H-ras dependent estrogenic effects of epidermal growth factor in the estrogen-independent breast cancer cell line MDA-MB-231

Change of Ras and its guanosine triphosphatases (GTPases) during development and regression in bovine corpus luteum

The aim of this study was to determine the change of Ras and its guanosine triphosphatases (GTPases) proteins in the bovine corpus luteum (CL) during estrous cycle and investigate protein-protein interaction between hormone receptors and Ras proteins via angiogenetic and apoptotic factors using bioinformatics database. The bovine CLs at proliferation phase (PP), secretion phase (SP), and regression phase (RP) were dissected from abattoir ovaries (n = 4/stage), whole of the tissue samples was used to analyze two-dimensional electrophoresis (2-DE), mRNA, and protein analysis. The protein-protein interaction between the Ras GTPases proteins and hormone receptors were analyzed using Search Tool for the Retrieval of Interacting Genes (STRING) database. The Ras protein activator like 3 (RASAL3), Ras GTPase activating protein 3 (RASA3), Ras guanine nucleotide exchange factors 1 beta (RasGEF1B) were discovered by the 2-DE and mass spectrometry in bovine CLs, and the protein spots of RASA3 and RASAL3 were significantly increased in the SPCL compared to the PPCL, whereas the RasGEF1B was reduced in the PPCL (P < 0.05). The mRNA and proteins expression of progesterone receptor, estrogen receptor alpha (ERα), vascular endothelial growth factor A (VEGFA), angiopoietin 1 (Ang1), VEGF receptor2 (VEGFR2), and Tie2 were significantly increased, but intrinsic and extrinsic apoptotic factors were decreased in PPCL and SPCL compared to RPCL (P < 0.05). Based on STRING database, we determined that RasGEF1B is activated by ERα via VEGFA and VEGFR2, then RasGEF1B activates H-Ras and R-Ras. In addition, the RasGAP protein was significantly increased, however, the RasGEF, H-Ras and R-Ras proteins were reduced in SPCL compared to PPCL and RPCL (P < 0.05). In summary, the RasGEF and Ras proteins were raised during the development, whereas the RasGAP was increased when development was completed, then the Ras and its GTPases dramatically decreased at the regression in bovine CL. In conclusion, these results suggest that Ras and Ras GTPases could be changed during development and regression, activated by the ERα via angiogenetic signaling during proliferation, and may be important to understanding of the Ras and its GTPases system for estrous cycle in bovine CL.

Isolation and identification of three new chromones from the leaves of Pimenta dioica with cytotoxic, oestrogenic and anti-oestrogenic effects

CONTEXT

Pimenta dioica (L.) Merr. (Myrtaceae) is used in Costa Rican traditional medicine for women's health. Our previous work showed that P. dioica extracts were oestrogenic.

OBJECTIVES

This work identifies phytochemicals from P. dioica that are responsible for the plant's oestrogen-like activities.

MATERIALS AND METHODS

P. dioica leaves were collected in Costa Rica in 2005. Fractions resulting from chromatographic separation of a methanol extract were tested at 50 μg/mL in a competitive oestrogen receptor-binding assay. Active compounds were isolated by HPLC and identified by NMR and MS. Pure compounds were tested at 1 μM in the oestrogen-responsive SEAP reporter gene assay. The effects on cell viability, cytotoxicity and apoptosis were investigated in breast cancer (MCF-7 and SK-BR3) and gastric cancer (AGS and NCI-N87) cell lines using the ApoTox-Glo and Caspase-Glo assays and qPCR.

RESULTS

Quercitrin and three new chromones, including a 2-phenoxychromone, 6,8-di-C-methylcapillarisin (1) were isolated and identified. Compound 1 caused a 6.2-fold increase in SEAP expression at 1 μM (p < 0.05). This activity was blocked by the ER antagonist ICI 182,780. Compound 2 caused a 6.0-fold increase in SEAP, inhibited the growth of MCF-7, AGS and NCI-N87 cells (IC50 54.27, 38.13 and 51.22 μg/mL, respectively), and induced apoptosis via caspase 8 and increased the Bax/Bcl-2 mRNA ratio in MCF-7 cells. Compound 3 was anti-oestrogenic in MCF-7 cells.

DISCUSSION AND CONCLUSIONS

Compounds from P. dioica have oestrogenic, anti-oestrogenic and cytotoxic effects that may explain the ethnomedical use of this plant.

Genomic-Epidemiologic Evidence That Estrogens Promote Breast Cancer Development

Background: Estrogens are a prime risk factor for breast cancer, yet their causal relation to tumor formation remains uncertain. A recent study of 560 breast cancers identified 82 genes with 916 point mutations as drivers in the genesis of this malignancy. Because estrogens play a major role in breast cancer development and are also known to regulate the expression of numerous genes, we hypothesize that the 82 driver genes are likely to be influenced by estrogens, such as 17ß-estradiol (E2), and the estrogen receptor ESR1 (ERα). Because different types of tumors are characterized by unique sets of cancer driver genes, we also argue that the fraction of driver genes regulated by E2-ESR1 is lower in malignancies not associated with estrogens, e.g., acute myeloid leukemia (AML).Methods: We performed a literature search of each driver gene to determine its E2-ESR1 regulation.Results: Fifty-three of the 82 driver genes (64.6%) identified in breast cancers showed evidence of E2-ESR1 regulation. In contrast, only 19 of 54 mutated driver genes (35.2%) identified in AML were linked to E2-ESR1. Among the 916 driver mutations found in breast cancers, 813 (88.8%) were linked to E2-ESR1 compared with 2,046 of 3,833 in AML (53.4%).Conclusions: Risk assessment revealed that mutations in estrogen-regulated genes are much more likely to be associated with elevated breast cancer risk, while mutations in unregulated genes are more likely to be associated with AML.Impact: These results increase the plausibility that estrogens promote breast cancer development. Cancer Epidemiol Biomarkers Prev; 27(8); 899-907. ©2018 AACR.

Troglitazone suppresses telomerase activity independently of PPARgamma in estrogen-receptor negative breast cancer cells

Background

Breast cancer is one the highest causes of female cancer death worldwide. Many standard chemotherapeutic agents currently used to treat breast cancer are relatively non-specific and act on all rapidly dividing cells. In recent years, more specific targeted therapies have been introduced. It is known that telomerase is active in over 90% of breast cancer tumors but inactive in adjacent normal tissues. The prevalence of active telomerase in breast cancer patients makes telomerase an attractive therapeutic target. Recent evidence suggests that telomerase activity can be suppressed by peroxisome proliferator activated receptor gamma (PPARγ). However, its effect on telomerase regulation in breast cancer has not been investigated.

Methods

In this study, we investigated the effect of the PPARγ ligand, troglitazone, on telomerase activity in the MDA-MB-231 breast cancer cell line. Real time RT-PCR and telomerase activity assays were used to evaluate the effect of troglitazone. MDA-MB-231 cells had PPARγ expression silenced using shRNA interference.

Results

We demonstrated that troglitazone reduced the mRNA expression of hTERT and telomerase activity in the MDA-MB-231 breast cancer cell line. Troglitazone reduced telomerase activity even in the absence of PPARγ. In agreement with this result, we found no correlation between PPARγ and hTERT mRNA transcript levels in breast cancer patients. Statistical significance was determined using Pearson correlation and the paired Student's t test.

Conclusions

To our knowledge, this is the first time that the effect of troglitazone on telomerase activity in breast cancer cells has been investigated. Our data suggest that troglitazone may be used as an anti-telomerase agent; however, the mechanism underlying this inhibitory effect remains to be determined.

Absence of ligand-independent transcriptional activation of the estrogen receptor via the estrogen response element in pituitary lactotrophs in primary culture

The estrogen receptor (ER) is a ligand-activated transcription factor that enhances gene expression by binding to specific regulatory DNA sequences called estrogen response elements (EREs). In some cell lines, the ER is also activated in a ligand-independent manner by multiple signaling pathways. In this study, we developed a novel adenovirus-mediated assay for promoter activation, termed LASETA, which we then used to examine whether ligand-independent activation of the ER occurred in normal pituitary lactotrophs in primary culture. In the LASETA adenovirus vector, the loxP-flanked stop sequence was deleted by prolactin (PRL) promoter-regulated expression of Cre recombinase. This led to lactotroph-specific expression of a reporter gene driven by an ERE-containing promoter. Estrogen-induced expression of the reporter protein luciferase in LASETA was specific for lactotrophs and was ER-dependent. LASETA was shown to be reliable even with varying Cre recombinase expression levels, which were caused by changes in PRL promoter activity. Using LASETA, we observed no change in ERE-mediated ER activity in the absence of estrogen after treatment of normal lactotrophs with agents such as insulin-like growth factor-1, epidermal growth factor, the adenylate cyclase activator forskolin, the extracellular signal-regulated kinase kinase inhibitor U0126, and the protein kinase A inhibitor H89. The ERE-mediated ligand-independent ER activity was induced by the growth factors and forskolin in the somatolactotroph tumor cell line GH4C1 cells. These results suggest that ERE-mediated ligand-independent activation of ER does not occur in normal lactotrophs in primary culture, and is a phenomenon likely restricted to transformed cells.

Positive correlation of steroid hormones and EGF in canine mammary cancer

There are no published studies focused on the potential crosstalk between steroid hormones and EGF in canine mammary tumourigenesis. The objective was to investigate the role of EGF in canine mammary tumours (CMT) and the relationship with steroid hormones. Sixty-three CMT (39 malignant including 10 inflammatory mammary carcinomas (IMC); 19 benign and 5 dysplasias), and 13 normal mammary glands from dogs without history of neoplastic disease were analysed. Levels of EGF and steroid hormones [progesterone (P4); 17beta-estradiol (E2); androstenedione (A4) and dehydroepiandrosterone (DHEA)], were analysed by EIA in CMT homogenates. Levels of EGF were significantly higher in malignant compared with benign tumours, dysplasias and normal mammary glands (p<0.001). IMC presented the highest EGF levels, with statistical significant difference between IMC and non-IMC cases (p<0.05). Steroid hormone levels were also significantly higher in malignant tumours compared with benign tumours, dysplasias and normal mammary glands (p<0.001). In malignant tumours (non-IMC and IMC), a strong correlation was observed between EGF and: P4 (r=0.452; p=0.003); E2 (r=0.624; p=0.023); A4 (r=0.496; p=0.038); DHEA (r=0.431; p=0.005). These results suggest that EGF is implicated in canine mammary tumourigenesis. The positive correlation observed, opens an interesting perspective of interaction that should be further investigated.

Behavioral genetics of the depression/cancer correlation: a look at the Ras oncogene family and the 'cerebral diabetes paradigm'

This study investigates the causes of the observed linkage between depression and later onset of cancer. The prevailing view is that cancer in depressed patients results from a weakened immune system. However, molecular biologists have recognized that dysregulation of the ras proto-oncogene results in impaired serotonin and dopamine synthesis manifesting as major depression. A qualitative review of the literature showed that (1) studies using the Minnesota Multiphasic Personality Inventory showed a greater correlation between depression and later cancer onset than those employing other measures and (2) the more related the cancer type was to the Ras oncogene family, the greater the correlation between depression and later cancer onset. These results support the hypothesis that the ras proto-oncogene plays a role in the etiology of depression and could be the common denominator in long-observed depression/cancer linkages. Previous depression/cancer linkage studies are confounded in that they failed to analyze cancer type and accurately diagnose depression.