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Letters to the Editor

Response to Dr. Chow

Department of Food Science and Biotechnology National
Chung Hsing University Taichung, Taiwan 402

^* E-mail: mlhuhu{at}nchu.edu.tw.

Dear Editor,

We recently reported in The Journal of Nutrition that orally administered lycopene inhibits experimental metastasis of human hepatoma SK-Hep-1 cells in athymic nude mice (1). We thank Dr. Chow for the comment that "The inclusion of target tissue concentration before and after treatment, such as the lung lycopene and β-carotene concentrations reported in this study, is likely to provide a better understanding of the role of carotenoids in the etiology of human cancer." As pointed out by Dr. Chow, "the tissue uptake and retention of a compound is determined not only by the amount treated or administered, but also by other factors."

Dr. Chow noticed from our data in Table 5 that after treatment with 20 mg lycopene or β-carotene per kg body weight (twice per week for 12 wk), lycopene concentration in the lungs increased from below the detection limit (<1 nmol/g) to 332 ± 181 nmol/g, whereas β-carotene increased from 13 ± 5 to 35 ± 4 nmol/g; a net increase of only 22 nmol/g in lung β-carotene concentration. Based on this insightful observation, Dr. Chow concluded that "β-carotene is far more effective than lycopene in terms of the end-points studied." However, the lung tissues, at least in nude mice, are able to accumulate far greater lycopene concentrations (332 ± 181 nmol/g) than β-carotene (35 ± 4 nmol/g) at the same dosage level (20 mg/kg body weight). We showed earlier that nude mice and gerbils were more appropriate than rats and mice as animal models for studying the in vivo effects of lycopene for humans (2). Because lycopene has many important physiological functions, such as antiinflammation (3), antitumor proliferation (4), and enhancement of gap junction intercellular communication (5), this selective accumulation of lycopene in lung tissues suggests that lycopene may play an important role in protecting lung tissues against various pathological states, including tumor metastasis.

Manuscript received 3 September 2008.

	LITERATURE CITED

TOP LITERATURE CITED

 

1. Huang C-S, Liao J-W, Hu M-L. Lycopene inhibits experimental metastasis of human hepatoma SK-Hep-1 cells in athymic nude mice. J Nutr. 2008;138:538–43.[Abstract/Free Full Text]

2. Huang C-S, Chuang C-H, Hu M-L. Effects of lycopene supplementation on plasma and tissue lycopene levels in various rodent strains. Int J Vitam Nutr Res. 2006;76:377–84.[Medline]

3. Herzog A, Siler U, Spitzer V, Seifert N, Denelavas A, Hunziker PB, Hunziker W, Goralczyk R, Wertz K. Lycopene reduces gene expression of steroid targets and inflammatory markers in normal rat prostate. FASEB J. 2005;19:272–4.[Abstract/Free Full Text]

4. Cheng HC, Chien H, Liao CH, Yang YY, Huang SY. Carotenoids suppress proliferating cell nuclear antigen and cyclin D1 expression in oral carcinogenic models. J Nutr Biochem. 2007;18:667–75.[Medline]

5. Wertz K, Siler U, Goralczyk R. Lycopene: modes of action to promote prostate health. Arch Biochem Biophys. 2004;430:127–34.[Medline]

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