The immune system and breast carcinoma : implications of dietary and other associated factors




Hoption Cann, Stephen A.

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Introduction: A review of animal and human studies demonstrates that the immune system is a major factor in both the enhancement and inhibition of malignant tumour growth. Macrophages, one of the most durable and versatile immune cells, may be key to this immune duality. Macrophages have been observed in particularly high concentrations in and around breast tumours. It has been suggested that these cells generally aid tumour growth, unless activated by an acute infections, immunomodulators or other means. Study l: Using immunohistochemistry and computer-aided image analysis, macrophage concentrations in and around breast tumours were examined. Other pathological tissues were also examined for comparative purposes. Macrophage density was found to correlate positively with the Modified Bloom Richardson (MBR) grade (r = 0.41) and MBR subscore (r = 0.44), suggesting that macrophage concentrations increase as tumours become more aggressive. Similar infiltrations of macrophages were observed in lung, prostate and hyperplastic thyroid tissues; although in these latter tissues, macrophages were generally confined to the tumour periphery. Study II: Iodine has been shown to play many roles in normal human physiology. In addition to its incorporation into thyroid hormones, iodine also has antibiotic and antitumour properties. Epidemiological studies of iodine in breast cancer have not been conducted. In this pilot case-control study, whole blood levels of 10 trace elements (Br, Cr, Fe, I, Mb, Mg, Mn, Se, V, and Zn) and their association with breast cancer was investigated. Other general, medical and dietary characteristics were examined as well. In comparison with iodine levels in Japan, iodine levels in the population under study were considerably lower, with a mean of 28.4 μg/l and a range of 19–35 μg/l. In the univariate logistic regression analysis, a number of significant associations with breast cancer were observed. A high education status (OR = 0.31) and high iron status (OR = 0.15) were associated with reduced risks, whereas previous hysterectomy or ovariectomy was associated with an increased risk of breast cancer (OR = 3.64). In the adjusted multivariate analysis, a high iron status remained associated with a reduced risk (OR = 0.01) and a history of breast pain with an increased risk (OR = 11.25). Conclusion: Understanding the duality of immune function, not only provides insight into cancer progression, but offers two primary avenues for treatment. First, one may down-regulate immune reparative activities, which aid tumour growth. This may be accomplished by using immunosuppressants. A second approach is to take advantage of the large population of tumour-associated immune cells, particularly macrophages, and stimulate these cells into their defensive activities. A wide variety of infectious agents may be used to stimulate this response. Finally, iodine is one immunomodulator that may be used to enhance immune activity for treatment, or alternatively, prevent tumour growth through long-term intake; unfortunately, blood iodine levels noted in this study would be too low to afford protection.



Breast carcinoma, Immune system, Dietary