Mushroom-supplemented soybeam extract and advanced prostate cancer (in mice, not yet in man)

According to a media release issued by the University of California Davis Comprehensive Cancer Center in Sacramento earlier today, “Mushroom-supplemented soybean extract shows therapeutic promise for advanced prostate cancer.”

Now so that we are very clear, the data on which this media release is based have nothing to do with effects in man. They are based on a study by Mooso et al., recently published in Endocrine-Related Cancer, that was conducted in prostate cancer cells and in mice. As a consequence, we should be careful not to over-interpret the results. Lots of things that happen in Petri dishes and in laboratory mice can never be replicated in humans!

Basically, this study shows that genistein combined polysaccharide (GCP), a proprietary extract derived from soybeans and shiitake mushrooms and marketed by a Japanese company, can help to block a key mechanism used by prostate cancer cells to survive in the face of testosterone deprivation. GCP contains a combination of the compounds genistein and daidzein.

The “key mechanism” that GCP may be able to block is the elimination from the cancer cells of a protein called filamin A. When a patient’s androgen levels are lowered, prostate cancer cells stop production of filamin A, which would otherwise be attached to the androgen receptor in the cells’ nuclei. Androgen receptors nromally regulate growth of prostate cancer cells. Once filamin A is eliminated from the nuclei of cancerous cells, those cells cell no longer require androgens to survive. Thus, loss of filamin A allows these cells to survive androgen deprivation; essentially, the cancer then becomes incurable.

The basic hypothesis underlying this research is that men with metastatic prostate cancer who have the weakest levels of response to androgen-deprivation therapy (ADT) could be given GCP concurrently with ADT, allowing them to retain the presence of a protein known as filamin A in the nucleus of cancer cells, and thereby allowing cancer cells to die off.

The research team is apparently seeking funding to initiate clinical trials of GCP in the treatment of men with metastatic prostate cancer.

Dr. Ralph de Vere White is quoted as follows in the media release:

We should know within the first 8 months or so of human clinical trials if GCP works to reduce PSA levels. We want to see up to 75 percent of metastatic prostate cancer patients lower their PSA levels, and GCP holds promise of accomplishing this goal. If that happens, it would probably be a greater therapy than any drug today.

We’ll just have to wait and see whether Dr. de Vere White and his colleagues are able to move this study into successful clinical trials.

One Response

  1. The GCP story is not as new as it looks like in the press release. There have been several reports in recent years from the same institution (UC Davis Cancer Center) with more or less changing authors. The report by Burich et al. from 2008 has nearly the same conclusions as the recent paper by Mooso et al. See:

    — Mooso BA, et al. Enhancing the effectiveness of androgen deprivation in prostate cancer by inducing filamin A nuclear localization. Endocr Relat Cancer. 2012;19:759-77
    — McCall JL, et al. GCP, a genistein-rich compound, inhibits proliferation and induces apoptosis in lymphoma cell lines. Leukemia Res. 2010;34:69-76.
    — Burich RA, et al. Genistein combined polysaccharide enhances activity of docetaxel, bicalutamide and Src kinase inhibition in androgen-dependent and independent prostate cancer cell lines. BJU Int. 2008;102:1458-66.
    — Vinall RL, et al. Combination treatment of prostate cancer cell lines with bioactive soy isoflavones and perifosine causes increased growth arrest and/or apoptosis. Clin Cancer Res. 2007;13:6204-16.
    — Tepper CG, et al. GCP-mediated growth inhibition and apoptosis of prostate cancer cells via androgen receptor-dependent and -independent mechanisms. Prostate. 2007;67:521-35.

    One of the distributors of GCP pills in US is GeniKinoko. (See Amino Up chemical is the producer of GCP.)

    There are some case studies of GCP in men. >Here is a link to an old one from 2002 in the context of prostate cancer, but with only one man, and others in different types of cancer with also very small number of men, two or so.

    As GCP is available without a prescription in the USA, one has to assume that, since 2002, when the first reports about GCP in the context of cancer were published, some cancer patients may have experience with GCP, but there are no reports about that published and there have been no clinical trials to date.

    If GCP, which contains antioxidants, can really show positive effects in cancer treatment, it would be an mosaic stone in the dis-proof of the hypothesis put forward by Nobel prize winner James Watson in his paper “Oxidants, antioxidants and the current incurability of metastatic cancers.” In that article, he argues that antioxidant supplements are a bad thing in high risk cancers, especially in metastatic cancers!

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