To compare the levels of n-3 polyunsaturated fatty acids (PUFAs) in leukocytes and prostate tissue in men with prostate cancer or benign prostatic hyperplasia (BPH), as dietary intake of n-3 PUFAs has been linked to the risk of prostate cancer; the prostate-specific antigen (PSA) level was also compared to prostate tissue levels of n-3 PUFAs.
Prostate tissue was obtained and leukocytes isolated from 20 men with prostate cancer and 35 with BPH. The n-3 PUFAs alpha-linolenic acid (ALA), eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) were measured in prostate tissue and in peripheral blood leukocytes using gas chromatography. PSA levels were measured in all of the men.
There was a strong positive correlation between EPA and DHA in leukocytes and in prostate tissue (EPA: r = 0.80, DHA: r = 0.53, both P < 0.001) in all the men, whereas there was no association between the content of ALA in leukocytes and in prostate tissue (r = -0.15). Men with BPH had similar levels of ALA in leukocytes and in prostate tissue, but men with prostate cancer had more ALA in prostate tissue than in leukocytes. The PSA level was significantly positively correlated with ALA level in prostate tissue (r = 0.42, P < 0.01) but there was no significant correlation between PSA level and EPA and DHA levels. There were no significant correlations between PSA level and n-3 PUFA levels in leukocytes.
Dietary intake of the marine n-3 PUFAs reflected in EPA and DHA levels in leukocytes are also reflected in EPA and DHA levels in prostate tissue in men with and without prostate cancer. However, there is a discrepancy between the levels of ALA in leukocytes and in prostate tissue, with higher levels in men with prostate cancer. This is in accordance with the strong positive association between PSA and ALA levels in prostate tissue. This study therefore does not support the hypothesis that intake of marine n-3 PUFAs might protect against prostate cancer, but lends support to the deleterious role of ALA in the development of prostate cancer.