Tomatoes protect against development of UV-induced keratinocyte carcinoma via metabolomic alterations

Prolonged tomato consumption can mitigate ultraviolet (UV) light induced sunburn via unknown mechanisms. Dietary carotenoids distributed to skin are hypothesized to protect skin against UV-induced damage, although other phytochemicals may play a role. We hypothesize that tomato consumption would protect against skin cancer. SKH-1 hairless and immunocompetent mice (n = 180) were fed AIN-93G or AIN-93G + 10% tangerine or red tomato powder for 35 weeks. From weeks 11-20, mice (n = 120) were exposed to 2240 J/m² UV-B light, 3x/week, and tumors were tracked weekly. Control mice were fed the same diets but not exposed to UV. Tumor number was significantly lower in male mice consuming red tomato diets (1.73 ± 0.50, P = 0.015) or pooled tomato diets (2.03 ± 0.45, P = 0.017) compared to controls (4.04 ± 0.65). Carotenoid levels in plasma and skin were quantitated, with total lycopene higher in skin of tangerine fed animals despite a lower dose. Metabolomic analyses elucidated compounds derived from tomato glycoalkaloids (including tomatidine and hydroxylated-tomatidine) as significantly different metabolites in skin after tomato exposure. Here, we describe that tomato consumption can modulate risk for keratinocyte carcinomas; however, the role of the newly identified specific phytochemicals possibly responsible for this action require further investigation.