Investigating the role of inflammation, progestins and steroid receptors in breast cancer

Date
2019-04
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Progestins are used by women all over the world in menopausal hormone therapy (HT) and contraception. Numerous clinical trials have, however, reported that some progestins are associated with an increased risk for developing breast cancer. Although multiple progestins with different chemical structures and biological activities have been synthesised, not all progestins have been evaluated for increased breast cancer risk. Obesity-related inflammation is also strongly associated with increased breast cancer risk, particularly amongst postmenopausal women. This increased inflammatory state is characterised by enhanced production of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNFα). Both these inflammatory mediators have been implicated in breast cancer development and progression. However, the exact mechanism whereby inflammation and progestins contribute to breast cancer risk is yet to be established. The aim of this study was thus to investigate the effects of different progestins, in the absence and presence of IL-6 or TNFα, on the proliferation, apoptosis, migration and invasion of breast cancer cells. Given that some progestins can interact with multiple steroid receptors, all of which are known to play important roles in breast cancer biology, the first part of the study investigated effects on steroid receptor expression in the T47D breast cancer cell line. Western blot analysis showed that all the progestins decreased the expression of the estrogen receptor (ER)-subtypes, progesterone receptor (PR)-isoforms and the androgen receptor (AR), while no effects were observed on the expression of the glucocorticoid receptor (GR). This study also showed that IL-6 has no effect on steroid receptor expression levels, while TNFα increased the expression of the GR. Results from this study also show that the selected progestins differentially increased cell survival of T47D and MCF-7 BUS breast cancer cells, while all progestins and both inflammatory mediators increased the migration of T47D breast cancer cells. IL-6 had no effect on cell survival of either cell line, while TNFα decreased the survival of the MCF-7 BUS cells. In addition, the progestins medroxyprogesterone acetate (MPA) and drospirenone (DRSP), as well as IL-6, appeared to increase invasion of the MDA-MB-231 breast cancer cell line. In contrast, TNFα appeared to decrease invasion of the MDA-MB-231 cells. This study is the first to show that none of the progestin-mediated effects on steroid receptor expression, proliferation, apoptosis and migration were modulated by either IL-6 or TNFα. On the other hand, TNFα appeared to decrease the progestin-induced effects on the invasion of the MDA MB-231 breast cancer cell line. Taken together, the results show that even though the progestins and the pro inflammatory cytokines may differentially affect breast cancer growth and survival, all the selected progestins, as well as IL-6 and TNFα, increase migration of T47D breast cancer cells. These results suggest that all these progestins and the inflammatory mediators may possibly increase the risk of developing metastatic breast cancer. Finally, the results obtained in this study indicate that the effects of the progestins on steroid receptor expression and hallmarks of cancer, were not exacerbated by the addition of the inflammatory mediators, suggesting that the combination of inflammation and progestins used in HT does not further increase breast cancer risk.
AFRIKAANSE OPSOMMING: Vroue regoor die wêreld gebruik progestiene in hormoonvervanginsterapie (HVT) en as voorbehoedmiddels. Verskeie kliniese proewe het egter al getoon dat sommige progestiene geassosieer word met ʼn verhoogde kans om borskanker te ontwikkel. Hoewel verskeie progestiene met verskillende chemiese strukture en biologiese aktiwiteite reeds gesintetiseer is, is nie alle progestiene vir ʼn verhoogde borskankerrisiko geëvalueer nie. Vetsugverwante inflammasie word ook sterk geassosieer met ʼn verhoogde kans vir borskanker, veral onder na-menopousale vroue. Hierdie verhoogde inflammatoriese toestand word gekenmerk deur ʼn verhoogde produksie van pro inflammatoriese sitokiene, soos interleukien-6 (IL-6) en tumornekrosefaktor-alfa (TNFα). Albei hierdie inflammatoriese mediators is al geassosieer met die ontwikkeling en progressie van borskanker. Die presiese meganisme waardeur inflammasie en progestiene tot verhoogde borskankerrisiko bydra, is egter nog nie vasgestel nie. Die doel van hierdie studie was dus om die uitwerking van verskillende progestiene, in die afwesigheid en teenwoordigheid van IL-6 óf TNFα, op die proliferasie, apoptose, migrasie en indringing van borskankerselle te ondersoek. Aangesien sommige progestiene met verskeie steroïedreseptore interaksie kan hê, en almal bekend is om belangrike rolle in borskankerbiologie te speel, ondersoek die eerste deel van die studie die uitwerkings op steroïedreseptor-uitdrukking in die T47D borskankersellyn. Western klad-analise het getoon dat al die progestiene die uitdrukking van die estrogeenreseptor (ER)-subtipes, progesteroonreseptor (PR)-isoforms en die androgeenreseptor (AR) verlaag het, terwyl geen effek op die uitdrukking van die glukokortikoïedreseptor (GR) waargeneem was nie. Hierdie studie het ook getoon dat IL-6 geen effek op steroïedreseptor-uitdrukkingsvlakke het nie, terwyl TNFα die uitdrukking van die GR verhoog. Die resultate van hierdie studie toon ook dat die geselekteerde progestiene die seloorlewing van die T47D en MCF-7 BUS borskankerselle differensieel verhoog, terwyl alle progestiene en albei inflammatoriese mediators die migrasie van die T47D borskankerselle verhoog het. IL-6 het geen effek op seloorlewing van enige van die sellyne getoon nie, terwyl TNFα die oorlewing van die MCF-7 BUS selle verlaag het. Daarbenewens het die progestiene medroksieprogesteroonasetaat (MPA) en drospirenoon (DRSP), sowel as IL-6, die indringing van die MDA-MB-231 borskankersellyn verhoog. In teenstelling hiermee het TNFα die indringing van die MDA-MB-231 selle verlaag. Hierdie studie is die eerste om te wys dat geen van die progestien gemedieerde effekte op steroïedreseptor-uitdrukking, proliferasie, apoptose en migrasie deur óf IL-6 óf TNFα gemoduleer is nie. Aan die anderkant het TNFα die progestien-geïnduseerde effekte op die indringing van die MDA-MB-231 borskankersellyn verminder. Gesamentlik wys hierdie resultate dat hoewel die progestiene en die pro-inflammatoriese sitokiene die groei en oorlewing van borskanker differensieel kan beïnvloed, kon al die geselekteerde progestiene, sowel as IL-6 en TNFα, die migrasie van T47D borskankerselle verhoog. Hierdie resultate dui daarop dat al hierdie progestiene en die inflammatoriese mediators moontlik die risiko van die ontwikkeling van metastatiese borskanker kan verhoog. Laastens, die resultate wat in hierdie studie verkry is, dui daarop dat die uitwerking van die progestiene op steroïedreseptor-uitdrukking en kenmerke van kanker nie vererger word deur die toevoeging van die inflammatoriese mediators nie. Dit dui daarop dat die kombinasie van inflammasie en progestiene wat in HVT gebruik word, nie die risiko vir borskanker verder verhoog nie.
Description
Thesis (MSc)--Stellenbosch University, 2019.
Keywords
Breast cancer, Progestational hormones, Menopausal hormone therapy, Inflammation -- Mediators, Steroid receptors, UCTD
Citation