Dietary Omega-6 and Omega-3 Fatty Acids and Prostate Cancer – Response

We truly appreciate the comments from Drs. Azrad and Demark-Wahnefried with regard to the potential for the proliferation bioassay reported in our article to potentially act as a surrogate biomarker for proliferation in the prostate cancer tissue. We would first like to clarify that there are 2 methods we use to assess mitogenic effects of patient serum on prostate cancer cell lines. The technique used in the present article and described in the Methods was a proliferation ex vivo bioassay in which we measure bromodeoxyuridine (BrdU) incorporation. Another bioassay that we have used in the past (references 1–3 in the letter above from Drs. Azrad and Demark-Wahnefried) is a cell viability ex vivo bioassay in which we use an MTS assay to measure the effect of patient serum on cell viability which is the result of sera mitogenic and apoptotic activities. We are in agreement with Drs. Azrad and Demark-Wanhefried's comments and we are also interested in determining whether results from the proliferation and cell viability ex vivo bioassays correlate with proliferation levels in the tissue. One way to address this issue would be to see whether the changes in ex vivo bioassay results (pre- vs. post-intervention) correlate with the changes in proliferation between the diagnostic prostate biopsy tissue and the radical prostatectomy tissue. This work is ongoing and we do not have results to report. Another approach would be to determine whether a correlation exists between the post-intervention ex vivo bioassay results and the proliferation level in the radical prostatectomy tissue. We carried out this analysis for the group as a whole (n = 48) using Spearman correlation analysis and found no significant correlation (r = −0.14, P = 0.34) between the BrdU ex vivo bioassay results and the proliferation level in the radical prostatectomy malignant tissue. Work is ongoing in our laboratory to determine the potential causative factors linking the low-fat fish oil diet with decreased proliferation levels in the prostate tissue. Again, we thank Drs. Azrad and Demark-Wahnefried for their insightful comments.

See the original Letter to the Editor, p. 798