A study by Dutch and German researchers has provided evidence that lycopene may be able to inhibit the growth of prostate tumours and that its effect may be enhanced if it is combined with vitamin E.
A number of epidemiological studies have already indicated that high intake of lycopene – a carotinoid that gives the red colour to tomatoes and other fruits – is associated with a reduced risk of prostate cancer.
But, these observational findings have now been underpinned by new research demonstrating a beneficial effect in human prostate tumours grown in mice. A Phase II study testing the compounds in cancer patients is now under way. The findings of the animal study are being reported by Dutch research scientist Dr. Jacqueline Limpens at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Geneva.
The study involved testing one low and one high dose of synthetic lycopene alone, one low and one high dose of synthetic vitamin E alone and a combination of low dose synthetic lycopene and vitamin E or a placebo. The researchers injected human tumour cells into the prostate of mice to see what effect the lycopene and vitamin supplements would have on the tumour growth and PSA (prostate specific antigen) and to compare any effects against the placebo.
Dr. Limpens, who is from the Department of Urology at the Josephine Nefkins Institute at the Erasmus Medical Center in Rotterdam, said: "We found that low dose lycopene suppressed the growth of the human prostate tumours by over half (at day 42 of the study), extending the tumour doubling time accordingly, while all other single treatments had no significant effect. However, the combination of low-dose lycopene and vitamin E produced the greatest tumour inhibition – 73% (at day 42). Importantly, we also saw that the doubling time of PSA values matched the tumour responses in all the experimental groups. This means that we can use PSA values as a surrogate marker in short phase II/III human trials as it is clear that PSA values are accurately reflecting the inhibiting activity of the lycopene and vitamin E on tumour growth.
The question though to be answered is exactly how much Lycopene should men take?