Protease inhibitors and carcinoma of the esophagus

BACKGROUND: Squamous cell carcinoma of the esophagus is endemic in parts of South Africa. Previous case-control studies have shown many associations but no clear etiologic pathway has been established. METHODS: A case-control study of dietary and social factors was performed for 130 patient/control pairs matched for age, gender, and educational level. Staple diet, consumption of wild vegetables, use of tobacco, and traditional beer consumption were compared between the two groups. RESULTS: New significant associations were found with the consumption of beans (P = 0.016) and consumption of the full traditional diet of maize, pumpkin, and beans (P = 0.027). Known associations with the consumption of Solanum nigrum (P = 0.018) and with smoking (P = 0.002) were confirmed by multiple regression analysis. CONCLUSIONS: Solanum nigrum, beans, and pumpkin all contain protease inhibitors. Suppression of protease inhibitors can lead to overexpression of growth factors in the esophagus, resulting in a proliferative and oncogenic drive.