BH3 profiling discriminates on-target small molecule BH3 mimetics from putative mimetics

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Inhibiting cancer cell anti-apoptotic proteins with BH3 mimetics is a key therapeutic strategy.
• Authentic BH3 mimetics must directly target mitochondria, bind selectively to anti-apoptotic proteins, and induce apoptosis.
• Current validation methods are insufficient, leading to misidentification of BH3 mimetics.

Purpose of the Study:

• To develop and validate a comprehensive biochemical toolkit for assessing BH3 mimetic candidates.
• To ensure compounds function directly on mitochondria and induce apoptosis in a BAX/BAK-dependent manner.
• To improve the identification and development of potent and selective BH3 mimetics, especially MCL-1 inhibitors.

Main Methods:

• BH3 profiling to measure cytochrome c release, a marker for mitochondrial outer membrane permeabilization (MOMP).
• Parallel high-throughput Annexin V/Hoechst viability testing.
• Utilized standardized cell lines with known anti-apoptotic dependence, including a BAX/BAK double knockout (DKO) control line.

Main Results:

• The toolkit successfully validated eighteen putative BH3 mimetics.
• The BAX/BAK DKO line effectively identified compounds acting independently of the BCL-2 family.
• The proposed toolkit provides a rapid and efficient means for validating BH3 mimetic candidates.

Conclusions:

• The developed toolkit offers a reliable method for validating BH3 mimetic activity at the mitochondrial level.
• This approach is crucial for distinguishing true BH3 mimetics from off-target agents.
• Adoption of this toolkit will enhance the discovery of potent and selective BH3 mimetics for clinical applications, particularly for MCL-1 inhibition.