Thai plant can prevent breast cancer, better than soy



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November 17, 2007  
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pueraria.jpgCM NEWS – A phytoestrogen-rich Thai plant is an effective preventative agent against breast cancer, a new study concludes. Pueraria mirifica (ye ge, ye ge gen, ?? in Chinese medicine) has the potential to “eventually be recommended as a complement to soy having the same purpose but being more effective.”

CM News reports earlier that Thai plant Pueraria mirifica may alleviate vaginal dryness in postmenopausal women. In the current issue of the European menopause journal Maturitas, Pueraria mirifica seems to have the ability to bind its phytoestrogens to the estrogen receptor or its suppressor. Estrogen receptor Alpha is linked to breast cancer.

What is estrogen receptor? Estrogen receptors are overexpressed in around 70% of breast cancer cases, referred to as “ER positive”. Two hypotheses have been proposed to explain why this causes tumorigenesis, and the available evidence suggests that both mechanisms contribute:

  • Firstly, binding of estrogen to the ER stimulates proliferation of mammary cells, with the resulting increase in cell division and DNA replication leading to mutations.
  • Secondly, estrogen metabolism produces genotoxic waste.

The result of both processes is disruption of cell cycle, apoptosis and DNA repair and therefore tumour formation. ER? is certainly associated with more differentiated tumours, while evidence that ER? is involved is controversial. Different versions of the ESR1 gene have been identified (with single-nucleotide polymorphisms) and are associated with different risks of developing breast cancer.

Another SERM, raloxifene, has been used as a preventative chemotherapy for women judged to have a high risk of developing breast cancer. Another chemotherapeutic anti-estrogen, ICI 182,780 (Faslodex) which acts as a complete antagonist also promotes degradation of the estrogen receptor.

Estrogen and the ERs have also been implicated in breast cancer, ovarian cancer, colon cancer, prostate cancer and endometrial cancer. Advanced colon cancer is associated with a loss of ER?, the predominant ER in colon tissue, and colon cancer is treated with ER? specific agonists.

In the present study, weanling female rats were pretreated with Pueraria mirifica tuberous powder at a dosage of 0, 10, 100 and 1000mg/kg for four consecutive weeks. Mammary tumour development was then induced, followed by a weekly examination for size and multiplicity of mammary tumors for 20 weeks and finally a necropsy. Mammary tissues were investigated for the virulence of tumour and also monoclonal antibody stained against ER? and ER?.

The results said that dosages at 10mg and 100mg showed a mild preventive effect to induced breast cancer. The 10mg dosage initiated short-term inhibitory effect on the latency period of mammary tumour development, but lowered ER?/ER?. The 100mg dosage showed 2 weeks delay in tumourigenesis, lowered ER?, and ER?/ER?.

Moreover, the significant protective action of Pueraria mirifica on mammary tumours was clearly seen in the 1000mg dosage, which initiated differences with the control in all evaluated parameters. The 1000mg dosage also exhibited no papillary patterns of tumour tissue as found in the control. Nonetheless, only the 1000mg dosage initiated a lower body weight gain than the control during the 6–19th week, which might be explained by the lower amount of tumour mass and multiplicity than the control.

“It is thus clear evidence that pretreatment of Pueraria mirifica phytoestrogens could significantly reduce the severity of the induced mammary tumours in a dose-dependent manner,” the researchers say.

An analysis revealed that Pueraria mirifica exhibited dose-dependent anti-proliferation to the two types of estrogen receptor, with a stronger anti-proliferation effect to ER? than ER?. The sharp reduction in ER? than ER?, and the reduction in ER?/ER? in all treated groups should initiate less nuclear receptor sites for estrogen binding resulting in fewer proliferated mammary tumours. The researchers believed this could be the principle cause of the protective effect against induced breast cancer.

The researchers explained that phytoestrogens from the plant may influence mammary tissue differentiation by initiating changes in the structure of mammary ducts and lobules of the weanling rats and subsequently initiate less response to the induction of mammary-specific carcinogens.

“Our results strongly suggest that Pueraria mirifica phytoestrogens is the first herbal product besides those of a soy origin, exhibiting anti-proliferation in vivo to breast cancer development induced by a specific carcinogen,” the researchers say. “The consumption of the Thai traditional herb for menopausal treatment Pueraria mirifica could eventually be recommended as a complement to soy having the same purpose but being more effective.”

[Maturitas Volume 58, Issue 2, Pages 174-181]