Organoids model distinct vitamin E effects at different stages of prostate cancer evolution

Njoroge, Rose Nyawira

doi:https://doi.org/10.21985/n2-7q1r-9e30

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Organoids model distinct vitamin E effects at different stages of prostate cancer evolution

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Prostate cancer (PCa) is the most common non-cutaneous cancer among U.S. men. Lack of effective treatments for advanced disease make it a significant public health concern. However, PCa’s long natural history makes it an excellent target for prevention approaches that reduce overtreatment of indolent disease, treatment related morbidity, and mortality. Oxidative stress has long been linked to prostate carcinogenesis. This fueled interest in the use of antioxidant supplements to inhibit, reverse or slow precancerous events or disease progression (chemoprevention). Analyses of the Alpha-Tocopherol, Beta Carotene (ATBC) prevention and the Nutritional Prevention of Cancer (NPC) trials showed a reduction in risk of PCa as a secondary end point after supplementation with the antioxidants, alpha tocopherol and selenium respectively. Additionally, epidemiological and preclinical data suggest an anti-tumorigenic role for vitamin E and selenium against PCa. However, the selenium and vitamin E Cancer Prevention Trial (SELECT), testing the efficacy of vitamin E and/or selenium on reducing PCa incidence in 35,533 healthy men found vitamin E to be associated with an increased risk of PCa while selenium was not efficacious. The work in this dissertation focused on understanding SELECT’s negative outcome. We hypothesized that the lack of clinical translation for the preclinical in vitro data was because the latter were derived by testing vitamin E and selenium on advanced PCa cell lines grown in non-physiologic two dimensional cell cultures. Further, we hypothesized that the more physiologic three-dimensional cultures would yield more clinically relevant data and that the outcome of antioxidant treatment would depend on the stage of the cancer. To test this, we studied the effects of vitamin E and selenium on a continuum of prostate carcinogenesis from benign, premalignant to malignant cells in three-dimensional organoid cultures which mimic in vivo prostate gland architecture. We found that while the supplements decreased proliferation and induced cell death in cancer (LNCaP) organoids, they had no effect on benign organoids derived from normal primary human prostate epithelial cells. This confirms that antioxidants have a different impact on different stages of cancer. Additionally, vitamin E but not selenium alone or in combination, enhanced cell proliferation and survival in premalignant (RWPE-1) organoids, recapitulating the SELECT results. Relative to vehicle, the vitamin E treated premalignant organoids had low ROS levels and more luminal filling. Furthermore, microarray analysis revealed downregulation in the expression of integrins, glucose transporters and glycolytic enzymes in the vitamin E treated premalignant organoids, suggesting matrix detachment and metabolic alterations. Accordingly, detached RWPE-1 cells treated with vehicle had low ATP levels due to diminished glucose uptake and glycolysis. However, treating detached RWPE-1 cells with vitamin E rescued ATP by activating fatty acid oxidation (FAO). FAO inhibition abrogated vitamin E’s ATP rescue in detached RWPE-1 cells and diminished survival of the inner matrix deprived cells, restoring the normal hollow lumen morphology in vitamin E treated organoids. Organoid models therefore clarified the paradoxical findings from SELECT. These findings demonstrate that vitamin E promotes tumorigenesis in the early stages of prostate cancer evolution by promoting cell survival in matrix deprived cells by activating FAO.

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