Study of BiP and TARDBP clinical significance as immunohistochemical markers for breast cancer prognosis

• Autor(a) principal: Gomes, Daniela Filipa Costa
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/35649
• topic: Protein aggregation; Chaperone; Breast cancer; Tumour heterogeneity; BiP; TARDBP; UPR; Immunohistochemistry; Antiestrogen resistance; Hormonal therapy; Metanalysis

Breast cancer (BC) is the most common cancer among women and one of the most common malignancies worldwide. BC is classified into subgroups to facilitate diagnosis, prognosis, and therapy options. Nearly 70% of breast tumours express the estrogen receptor (ER), offering hormone therapy as a viable treatment option. BC is a heterogeneous disease with many invasiveness-related variables, such as stage, grade, lymph node invasion, histology and hormone-receptor status. Resistance to antiestrogenic (AE) therapy remains the main problem of breast cancer treatment. In this work, the focus was on two proteins: TARDBP and BiP. TARDBP is a protein that plays important roles in transcription, pre-mRNA processing, splicing, and translation. This protein is well characterized in neurodegenerative disorders; however, little is known of its effects in BC. BiP is an endoplasmic reticulum (EndR) chaperone responsible for protein folding, calcium homeostasis and also acts as stress sensor. BiP is the primary regulator of EndR stress and exhibits antiapoptotic properties that regulate the unfolded protein response (UPR) signaling. BC therapies increase UPR signaling, hence promoting cell survival and drug resistance. The purpose of this research was to determine if BiP and TARDBP expression might be employed as predictive and prognostic indicators in luminal BC. The expression of TARDBP and BiP was analyzed in two small retrospective cohorts: cohort 1 with treatment naïve biopsies and its paired treated tumour sample; and cohort 2 with primary tumour samples and its corresponding metastasis. TARDBP expression was reduced in treated tumours relative to untreated biopsies, and this drop may be related with lower grade and increased progesterone receptor (PR) expression. BiP expression increased in metastasis compared to the primary tumour, which might be connected to the HER2 receptor. A knockdown of TARDBP was also performed, using siRNA, following treatment with tamoxifen. Regardless of treatment, cell proliferation decreased, demonstrating that this protein is essential for cell survival. To study BiP’s clinicopathological potential, complementary approaches were used: a systematic review and meta-analysis of immunohistochemistry (IHC) detection of BIP in human BC, as well as an examination of publicly accessible RNA-seq and proteomics datasets stratified by high and low quartile, were conducted. HER2, Basal-like subtypes, and greater immune score were related with elevated BiP mRNA and protein in the TCGA PanCancer dataset and CPTAC. BiP positivity was associated with worse relapse-free survival in BiP IHC meta-analysis. BiP IHC demonstrated elevated BiP expression in metastatic tumours, a correlation between BiP positivity and HER2 expression, and nuclear BiP localization as a predictor of advanced tumour stage and poor prognosis was observed. Thus, distinct methods demonstrated that BiP protein is associated with worse outcomes and may have a predictive value for BC. In conclusion, TARDBP expression is essential for cell survival and its decrease following AE therapy may be associated with less aggressive tumours. In contrast, complementary analyses of BiP reveal that BiP expression is higher in metastasis and in triple negative BC (TNBC), both associated with more aggressive tumors, suggesting that BiP is indicative of a poor prognosis.