Beneficial Effects of Mifepristone Treatment in Patients with Breast Cancer Selected by the Progesterone Receptor Isoform Ratio: Results from the MIPRA Trial

PURPOSE

Preclinical data suggest that antiprogestins inhibit the growth of luminal breast carcinomas that express higher levels of progesterone receptor isoform A (PRA) than isoform B (PRB). Thus, we designed a presurgical window of opportunity trial to determine the therapeutic effects of mifepristone in patients with breast cancer, based on their high PRA/PRB isoform ratio (MIPRA; NCT02651844).

PATIENTS AND METHODS

Twenty patients with luminal breast carcinomas with PRA/PRB > 1.5 (determined by Western blots), and PR ≥ 50%, naïve from previous treatment, were included for mifepristone treatment (200 mg/day orally; 14 days). Core needle biopsies and surgical samples were formalin fixed for IHC studies, while others were snap-frozen to perform RNA sequencing (RNA-seq), proteomics, and/or Western blot studies. Plasma mifepristone levels were determined using mass spectrometry. The primary endpoint was the comparison of Ki67 expression pretreatment and posttreatment.

RESULTS

A 49.62% decrease in Ki67 staining was observed in all surgical specimens compared with baseline (P = 0.0003). Using the prespecified response parameter (30% relative reduction), we identified 14 of 20 responders. Mifepristone induced an increase in tumor-infiltrating lymphocytes; a decrease in hormone receptor and pSer118ER expression; and an increase in calregulin, p21, p15, and activated caspase 3 expression. RNA-seq and proteomic studies identified downregulated pathways related to cell proliferation and upregulated pathways related to immune bioprocesses and extracellular matrix remodeling.

CONCLUSIONS

Our results support the use of mifepristone in patients with luminal breast cancer with high PRA/PRB ratios. The combined effects of mifepristone and estrogen receptor modulators warrant clinical evaluation to improve endocrine treatment responsiveness in these patients. See related commentary by Ronchi and Brisken, p. 833.

Abstract P5-16-09: Transcriptome modulation by mifepristone treatment in breast cancer patients with higher levels of progesterone receptor A than B

Background: Preclinical data suggests that antiprogestins inhibit the growth of luminal breast carcinomas expressing higher levels of progesterone receptor isoform A (PRA) than isoform B (PRB). Thus, we designed a pre-surgical window of opportunity trial to determine the therapeutic effects of oral mifepristone (MFP) in 20 breast cancer patients selected by their high PRA/PRB isoform ratio (MIPRA; NCT02651844).Methods. MIPRA is an open-label, one-arm, prospective interventional study. After the selection process, 20 patients that met the inclusion criteria, with ER+, PRA/PRB>1.5 determined by Western blots, and total PR ≥50% determined by immunohistochemistry (IHC), were included for daily MFP treatment (200 mg/day p.o., 14 days). Core needle biopsies and surgical samples were formalin-fixed for IHC studies, and others were snap-frozen for further molecular studies. Besides, plasma samples were obtained for MFP dosing by LC-MS/MS. RNA was extracted from frozen tissue with a column-based method. The library for sequencing was constructed using SMART-Seq v4 Ultra Low Input RN from 8 paired samples in which tissue was available and passed the RNA quality control. Sequencing data was aligned with STAR and processed in R/Bioconductor. The counts matrix was obtained with featureCounts and differential expression paired analysis was performed with DESeq2. Gene set enrichment analysis (GSEA) was executed with the MSigDB collection.Results: A 49.62% decrease in Ki-67 staining was registered in all surgical specimens compared to baseline (p = 0.0003). Using the pre-specified response parameter (30% relative reduction) we identified 14/20 responders. Mifepristone was detected in all available plasma samples and the mean concentration was 308.33 ±57.91 ng/ml (716.71 ±134.62 nM). We conducted an RNA-seq analysis to explore changes at the transcript level. First, we conducted the study with all pairs of samples, without considering the response to MFP in Ki-67 studies. Unsupervised analysis showed the paired samples clustered together but neither the principal component analysis, nor the hierarchical clustering, showed any relevant cluster. The differential expression analysis identified 11 and 76 genes down- and up-regulated, respectively. We performed a GSEA based on KEGG databases and determined enriched pathways related to modulation of cell cycle and apoptosis. When the analysis was conducted with the REACTOME up-modulation of immune bioprocess and extracellular matrix re-modeling pathways such as degradation of extracellular matrix, activation of matrix metalloproteinases and collagen formation, were observed in the latter. Additionally, we observed down-modulation of pathways related to cell cycle such as DNA replication and synthesis, APC/C, and phase transition pathways. Interestingly, when we considered the tumors that responded to MFP according to Ki-67 data (n=4) and those that did not respond (n=4), we found that the non-responsive group shared some of the up and down modulated pathways as the responsive group.Conclusion: The results obtained in RNA-Seq data support the findings obtained by IHC indicating that MFP inhibits cell proliferation in luminal breast carcinomas with higher levels of PRA than PRB. The fact that MFP increased immune-related pathways is in line with previous preclinical data from our laboratory suggesting that MFP may prime this group of tumors for. further immune therapy. Interestingly, we found that some relevant pathways regarding inhibition of cell proliferation were also modulated in the non-responsive group suggesting that tumors in which a decrease in Ki-67 was not evident, may be still responding to MFP treatment. Ongoing analysis will determine changes in other markers that may help to further define MFP-responsive patients.

Citation Format: Andres Elia, Martin Abba, Hugo Gass, Caroline A Lamb, Victoria T Fabris, Paula Martinez Vazquez, Javier Burruchaga, Eunice Spengler, Ines Caillet Bois, Alejandra Castets, Silvia Lovisi, Marcos Liguori, Gabriela Pataccini, Maria Florencia Abascal, Virginia Novaro, Alfredo Molinolo, Silvia I Vanzulli, Paola Rojas, Claudia Lanari. Transcriptome modulation by mifepristone treatment in breast cancer patients with higher levels of progesterone receptor A than B [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-16-09.

Abstract PS11-35: Mipra, a window of opportunity study evaluating mifepristone treatment for postmenopausal breast cancer patients with higher levels of progesterone receptor isoform a than b

Background: Different antiprogestins have been clinically evaluated in gynecological andbreast cancers. Mifepristone (MFP), as well as onapristone and telapristone acetate, showedpartial responses in breast cancer clinical trials. Preclinical data indicates that antiprogestinsinhibit cell proliferation of luminal breast carcinomas expressing higher levels of progesteronereceptor isoform A (PRA) than those of isoform B (PRB) evaluated by western blots (WB). Thus,we designed a pre-surgical window trial to determine the therapeutic effects of oral MFP oncell proliferation and on differential gene expression in 20 breast cancer patients selected bytheir high PRA/PRB isoform ratio.Methods. MIPRA is an open-label, one-arm, prospective interventional study (NCT02651844).We interviewed 140 naive breast cancer patients and 133 accepted to participate. Four coreultrasound-guided biopsies were performed, two were formalin-fixed for diagnosis, ER, PR,HER2, and Ki67 evaluation and two were snap-frozen for WB and molecular studies. Patientsthat met the inclusion criteria, with ER+, PRA/PRB>1.5 and total PR ≥50% determined by WBand immunohistochemistry (IHC), respectively, were included for MFP treatment. Plasma wasobtained before and after treatment for future studies. Patients were treated with oral MFP(200 mg/day) for 14 days before surgery which was performed on day 15. Clinical examinationwas performed at days 7 and 14 to register possible adverse effects and to measure tumorsize. During surgery, samples were formalin-fixed for IHC studies, and others were snap-frozenfor further molecular studies. One patient had a bilateral breast cancer, and both tumorsmatched with the inclusion criteria and were included. The primary endpoint was Ki67labeling, comparing diagnostic core needle biopsy to post-therapy surgical specimens.Considering previous studies performed with tamoxifen, we pre-specified that 30% of relativereduction in Ki67 would be considered as a positive response. Differences in Ki67 expressionwere quantitated by an expert pathologist counting at least ten 40x fields per slide. Theseresults are currently being validated by a second pathologist. One patient, with a core biopsywith less than 500 total cells, was excluded. Ongoing experiments include secondary and otherendpoints: comparison of apoptotic, proliferative and hormone receptor markers by IHC,measurement of MFP plasma levels and, RNAseq analysis in samples pre- and post-treatment. Ki67 changes from baseline were tested with paired Wilcoxon matched-pairssigned-rank test.Results: The median (range) Ki67 value of biopsies was 11.87% (2.70- 34.56) and for surgicalspecimens was 6.45% (0.48-23.77). A 45.67% of decrease in the median % Ki67 (41.63%comparing the arithmetic mean values and 50.83% comparing the geometric mean values) wasregistered in all surgical specimens compared to baseline (p= 0.003). Using the pre-specifiedresponse parameter (30% relative reduction in Ki67), we identified 15/20 (75%) responders.Considering only responsive tumors, a 49.87% decrease in the median % Ki67 (50.83%,arithmetic mean; 62.34% geometric mean) was observed (p<0.0001) between baseline andsurgical specimens. In those cases with the highest response, the decrease in Ki-67 wasaccompanied by a decrease in tumor volume (ultrasound measurements).Conclusion: Our results show that MFP treatment may be effective in patients showing a highPRA/PRB ratio. The magnitude of the inhibition was similar or higher to that reported fortamoxifen in ER+ breast cancer patients in short-term treatment studies. Ongoing analysis willdetermine if there are changes in other markers that may help to further define MFP-responsive patients.

Citation Format: Andres Elia, Silvia I Vanzulli, Hugo Gass, Caroline A Lamb, Victoria T Fabris, Paula Martinez Vazquez, Javier Burruchaga, Eunice Spengler, Ines Caillet Bois, Alejandra Castets, Silvia Lovisi, Marcos Liguori, Gabriela Pataccini, M Florencia Abascal, Virginia Novaro, Gabriela Acosta Haab, Alfredo Molinolo, Paola Rojas, Claudia Lanari. Mipra, a window of opportunity study evaluating mifepristone treatment for postmenopausal breast cancer patients with higher levels of progesterone receptor isoform a than b [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-35.

Abstract OT1-04-02: Mifepristone treatment for breast cancer patients expressing levels of progesterone receptor isoform A (PRA) higher than those of isoform B (PRB)

Seventy percent of breast cancers express estrogen (ER) and progesterone receptors (PR) and respond to antiestrogen therapies. Emerging evidence from experimental studies and human epidemiology, points to a relevant role for progestins in breast carcinogenesis and cancer growth. Others and we have proposed that there is a role for antiprogestins in the therapeutic armamentarium, but the challenge remains to identify which patients would benefit from targeting the PR in addition to ER. Preclinical data indicates that antiprogestins block cell proliferation and increase apoptosis only in ER+ breast cancers expressing levels of PRA higher than those of PRB. The aim of this study is to evaluate the therapeutic effects of Mifepristone (MFP) on breast cancer patients selected by their PRA/PRB isoform ratio, for 14 days in between core biopsy and surgery (MIPRA trial ClinicalTrials.gov Identifier: NCT02651844). Methods: This is an open label, interventional with single group assignment study. We perform core biopsies on menopausal patients with clinically palpable breast cancers larger than 1.5 cm to confirm diagnosis. We will assess the PRA/PRB ratio by western blotting in frozen samples and total PR in formalin-fixed samples by immunohistochemistry (IHC). Twenty eligible PR+ patients (PR > 50 %) with PRA/PRB ≥1.5 who have signed consent forms, and meet the inclusion criteria will be recruited. Patients will be treated for 14 days with MFP p.o 200 mg. Surgery will be performed on day 15. Samples will be frozen for molecular studies or fixed for IHC. The primary outcome is the evaluation of Ki-67 staining pre- and post treatment. Secondary outcomes include comparatively expression of proliferation/apoptosis/PR signaling markers in core and surgical biopsy samples. Other pre-specified outcomes include molecular profiling, study of liquid biopsies, mammography, and ultrasound studies. Wilcoxon signed rank test will be used to evaluate differences in biomarker expression between core biopsy and surgical samples of each patient.

Citation Format: Liguori M, Lanari C, Gass H, Rojas P, Elia A, Martinez Vazquez P, Burruchaga J, Gonzalez P, Caillet Bois I, Ventura C, San Martin G, Castets A, Lovisi S, Acosta Haab G, Lamb C, Fabris V, Novaro V, Molinolo A. Mifepristone treatment for breast cancer patients expressing levels of progesterone receptor isoform A (PRA) higher than those of isoform B (PRB) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-04-02.

NMR study of the LiMnPO(4)·OH and MPO(4)·H(2)O (M = Mn, V) homeotypic phases and DFT calculations

Following our previous work on the tavorite-like LiFePO(4)·OH and FePO(4)·H(2)O phases, we report here the magnetic and NMR characterizations of analogous LiMnPO(4)·OH, MnPO(4)·H(2)O and VPO(4)·H(2)O phases together with the DFT calculations of the NMR shifts. The first two compounds exhibit Curie-Weiss type magnetic behavior with Curie constants close to the theoretical ones for HS Mn(3+), while the vanadium compound is very close to a pure Curie-type behavior. (7)Li, (31)P and (1)H MAS NMR spectra are reported for the three compounds, and show strong Fermi-contact shifts for the first two nuclei, while the sign and magnitude of the (1)H shifts are very different for the three phases. DFT calculations (FLAPW in GGA+U approximation) using the WIEN2k code and the experimental susceptibilities are shown to reproduce closely the experimental data. This situation is compared to the case of the homologous and isostructural Fe compounds, which exhibit much more complex magnetic behaviors.