In vitro Antitumour Activity of Tomato-Extracted Carotenoids on Human Colorectal Carcinoma

Abstract

The aim of this research was to establish whether all-trans lycopene extracted from fresh and frozen tomatoes is able to inhibit the in vitro proliferation of colon cancer cells, to trigger apoptosis by reactive oxygen species modulation and to reveal its influence on NF-kβ signalling, through the p65 transcription factor and expression of two TNF receptors: GITR and CD27. The carotenoid extracts containing all-trans lycopene were obtained from fresh (E1) and frozen/thawed (E2) tomatoes (Lycopersicon esculentum Mill.), hybrid ‘Menhir’ F1. DLD-1 and HT-29 human colon adenocarcinoma cell lines were co-cultivated with the two extracts and cytotoxicity, apoptosis, antioxidant activity, reactive oxygen species as well as modulation of NF-kβ signalling pathway were assessed. Tomato extracts E1 and E2 were able to inhibit colon cancer cell growth in vitro. E2 contained a higher proportion of all-trans lycopene and displayed superior cytotoxicity and a better apoptosis inducing capacity. The two extracts proved antioxidant activity against DPPH radicals and were able to scavenge the reactive oxygen species in the treated tumour cells. This study also showed that lycopene acts mainly through p65 protein and moderately by TNF receptors GITR and CD27 to deactivate the NF-kβ signalling pathway involved in cancer cell proliferation.