Relative Uptake of Tomato Carotenoids by In Vitro Intestinal and Prostate Cancer Cells.

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 (Lymph Node Carcinoma of the Prostate cell line), RWPE-1 (a human prostate epithelial cell line), and PC-3 (aprostate cancer cell line)] 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. SCARBI 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.