Transcriptomic Profile of Breast Tissue of Premenopausal Women Following Treatment with Progesterone Receptor Modulator: Secondary Outcomes of a Randomized Controlled Trial

Abstract

Progesterone receptor antagonism is gaining attention due to progesterone's recognized role as a major mitogen in breast tissue. Limited but promising data suggest the potential efficacy of antiprogestins in breast cancer prevention. The present study presents secondary outcomes from a randomized controlled trial and examines changes in breast mRNA expression following mifepristone treatment in healthy premenopausal women. We analyzed 32 paired breast biopsies from 16 women at baseline and after two months of mifepristone treatment. In total, 27 differentially expressed genes were identified, with enriched biological functions related to extracellular matrix remodeling. Notably, the altered gene signature induced by mifepristone in vivo was rather similar to the in vitro signature. Furthermore, this gene expression signature was linked to breast carcinogenesis and notably linked with progesterone receptor expression status in breast cancer, as validated in The Cancer Genome Atlas dataset using the R2 platform. The present study is the first to explore the breast transcriptome following mifepristone treatment in normal breast tissue in vivo, enhancing the understanding of progesterone receptor antagonism and its potential protective effect against breast cancer.

Keywords: breast cancer; mifepristone; progesterone receptor antagonist; progesterone signaling.

Figure 1

(A) Characterization of normal primary breast cells (basal, luminal progenitor and mature cells). The upper panel displays immunofluorescent images depicting breast cells stained with CD49f (green) and EPCAM (red), while the lower panel showcases cells stained with CK14 (red) and CK8 (green). Scale bars indicate 50 µm. DAPI was used to detect the nuclei. (B) Assessment of relative gene expression in normal primary breast cells. Real-time PCR analysis was conducted on selected genes (CCL18, CTSG, ABI3BP, WNT2, IL1B, LAMA1) to evaluate their expression levels in normal primary breast cells treated with varying concentrations of mifepristone (control, 5 μM, 50 μM, 100 μM) for a three-day duration. Statistical significance is denoted as follows: * p < 0.05; ** p < 0.01; *** p < 0.001; **** p < 0.0001. A scale bar indicating 50 µm is included in the figure for size reference.

Figure 2

GEM-B signature enrichment in breast cancer. Utilizing the R2 platform and the TCGA breast cancer dataset, the expression patterns of each gene within the GEM-B signature were examined. Comparative analysis involved RNA-seq data between two the groups of primary breast cancer tissue (n = 1101) and adjacent normal breast tissue (n = 113). Up- and downregulated DEGs are compiled and presented gradually by enrichment status in each condition.

Figure 3

Mifepristone-driven transcriptomic changes in the context of PR status in breast cancer. Employing the R2 platform and the TCGA breast cancer dataset, seventeen genes within the GEM-B signature show significant enrichment in PR-positive cohort, whereas three genes were enriched in the PR-negative cohort. The results are presented as a heatmap illustrating the mean log2 values for each gene, with p-values indicated on a log10 scale. (A) Shows the upregulated DEGs. (B) Shows the downregulated DEGs. The analysis involved RNA-seq data from 1114 breast cancer tissues, comparing PR-positive cases (n = 777) to PR-negative cases (n = 337).