Abstract/Summary

Al-based antiperspirant salts have been implicated as a causative factor in the development of breast cancer due to their proximity of application to the upper outer quadrant of the breast where the majority of breast cancers originate. Since mortality results from metastasis of breast cancer, this thesis has investigated the effects of Al chloride and Al chlorohydrate at 10-4M and 10-5M concentrations on the migratory and invasive abilities of four human breast cell lines. 10-5M was chosen as the concentration of Al previously measured in human nipple aspirate fluids. Effects on migration and invasion of MCF-7, MDA-MB-231, MCF-12A and HMF-3A human breast cells were explored using time-lapse microscopy, wound-healing assays and xCELLigence technology. Molecular pathways involving MMP-9, MMP-2, MMP-14, TIMP-1, TIMP-2, TIMP-3, ferritin and NDRG-1 were studied using RT-PCR, western immunoblotting and gelatin zymography. Prior exposure to Al increased the motility of MCF-7 cells after 32 weeks, of MDA-MB-231 cells after 25 weeks of prior exposure and of MCF-12A cells after 11 weeks. At a molecular level, Al chloride and Al chlorohydrate at 10 -5 M and 10 -4 M concentrations affected MMP-9 and MMP-14 mRNA and protein levels in MCF-7, MDA-MB-231 and MCF-12A cells. Although Al did not alter the motility of HMF-3A cells, changes in MMP-9, MMP-2 and MMP-14 mRNA expression and MMP-14 protein levels were found. Levels of the MMP inhibitors, TIMP 1, 2, and 3 were altered in MDA- MB-231 cells. Changes were observed in TIMP-3 levels in MCF-12A cells and TIMP-2 expression in HMF-3A cells. In considering the effects of Al on iron homeostasis, Al chloride was found to enhance ferritin levels in MCF-7 cells after 27weeks and in MCF-12A cells after 1week. Al chlorohydrate increased ferritin levels in MDAMB-231 cells after 21weeks. NDRG-1 mRNA and protein levels in MCF-7, MDA-MB-231 and MCF-12A cells were also affected but only NDRG-1 mRNA was altered in HMF-3A cells. Overall, it can be concluded that Al salts increase migration and invasion of human breast epithelial cells irrespective of whether they are transformed (MCF-7, MDA-MB-231cells) or not (MCF-12A cells), and irrespective of whether the cancer cells are oestrogen responsive (MCF-7 cells) or not (MDA-MB-231 cells). The changes observed in the levels of MMP-2, MMP-9 and MMP-14 and their inhibitors are indicative of a potential molecular pathway. The results demonstrate that exposure to Al chloride can increase ferritin levels, implicating alteration to iron homeostasis which is a known factor in the development of breast cancer. The results also showed that NDRG-1 expression, whose increase may depend on cell stress as for nickel, may not cause alterations observed in migration and invasion. In the light of these findings, it can be concluded that Al has mechanistic potential to cause metastatic tumour spread, which is the major reason for breast cancer mortality.