The following abstract shows vitamins have more influence early rather than in later cancer stages:

'Chemopreventive effects of early-stage and late-stage supplementation of vitamin E and selenium on esophageal carcinogenesis in rats maintained on a low vitamin E/selenium diet

Hui Yang, Jin Fang, Xudong Jia, Chi Han, Xiaoxin Chen1, Chung S. Yang2 and Ning Li*

+ Author Affiliations

Department of Food Toxicology, Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, 7 Panjiayuan Nanli, Beijing 100021, China
¹Cancer Research Program, Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, 700 George Street, Durham, NC 27707, USA
²Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA

Received August 25, 2010. Revision received December 9, 2010.
Accepted December 17, 2010.

Abstract

Low vitamin E and selenium (Ve/Se) nutritional status is known to be associated with increased risk of esophageal squamous cell carcinoma (ESCC). A previous human intervention trial demonstrated that Ve/Se supplementation decreased the occurrence of esophageal cancer death among younger participants but not among older ones. In this study, we intended to mimic this human nutritional status to determine the chemopreventive effects of Ve/Se supplementation at the early or late stage of esophageal carcinogenesis in rats maintained on a low Ve/Se diet. ESCC was induced in F344 rats with N-nitrosomethylbenzylamine (NMBzA) (0.35 mg/kg body wt, subcutaneously, three times per week for 5 weeks). The rats were maintained on a modified AIN-93M diet with low levels of Ve/Se or supplementation to the normal level by using the AIN-93M diet. At Week 25, the numbers of visible tumors and ESCC were significantly lower in rats on AIN-93M diet during the entire experimental period (Group D) or during the early stage (Group B) but not during the late stage (Group C). Ve/Se supplementation (switching from the low Ve/Se diet to the AIN-93M diet) also decreased cell proliferation, angiogenesis, 8-hydroxy-2′-deoxyguanosine, biosynthesis of prostaglandin E2 and leukotriene B4, expression of cyclooxygenase 2 and 5-lipoxygenase in the esophagus. Our results demonstrated that Ve/Se supplementation inhibited NMBzA-induced esophageal carcinogenesis in rats on low Ve/Se diet, and supplementation during the early stage is more effective than during the late stage of carcinogenesis.' (end copy article)