Morphological and protein aggregation changes in the aging mammary gland and breast cancer

• Autor(a) principal: Figueira, Daniela Filipa Duarte
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/28408
• topic: Aging; Adaptative stress responses; Protein damage; Unfolded protein response; Aggresomes; Mammary gland; Breast cancer; Proteostasis

Breast cancer risk increases with aging. Aberrations occurring in the mammary cell differentiation process increase the risk of breast cancer. In general, cell aging is associated with increased protein damage which can result in toxic intra – and extracellular protein aggregates and influence cell survival. Consequently, the cells activate a series of adaptive stress responses to resolve this potentially lethal toxicity. However, with aging cells appear to become less efficient as protein aggregation in different biological systems has been reported to increase with age. Protein aggregation is associated to human diseases which have higher incidence in the aging population and are related to cell degeneration and death, such as Alzheimer’s. Little information exists regarding how human cells from different embryonic origin and differentiation stage resolve toxic protein aggregates and how this can influence carcinogenesis. Since the mammary gland develops after birth through differentiation of adult mammary stem and progenitor cells, we hypothesized that the different cell hierarchies found in the mammary tissue deal differently with age-related protein aggregation. This in turn would make certain mammary cell types more prone to suffer alterations during differentiation. This work has two objectives: 1) the study of differentiation markers in the mammary epithelium throughout aging; and 2) the evaluation of the protein aggregates observed by fluorescence in human breast cancer cases to assess the changes in proteostasis before and after hormone therapy. For objective 1, the experimental model consisted of tissue samples from C57BL/6 mice aged 1 to 29 months; and human samples of hormone therapy resistant breast tumors (samples before and after treatment) for objective 2. Methods included histological evaluation of the mouse mammary gland during aging, namely constitution and architecture of the gland and immunohistochemistry to evaluate expression of epithelial markers and mammary gland differentiation (such as CK5, CK8, ER and PR); and for objective 2, it was necessary to optimize the protocol with ProteoStat® for histological samples. Objective 1 was not achieved, possibly due to the fixation artifacts found in the samples, which made the immunohistochemical study impossible. In Objective 2, opposing the expectations, more protein aggregates were detected in tumor samples after hormone therapy, and further studies will be needed to discriminate intra and extracellular aggregates.