Related Experiment Video
Updated: Jun 5, 2026
Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins
Published on: October 4, 2017
Alkylation of cysteine 468 in Stat3 defines a novel site for therapeutic development
Ralf Buettner1, Renzo Corzano, Rumana Rashid
1Beckman Research Institute, City of Hope Comprehensive Cancer Center, Duarte, California 91010, USA.
Abstract:
Stat3 is a latent transcription factor that promotes cell survival and proliferation and is often constitutively active in multiple cancers. Inhibition of Stat3 signaling pathways suppresses cell survival signals and leads to apoptosis in cancer cells, suggesting direct inhibition of Stat3 function is a viable therapeutic approach. Herein, we identify a small molecule, C48, as a selective Stat3-family member inhibitor. To determine its mechanism of action, we used site-directed mutagenesis and multiple biochemical techniques to show that C48 alkylates Cys468 in Stat3, a residue at the DNA-binding interface. We further demonstrate that C48 blocks accumulation of activated Stat3 in the nucleus in tumor cell lines that overexpress active Stat3, leading to impressive inhibition of tumor growth in mouse models. Collectively, these findings suggest Cys468 in Stat3 represents a novel site for therapeutic intervention and demonstrates the promise of alkylation as a potentially effective chemical approach for Stat3-dependent cancers.
Insights
A novel small molecule, C48, selectively inhibits Signal Transducer and Activator of Transcription 3 (Stat3) by alkylating Cys468. This targeted approach effectively blocks tumor growth in preclinical cancer models.
Area of Science:
- Molecular Biology
- Cancer Therapeutics
- Drug Discovery
Background:
- Signal Transducer and Activator of Transcription 3 (Stat3) is a transcription factor crucial for cell survival and proliferation.
- Constitutive activation of Stat3 is frequently observed in various cancers, making it a promising therapeutic target.
- Inhibiting Stat3 signaling can induce apoptosis in cancer cells, highlighting the potential of direct Stat3 inhibition.
Purpose of the Study:
- To identify and characterize a novel small molecule inhibitor of Stat3.
- To elucidate the mechanism of action of the identified inhibitor, C48.
- To evaluate the therapeutic potential of C48 in preclinical cancer models.
Main Methods:
- Identification of C48 as a selective Stat3-family member inhibitor.
- Site-directed mutagenesis and biochemical assays to determine the alkylation site of C48 on Stat3.
- Assessment of C48's effect on activated Stat3 nuclear accumulation in tumor cell lines.
- Evaluation of tumor growth inhibition in mouse models.
Main Results:
- C48 was identified as a selective inhibitor of Stat3.
- C48 was shown to alkylate Cys468, a residue located at the DNA-binding interface of Stat3.
- C48 treatment blocked the nuclear accumulation of activated Stat3 in cancer cells.
- Significant inhibition of tumor growth was observed in mouse models treated with C48.
Conclusions:
- Cys468 in Stat3 represents a novel and viable target for therapeutic intervention.
- Alkylation of Cys468 by C48 is an effective mechanism for inhibiting Stat3.
- C48 demonstrates promise as a chemical approach for treating Stat3-dependent cancers.
Related Concept Videos
02:04Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
01:20The JAK-STAT Signaling Pathway
00:49Ligand Binding and Linkage