methods: BRAFi-sensitive and -resistant AM38 and MAF794 CNS tumor cell lines were treated with pharmacologic and genetic inhibitors targeting ULK1 and VPS34—key regulators of autophagy initiation. Autophagic activity was measured using western blotting and flow cytometry. Cell viability was assessed in both short- and long-term assays.

Results: Both pharmacologic and genetic inhibition of ULK1 and VPS34 suppressed autophagic flux and reduced tumor cell survival in a dose-dependent manner. Genetic approaches confirmed the specificity of the autophagy-related effects. Furthermore, early-stage inhibition synergized with BRAFi treatment, regardless of intrinsic sensitivity.

Conclusions: Targeting autophagy initiation via ULK1 and VPS34 may be a viable therapeutic strategy for BRAFV600E-mutant CNS tumors. Further studies are warranted to compare the efficacy of early- versus late-stage inhibition VPS34-IN1 and optimize autophagy-targeted interventions in clinical settings.