Lycopene Oxidation, Uptake, and Activity in Human Prostate Cell Cultures - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 442

lycopene concentration of the stock “solution” must be measured and adjusted after i ltration. A
number of solubilization methods have been used over the years to assure the availability of lyco-
pene to the cells in culture, such as solvents tetrahydrofuran (THF), dimethylsulfoxide (DMSO),
water miscible gelatin beadlets, micelles, and prostasomes. The i rst successful effort was the use
of THF, which tends to form a molecular cage around the lycopene molecules (Zhang et al. 1991).
Great care must be taken to prevent the formation of THF peroxides. Although the use of THF/
lycopene delivery with other cell lines has been successful, apparent lycopene uptake was lower
than with beadlets (Shahrzad et al. 2002), and the LNCaP cells were not viable when exposed
to the small amount of THF required for lycopene solubilization (Xu et al. 1999) in the hands of
some investigators. Also, lycopene dissolved in THF and LNCaP culture medium, and incubated
in glass under standard culture conditions was rapidly degraded with a half-life of approximately
2 h (Xu et al. 1999). DMSO has also been used as a solubilizing agent for lycopene, especially in
combination with lycopene-containing water dispersible beadlets (Borthakur et al. 2005, Offord et
al. 2002) and does not harm LNCaP cell viability. In our laboratory, the addition of DMSO to help
solubilize lycopene from beadlets showed no special advantage. Micelles containing 263 M lyco-

pene (maximal concentration that can be incorporated into micelles) have been used to overcome
these problems and found to be stable in cell culture medium under standard incubation conditions
for 50 h with only slight losses at 100 h. LNCaP growth over a 4 day period was slightly inhibited
by 5 and 10

μ

M lycopene-containing micelles (Xu et al. 1999). Micelle preparations are difi cult to
handle since i ltration to eliminate microbes in the preparation of the culture medium leaves many
of the micelles on the i lter. The availability of water-dispersible beadlets containing lycopene and
control beadlets containing no lycopene (DSM Nutritional Products, Inc, Persippany, NJ or BASF
Nutrition, Mt. Olive, NJ) have been used in recent studies. A careful evaluation of lycopene stability,
and lycopene uptake in cell culture medium with and without LNCaP cells showed that 76% of the
lycopene was recovered from the medium after 72 h using 10% lycopene DSM beadlets that were
supplied at concentrations ranging from 0.17 to 22.3

μ

M. The presence of LNCaP cells showed a
slightly greater loss of lycopene from the medium, which would be expected if there was an uptake
by prostate cells (Liu et al. 2006). Another comparison of fetal bovine serum (FBS) (with endog-
enous lipoproteins), micelles, or THF or THF/BHT showed an 80% loss of lycopene (2-5 h) in cell
free medium with the THF systems with no loss with FBS or micelles during the same time frame.
At 24 h, 60% of the lycopene was lost in the FBS system but the micelle formulation had only a 20%
loss. Surprisingly the micelle preparation (without lycopene) was extremely cytotoxic to DU 145
cells. Lycopene uptake by DU 145 and PC-3 cells was greater with the FBS system compared to the
THF system (Lin et al. 2007). Prostasomes have also been explored as a vehicle for lycopene deliv-
ery. At high (4.38

μ

M) lycopene concentrations, seminal prostasomes
took up the lycopene in a dose-dependent manner and lycopene stability in prostasomes (normal-
ized to prostasome protein) suspended in PBS over a 24 h period was excellent (Goyal et al. 2006a).
Also, lycopene supplementation of PNT2 and PC-3 cells resulted in the incorporation of lycopene
into the prostasomes secreted by these cells at concentrations of 3.71 and 1.41 mg/mg of exosomal
protein, respectively (Goyal et al. 2006b).

μ M) and physiological (0.876 μ

21.4.2 P RESENCE OF L YCOPENE I SOMERS AND O XIDATION P RODUCTS IN C ULTURE M EDIA
All- trans lycopene is rapidly isomerized to an equilibrium mixture with its cis isomers both in cell
culture medium (Liu et al. 2006) and in vivo in prostate tissue (Clinton et al. 1996, van Breemen
et al. 2002). The cis isomers of lycopene are absorbed better than the all- trans isomers when fed
to humans (Unlu et al. 2007). The 5 - cis isomer predominates in plasma (Gustin et al. 2004). Since

lycopene absorption by prostate cells might be due to facilitated diffusion (Liu et al. 2006), it is
likely that the cis isomers of lycopene form a signii cant proportion of intracellular lycopene in the
experiments that are reviewed later.

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