Design, synthesis, and biological evaluation of substrate-competitive inhibitors of C-terminal Binding Protein (CtBP)
Sudha Korwar1, Benjamin L Morris2, Hardik I Parikh1
1Department of Medicinal Chemistry, School of Pharmacy, The Institute for Structural Biology, Drug Discovery, and Development, and the Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States.
Abstract:
C-terminal Binding Protein (CtBP) is a transcriptional co-regulator that downregulates the expression of many tumor-suppressor genes. Utilizing a crystal structure of CtBP with its substrate 4-methylthio-2-oxobutyric acid (MTOB) and NAD(+) as a guide, we have designed, synthesized, and tested a series of small molecule inhibitors of CtBP. From our first round of compounds, we identified 2-(hydroxyimino)-3-phenylpropanoic acid as a potent CtBP inhibitor (IC50=0.24μM). A structure-activity relationship study of this compound further identified the 4-chloro- (IC50=0.18μM) and 3-chloro- (IC50=0.17μM) analogues as additional potent CtBP inhibitors. Evaluation of the hydroxyimine analogues in a short-term cell growth/viability assay showed that the 4-chloro- and 3-chloro-analogues are 2-fold and 4-fold more potent, respectively, than the MTOB control. A functional cellular assay using a CtBP-specific transcriptional readout revealed that the 4-chloro- and 3-chloro-hydroxyimine analogues were able to block CtBP transcriptional repression activity. This data suggests that substrate-competitive inhibition of CtBP dehydrogenase activity is a potential mechanism to reactivate tumor-suppressor gene expression as a therapeutic strategy for cancer.
Insights
Small molecule inhibitors targeting C-terminal Binding Protein (CtBP) were designed and synthesized. These inhibitors show potential for reactivating tumor-suppressor genes, offering a new cancer therapy strategy.
Area of Science:
- Biochemistry
- Molecular Biology
- Medicinal Chemistry
Background:
- C-terminal Binding Protein (CtBP) acts as a transcriptional co-regulator, suppressing tumor-suppressor gene expression.
- Dysregulation of CtBP activity is implicated in various cancers.
Purpose of the Study:
- To design and synthesize novel small molecule inhibitors of CtBP.
- To evaluate the efficacy of these inhibitors in blocking CtBP's transcriptional repression activity.
- To explore CtBP inhibition as a potential cancer therapeutic strategy.
Main Methods:
- Structure-based drug design utilizing crystal structures of CtBP.
- Chemical synthesis and structure-activity relationship (SAR) studies of small molecule inhibitors.
- In vitro enzyme inhibition assays and cellular assays for gene expression and cell viability.
Main Results:
- Identified 2-(hydroxyimino)-3-phenylpropanoic acid derivatives as potent CtBP inhibitors.
- 4-chloro and 3-chloro analogues demonstrated significant inhibitory activity (IC50 values of 0.18µM and 0.17µM, respectively).
- In cellular assays, these analogues effectively blocked CtBP's transcriptional repression and showed enhanced potency compared to the substrate control.
Conclusions:
- Substrate-competitive inhibition of CtBP dehydrogenase activity is a viable strategy.
- Developed potent CtBP inhibitors that can reactivate tumor-suppressor gene expression.
- These findings support CtBP inhibition as a promising therapeutic approach for cancer treatment.
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