ATG4B inhibitors with a benzotropolone core structure block autophagy and augment efficiency of chemotherapy in mice

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• Autophagy is a cellular process crucial for survival, often exploited by tumors to withstand harsh microenvironments.
• Existing autophagy inhibitors like (hydroxy)chloroquine show limited success and toxicity, necessitating novel therapeutic targets.
• The autophagy protein ATG4B is essential for this process and presents a potential target for cancer therapy.

Purpose of the Study:

• To synthesize and evaluate novel benzotropolone derivatives as ATG4B inhibitors.
• To assess the efficacy of these compounds in inhibiting autophagy both in vitro and in vivo.
• To determine if ATG4B inhibition can enhance the effectiveness of chemotherapy in preclinical cancer models.

Main Methods:

• A library of 27 benzotropolone compounds was synthesized and screened for inhibition of recombinant ATG4B.
• Active compounds were tested in cellular assays to confirm ATG4B inhibition and autophagy suppression, including LC3 processing and autophagosome formation.
• The lead compound, UAMC-2526, was evaluated in vivo using mouse models with nutrient deprivation and colorectal tumor xenografts, and in combination with oxaliplatin.

Main Results:

• Benzotropolone derivatives exhibited varying degrees of ATG4B inhibition, with some reaching 82% efficacy.
• Seven compounds successfully inhibited LC3 processing and autophagosome formation in cellular assays.
• UAMC-2526 demonstrated significant autophagy suppression in vivo and markedly improved tumor growth inhibition when combined with oxaliplatin.

Conclusions:

• ATG4B is a viable target for developing novel autophagy inhibitors.
• Benzotropolone derivatives, particularly UAMC-2526, show promise for suppressing tumor autophagy.
• Targeting ATG4B-mediated autophagy represents a feasible strategy to enhance chemotherapy efficacy and combat tumor progression.