More suggestions of connection between iodine breast health and estrogen metabolism; the paper also suggests that iodine may indirectly affect BRAC1 related metabolism . . . thought provoking stuff.
Interestingly breast health appears to be dependent at least in part on iodine rather than iodide and at least in part of the independent of supply of iodine by T3 and T4 indicating thyroid independent effects of iodine, in addition to possible as yet unidentified mechanisms
Iodine Alters Gene Expression in the MCF7 Breast Cancer Cell Line: Evidence for an Anti-Estrogen Effect of Iodine
Frederick R. Stoddard II,1,2 Ari D. Brooks,1 Bernard A. Eskin,3 and Gregg J. Johannes2
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2452979/
The protective effects of iodine on breast cancer have been postulated from epidemiologic evidence and described in animal models. The molecular mechanisms responsible have not been identified but laboratory evidence suggests that
iodine may inhibit cancer promotion through modulation of the estrogen pathway. To elucidate the role of iodine in breast cancer, the effect of Lugol's iodine solution (5% I2, 10% KI) on gene expression was analyzed in the estrogen responsive MCF-7 breast cancer cell line. Microarray analysis identified 29 genes that were up-regulated and 14 genes that were down-regulated in response to iodine/iodide treatment. The altered genes included several involved in hormone metabolism as well as genes involved in the regulation of cell cycle progression, growth and differentiation. Quantitative RT-PCR confirmed the array data demonstrating that iodine/iodide treatment increased the mRNA levels of several genes involved in estrogen metabolism (CYP1A1, CYP1B1, and AKR1C1) while decreasing the levels of the estrogen responsive genes TFF1 and WISP2. This report presents the results of the first gene array profiling of the response of a breast cancer cell line to iodine treatment. In addition to elucidating our understanding of the effects of iodine/iodide on breast cancer, this work suggests that iodine/iodide may be useful as an adjuvant therapy in the pharmacologic manipulation of the estrogen pathway in women with breast cancer.
The high rate of breast disease in women with thyroid abnormalities (both dietary and clinical) suggests a correlation between thyroid and breast physiology 1-3. In addition, women with breast cancer have larger thyroid volumes then controls 2. Multiple studies suggest that abnormalities in iodine metabolism are the likely link 4-7. Additionally, the impact of iodine therapy for the maintenance of healthy breast tissue has been reported in both animal 4-7 and clinical studies 8, 9 yet the mechanisms responsible remain unclear . . . http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2452979/ FREE FULL TEXT
Evidence indicates that the impact of iodine treatment on breast tissue is independent of thyroid function. For example, iodine deficient rats given the thyroid hormone thyroxine (T4) did not achieve reduced tumor growth following NMU treatment suggesting that the effect of iodine on tumor growth is independent of the thyroid gland or thyroid hormone 7. Additionally, Eskin et al and others have reported that administration of molecular iodine has a greater impact on tumor growth than the equivalent dose of iodide 5-9. Since the thyroid primarily utilizes iodide as opposed to iodine 5, this data supports the hypothesis that iodine is not acting through the thyroid.
In addition to differences in the metabolism of iodine, the mechanisms of iodine and iodide uptake appear to differ. While iodide uptake is essentially via the Sodium-Iodide Symporter (NIS) in the thyroid, data suggests that iodine uptake in the breast may be NIS-independent, possibly through a facilitated diffusion system 12. Together this data indicates that the effect of iodine on breast cancer progression is in part independent of thyroid function and suggests that iodine's protective effect on breast cancer progression is elicited through its direct interactions with breast cancer cells.