Background: Consumption of tomatoes and tomato carotenoids is associated with a reduced risk of prostate cancer. Prostate tissue accumulates tomato carotenoids, including lycopene, β-carotene, and phytoene. Phytoene accumulation is relatively greater in the prostate than that of lycopene, but the metabolic determinants of tissue carotenoid profiles are poorly understood.
Objectives: The purpose of this study was to determine if differences in stability, cellular uptake, and clearance of phytoene compared with lycopene or β-carotene by prostate and intestinal cells may explain differences in observed tissue carotenoid profiles.
Methods: Gene and protein expression for carotenoid metabolism in prostate cell lines were analyzed by qRT-PCR and Western blot, respectively. Uptake, efflux, and clearance of phytoene, lycopene, or β-carotene by prostate cell (LNCaP, RWPE-1, and PC-3) and absorptive enterocyte (Caco-2) cultures were compared. The effect of scavenger receptor class B member 1 (SCARB1) inhibition on carotenoid uptake by LNCaP, RWPE-1, and Caco-2 cells was tested.
Results: SCARB1 was expressed across prostate cell lines. Lycopene, phytoene, and β-carotene uptakes were similar in LNCaP and PC-3 cells, whereas RWPE-1 cells absorbed a smaller portion of the phytoene dose than lycopene or β-carotene doses. The clearance rates of carotenoids from LNCaP cells did not differ. Intestinal cell uptake of phytoene was greatest, followed by β-carotene and lycopene. SR-BI inhibitor treatment did not significantly reduce the uptake or efflux of carotenoids by LNCaP or Caco-2 cells at the dose concentration provided.
Conclusions: Overall, this study suggests that greater bioavailability at the point of the intestine and greater stability of phytoene are determinants of the relative enrichment of phytoene in prostate tissue.
Keywords: Caco-2; SCARB1; lycopene; phytoene; β-carotene.
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