Monday November 30 2009
There is no evidence that the maitake mushroom cures cancer
“A mushroom popular in Chinese cooking can help shrink tumours and beat cancer”, according to the Daily Express. The newspaper says that tests on the maitake mushroom have shown that it can shrink tumours by 75%.
The research behind this news is a lab study in which extracted human bladder cancer cells were exposed to a combination of a cancer treatment drug called interferon alpha and a mushroom extract called PDF. After 72 hours, combined treatment with PDF and interferon had a greater effect than either drug used in isolation. The researchers say that PDF possibly enhances the activity of the interferon alpha, and that clinical trials in humans are warranted.
It will take more research to establish whether the PDF mushroom extract can enhance the effects of interferon treatment for bladder cancer. Until then, it is far too soon to suggest that this mushroom can cure cancer. It should also be noted that the study was only in extracted cells and not in ‘tumours’, as the Express has suggested.
Where did the story come from?
This study was carried out by Dr Brandon Louie and colleagues from the Department of Urology at New York Medical College in New York. The research was funded internally by the college and published in the British Journal of Urology International, a peer-reviewed medical journal.
The Daily Express has reported this study poorly and has made claims that are not supported by this piece of research. The newspaper does not make it clear that this was a laboratory study, and its description of the study methods is not consistent with the research itself.
What kind of research was this?
In this study, researchers investigated an alternative therapy for bladder cancer by testing it on cancerous cells in a laboratory.
There are a number of different treatments that can be used to fight bladder cancer. These include:
- Surgery, commonly for early-stage bladder cancer.
- Bacillus Calmette Guerin (BCG) therapy. BCG is also used as a vaccine against TB, which also stimulates an immune response in the bladder. However, there can be severe side effects, including cystitis, fever or allergic reactions.
- Interferons, which are man-made substances similar to those produced by certain white blood cells as part of the normal immune response.
Potential treatments using a combination of interferon alpha and BCG are being explored by research.
In this study, the researchers investigated a chemical that might be used in immunotherapy, a type of treatment where substances trigger the immune system to attack cancerous cells in the body.
They assessed how cultures of human bladder cancer cells were affected by a combination of a type of interferon and a substance called proteoglucan D-fraction (PDF). The chemical PDF is an extract of maitake mushrooms (Grifola frondosa) which, according to the researchers, has been shown to have anti-tumour activities in previous research. The extract is also being tested in phase II studies on patients with advanced breast and prostate cancer.
What did the research involve?
Bladder cancer cells were extracted from a patient and grown in culture in a laboratory. The cultured samples were then mixed with either interferon alpha, PDF or a combination of the two. After 72 hours exposure the researchers assessed the effects each substance had on the number of cancerous cells in the culture. The effects of different doses were also investigated. They then extracted DNA from the cells and examined it for evidence of the cancerous cells dying or replicating.
The effects of the substances individually and in combination were compared. The researchers also undertook further biochemical experiments to explore the mechanisms behind the substances’ effects, specifically looking to identify which enzymes might be involved, and which stage of cell growth the substances were affecting.
Overall, the study seems well-conducted and well-described by the researchers.
What were the basic results?
Both interferon alpha and PDF reduced cell growth compared with placebo cultures. When a combination of the two was used, growth was further reduced, suggesting that they worked in combination to give a ‘synergistic’ effect.
How did the researchers interpret the results?
The researchers say that compared with the amount of interferon alpha needed to be effective when used on its own, only a fifth of the dose is needed to achieve the same effect when combined with PDF. They say “it is plausible that PDF may not only help to [increase the effect of] interferon alpha activity, but may also reduce the cost of treatment”. Importantly, they say that clinical studies/trials are warranted. This puts these results in their correct context, i.e. very early research of substances that have yet to be tested in humans.
The findings of this study should be considered as preliminary ones that may lead to further research.
The findings that a combination of interferon alpha (a common immunotherapy for bladder cancer) and the PDF extract can reduce bladder cancer cell growth in a laboratory setting are the first step towards future studies. However, the potential benefits of PDF as a combination treatment for bladder cancer will only be established through studies to fully assess toxicity and longer-term benefits and harms. Investigating new treatments in this way is often a lengthy process, usually beginning with animal studies and only later followed by human studies.
It is too soon to claim, as the Daily Express has, that maitake mushrooms are a cure for cancer. The substance tested was only a chemical extract of the mushrooms, and this study provides no evidence that either the extract or the mushrooms themselves have health benefits in humans. People should resist the temptation for people to eat large amounts of mushrooms if they develop bladder cancer, as it is not clear from this research if any potentially active ingredients can even be absorbed through digestion. It is also unclear whether the effects of high doses in humans are harmful.
According to Cancer Research UK, bladder cancer is the seventh most common cancer in the UK, with five-year survival rates of 66% for women and 57% for men. The risk increases with age, and established risk factors include smoking and occupational exposure to chemicals.