Browsing by Author "Rademeyer, Anina Zenda"
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- ItemInvestigating the influence of the progesterone receptor isoforms on androgen receptor activity in breast and prostate cancer cell lines(Stellenbosch : Stellenbosch University, 2021-04) Rademeyer, Anina Zenda; Africander, Donita; Storbeck, Karl-Heinz; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.ENGLISH ABSTRACT: Breast cancer growth and survival are primarily dependent on signalling of estrogens via the estrogen receptor (ER), while for prostate cancer it is dependent on androgens acting via the androgen receptor (AR). However, other steroid receptors such as the progesterone receptor (PR) have also been found in both breast and prostate cancer tumours. Results from a previous study in our laboratory, have suggested crosstalk between the AR and both the PR isoforms, PRA and PRB, in both breast and prostate cancer cell lines. This study also showed that, in addition to transactivation on an androgen response element (ARE), the AR could also transactivate an estrogen response element (ERE), which is the binding site for the ER. As the aforementioned study used synthetic ARE- and ERE-containing promoters in reporter assays, the aim of this study was to assess whether similar responses would also be observed on endogenous AR- and ER-regulated genes in the MDA-MB-231 breast cancer cell line. As a proof of concept, a preliminary experiment was also performed in the PC3 prostate cancer cell line. Whether the AR and PRA or PRB occur in a molecular complex was also investigated using co-immunoprecipitation (Co-IP) assays. Realtime quantitative PCR (qPCR) results showed that both PRA and PRB, modulate the activity of the AR on the expression of the endogenous AR-regulated gene, prostate specific antigen (PSA) and on the ER-regulated genes, cathepsin-D (CTSD) and PR. More specifically, both the unliganded and progesterone (P4)-liganded PR, further increased the dihydrotestosterone (DHT)-induced expression of the AR-regulated PSA gene in the MDA-MB-231 breast cancer cell line. While neither the unliganded PR isoforms, nor liganded PRB, modulated the AR-mediated downregulation of the ER-regulated CTSD gene by DHT, the P4-activated PRA, when expressed in excess, reversed this downregulation. Ligand-activated AR also decreased PR mRNA expression, while both the unliganded and liganded PRA and PRB reversed this decrease. Preliminary results in the PC3 prostate cancer cell line show that ligand activated AR downregulated the expression of the AR-regulated TMPRSS2 gene. Unliganded PRA, expressed at equivalent levels to the AR, lifted this decrease, while when either unliganded or liganded PRA and PRB was present in excess relative to AR, TMRPSS2 mRNA expression was increased. CTSD mRNA expression was increased in MDA-MB-231 breast cancer cells transfected with PRA, suggesting that PRA can activate transcription of an ER-regulated gene. In contrast, PRB decreased expression of an ER-regulated gene, as indicated by the decreased CTSD mRNA expression in MDA-MB-231 cells transfected with PRB. Under the experimental conditions used in this study, we could not show a molecular interaction between the AR and PRA or PRB in COS-1 or MDA-MB-231 cells. However, collectively, the realtime qPCR results support previous findings with promoter-reporters showing crosstalk between the AR and PR in breast cancer, and contribute to our knowledge of steroid receptor crosstalk in breast cancer.