Breast Cancer Prevention with Phytochemicals in Mushrooms

Institution: Beckman Research Institute of the City of Hope
Investigator(s): Shiuan  Chen , Ph.D. -
Award Cycle: 2004 (Cycle 10) Grant #: 10PB-0140 Award: $759,667
Award Type: Request for Applications
Research Priorities
Prevention & Risk Reduction>Other searches for the causes



Initial Award Abstract (2004)
White button mushrooms are found to suppress breast cancer cell growth by preventing the synthesis of estrogen, the female hormone. Estrogen plays a major role in the development of breast cancer. In estrogen-dependent breast tumors, estrogen stimulates the formation of growth factors that are essential for breast cancer growth. In cells, a protein called aromatase produces estrogen, and in breast cancer patients, tumors contain an abnormally high level of aromatase, which generates a large amount of estrogen.

During the last several years, both preclinical and clinical studies have demonstrated that aromatase inhibitors (such as letrozole and anastrozole) are better drugs than tamoxifen (an antiestrogen) in treating hormone-dependent breast cancer. Results have also been obtained that suggest that aromatase inhibitors are useful drugs to prevent breast cancer. Preliminary results from this laboratory have shown that mushrooms contain chemicals that inhibit aromatase and that the oral intake of mushroom extract suppresses breast tumor formation in mice. Therefore, it is thought that white button mushrooms (species Agaricus bisporus) may be a useful chemopreventive agent for breast cancer, given that they suppress aromatase/estrogen biosynthesis. In this proposed study, more extensive animal studies using nude mice will be performed to critically evaluate the preliminary findings. Gene array analysis will be performed to identify genes in tumors whose expressions are modified by mushroom feeding. In addition, experiments will be designed to identify the active components in mushrooms that are responsible for the suppression of breast tumor formation.

This research will provide us with a scientific basis as to why mushrooms are capable of suppressing breast tumor formation. The proposed research has potential for a translational impact on breast cancer in that the results generated should be very useful for designing prevention strategies against breast cancer by using mushrooms. Such a prevention method should be readily available and affordable to the general community of California.


Final Report (2008)
Aromatase is a protein that makes estrogen which plays a key role in the development of hormone-dependent breast cancer. Clinical trials on third generation aromatase inhibitors (AIs) demonstrate that they are not only potent drugs to treat this type of breast cancer, but are also effective in preventing its recurrence. Therefore, phytochemicals (plant-derived compounds) with anti-aromatase activity are potentially important agents in the prevention of hormone-dependent breast cancer. Research in our laboratory has found that among the seven vegetables tested, white button mushrooms (Agaricus bisporous) contain chemicals that effectively suppress human aromatase activity.

Conjugated linoleic acid (CLA), one type of fatty acid, was isolated from mushrooms and shown to be an aromatase inhibitor. The anticancer activity of this fatty acid has been demonstrated in other laboratories. Mushroom extract containing CLA suppresses the proliferation of aromatase-positive breast cancer cells. Furthermore, we have found that oral intake of mushroom extract decreases both tumor cell proliferation and tumor weight in mice. For a better understanding of the anti-breast cancer effect of mushrooms, we also performed experiments to identify genes in tumors whose expressions are modified by mushroom feeding. We identified that the expression of 515 genes was increased, and that of 1805 genes was decreased in tumors from mushroom-fed mice versus those in control mice. Our results indicate that mushroom feeding blocks the expression of genes that are involved in cell growth and energy production. Our experiments also determined that the intake of mushrooms may modulate our immune function. As demonstrated by our preclinical studies, the anti-aromatase effect of mushrooms remains even after they are cooked.

This translational research has generated results for designing prevention strategies against breast cancer by using mushrooms. Such a prevention method should be readily available and affordable to the general community of California. Based on results from these preclinical studies, a clinical trial to test whether mushroom intake can inhibit estrogen production in postmenopausal breast cancer survivors has been approved by the IRB and will be initiated at the City of Hope.


Symposium Abstract (2005)
Aromatase is the enzyme that converts the hormone androgen to estrogen. An abnormally high expression of aromatase in breast tissue is considered to be a risk factor for breast cancer. A species of white button mushroom (Agaricus bisporus) is thought to be a useful chemopreventive agent for breast cancer, given that it suppresses aromatase/estrogen biosynthesis.

In our laboratory we prepared extracts from green onion, carrot, bell pepper, white mushroom, broccoli and spinach to test for their ability to inhibit aromatase expression. None of these extracts exhibited significant aromatase inhibition under our experimental conditions. Cell culture experiments were performed to further evaluate the anti-aromatase and anti-breast cancer activity of mushrooms. Our laboratory has prepared one breast cancer cell line, MCF7aro. This cell line is ER-positive/aromatase-positive and demonstrates increased cell proliferation in the presence of testosterone. The addition of mushroom extract decreased the advantage gained by the addition of testosterone to a similar level as seen with 4-OHA, a known aromatase inhibitor. Furthermore, mushroom extract was found not to affect the proliferation of MCF-10A, a non-cancer cell line.

These findings suggest that the inhibitory effect of white button mushroom extract is through a specific anti-aromatase action, not a cytotoxic (cell-killing) effect. To better understand the cancer protective effects of mushrooms, our laboratory decided to characterize the anti-aromatase chemicals and to investigate the in vivo action of mushroom extract using an animal model. Three sets of animal experiments have been conducted and the results suggest that the oral intake of mushroom extracts might slow down MCF-7aro-derived tumor growth in nude mice. Histological examination of the tumors revealed that the levels of apoptosis (cell death) between tumors from the control and mushroom extract-fed animals were similar, therefore indicating again that the tumor suppressing effect of mushroom extract is not through a cytotoxic effect. These results significantly indicate that these phytochemicals in mushroom are orally active and maintain their activity after ingestion. Preliminary studies from our laboratory have found more than one chemical in mushrooms that can inhibit aromatase and some of them may be fatty acid derivatives. The exact nature of the active chemicals is not yet determined. Based on these results, we hypothesize that postmenopausal women can benefit from a diet which includes mushrooms, a common vegetable, since they contain phytochemicals which has been shown to be effective aromatase inhibitors.


Symposium Abstract (2005)
An abnormal expression of aromatase in breast tissue is considered to be a risk factor for breast cancer. Aromatase inhibitors have been shown to be effective drugs to treat hormone-dependent breast cancer and potentially to be useful to prevent this cancer in postmenopausal women.

Based on our results, we hypothesize that postmenopausal women can benefit from a diet which includes white button mushrooms (species Agaricus bisporus), a common vegetable, since they contain phytochemicals which have been shown to be effective aromatase inhibitors. To better understand the cancer-protective effects of mushrooms, our laboratory has investigated the in vivo action of mushroom extract. Three sets of animal experiments have been conducted and the results suggest that the oral intake of mushroom extracts might slow down MCF-7aro-derived tumor growth in nude mice. MCF-7aro is ER-positive/aromatase-positive breast cancer cell line and demonstrates increased cell proliferation in the presence of testosterone. While it is exciting to find that mushroom extract contains anti-aromatase chemicals, it is reasonable to think that mushroom chemicals also affect other cellular pathways. As the first step, we have performed gene expression microarray analysis on MCF-7aro tumors from the mushroom-fed animals and those from control animals. It was our goal to identify additional gene targets whose expression could also be modulated by mushroom feeding.

We have performed an analysis using Affymetrix Human Genome U133A across three biological replicates, i.e., tumor RNAs which were isolated from three individual animals and analyzed separately. We identified 124 genes that were up-regulated and 332 genes that were down-regulated in tumors from mushroom-fed mice versus those in control mice. Specifically, the results showed that a higher percentage of signal transduction genes are up-regulated and a higher percentage of genes involving in DNA processing and transcription/translation are down-regulated in tumors from mushroom-fed mice versus those in control mice. A careful evaluation of the results from microarray analysis will yield novel insights into the mechanisms as well as important signal-transduction pathways regulated by the phytochemicals in white button mushrooms.


Symposium Abstract (2007)
White button mushrooms (Agaricus bisporous) are a potential breast cancer chemopreventive agent, as they suppress aromatase activity and estrogen biosynthesis. Therefore, we evaluated the activity of mushroom extracts in the estrogen receptor positive/aromatase positive MCF-7aro cell line in vitro and in vivo. Mushroom extract decreased testosterone-induced cell proliferation in MCF-7aro cells but had no effect on the MCF-10A, a non-tumorigenic cell line. Most potent mushroom chemicals are soluble in ethyl acetate (EA). The major active compounds found in the EA fraction are unsaturated fatty acids such as linoleic, linolenic and conjugated linoleic acids. The interaction of linoleic acid and conjugated linoleic acid (CLA) with aromatase mutants expressed in CHO cells showed that these fatty acids inhibit aromatase with similar potency and that mutations at the active site regions affect its interaction with these two fatty acids. While these results suggest that these two compounds bind to the active site of aromatase, inhibition kinetic analysis indicates that they are non-competitive inhibitors with respect to androstenedione. Since only CLA was found to inhibit the testosterone-dependent proliferation of MCF-7aro cells, the physiologically relevant aromatase inhibitors in mushrooms are most likely CLA and its derivatives. The in vivo action of mushroom chemicals was demonstrated using nude mice injected with MCF-7aro cells. The studies showed that mushroom extract decreased both tumor cell proliferation and tumor weight with no effect on rate of apoptosis. Therefore, our studies illustrate the anti-cancer activity in vitro and in vivo of mushroom extract and its major fatty acid constituents.

Anti-aromatase activity of phytochemicals in white button mushrooms (Agaricus bisporus)
Periodical:Cancer Research
Index Medicus: Cancer Res
Authors: Chen, S., Oh, S.-R., Phung, S., Hur, G., Ye, J.-J., Kwok, S.L., Shrode, G.E., et al.
Yr: 2006 Vol: 66 Nbr: Abs: Pg:12026-34