Dehydroepiandrosterone (DHEA) is the most abundant endogenous adrenal steroid in humans and declines markedly with aging. It is increasingly consumed as an over-the-counter dietary supplement for its purported anti-aging effects, yet its usefulness, long-term safety and effects on prostate tissues remain uncertain. This laboratory reported that DHEA metabolism to testosterone (T) is increased in a reactive prostate stroma microenvironment in the presence of proinflammatory cytokines such as TGFβ1. While TGFβ1 has been shown to inhibit Nrf2-mediated gene expression, we investigated whether activation of Nrf2 could decrease TGFβ1 induction of reactive stroma, and decrease T levels and paracrine-induced prostate specific antigen (PSA) expression.

Primary prostate stromal cells, derived from radical prostatectomy tissue (6S) and normal prostate (PRSC), were treated with DHEA+/− TGFβ1. Nrf2 was activated by treatment with tert-butylhydroquinone (tBHQ) or curcumin. Expression of Nrf2-regulated detoxification enzymes was analyzed by real-time PCR and Western blot. T levels and PSA expression were determined using ELISA.

When stromal cells were treated with DHEA + TGFβ1(D+T), Nrf2-mediated gene expression of detoxification enzymes, including NAD(P)H: quinone oxidoreductase 1) NQO1, and heme oxygenase 1 (HO-1), was decreased. Importantly, we also found the levels of the potent androgen, dihydroxy testosterone (DHT). inactivating enzymes, AKR1C1 and AKR1C2, were decreased by this treatment. In other words, TGFβ1 treatment could result in increased DHT levels by inhibiting Nrf2-induction of AKR1C1/2 leading to a localized increase in DHT levels. The D+T-mediated effects were reversed by treating both 6S and PRSC stromal cultures with tBHQ or curcumin, increasing Nrf-2-induced detoxification enzymes (NQO1, HO1 and AKR1C1/2).

As previously reported, when stromal cells were cocultured with LAPC-4 cancer epithelial cells and treated with D+T, T and PSA levels were increased. This study reports that activation of Nrf2 pathway with treatment of tBHQ or curcumin decreased T and PSA levels.

In this model of endocrine-immuno-paracrine interactions in the prostate, D+T decreased Nrf2-induced detoxification and androgen-inactivating enzymes while activation of Nrf2 reverses this effect. By demonstrating that Nrf2 alters AKR1C1/2 levels and paracrine-induced, androgen mediated PSA expression, we demonstrate that Nrf2 is an integral part of the TGFβ1-induced reactive stroma microenvironment and is involved in steroid metabolism in stromal cells. This implies that activation of Nrf2 may alleviate some of the negative effects of the reactive stromal environment. Additional natural products or botanical agents that are known to activate the Nrf2 pathway should be tested to determine effectiveness in normalizing reactive stroma in the prostate.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4030.