Clinical Abstracts From Overseas

By Stanton R. Mehr
Published: Wednesday, May 26, 2010
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United Kingdom

How Do Vegetables Fight Prostate Cancer?

It has long been suspected that eating plenty of fruits and vegetables had a protective effect against cancer, but it was not understood why this relationship existed. Recently, British researchers reported a seemingly important mechanism in this process.

It is known that cruciferous vegetables contain isothiocyanate, which has been suspected to play a role. Broccoli has high concentrations of sulforaphane, a potent inducer of phase 2 enzyme gene transcription, which can also cause cell-cycle arrest and apoptosis. Investigators hypothesized that this could translate into anticarcinogenic activity.

The study group comprised 21 men (age range, 57–70 yr) who had high-grade prostatic intraepithelial neoplasia, which has a high risk of developing into adenocarcinoma. Over the course of 12 months, 13 were given 400 g of steamed broccoli each week, and eight were given given 400 g of steamed peas per week, in addition to their normal diet. Prostate samples were obtained by biopsy at baseline, at six, and after 12 months. To monitor whether participants ate their veggies, all subjects were asked to complete weekly sheets, documenting on which days they ate their assigned food and in what quantity.

The researchers found that a comparison of biopsies obtained at baseline and after the dietary intervention revealed more changes in gene expression occurred in individuals on a broccoli-rich diet than in those on a pea-rich diet. Although they reported changes in androgen signaling in both groups of men, men eating the broccoli-rich diet had additional changes to mRNA processing, and TGFβ1, EGF and insulin signaling. For instance, they could not detect differences in gene expression between participants receiving the pea-rich diet who were positive for glutathione S-transferase mu 1 (GSTM1) and those who tested negative for activity of this gene. However, for those receiving the broccoli-rich diet, gene expression was significantly different for those with GSTM1-positive and -negative genotypes. This gene expression is associated with transforming growth factor beta 1 (TGFβ1) and epidermal growth factor (EGF) signalling pathways.

They did not report on the number of participants whose high-grade neoplasia had evolved to adenocarcinoma in each group, but the study group size would not likely result in valid measures of statistical significance.

The investigators concluded that a broccoli-rich diet activated certain cancer-fighting genes, and deactivated others that help cancers develop, which may explain the association between high broccoli intake and low prostate cancer incidence.

Traka M, Gasper AV, Melchini A, et al: Broccoli consumption interacts with GSTM1 to perturb oncogenic signalling pathways in the prostate. PLoS ONE 2008;3(7): e2568.


More Implications of BRCA2: Note for Women Only

An interesting oncological twist was reemphasized recently by Canadian researchers, who found that the mutated BRCA2 gene, the expression of which portends higher breast cancer risk, also may point to significantly worse prostate cancer outcomes in men.

Investigators from the University of Toronto studied 301 men with prostate cancer and compared the survival of those with a BRCA2 mutation with those who had a BRCA1 mutation. Men with the BRCA2 mutation lived roughly half as long as those with the BRCA1 mutation (median survival, 4.0 vs. 8.0 yr, respectively; P < .01). Previously, the existence of the BRCA2 mutation had been linked to a multifold higher likelihood for developing prostate cancer compared with men without the mutation. Now, it seems that its presence has implications for prostate cancer survival as well.

Narod SA, Neuhausen S, Vichodez G, et al: Rapid progression of prostate cancer in men with a BRCA2 mutation. Br J Cancer 2008;99:371-374.

Multiple Centers in Europe

Endometrial Cancer Risk and Endogenous Sex Hormone Levels in Postmenopausal Women

It is well known that exogenous sex hormone intake can affect the risk of several cancers in women; however, relatively little is known about the risk associated with high endogenous sex hormone levels. Investigators from multiple centers in Europe utilized the European Prospective Investigation into Cancer and Nutrition (EPIC) study to address this question.

In the EPIC trial, 500,000 women across Europe completed extensive questionnaires in the 1990s and provided blood samples. Patients’ menopausal status was assessed at the time they gave blood. For this study, 247 patients with endometrial cancer were matched to 481 random healthy women based on multiple factors.

Fifty-five women with endometrial cancer had not reached menopause at the time of the blood sampling, and 192 had. The median time between recruitment into the study and cancer incidence was approximately three years. One of the principal differences among case patients and matched controls was a higher body mass index in the former group (27.4 vs. 26.0 kg/m2, respectively, P = .0001).

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