Effect of administration of selective progesterone receptor modulators (SPRMs) on uterine and endometrial morphology

Introduction: The human menstrual cycle is regulated by sex-steroid hormones, including oestrogen (E), progesterone (P4) and androgens which act by ligand binding to their cognate receptors. Perturbation of the complex series of events governing the menstrual cycle may lead to heavy menstrual bleeding (HMB). This is a common debilitating condition and often associated with uterine fibroids. There remains an unmet need for effective, long-term medical treatment so women avoid surgery and preserve their fertility. Selective progesterone receptor modulators (SPRMs, e.g. ulipristal acetate, UPA) are synthetic ligands that bind the progesterone receptor (PR). Many SPRMs have been developed but only mifepristone (for the management of unwanted pregnancy) and UPA are in current clinical use. UPA is licensed for the intermittent treatment of symptomatic fibroids. SPRMs have potential utility for treatment of HMB as administration rapidly induces amenorrhoea but the mechanisms by which this is achieved are unknown. SPRM administration results in unique endometrial morphological changes (progesterone receptor modulator-associated endometrial changes; PAEC). Despite endometrial unopposed estradiol exposure these morphological changes do not appear to be associated with malignancy or pre-malignancy risk. Indeed endometrial cell proliferation appears reduced despite relative progesterone-antagonism. Based upon findings with other SPRMs it was hypothesised that: (i) administration of UPA would have an endometrial specific effect upon the reproductive tract, with regard to alteration in morphology, localisation of sex steroid receptors (SSR) and cell proliferation.; (ii) administration of UPA would impact upon progesterone-regulated (Pregulated) genes in the endometrium. Methods: The data presented within this thesis are derived from biopsies obtained at hysterectomy from the endometrium, fallopian tubes and cervices of women with symptomatic fibroids administered UPA for 8-15 weeks. Samples were obtained for histological assessment, immunohistochemistry and RNA extraction for subsequent quantitative RT-qPCR of sex-steroid receptors (SSR) and proliferation markers. In addition key P-regulated genes within the endometrium were investigated by RT-qPCR and selected protein expression. To further interrogate the anti-proliferative effect, RNA was extracted from “paired” endometrial biopsies from the same woman in the proliferative phase of the menstrual cycle and following subsequent treatment with UPA for at least eight weeks and microarray gene analyses undertaken. Results: Morphological alteration of the endometrium with UPA administration was consistent with previously published data, but with a higher prevalence than previously described. There was a striking alteration in expression and localization of SSRs, particularly PR and androgen receptor (AR), and alteration of many P-regulated genes, consistent with UPA acting with low progesteroneagonism within the endometrium. There was no alteration of SSR expression within the cervix and proliferation was unchanged. Fallopian tube morphology and SSR expression was consistent with proliferative phase but cell proliferation was reduced following UPA administration, consistent with secretory phase levels. Microarray analyses identified multiple transcripts altered relative to proliferative phase, with GREM2 the most significantly down-regulated gene and MUC1 one of the most significantly upregulated genes. Consistent with low levels of mitotic figures and cell proliferation, the most down regulated KEGG pathway was the cell cycle. Multiple elements within this were subsequently validated (RT-qPCR) and included key regulators of all elements of the mitotic cell cycle, many of which were novel to those previously described following administration of another SPRM, mifepristone. In summary the novel data presented in this thesis considerably extend the data available to date concerning the actions of the SPRM, UPA, on the female reproductive tract, and increases knowledge regarding a compound with promising utility for the management of the debilitating complaint of HMB