The Inhibitory Effects of the Standardized Extracts of Ginkgo biloba on Aromatase Activity in JEG-3 Human Choriocarcinoma Cells

Ginkgo biloba Golden Leaf Extract (GGLE) Inhibits Melanoma Cell Invasion and Angiogenesis Through Inhibition of Angiogenin

The popular dietary supplements of Ginkgo biloba (Ginkgo) products have been reported to have anti-cancer activities in multiple cellular and animal studies, with the benefits yet to be proven with clinical trials. The mechanisms of action are not clear, forming a barrier to investigation in Gingko-specific benefits to cancer patients, especially when combined with other therapies. Here we reported on the discovery of a novel mechanism by which a Ginkgo golden leaf extract (GGLE) inhibited melanoma cell invasion and angiogenesis. GGLE did not inhibit melanoma cells via direct cytotoxicity. Instead, GGLE significantly inhibited total RNase activities in melanoma cells under both normoxia and hypoxia conditions. The RNase angiogenin was induced twofolds by hypoxia, and the induction was significantly suppressed by GGLE treatment in a dose dependent manner. As a result of angiogenin inhibition, GGLE inhibited melanoma cell migration and invasion in a dose dependent manner. Conditioned media from melanoma cell culture sufficiently induced in vitro angiogenesis in human endothelial cells, whereas the conditioned media of GGLE-treated melanoma cells significantly inhibited this angiogenetic activity. This was accompanied with markedly reduced angiogenin concentrations in the GGLE-treated melanoma cell conditioned media. We concluded that, instead of direct cytotoxicity, GGLE inhibited angiogenin synthesis and secretion by melanoma cells, resulting in inhibition of tumor cell invasion and tumor-induced angiogenesis. This new mechanism opens the door for investigation in GGLE influencing tumor microenvironment, and warrants further investigation and validation in vivo.

Naringenin suppresses growth of human placental choriocarcinoma via reactive oxygen species-mediated P38 and JNK MAPK pathways

BACKGROUND

Human placental choriocarcinoma is a gestational trophoblastic tumor with high rates of metastasis and reoccurrence. However, some patients with choriocarcinoma are chemoresistance to conventional chemotherapeutic agents.

HYPOTHESIS

Naringenin increases apoptosis in human placental choriocarcinoma cells.

METHODS

We investigated the effects of naringenin on proliferation and migration of JAR and JEG3 cells, and performed TUNEL and Annexin V/PI staining assays to examine apoptotic effects of naringenin on both cells. In addition, we studied the loss of mitochondrial membrane potential (MMP) and the production of mitochondrial reactive oxygen species (ROS) to determine the specific reason for apoptosis of choriocarcinoma cells being mediated via mitochondria. Consistent with the induction of production of ROS by naringenin in both choriocarcinoma cell lines, we investigated lipid peroxidation and glutathione levels in both JAR and JEG3 cells since both are affected by ROS. We next determined dose-dependent effects of naringenin and its pharmacological inhibitors on signal transduction pathways in JAR and JEG3 cells by western blot analyses.

RESULTS

Naringenin reduced viability and migratory functions of both cell lines, and increased mitochondria related apoptosis induced by ROS and lipid peroxidation, decreased glutathione and decreased mitochondrial membrane potential MMP in a dose-dependent manner. We also determined naringenin activated phosphorylation of ERK1/2, P38, JNK and P70S6K in JAR and JEG3 cells in a dose-response manner. Although naringenin induced phosphorylation of AKT proteins in JAR cells, it suppressed phosphorylation of the protein in JEG3 cells. In addition, we confirmed the mechanism of naringenin-induced cell signaling by using a combination of naringenin and pharmacological inhibitors of the PI3K and MAPK pathways, as well as a ROS inhibitor in JAR and JEG3 cell lines.

CONCLUSIONS

Collectively, results of this study indicate that naringenin is a potential therapeutic molecule with anti-cancer effects on choriocarcinoma cells by inducing generation of ROS and activation of the MAPK pathways.

Ginkgo biloba extract (EGb761) did not express estrogenic activity in an immature rat uterotrophic assay

Ginkgo biloba is a dioecious tree that has been used in traditional Chinese medicine for about 5,000 years. In previous studies on ginkgo biloba extract (EGb761) using in vitro systems, we confirmed that EGb761 has biphasic effects on estrogenicity. In this study, we evaluated the agonistic and antagonistic activities of EGb761 using a uterotrophic assay in immature female rats. To evaluate agonistic and antagonistic effects of EGb761 on uterus, 21-day-old immature Sprague-Dawley (SD) female rats were treated with EGb761 (100, 200, or 400 mg/kg) by oral gavage, 10 μg/kg of estradiol (E2) or 1 mg/kg tamoxifen (TM) by subcutaneous injection, or with EGb761 plus E2 or TM for 3 consecutive days. At the end of the treatment period, animals were sacrificed and their body weights and organ weights (liver, lung, spleen and kidney) were measured. In addition, estrogen-related gene expressions (IGFBP-1 in liver and CaBP-9 in uterus) were determined. During the experiment, no animal showed clinical signs, a change in body weight or died. EGb761 treatment alone had no effect on absolute/relative uterine weight, luminal epithelial cell height (LECH, μm), or luminal circumference (LC, μm). In addition, uterine weights, LECHs, and LC induced by E2 or TM were not significantly changed by EGb761 at any dose. These results collectively suggested EGb761 has no agonistic/antagonistic effects in utero.

The effects of the standardized extracts of Ginkgo biloba on steroidogenesis pathways and aromatase activity in H295R human adrenocortical carcinoma cells

OBJECTIVES

Aromatase inhibitors that block estrogen synthesis are a proven first-line hormonal therapy for postmenopausal breast cancer. Although it is known that standardized extract of Ginkgo biloba (EGb761) induces anti-carcinogenic effects like the aromatase inhibitors, the effects of EGb761 on steroidogenesis have not been studied yet. Therefore, the effects of EGb761 on steroidogenesis and aromatase activity was studied using a H295R cell model, which was a good in vitro model to predict effects on human adrenal steroidogenesis.

METHODS

Cortisol, aldosterone, testosterone, and 17β-estradiol were evaluated in the H295R cells by competitive enzyme-linked immunospecific assay after exposure to EGb761. Real-time polymerase chain reaction were performed to evaluate effects on critical genes in steroid hormone production, specifically cytochrome P450 (CYP11/ 17/19/21) and the hydroxysteroid dehydrogenases (3β-HSD2 and 17β-HSD1/4). Finally, aromatase activities were measured with a tritiated water-release assay and by western blotting analysis.

RESULTS

H295R cells exposed to EGb761 (10 and 100 μg/mL) showed a significant decrease in 17β-estradiol and testosterone, but no change in aldosterone or cortisol. Genes (CYP19 and 17β-HSD1) related to the estrogen steroidogenesis were significantly decreased by EGb761. EGb761 treatment of H295R cells resulted in a significant decrease of aromatase activity as measured by the direct and indirect assays. The coding sequence/ Exon PII of CYP19 gene transcript and protein level of CYP19 were significantly decreased by EGb761.

CONCLUSIONS

These results suggest that EGb761 could regulate steroidogenesis-related genes such as CYP19 and 17β-HSD1, and lead to a decrease in 17β-estradiol and testosterone. The present study provides good information on potential therapeutic effects of EGb761 on estrogen dependent breast cancer.

Modulation of Aromatase by Phytoestrogens

The aromatase enzyme catalyzes the conversion of androgens to estrogens in many human tissues. Estrogens are known to stimulate cellular proliferation associated with certain cancers and protect against adverse symptoms during the peri- and postmenopausal intervals. Phytoestrogens are a group of plant derived naturally occurring compounds that have chemical structures similar to estrogen. Since phytoestrogens are known to be constituents of animal/human food sources, these compounds have received increased research attention. Phytoestrogens may contribute to decreased cancer risk by the inhibition of aromatase enzyme activity and CYP19 gene expression in human tissues. This review covers (a) the aromatase enzyme (historical descriptions on function, activity, and gene characteristics), (b) phytoestrogens in their classifications and applications to human health, and (c) a chronological coverage of aromatase activity modulated by phytoestrogens from the early 1980s to 2015. In general, phytoestrogens act as aromatase inhibitors by (a) decreasing aromatase gene expression, (b) inhibiting the aromatase enzyme itself, or (c) in some cases acting at both levels of regulation. The findings presented herein are consistent with estrogen's impact on health and phytoestrogen's potential as anticancer treatments, but well-controlled, large-scale studies are warranted to determine the effectiveness of phytoestrogens on breast cancer and age-related diseases.