Cucurbitacin B inhibits gastric cancer progression by suppressing STAT3 activity

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Aberrant Signal transducer and activator of transcription 3 (STAT3) expression is implicated in various cancers, including gastric cancer (GC).
• STAT3 overexpression and activation are critical drivers of tumorigenesis.
• Cucurbitacin B (CuB), a natural product, exhibits significant anti-cancer properties in solid tumors.

Purpose of the Study:

• To elucidate the molecular mechanisms by which CuB inhibits gastric cancer growth.
• To evaluate the direct inhibitory effect of CuB on STAT3.
• To assess the therapeutic potential of CuB, alone and in combination with cisplatin, for GC treatment.

Main Methods:

• In vitro studies using GC cell lines to assess STAT3 phosphorylation and target gene expression.
• Computational docking analysis to predict CuB binding sites on STAT3.
• Pull-down assays to confirm direct inhibition of STAT3 by CuB.
• In vivo xenograft mouse models to evaluate therapeutic efficacy.

Main Results:

• CuB significantly reduced STAT3 phosphorylation at TYR-705 and suppressed key STAT3 target genes (c-Myc, Bcl-xL) in GC cells at nanomolar concentrations.
• Computational and pull-down experiments confirmed CuB as a direct STAT3 inhibitor, binding to its DNA-binding domain.
• CuB enhanced the cytotoxicity of cisplatin in GC cells, likely through augmented STAT3 inhibition.
• In vivo studies demonstrated the therapeutic efficacy of CuB in a GC xenograft model.

Conclusions:

• CuB is a direct inhibitor of STAT3 with potent anti-gastric cancer activity.
• CuB demonstrates synergistic effects when combined with cisplatin, enhancing anti-cancer cytotoxicity.
• CuB represents a promising candidate for developing novel STAT3-targeted therapies for gastric cancer.