Inhibition of N-methyl-N-nitrosourea-induced mammary carcinogenesis by molecular iodine(I2) but not by iodide (I-) treatment evidence that I2 prevents cancer promotion

We analyzed the effect of molecular iodine (I-2), potassium iodide (KI) and a subclinicat concentration of thyroxine (T4) on the induction and promotion of mammary cancer induced by N-methyl-N-nitrosourea. Virgin Sprague-Dawley rats received short or continuous treatment. Continuous 12 treated rats exhibited a strong and persistent reduction in mammary cancer incidence (30%) compared to controls (72.7%). Interruption of short or long term treatments resulted in a higher incidence in mammary cancer compared to the control groups. The protective effect Of 12 was correlated with the highest expression of the I-/Cl- transporter pendrin and with the lowest levels of lipoperoxidation expression in mammary glands. Triiodothyronine serum levels and Na+/I- symporter, lactoperoxidase, or p53 expression did not show any changes. In conclusion continuous 12 treatment has a potent antineoplastic effect on the progression of mammary cancer and its effect may be related to a decrease in the oxidative cell environment. (c) 2005 Elsevier Ireland Ltd. All rights reserved.