Conditional lethality profiling reveals anticancer mechanisms of action and drug-nutrient interactions

Area of Science:

• Biochemistry
• Pharmacology
• Cancer Biology

Background:

• Human cancer drug sensitivity varies by genotype and lineage.
• Traditional cell culture media do not accurately reflect human blood metabolite levels.
• This limits the discovery of effective cancer therapeutics.

Purpose of the Study:

• To investigate drug efficacy using a more physiologically relevant cell culture medium.
• To identify novel drug-nutrient interactions and mechanisms of action in cancer cells.
• To explore conditional lethality as a strategy for drug discovery.

Main Methods:

• Performed chemical drug screens in traditional media and Human Plasma-Like Medium (HPLM).
• Compared compound activities across different media to identify conditional phenotypes.
• Analyzed media components to link phenotypes to specific nutrients, such as nucleotide synthesis substrates.
• Investigated the mechanism of action for brivudine, an antiviral drug, in cancer cells.
• Utilized gene essentiality data to identify potential off-target effects.

Main Results:

• Identified sets of compounds with conditional anticancer activity, including non-oncology drugs.
• Linked conditional phenotypes to nucleotide synthesis substrates by comparing media components.
• Characterized brivudine's dual mechanism: impaired cell growth in low folate by targeting one-carbon metabolism enzymes.
• Found evidence that conditional phenotypes for other drugs may result from off-target effects.

Conclusions:

• Human Plasma-Like Medium (HPLM) is crucial for uncovering context-dependent drug activities.
• Drug-nutrient interactions and mechanisms of action can be identified through conditional lethality screens.
• Brivudine exhibits selective toxicity in low-folate conditions via targeting one-carbon metabolism.
• This approach provides a general strategy for discovering cancer drugs and understanding their mechanisms.