Hypomorph mutation-directed small-molecule protein-protein interaction inducers to restore mutant SMAD4-suppressed...

Area of Science:

• Oncology
• Molecular Biology
• Chemical Biology

Background:

• Tumor suppressor genes are crucial in preventing cancer but are challenging to target directly when mutated.
• Loss-of-function mutations in tumor suppressors like SMAD4 are common in various cancers.
• Restoring tumor suppressor function offers a therapeutic strategy.

Purpose of the Study:

• To develop a chemical biology approach to reverse the lost function of tumor suppressors.
• To identify small molecules that can restore tumor suppressor activity using SMAD4 as a model.
• To explore the potential of protein-protein interaction (PPI) molecular glues for cancer therapy.

Main Methods:

• Development of a time-resolved Förster resonance energy transfer (TR-FRET) technology to study SMAD4 interactions.
• Screening for compounds that modulate the interaction between SMAD4 variants and SMAD3.
• Assessing the effect of identified compounds on transcriptional activity and tumor suppression in cancer cells.

Main Results:

• A TR-FRET assay successfully differentiated interactions of SMAD4 and its mutant SMAD4^R361H with SMAD3.
• Ro-31-8220, a bisindolylmaleimide derivative, was identified as an inducer of SMAD4^R361H/SMAD3 interaction.
• Ro-31-8220 restored SMAD4^R361H-mediated transcriptional activity and TGF-β-induced tumor suppression in SMAD4 mutant cancer cells.

Conclusions:

• The study demonstrates a strategy to reverse the lost function of tumor suppressors with hypomorphic mutations.
• Ro-31-8220 serves as a proof-of-concept for targeting SMAD4 mutations and restoring its tumor-suppressive role.
• This approach supports the development of small-molecule PPI molecular glues for therapeutic discovery in oncology.