A DHODH inhibitor increases p53 synthesis and enhances tumor cell killing by p53 degradation blockage

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• p53 is a crucial tumor suppressor, and activating its wild-type form is a promising non-genotoxic cancer therapy strategy.
• Identifying small-molecules that can activate wild-type p53 is of significant therapeutic interest.

Purpose of the Study:

• To identify novel small-molecules that activate wild-type p53 in cancer cells.
• To elucidate the mechanism of action for identified p53-activating compounds.
• To explore dihydroorotate dehydrogenase (DHODH) as a potential target for p53 activation-based cancer therapies.

Main Methods:

• High-throughput screening to identify p53-activating small-molecules.
• Target deconvolution and biochemical assays to determine the molecular targets of identified compounds.
• Crystal structure determination of drug-target complexes.
• Cell-based assays to assess cell cycle effects and p53 synthesis.
• In vivo tumor growth studies in combination with p53 degradation inhibitors.

Main Results:

• Over 100 small-molecules capable of activating p53 were identified.
• The chiral tetrahydroindazole HZ00 was found to inhibit dihydroorotate dehydrogenase (DHODH) via its active enantiomer, (R)-HZ00.
• Crystal structure analysis confirmed the chiral specificity of a more potent analog, (R)-HZ05, binding to DHODH.
• DHODH was identified as a frequent target for structurally diverse p53 activators.
• HZ compounds induced S-phase accumulation, increased p53 synthesis, and synergized with p53 degradation inhibitors to reduce tumor growth in vivo.

Conclusions:

• Dihydroorotate dehydrogenase (DHODH) is a validated target for small-molecules that activate wild-type p53.
• A strategy combining DHODH inhibition with impaired p53 degradation can promote cancer cell killing.
• These findings offer a novel therapeutic approach for cancer treatment by enhancing p53-mediated cell death.