BAX-BAK1-independent LC3B lipidation by BH3 mimetics is unrelated to BH3 mimetic activity and has only minimal effects on autophagic flux

<p>Inhibition of prosurvival BCL2 family members can induce autophagy, but the mechanism is controversial. We have provided genetic evidence that BCL2 family members block autophagy by inhibiting BAX and BAK1, but others have proposed they instead inhibit BECN1. Here we confirm that small molecule BH3 mimetics can induce BAX- and BAK1-independent MAP1LC3B/LC3B lipidation, but this only occurred at concentrations far greater than required to induce apoptosis and dissociate canonical BH3 domain-containing proteins that bind more tightly than BECN1. Because high concentrations of a less-active enantiomer of ABT-263 also induced BAX- and BAK1-independent LC3B lipidation, induction of this marker of autophagy appears to be an off-target effect. Indeed, robust autophagic flux was not induced by BH3 mimetic compounds in the absence of BAX and BAK1. Therefore at concentrations that are on target and achievable in vivo, BH3 mimetics only induce autophagy in a BAX- and BAK1-dependent manner.</p

Design, Synthesis, and Biological Activity of 1,2,3-Triazolobenzodiazepine BET Bromodomain Inhibitors

A number of diazepines are known to inhibit bromo- and extra-terminal domain (BET) proteins. Their BET inhibitory activity derives from the fusion of an acetyl-lysine mimetic heterocycle onto the diazepine framework. Herein we describe a straightforward, modular synthesis of novel 1,2,3-triazolobenzodiazepines and show that the 1,2,3-triazole acts as an effective acetyl-lysine mimetic heterocycle. Structure-based optimization of this series of compounds led to the development of potent BET bromodomain inhibitors with excellent activity against leukemic cells, concomitant with a reduction in c-<i>MYC</i> expression. These novel benzodiazepines therefore represent a promising class of therapeutic BET inhibitors