Effects of soy protein isolate consumption on prostate cancer biomarkers in men with HGPIN, ASAP, and low-grade prostate cancer.
Fifty-eight men at high risk of prostate cancer or with low-grade prostate cancer were randomly assigned to consume 1 of 3 protein isolates containing 40 g protein: 1) soy protein (SPI+, 107 mg isoflavones/d); 2) alcohol-washed soy protein (SPI-, <6 mg isoflavones/d); or 3) milk protein (MPI). Proliferating cell nuclear antigen (PCNA), epidermal growth factor receptor, B-cell non-Hodgkin lymphoma-2 (Bcl-2), and Bcl-2-associated X protein (Bax) were assessed in baseline and ending prostate biopsy cores. Serum collected at 0, 3, and 6 mo was analyzed for total and free prostate specific antigen (PSA). Consumption of SPI+ did not alter any of the prostate cancer tumor markers. Bax expression decreased from baseline in the SPI- group, resulting in lower Bax expression than the MPI group. PCNA expression also decreased from baseline in the SPI- group, but this was not different from the other 2 groups. PSA did not differ among the groups at 3 or 6 mo. Interestingly, a lower rate of prostate cancer developed in the soy groups compared to the milk group (P = 0.01). These data suggest that 6-mo SPI+ consumption does not alter prostate tissue biomarkers, SPI- consumption exerts mixed effects, and less prostate cancer is detected after 6 mo of soy consumption regardless of isoflavone content.
Hamilton-Reeves
Jill M
JM
Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55455, USA.
Rebello
Salome A
SA
Thomas
Will
W
Kurzer
Mindy S
MS
Slaton
Joel W
JW
D000368:Aged; D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D004044:Dietary Proteins / Q000008:administration & dosage; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage*; D009367:Neoplasm Staging; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D030262:Soybean Proteins / Q000008:administration & dosage*; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D015415:Biomarkers; D004044:Dietary Proteins; D007529:Isoflavones; D008894:Milk Proteins; D018809:Proliferating Cell Nuclear Antigen; D019253:Proto-Oncogene Proteins c-bcl-2; D030262:Soybean Proteins; D051028:bcl-2-Associated X Protein; D066246:ErbB Receptors; D017430:Prostate-Specific Antigen