British Journal of Nutrition

Full Papers

Molecular Nutrition

Effect of β-carotene-rich tomato lycopene β-cyclase (tlcy-b) on cell growth inhibition in HT-29 colon adenocarcinoma cells

Paola Palozzaa1, Diana Bellovinoa2 c1, Rossella Simonea1, Alma Boninsegnaa1, Francesco Cellinia3, Giovanni Monastraa2 and Sancia Gaetania2

a1 Institute of General Pathology, Catholic University School of Medicine, largo F. Vito, Roma, Italy

a2 National Research Institute on Food and Nutrition, via Ardeatina 546, Roma, Italy

a3 Metapontum Agrobios, Metaponto (MT), Italy

Abstract

Lycopene β-cyclase (tlcy-b) tomatoes, obtained by modulating carotenogenesis via genetic engineering, contain a large amount of β-carotene, as clearly visible by their intense orange colour. In the present study we have subjected tlcy-b tomatoes to an in vitro simulated digestion and analysed the effects of digestate on cell proliferation. To this aim we used HT-29 human colon adenocarcinoma cells, grown in monolayers, as a model. Digested tomatoes were diluted (20 ml, 50 ml and 100 ml/l) in culture medium and added to the cells for different incubation times (24 h, 48 h and 72 h). Inhibition of cell growth by tomato digestate was dose-dependent and resulted from an arrest of cell cycle progression at the G0/G1 and G2/M phase and by apoptosis induction. A down-regulation of cyclin D1, Bcl-2 and Bcl-xl expression was observed. We also found that heat treatment of samples before digestion enhanced β-carotene release and therefore cell growth inhibition. To induce with purified β-carotene solubilised in tetrahydrofuran the same cell growth inhibition obtained with the tomato digestate, a higher amount of the carotenoid was necessary, suggesting that β-carotene micellarised during digestion is utilised more efficiently by the cells, but also that other tomato molecules, reasonably made available during digestion, may be present and cooperate with β-carotene in promoting cell growth arrest.

(Received August 05 2008)

(Revised October 31 2008)

(Accepted October 31 2008)

(Online publication December 24 2008)

Correspondence:

c1 Corresponding author: Dr Diana Bellovino, fax +39 06 51494550, email bellovino@inran.it

Footnotes

Abbreviations: tlcy-b, tomato lycopene β-cyclase; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling

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