Natural Prenylated Xanthones as Potential Inhibitors of PI3k/Akt/mTOR Pathway in Triple Negative Breast Cancer Cells

Structure and activity relationship analysis of xanthones from mangosteen: Identifying garcinone E as a potent dual EGFR and VEGFR2 inhibitor

BACKGROUND

Xanthones are among the most fundamental phytochemicals in nature. The anti-cancer activities of xanthones and their derivatives have been extensively studied. Recently, we found that garcinone E (GE), an effective anti-cancer phytochemical isolated from mangosteen (Garcinia mangostanal.), showed promising anti-cancer effects in vitro and in vivo. However, little is known about its effects on epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor 2 (VEGFR2) activity.

PURPOSE

This study aimed to identify potent dual EGFR and VEGFR2 inhibitors from mangosteen-derived xanthones using structure-activity relationship analyses.

STUDY DESIGN

The interaction of xanthones with EGFR and VEGFR2 was analyzed using molecular docking experiments. The kinase activities of EGFR and VEGFR2 were determined using bioluminescence assays. The rat aortic ring and Matrigel plug angiogenesis assays were used to evaluate blood vessel formation ex vivo and in vivo. A breast tumor-bearing nude mouse model was established to examine the anti-tumor effects of different xanthones.

RESULTS

Molecular docking analysis showed that GE bound tightly to EGFR and VEGFR2, with binding energies of -9.73 and -9.56 kcal/mol, respectively. Kinase activity assessment showed that GE strongly inhibited both EGFR and VEGFR2 kinase activity, with IC50 values of 315.4 and 158.2 nM, respectively. Moreover, GE significantly abolished the EGF- and VEGF-induced phosphorylation of EGFR and VEGFR2, respectively. GE also showed strong inhibitory effects on cancer cell growth, endothelial cell migration, invasion, and tube formation. Ex vivo and in vivo angiogenesis assays showed that GE dose-dependently suppressed blood vessel formation in the rat aorta, Matrigel plugs, and transgenic zebrafish embryos, with the lowest effective concentration of 0.25 μM. Furthermore, GE (2 mg/kg) strongly inhibited tumor growth and reduced tumor weight in MDA-MB-231 breast tumor-xenografted mice. GE significantly reduced microvessel density and downregulated the expression of VEGFR2, EGFR, and Ki67 in tumor tissues.

CONCLUSION

The present study demonstrated that GE was the most potent dual inhibitor of EGFR and VEGFR2 among all xanthones tested. These findings may provide valuable information for the future development of novel and effective dual inhibitors of EGFR and VEGFR2.

Therapeutic Potential of Tumor Metabolic Reprogramming in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, with clinical features of high metastatic potential, susceptibility to relapse, and poor prognosis. TNBC lacks the expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). It is characterized by genomic and transcriptional heterogeneity and a tumor microenvironment (TME) with the presence of high levels of stromal tumor-infiltrating lymphocytes (TILs), immunogenicity, and an important immunosuppressive landscape. Recent evidence suggests that metabolic changes in the TME play a key role in molding tumor development by impacting the stromal and immune cell fractions, TME composition, and activation. Hence, a complex inter-talk between metabolic and TME signaling in TNBC exists, highlighting the possibility of uncovering and investigating novel therapeutic targets. A better understanding of the interaction between the TME and tumor cells, and the underlying molecular mechanisms of cell-cell communication signaling, may uncover additional targets for better therapeutic strategies in TNBC treatment. In this review, we aim to discuss the mechanisms in tumor metabolic reprogramming, linking these changes to potential targetable molecular mechanisms to generate new, physical science-inspired clinical translational insights for the cure of TNBC.