Patricia L. Tate

MCF-7 and T47D human breast cancer cells contain a functional peroxisomal response

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors that regulate transcription of target genes. Since attempts have been made to correlate the ingestion of high-fat diets, itself a peroxisome proliferator, with the occurrence of breast cancer, we set about to determine if human breast cancer cells contained a functional PPAR. In this report we demonstrate the presence of an mRNA in two breast cancer cell lines (MCF-7 and T47D) which is specifically recognized by a mouse PPARgamma2 probe. Furthermore, in gel shift assays a consensus PPAR response element (PPRE) was specifically bound by nuclear extracts from MCF-7 cells and was further retarded by antibodies raised to mouse PPARgamma. Finally, when transfected with a PPRE-luciferase transcriptional reporter construct, transcription was increased in response to activators of PPAR and its dimmeric partner the retinoic acid X receptor (RXR). These data indicate that peroxisomal proliferators are capable of mediating transcription in human breast cells and suggest the possibility of a physiological role in the breast.

Differential transcriptional activation of peroxisome proliferator-activated receptor gamma by omega-3 and omega-6 fatty acids in MCF-7 cells.

While the role of dietary fats in breast cancer remains controversial, the recent cloning of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor, from human breast cancer cells lines provides a potential molecular link. Several fatty acids from four classes of dietary fats were tested for their ability to mediate the transcriptional activity of PPARgamma in MCF-7 and MDA-MB-231 cells using growth media with minimal serum. Whereas omega-3 fatty acids inhibit transactivation of PPARgamma to levels below control, omega-6, monounsaturated and saturated fatty acids stimulate the activity of the transcriptional reporter. These studies indicate that individual fatty acids differentially regulate the transcriptional activity of PPARgamma by selectively acting as agonists or antagonists. Furthermore, the transcriptional activation of PPARgamma correlates with cell proliferation in MCF-7 cells. Understanding the effects of individual fats on breast cancer cells and PPARgamma transactivation could provide important new insights into the epidemiology of breast cancer and the role of dietary fat.

Mycotoxins in Root Extracts of American and Asian Ginseng Bind Estrogen Receptors α and β

The estrogenic activity of ginseng has been the subject of conflicting reports. Cell proliferation, induction of estrogen-responsive genes, and isolated cases of adverse reactions such as postmenopausal vaginal bleeding and gynecomastia have been reported after ginseng treatment. Other studies report antiproliferative effects with no induction of estrogen-responsive genes. We developed estrogen receptor (ER) α and ERβ competitive binding assays using recombinant receptors and [3H]-17β-estradiol to detect phytoestrogens in extracts of Asian ginseng root (Panax ginseng C. A. Meyer) and American ginseng root (Panax quinquefolius L.). Root extracts contained substances that bound both receptor isoforms. These substances had a two to three times greater affinity for ERβ. Significantly higher binding was found in methanol extracts than in hot water extracts. Subsequent analysis of the extracts revealed significant ER binding attributable to zearalenone, the estrogenic mycotoxin produced by several Fusarium species. The ER showed no binding affinity for Rb1 and Rg1, the major ginsenosides found in P. quinquefolius and P. ginseng, respectively. Thus, ginseng extraction methods, plant species tested, and mycotoxin contaminants may help to explain the disparate literature reports. The prevalence and health significance of fungal contamination in herbal products used for medicinal purposes should be further investigated.

Comparative effects of eight varieties of blackberry on mutagenesis

Abstract Diets containing large amounts of fruits and vegetables are known to decrease the probability of developing cancer. The chemical composition of fruits can vary with their genetic characteristics and the environmental conditions under which they are cultivated. Because of this variability, different varieties of the same fruit could be expected to have different effects on processes leading to carcinogenesis. Blackberries have been shown to have anti-carcinogenic potential. Since somatic mutations play a major role in the initiation and progression of cancer, we have compared eight varieties of blackberry grown under the same conditions for their abilities to inhibit carcinogen-induced mutagenesis. Using the Ames assay, we have measured the effects of each of the eight varieties on: 1) mutation induction by 2-amino anthracene (2AA), 2) mutation induction by methyl methanesulfonate (MMS) and 3) cell survival. All varieties were found to strongly suppress 2AA mutagenesis, but have minimal effect on MMS mutagenesis. Experiments were performed with berry juice and with homogenized berries. In addition, berries extracts were acidified to simulate changes which might be caused by the digestive process.

Milk stimulates growth of prostate cancer cells in culture.

Concern has been expressed about the fact that cows’ milk contains estrogens and could stimulate the growth of hormone-sensitive tumors. In this study, organic cows’ milk and two commercial substitutes were digested in vitro and tested for their effects on the growth of cultures of prostate and breast cancer cells. Cows’ milk stimulated the growth of LNCaP prostate cancer cells in each of 14 separate experiments, producing an average increase in growth rate of over 30%. In contrast, almond milk suppressed the growth of these cells by over 30%. Neither cows’ milk nor almond milk affected the growth of MCF-7 breast cancer cells or AsPC-1 pancreatic cancer cells significantly. Soy milk increased the growth rate of the breast cancer cells. These data indicate that prostate and breast cancer patients should be cautioned about the possible promotional effects of commercial dairy products and their substitutes.

Red raspberries have antioxidant effects that play a minor role in the killing of stomach and colon cancer cells.

Berries and berry extracts possess properties that make them important in the prevention of cancer. The high antioxidant levels of these extracts play a role, but components of the berries can have other effects on cell replication and survival. We chose to test the hypothesis that (i) although the antioxidant capacity of raspberry extracts is important for inhibiting the proliferation of tumor cells, other characteristics of the berry extracts are responsible for a major part of their antiproliferative activity, and that (ii) the relative importance of the antioxidant effect can depend on the cell type being studied. The aim of this study was to assess the relative roles of low pH and high antioxidant levels in the killing of 3 cell types by an aqueous extract from Meeker red raspberries. Stomach, colon, and breast cancer cells were treated with berry extract and with HCl and ascorbic acid solutions of the same pH. A dilution of 7.5% ascorbic acid solution, of the same pH and slightly higher antioxidant concentration than the berry extract, killed less than 10% of the stomach and colon cancer cells. In contrast, the berry extract at this same dilution killed more than 90% of these cells. Antioxidants played a more significant role in the killing of breast cancer cells, however. For these cells, approximately 50% of the killing could be attributed to antioxidant effects. We conclude that the antioxidant effect plays a minor role in the killing of 2 gastrointestinal cell types, but its role in inactivating a breast cancer cell line is much more significant. No evidence of apoptosis was observed, and caspase activation did not contribute to cell killing by the extract.

Target directed enediyne prodrugs: hER and AhR degradation by a synthetic oxo-enediyne

Abstract An efficient route to oxo-enediynes is presented. A simple oxo-enediyne has been synthesized, which cyclizes to give an isochroman. The agent shows cytotoxicity for ER rich breast cancer cells and a model for its mode of action is proposed.

The Phylogenetic Relationships of the Species within the Section Arachis Utilizing a Fatty Acid Synthesis Gene

The original ancestors of the cultivated peanut (Arachis hypogaea), an allotetraploid, have not been conclusively determined, although several wild diploid species have been suggested. To identify the wild progenitors and to study the phylogenetic relationship of the species in the section Arachis, the sequence of a specific peanut gene was utilized. A cDNA of the fatty acid synthesis gene, stearoyl-ACP desaturase, was isolated and characterized. A region of this gene was then amplified from genomic DNA of nine wild species and sequenced. This sequence data, and the sequence information from the same region for the two cultivated peanut genes, were analyzed to determine the relatedness of the species. The results indicated that the cultivated peanut is derived from two separate lineages and supports the allopolyploid nature of the cultivated peanut. The amplified products were also digested with the Rsal restriction enzyme. A species-specific banding pattern unique to the DNA for some of the diploid species and one of the cultivated peanut genes was demonstrated. This technique provides a method for distinguishing diploid species and for analyzing gene expression in different tissues in the cultivated peanut.