Mammary cancer is the world's most common malignant neoplasia for women. Recently, the mortality for breast cancer has fallen due principally to early detection and to use of neoadjuvant chemotherapy. Anthracycline antibiotics are the most commonly used anticancer drugs, and Doxorubicin (DOX) is the first choice to treat mammary cancer. Nevertheless, its use has limited by its cadiotoxic side effects, which are generated by free radicals. Our studies in methylnitrosourea (MNU)-induced mammary cancer models have shown that supplementation with moderately high doses of molecular iodine (I2) exhibits two distinctive and beneficial effects: antineoplastic and antioxidant. In the present work we explored these dual characteristic of I2 (0.05%) as an adjuvant to DOX16 (therapeutic dose of 16 mg/kg) and DOX8 (8 mg/kg) in female Sprague Dawley rats (200 g) with tumors induced by a single dose of 50 mg MNU per Kg. Iodine intake is initiated 2 days before DOX application and continues up to sacrifice 7 days later. The following parameters were registered: body weight, tumor size, tumor proliferation rate (proliferating cell nuclear antigen, PCNA), serum creatinine kinase-MB activity (CK-MB), cardiac lipoperoxidation (cLPO), and cardiac catalase activity (cCAT). Values correspond to mean± SD. Different superscripts represent significant (p≥0.05). Tumor reduction was greater in the DOX16 + I2 group than in the DOX 16 group (75% vs. 50%, respectively), and was associated with a significantly greater decrease in the rate of tumor cell proliferation (25% vs 10% decrease in PCNA-positive cells), showing the synergistic effect of I2. In contrast, at both DOX doses, the DOX + I2, groups had lower body weight loss and less cardiac damage (CK-MB; 280% vs 100%, cLPO 100% vs 0%) than with DOX alone. cCAT was not changed by any of the treatments.Conclusions: Iodine acts as an adjuvant by significantly enhancing the antiproliferative effect of DOX at a therapeutic dose (DOX16), and it exerts significant general and cardiac protective effects that do not involve catalase activation. Cellular and molecular mechanisms involved in these dual effects of iodine are currently being analyzed. The authors thank Drs. Mauricio Diaz, Marcela Lizano, and Brenda Anguiano as well as Biol. Felipe Ortiz for their technical assistance and Leonor Casanova for academic supports. We also thank Dr. Dorothy Pless for proof-reading. Supported in part by PAPIIT/UNAM 201210 and CONACYT 78955 and 47928/47928. Figure available in online version.
Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-10-16.