Abstract Background: African American (AA) men are significantly more likely to be diagnosed with prostate cancer at younger ages, exhibit more aggressive and metastatic forms, and suffer double the mortality compared to European American males. While the cause of this disparity is unclear, the Nonn lab has previously demonstrated that African American men have a greater concentration of the active androgen dihydrotestosterone within the prostate. We hypothesize that these higher levels of prostate androgens contribute to the observed prostate cancer disparities in AA men. Here, we examine the mechanistic mediators resulting from prolonged exposure to higher androgens in vitro, aiming to mimic the patient observations. Methods: Three different prostate cancer cell lines of either African American and European American ancestry (LAPC4 and LNCaP, and MDA-PCa-2b) were cultured in the presence of 0nM, 1nM, and 10nM R1881, a synthetic androgen, for over 6 months. The cells were analyzed via in vitro proliferation, growth as xenografts in nude mice, RNA-sequencing analysis, and examination of gene and protein expression in cells. These phenotypes were compared to cells treated acutely with R1881 for 14-72h, depending on the assay. Results: Subcutaneous xenografts exhibit a biphasic effect of long-term androgen, with 1nM having a greater growth rate compared to control and 10nM in all three cell lines. In vitro, proliferation differences were not as pronounced; however, differences were observed between extended and acute androgen exposure. Globally, RNA-seq showed distinct and overlapping pathways in cells treated for six months or longer compared to 24 hours for all three cell lines. Individual gene expression, as well as the expression of androgen-regulated genes, also showed differences between those exposed for 6 months or longer and those exposed acutely to androgens. Ongoing experiments include protein expression and the ability to grow as spheroids. Conclusions: Tumor aggressiveness is highest in cells with prolonged exposure to moderate androgens compared to control or high androgens. Furthermore, androgen targets differ when cells are exposed to androgens for long-term compared to short-term exposure, suggesting adaptive signaling mechanisms. The findings indicate sustained elevated androgen levels, like those observed in prostate African American men, may promote a more proliferative cancer, distinct from that induced by acute androgen exposure. This model may better reflect the biology underlying prostate cancer disparities, providing a more accurate framework for identifying race-specific biomarkers of risk, as well as for testing prevention or therapeutic strategies tailored to androgen metabolism and signaling in AA men. Citation Format: Robert A. Holt, John F. Smetana, Candice Loitz, Lillian Perez, Reem B. Zalloum, Donald Vander Griend, Larisa Nonn. Prolonged Androgen Exposure in vitro as a Model to Identify Mechanistic Differences Contributing to Racial Disparities in Prostate Cancer abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86 (2Suppl): Abstract nr A024.
Holt et al. (Tue,) studied this question.