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Title: Molecular aspects of the link between obesity, insulin resistance and breast cancer.
Authors: Weichhaus, Michael Georg
Supervisors: Bermano, Giovanna
Broom, John
Wahle, Klaus
Keywords: Obesity
Insulin Resistance
Breast cancer
Adipokines
Cell proliferation
Cell signalling pathways
Cell cycle
Apoptosis
Issue Date: Nov-2010
Publisher: The Robert Gordon University
Citation: WEICHHAUS, M., BROOM, I. and BERMANO, G., 2010. The molecular contribution of TNF-alpha in the link between obesity and breast cancer. Oncology Reports (in press)
WEICHHAUS, M., BROOM, I., WAHLE, K. and BERMANO, G., 2009. Insulin-induced gene expression changes in breast cancer cells and normal breast epithelial cells. Poster presented at 17th European Congress in Obesity (ECO) in Amsterdam. Obesity Facts, 2 (Suppl. 2 ), p. S172
WEICHHAUS, M., BROOM, I., WAHLE, K. and BERMANO, G., 2008. Molecular aspects linking insulin resistance to breast cancer by activation of cell signalling pathways. Poster presented at 6th Annual World Congress on the Insulin Resistance Syndrome (WCIRS) in Los Angeles. Diabetes and Vascular Disease Research, 5 (3), P. 233
WEICHHAUS, M., BROOM, I., WAHLE, K. and BERMANO, G., 2008. Molecular aspects of insulin resistance, cell signalling pathways and breast cancer in relation to obesity. Poster presented at the 16th European Congress on Obesity (ECO2008) in Geneva. International Journal of Obesity, 32 (Suppl. 1), P. S38
WEICHHAUS, M., BROOM, I., WAHLE, K. and BERMANO, G., 2009. Effect of hypeinsulinaemia and impaired adipokines secretion on proliferation of human breast cancer and normal human breast epithelial cells. Oral presentation at the 5th Asia-Oceania Conference on Obesity (AOCO) in Mumbai. International Journal of Diabetes in Developing Countries, 28, P. S21
Abstract: Obesity is a multi-factorial metabolic disease, resulting in increased adipose tissue acquisition by the host. This disease increases the risk for developing co-morbidities, including Metabolic Syndrome and other disorders such as breast cancer. Obesity, and particularly abdominal obesity, is characterised by metabolic changes, including chronically elevated insulin concentrations and aberrant secretion of cytokines released from fat tissue, called adipokines. Epidemiologically, the risk of developing postmenopausal breast cancer is increased in obese individuals. The molecular link between obesity and breast cancer however is not well understood. The study presented here aimed at identifying the molecular mechanisms involved in this link, by testing the hypothesis that high insulin concentration and certain adipokines may promote breast cancer progression and/or breast cancer aetiology. A cell culture system of breast cancer cells and breast epithelial cells was employed to investigate changes in cell proliferation, activation of cell signalling pathways, cell cycle progression and apoptosis after treatment with insulin, leptin, TNF-α, adiponectin and IL-6. In MDA-MB-231 breast cancer cells, insulin treatment did not affect cell proliferation, cell cycle or apoptosis. Conversely, IR-phosphorylation, AKT-phosphorylation and ERK1/2-phosphorylation were all significantly increased. Microarray analysis indicated several important changes in gene expression with insulin treatment. Leptin treatment increased proliferation by 21%. Additional analyses of the effect of leptin indicated that neither the PI3-kinase pathway nor the MAP-kinase pathway was involved in mediating this effect. Treatment with TNF-α increased apoptosis, but did not affect cell proliferation or activation of cell signalling pathways. In MCF-10A breast epithelial cells, cell proliferation increased after insulin treatment by 180%. IR-phosphorylation, AKT-phosphorylation and ERK1/2 phosphorylation were all significantly increased while early apoptosis decreased after insulin treatment. Analysis of cell cycle however did not indicate a change in progression. Microarray analysis indicated that insulin treatment may increase expression of genes related to cancer growth. Leptin treatment increased cell proliferation and also increased ERK1/2-phosphorylation, while AKT-phosphorylation was not affected. Leptin did not change cell cycle progression. TNF-α treatment increased cell proliferation and also increased ERK1/2 phosphorylation, while AKT-phosphorylation was not changed. TNF-α treatment tended to increase apoptosis, the change however was not statistically significant. In SK-BR-3 breast cancer cells, cell proliferation did not change after insulin treatment. IR-phosphorylation and AKT-phosphorylation increased after insulin treatment, while ERK1/2-phosphorylation decreased. Gene expression of cyclin D and cyclin E increased with insulin treatment, while apoptotic rate and cell cycle profile were also not affected. Cell proliferation increased by 115% after treatment with 100 ng/ml leptin. ERK1/2-phosphorylation however decreased, while AKT-phosphorylation tended to increase, but the change was not statistically significant. Cell cycle profile was not affected by leptin treatment, G1-phase however tended to increase, but the change was again not statistically significant. Cell proliferation increased by 59% after 48 h treatment with 10 ng/ml TNF-α. AKT-phosphorylation and ERK1/2-phosphorylation increased with TNF-α treatment. Cell cycle analysis showed a decrease in S-phase and G2-phase, indicative of a decrease in cell cycle progression. These results indicate that none of the examined obesity-related factors is convincingly identified as the main molecular link between obesity and postmenopausal breast cancer. Conversely, all treatments affected each of the cell lines in, at least, one of the examined aspects. This indicates that many of the obesity-related factors may affect breast cancer and that a single breast tumour may utilise a unique combination of those factors to promote growth. All treatments increased proliferation in MCF-10A breast epithelial cells, with additional analysis generally supporting growth promotion. Insulin treatment particularly increased cell proliferation, while leptin and TNF-α increased MAP-kinase signalling. This may indicate that insulin and adipokines may have a higher impact on breast cancer aetiology than on breast cancer progression.
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