Cucurbitacin-E-Glucoside Augments Tamoxifen's Anticancer Efficacy by Targeting PPARγ and NF-kB: In Vivo and In Silico Studies

Background

Cucurbitacin-E-glucoside (CEG), a natural compound from the Cucurbitaceae family, has shown anti-proliferative effects on various human cancer cell lines and is believed to inhibit the peroxisome proliferative activated receptor gamma (PPARγ) signaling pathway. We aimed to investigate the anti-cancer effects of CEG in a mouse model of Ehrlich ascites carcinoma (EAC) and its capacity to improve the efficacy of tamoxifen (TAM) treatment. By examining the in vivo and in silico interactions between CEG and tamoxifen with PPARγ, this study presents a novel approach to cancer management.

Methods

CEG (50 mg/k.g.b.w.) and TAM (20 mg/k.g.b.w.) were administered individually and/or in combination with the EAC-bearing mice. After 4 weeks of treatment, tumor weight and volume were measured. Additionally, inflammation and oxidative stress biomarkers, as well as apoptotic and antiapoptotic genes, were evaluated using ELISA and qRT-PCR. DNA cell cycle analysis of cancer cells was also performed using flow cytometry. To elucidate the molecular mechanism of CEG, PPARγ and NF-κB, the key transcription factor, were studied using Western blot and molecular docking studies.

Results

Oral administration of CEG and tamoxifen individually and/or in combination led to significant decreases in tumor volume and weight. Additionally, the drug combination led to significant decreases in the proliferation index S phase and G2 phase. Moreover, treatment of CEG induces the expression of apoptotic PPARα and PPARγ as well as inhibits the expression of antiapoptotic Bcl-2 and HIF-1Α genes. Meanwhile, combining CEG with TAM showed a significant increase in liver GSH, CAT, SOD, NP-SH, and protein as well as significant decreases in levels of the plasma inflammatory markers IL-2, IL-6, TGF- β1, and the angiogenesis marker VEGF-C. Western blot analyses showed that CEG alone induced 2.8-fold PPARγ upregulation and 1.9-fold NF-κB suppression (p < 0.01) compared to the EAC group. Molecular docking analyses of CEG within the ligand-binding domains of the PPARγ and the inflammation transcription factor NF-KB proteins demonstrated comparable binding affinities to the PPARγ agonist Rosiglitazone and the NF-KB inhibitor MG-132, corroborating results obtained in vivo.

Conclusion

Our findings show that CEG therapy activates apoptotic PPARα and PPARγ genes and suppresses anti-apoptotic Bcl-2 and HIF-1Α genes, while reducing the oxidative stress and inflammation in EAC cells through a mechanism involving inhibition of NF-kβ. Finally, CEG creates a safe and synergistic environment that amplifies the therapeutic benefits of tamoxifen.