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Old 06-03-2011, 04:30 PM   #21
Rich66
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Re: No need to avoid soy - new research

got me looking again and came across this which suggests some variables:

Clin Exp Metastasis. 2010 Oct;27(7):465-80. Epub 2010 Jun 2.
Individual and combined soy isoflavones exert differential effects on metastatic cancer progression.


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MartÃ*nez-Montemayor MM, Otero-Franqui E, Martinez J, De La Mota-Peynado A, Cubano LA, Dharmawardhane S.
Source

Department of Biochemistry and Cell Biology, Universidad Central del Caribe, Bayamón, PR, USA.

Abstract

To investigate the effects soy isoflavones in established cancers, the role of genistein, daidzein, and combined soy isoflavones was studied on progression of subcutaneous tumors in nude mice created from green fluorescent protein (GFP) tagged-MDA-MB-435 cells. Following tumor establishment, mice were gavaged with vehicle or genistein or daidzein at 10 mg/kg body weight (BW) or a combination of genistein (10 mg/kg BW), daidzein (9 mg/kg BW), and glycitein (1 mg/kg BW) three times per week. Tumor progression was quantified by whole body fluorescence image analysis followed by microscopic image analysis of excised organs for metastases. Results show that daidzein increased while genistein decreased mammary tumor growth by 38 and 33% respectively, compared to vehicle. Daidzein increased lung and heart metastases while genistein decreased bone and liver metastases. Combined soy isoflavones did not affect primary tumor growth but increased metastasis to all organs tested, which include lung, liver, heart, kidney, and bones. Phosphoinositide-3-kinase (PI3-K) pathway real time PCR array analysis and western blotting of excised tumors demonstrate that genistein significantly downregulated 10/84 genes, including the Rho GTPases RHOA, RAC1, and CDC42 and their effector PAK1. Daidzein significantly upregulated 9/84 genes that regulate proliferation and protein synthesis including EIF4G1, eIF4E, and survivin protein levels. Combined soy treatment significantly increased gene and protein levels of EIF4E and decreased TIRAP gene expression. Differential regulation of Rho GTPases, initiation factors, and survivin may account for the disparate responses of breast cancers to genistein and daidzein diets. This study indicates that consumption of soy foods may increase metastasis.

PMID:20517637



Quote:
Soy isoflavones are present in soy foods as aglycones where genistein, daidzein, and glycitein make up 50%, 40%, and 10%, respectively, of the total soybean isoflavones [8]


Quote:
Herein, using the highly metastatic ER (−) MDA-MB-435 cell line to establish mammary fat pad tumors in nude mice, we show that dietary daidzein increased tumor growth and metastatic efficiency indicating that the tumor promoting effect of daidzein is not ER dependent. Dietary genistein and soy phytochemical concentrate have been shown to reduce primary tumor growth and metastasis in bladder and prostate cancer models [17, 33], while other studies have shown that soy isoflavones, particularly genistein, increased the growth of MCF-7 human breast cancer cells and tumors in ovariectomized nude mice and metastatic progression of prostate cancer [20, 21]. The results shown herein using an ER (−) Her-2 (++) highly metastatic cancer cell line may reflect the role of soy isoflavones on mammary tumor growth and metastases from such aggressive cancers.

Quote:
This study indicates that consumption of soy products may have differential and complex effects on breast cancer progression and metastasis to different organs. Recent studies have shown that while dietary soy isoflavones do not affect breast cancer, they may increase the risk of colorectal cancer among women and prostate cancer among men [76]. Others have shown that soy food consumption was significantly associated with decreased risk of death and recurrence for breast cancer [77]. Thus, this investigation is of considerable interest in the debate about whether soy isoflavones promote or prevent breast cancer, particularly the perils of using soy in women diagnosed with breast cancer or those at high risk. However, caution must be exercised with interpretation of our results, since this study represents the effect of a single concentration of soy isoflavones that reflect a high soy diet conducted with an ER negative cancer cell line in non-ovariectomized nude mice.
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