Consumption of soy isoflavone enriched bread in men with prostate cancer is associated with reduced pro-inflammatory cytokines and immunosuppressive cells.

We hypothesized that soy phytochemicals may have immunomodulatory properties that may impact prostate carcinogenesis and progression.

A randomized, phase II trial was conducted in 32 prostate cancer patients with asymptomatic biochemical recurrence but no measurable disease on standard staging studies. Patients were randomized to 2 slices of soy bread (34 mg isoflavones/slice) or soy bread containing almond powder daily as a source of β-glucosidase. Flow cytometry and bioplex assays were used to measure cytokines or immune cell phenotype in blood at baseline (day 0) and following intervention (day 56).

Adequate blood samples were available at enrollment and day 56 and evaluated. Multiple plasma cytokines and chemokines were significantly decreased on Day 56 versus baseline. Subgroup analysis indicated reduced Th1 (p=0.028) and MDSC-associated cytokines (p=0.035). Th2 and Th17 cytokines were not significantly altered. Phenotypic analysis revealed no change in CD8+ or CD4+ T cells, but showed increased CD56+ NK cells (p=0.038). The percentage of cells with a T regulatory cell phenotype (CD4+CD25+FoxP3+) were significantly decreased after 56 days of soy bread (p=0.0136). Significantly decreased monocytic (CD33+HLADRnegCD14+) MDSC were observed in patients consuming soy bread (p=0.0056).

These data suggest that soy bread modulates systemic soluble and cellular biomarkers relevant to immunomodulation consistent with limiting inflammation and suppression of MDSCs. Additional studies to elucidate impact on the carcinogenic process or as a complement to immune-based therapy are required.

Cancer Prev Res (Phila). 2015 Aug 14. pii: canprevres.0464.2014. [Epub ahead of print]

Lesinski GB1, Reville PK2, Mace TA2, Young GS3, Ahn-Jarvis J4, Thomas-Ahner J5, Vodovotz Y4, Ameen Z2, Grainger EM6, Riedl K7, Schwartz SJ4, Clinton SK8.

1 Internal Medicine, The Ohio State University
2 Internal Medicine, The Ohio State University.
3 Center for Biostatistics, The Ohio State University.
4 Food Science and Technology, The Ohio State University.
5 Comprehensive Cancer Center, Ohio State University.
6 Medicine, THe Ohio State University.
7 Food Science & Technology, Ohio State University.
8 Division of Medical Oncology, Wexner Medical Center.