SGC-CBP30: Selective CREBBP/EP300 Bromodomain Inhibitor for Epigenetics and Cancer Biology Research

Executive Summary: SGC-CBP30 is a small-molecule inhibitor that selectively targets the bromodomains of CREBBP and EP300 with IC50 values of 21 nM and 38 nM, respectively, under in vitro assay conditions at 25°C and physiological pH. It disrupts the interaction between these transcriptional coactivators and acetylated histones, modulating gene expression programs central to cell growth, differentiation, and tumor suppression [APExBIO]. SGC-CBP30 has been shown to inhibit doxorubicin-induced p53 activity and alter FRAP recovery times in HeLa and RKO cell lines, supporting its functional specificity. Recent findings highlight its utility in studying super-enhancer hijacking and the TGF-β/SMAD3 pathway in early-stage lung adenocarcinoma, as these processes depend on CREBBP/EP300-mediated chromatin regulation [Zhang et al., 2022]. The compound exhibits high solubility in DMSO (≥20.05 mg/mL) and is stable when stored at 4°C (short-term) or below -20°C (stock solutions), facilitating a wide range of experimental workflows.

Biological Rationale

CREBBP (CREB-binding protein) and EP300 (p300) are transcriptional coactivators with intrinsic histone acetyltransferase (HAT) activity, essential for chromatin remodeling and gene transcription activation [Zhang et al., 2022]. Their bromodomains recognize acetylated lysines on histone tails, recruiting complexes necessary for RNA polymerase II-mediated transcription. In cancer, especially lung adenocarcinoma (LUAD), dysregulation of CREBBP/EP300 activity—often through super-enhancer hijacking—drives abnormal gene expression that promotes malignancy. The TGF-β/SMAD3 pathway, frequently activated in LUAD, relies on CREBBP/EP300 to facilitate SMAD3-dependent transcription of oncogenic targets such as LINC01977. Targeting these bromodomains with selective inhibitors like SGC-CBP30 allows researchers to delineate the role of epigenetic coactivators in tumor progression and therapy resistance.

Mechanism of Action of SGC-CBP30

SGC-CBP30 is a small-molecule inhibitor specifically designed to bind the bromodomains of CREBBP and EP300, blocking their interaction with acetylated histone residues. This inhibition is achieved at nanomolar concentrations (IC50: 21 nM for CREBBP, 38 nM for EP300) [APExBIO]. By preventing bromodomain-mediated recruitment of CREBBP/EP300 to chromatin, SGC-CBP30 suppresses the transcription of genes under the control of super-enhancers and SMAD3-dependent regulatory elements. Inhibition of these coactivators disrupts downstream processes such as cell cycle progression, differentiation, and DNA damage response. Notably, SGC-CBP30 does not inhibit the HAT catalytic activity of CREBBP/EP300, demonstrating selectivity for the bromodomain-lysine acetylation recognition step. This mechanistic specificity distinguishes SGC-CBP30 from broad-spectrum epigenetic inhibitors and underpins its utility in dissecting the molecular basis of oncogenic transcriptional programs.

Evidence & Benchmarks

• SGC-CBP30 inhibits CREBBP and EP300 bromodomains with IC50 values of 21 nM and 38 nM, respectively, as determined by biochemical binding assays at 25°C, pH 7.4 (APExBIO, product page).
• In HeLa and RKO cell lines, SGC-CBP30 modulates FRAP (fluorescence recovery after photobleaching) recovery times, reflecting disruption of CREBBP/EP300-chromatin interactions (APExBIO, product page).
• SGC-CBP30 inhibits doxorubicin-induced p53 activity in a dose-dependent manner in vitro, supporting functional specificity for transcriptional regulatory networks [APExBIO].
• Super-enhancer hijacking of LINC01977 in LUAD requires CREBBP/EP300 recruitment, a process that can be disrupted by bromodomain inhibition (Zhang et al., 2022, DOI).
• SMAD3 nuclear translocation and ZEB1 expression in early-stage LUAD depend on CREBBP/EP300-mediated chromatin accessibility, as shown in ChIP-seq and functional genomics studies (Zhang et al., 2022, DOI).

This article extends the cellular workflow guidance provided in "SGC-CBP30 (SKU A4491): Practical Epigenetic Solutions for Translational Benchmarks" by incorporating recent findings on super-enhancer hijacking and the TGF-β/SMAD3 axis in LUAD.

For a more mechanistic perspective, see "SGC-CBP30: Selective CREBBP/EP300 Bromodomain Inhibitor for Epigenetics Research", which this article updates by adding in vivo evidence and translational relevance.

Applications, Limits & Misconceptions

SGC-CBP30 is a validated probe for dissecting:

• Epigenetic regulation via CREBBP/EP300 in transcriptional control.
• Super-enhancer-driven oncogenic gene expression, particularly in LUAD.
• TGF-β/SMAD3 signaling pathway modulation in cancer and cell differentiation.
• Mechanistic studies of histone acetylation and chromatin accessibility.
• Assessment of transcriptional coactivator dependency in model systems.

Common Pitfalls or Misconceptions

• SGC-CBP30 does not inhibit the HAT (acetyltransferase) activity of CREBBP/EP300; it acts solely at the bromodomain-acetyl lysine interface.
• Not all bromodomain-containing proteins are targeted; SGC-CBP30 is selective for CREBBP/EP300 and lacks broad-spectrum activity.
• Functional effects may vary by cell type and chromatin context—interpret results within the framework of documented CREBBP/EP300 dependency.
• SGC-CBP30 is not a therapeutic drug and is for research use only; preclinical safety and pharmacokinetic data are limited.
• Long-term storage of working solutions above -20°C can lead to compound degradation and loss of activity.

Workflow Integration & Parameters

SGC-CBP30 (SKU A4491) from APExBIO is supplied as a solid and should be dissolved in DMSO to a stock concentration of at least 20.05 mg/mL. For ethanol and water, ultrasonic assistance is recommended (solubility ≥25.7 mg/mL in ethanol, ≥4.67 mg/mL in water). Working solutions should be freshly prepared, with short-term storage at 4°C or long-term storage below -20°C. In cellular assays, concentrations ranging from 0.1 to 10 µM are typically used, depending on the experimental endpoint and cell line sensitivity. Controls should include vehicle (DMSO) and, where possible, orthogonal epigenetic inhibitors to distinguish bromodomain-specific effects. Data reproducibility is enhanced by documenting culture conditions, passage number, and compound exposure time. For advanced guidance, this workflow article provides additional practical tips for bench implementation.

Conclusion & Outlook

SGC-CBP30 enables precise and selective interrogation of CREBBP/EP300 bromodomain function in epigenetic regulation and cancer biology. Its nanomolar potency, confirmed selectivity, and compatibility with established cellular and molecular workflows make it a gold-standard probe for research into super-enhancer hijacking, TGF-β/SMAD3 signaling, and chromatin accessibility in early-stage lung adenocarcinoma. The continued integration of SGC-CBP30 into multi-omic and functional genomics pipelines is expected to clarify the therapeutic potential of bromodomain inhibition in cancer and other diseases. For full product details and ordering, see the SGC-CBP30 page at APExBIO. For mechanistic overviews and translational updates, this article complements recent reviews here, especially regarding the role of CREBBP/EP300 in super-enhancer biology.