A Small-Molecule Inhibitor of Lin28

Area of Science:

• RNA Biology
• Chemical Biology
• Drug Discovery

Background:

• The Lin28/let-7 interaction is a key regulator in certain cancers, blocking tumor suppressor microRNA synthesis.
• Targeting RNA-protein interactions, like Lin28 and let-7, is challenging for drug development.
• The Lin28/let-7 axis plays a critical role in stem cell biology and various diseases.

Purpose of the Study:

• To develop a chemical tool for targeting the Lin28/let-7 interaction.
• To identify small molecule antagonists of Lin28 that can restore let-7 function.
• To explore the potential of targeting the Lin28/let-7 axis as a therapeutic strategy for cancers.

Main Methods:

• Development of a protein/RNA Förster Resonance Energy Transfer (FRET) assay using GFP-Lin28 and a BHQ-labeled let-7 mimic.
• Screening of 16,000 molecules using the developed FRET assay.
• In vitro and in cell-based assays to validate the identified compound's mechanism and efficacy.

Main Results:

• Identified N-methyl-N-[3-(3-methyl[1,2,4]triazolo[4,3-b]pyridazin-6-yl)phenyl]acetamide as a Lin28/let-7 interaction inhibitor.
• The compound rescued let-7 processing and function in cancer cells, induced stem cell differentiation, and reduced tumor-sphere formation.
• A biotinylated derivative confirmed on-target engagement with Lin28 in cell lysates, although some off-target activity was noted.

Conclusions:

• The Lin28/let-7 interaction can be targeted by small molecules, offering a new therapeutic avenue for specific cancers.
• The developed FRET assay is a valuable tool for screening inhibitors of RNA-binding protein/RNA interactions.
• This study validates the Lin28/let-7 axis as a promising drug target for cancer therapy.