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.

Enhanced Antitumor Immunity via Endocrine Therapy Prevents Mammary Tumor Relapse and Increases Immune Checkpoint Blockade Sensitivity

The role of active antitumor immunity in hormone receptor-positive (HR+) breast cancer has been historically underlooked. The aim of this study was to determine the contribution of the immune system to antiprogestin-induced tumor growth inhibition using a hormone-dependent breast cancer model. BALB/c-GFP+ bone marrow (BM) cells were transplanted into immunodeficient NSG mice to generate an immunocompetent NSG/BM-GFP+ (NSG-R) mouse model. Treatment with the antiprogestin mifepristone (MFP) inhibited growth of 59-2-HI tumors with similar kinetics in both animal models. Interestingly, MFP treatment reshaped the tumor microenvironment, enhancing the production of proinflammatory cytokines and chemokines. Tumors in MFP-treated immunocompetent mice showed increased infiltration of F4/80+ macrophages, natural killer, and CD8 T cells, displaying a central memory phenotype. Mechanistically, MFP induced immunogenic cell death (ICD) in vivo and in vitro, as depicted by the expression and subcellular localization of the alarmins calreticulin and HMGB-1 and the induction of an ICD gene program. Moreover, MFP-treated tumor cells efficiently activated immature dendritic cells, evidenced by enhanced expression of MHC-II and CD86, and induced a memory T-cell response, attenuating tumor onset and growth after re-challenge. Finally, MFP treatment increased the sensitivity of HR+ 59-2-HI tumor to PD-L1 blockade, suggesting that antiprogestins may improve immunotherapy response rates. These results contribute to a better understanding of the mechanisms underlying the antitumor effect of hormonal treatment and the rational design of therapeutic combinations based on endocrine and immunomodulatory agents in HR+ breast cancer. SIGNIFICANCE: Antiprogestin therapy induces immunogenic tumor cell death in PRA-overexpressing tumors, eliciting an adaptive immune memory response that protects mice from future tumor recurrence and increases sensitivity to PD-L1 blockade. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/5/1375/F1.large.jpg.

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.

Photothermal effect by 808-nm laser irradiation of melanin: a proof-of-concept study of photothermal therapy using B16-F10 melanotic melanoma growing in BALB/c mice

The photothermal effect is undergoing great interest due to advances in new photosensitizing materials and better-suited light sources, but studies are frequently hampered by the need to employ exogenous photothermal agents and expensive irradiation devices. Here we present a simple strategy based on direct NIR irradiation of the melanin pigment with a commercial 808-nm laser pointer. Proof-of-concept studies showed efficient photothermal effects on melanin in vitro and in vivo. After NIR irradiation, BALB/c mice bearing B16-F10 melanotic melanoma tumors revealed severe histopathological damage and massive necrosis in melanin-containing tumor tissue, while surrounding healthy tissues showed no damage. Therefore, the feasibility of this approach may allow implementing direct procedures for photothermal therapy of pigmented tumors.

Dual knockdown of Galectin-8 and its glycosylated ligand, the activated leukocyte cell adhesion molecule (ALCAM/CD166), synergistically delays in vivo breast cancer growth

Galectin-8 (Gal-8), a 'tandem-repeat'-type galectin, has been described as a modulator of cellular functions including adhesion, spreading, growth arrest, apoptosis, pathogen recognition, autophagy, and immunomodulation. We have previously shown that activated leukocyte cell adhesion molecule (ALCAM), also known as CD166, serves as a receptor for endogenous Gal-8. ALCAM is a member of the immunoglobulin superfamily involved in cell-cell adhesion through homophilic (ALCAM-ALCAM) and heterophilic (i.e. ALCAM-CD6) interactions in different tissues. Here we investigated the physiologic relevance of ALCAM-Gal-8 association and glycosylation-dependent mechanisms governing these interactions. We found that silencing of ALCAM in MDA-MB-231 triple negative breast cancer cells decreases cell adhesion and migration onto Gal-8-coated surfaces in a glycan-dependent fashion. Remarkably, either Gal-8 or ALCAM silencing also disrupted cell-cell adhesion, and led to reduced tumor growth in a murine model of triple negative breast cancer. Moreover, structural characterization of endogenous ALCAM N-glycosylation showed abundant permissive structures for Gal-8 binding. Importantly, we also found that cell sialylation controls Gal-8-mediated cell adhesion. Altogether, these findings demonstrate a central role of either ALCAM or Gal-8 (or both) in controlling triple negative breast cancer.

Hormone receptors in breast cancer: more than estrogen receptors

Seventy per cent of breast cancers are luminal carcinomas that express estrogen receptor alpha (ER). For several decades, its expression has been used as a therapeutic target in patients with breast cancer. These therapies are aimed at blocking ER or inhibiting ligand synthesis. The expression of progesterone receptors (PR) is evaluated as a prognostic factor together with ER. It has been shown that there are two predominant PR isoforms with different molecular weight, isoform A and isoform B, which are not distinguished by immunohistochemical techniques. The available evidence indicates that the PR isoform ratio may have both a prognostic and predictive value of the response to antiprogestin treatment. In luminal mammary carcinomas, androgen receptors (AR) are expressed in a high percentage and the AR/ER or AR/PR ratio could be a prognostic factor. In ER negative (-) tumors, AR expression is an indicator of poor prognosis and it is proposed that they may be susceptible to antiandrogen treatment. Finally, the expression of glucocorticoid receptors (GR) would be an indicator of good or bad prognosis in luminal or ER- tumors, respectively. In ER- tumors, metastases express higher levels of nuclear GR than primary tumors and therapies that block GR could improve the efficacy of chemotherapy. Given the crosstalk of pathways triggered by different hormone receptors, it is possible that in the future, a therapeutic scheme can be administered that contemplates the expression of ER, PR isoforms, AR and GR.

Time-course study of different innate immune mediators produced by UV-irradiated skin: comparative effects of short and daily versus a single harmful UV exposure

The modulatory effects of solar UV radiation on the immune system have been widely studied. As the skin is the main target of UV radiation, our purpose was to compare the impact on skin innate immunity of two contrasting ways to be exposed to sunlight. Hairless mice were UV irradiated with a single high UV dose simulating a harmful exposure, or with repetitive low UV doses simulating short occasional daily exposures. Skin samples were taken at different times after UV irradiation to evaluate skin histology, inflammatory cell recruitment, epidermal T-cell population and the mitochondrial function of epidermal cells. The transcriptional profiles of pro-inflammatory cytokines, chemokines, antimicrobial peptides and Toll-like receptors were evaluated by RT-PCR and ELISA in tissue homogenates. Finally, a lymphangiography was performed to assess modification in the lymphatic vessel system. A single high UV dose produces a deep inflammatory state characterized by the production of pro-inflammatory cytokines and chemokines that, in turn, induces the recruitment of neutrophils and macrophages into the irradiated area. On the other hand, repetitive low UV doses drive the skin to a photo-induced alert state in which there is no sign of inflammation, but the epithelium undergoes changes in thickness, the lymphatic circulation increases, and the transcription of antimicrobial peptides is induced.

The effectiveness of nano chemotherapeutic particles combined with mifepristone depends on the PR isoform ratio in preclinical models of breast cancer

There is clinical and experimental evidence suggesting that antiprogestins might be used for the treatment of selected breast cancer patients. Our aim was to evaluate the effect of albumin-bound paclitaxel (Nab-paclitaxel) and pegylated doxorubicin liposomes (PEG-LD) in combination with mifepristone (MFP) in experimental breast cancer models expressing different ratios of progesterone receptor (PR) isoforms A and B. We used two antiprogestin-responsive (PRA>PRB) and two resistant (PRA<PRB) murine mammary carcinomas growing in BALB/c, GFP-BALB/c or nude mice, along with human T47D-YA and T47D-YB xenografts growing in immunocompromised NSG mice. MFP improved the therapeutic effects of suboptimal doses of Nab-paclitaxel or PEG-LD in murine and human carcinomas with higher levels of PRA than PRB. MFP induced tissue remodeling in PRA-overexpressing tumors, increasing the stromal/tumor cell ratio and the number of functional vessels. Accordingly, an increase in nanoparticles and drug accumulation was observed in stromal and tumor cells in MFP-treated tumors. We conclude that MFP induces an increase in vessels during tissue remodeling, favoring the selective accumulation of nanoparticles inside the tumors. We propose that antiprogestins have the potential to enhance the efficacy of chemotherapy in breast tumors with a high PRA/PRB ratio.

Abstract B126: Antiprogestins induce tumor vessels remodeling and increase the effects of albumin-bound paclitaxel or doxorubicin-pegylated liposomes in PR-A (+) but not in PR-B (+) T47D xenografts

Chemotherapy is the standard treatment for metastatic breast cancer today. To overcome undesired side effects and improve drug efficacy in tumor cells, different nanoparticle formulations were developed. Paclitaxel was bound with human albumin (Nab-paclitaxel; Abraxane), and pegylated liposomes have been developed for doxorubicin delivery (PEG-LD; Doxopeg). We have evaluated the effect of these therapeutic agents together with antiprogestins in experimental murine mammary carcinomas (MMC) expressing different ratios of progesterone receptor (PR) isoforms and showed an increased therapeutic effect of combined treatments vs. single treatments only in tumors over expressing PR isoform A (PR-A). We showed that in these tumors antiprogestins such as Mifepristone (MFP) or Proellex, induced tissue remodeling increasing the stroma/parenchyma ratio and the number of vessels, increasing doxorubicin or Abraxane concentration within the tumors. (Sequeira et al., CTRC-AACR San Antonio Breast Cancer Symposium, December 4-8 2012). The aims of this study were: a) to characterize the tumor vessels generated during antiprogestin treatment in the MMC and b) to evaluate the effect of chemotherapeutic agents together with MFP vs. single treatments, on the growth of human T47D breast cancer cells expressing PR-A or PR isoform B (PR-B), inoculated orthotopically into NOD/LtSz-scid/IL-2Rgamma null female mice. BALB/c female mice bearing 59-2-HI (PR-A&gt;PR-B) tumors on one flank and C4-2-HI (PR-B&gt;PR-A) on the other flank were treated for 5 days with MFP (10 mg/kg/day). Mice were then injected with Fluorescein labeled Lycopersicon Esculentum (Tomato) Lectin (TL), or with Count Control Beads (CCB) and sacrificed after 7 min or 60 min respectively. Immunofluorescence microscopy studies showed increased TL staining (p&lt;0.05), and vessels with increased diameter (p&lt;0.001) in MFP-treated tumors showing higher levels of PR-A than PR-B as compared to untreated mice. Similarly, higher levels of fluorescent CCB/total number of cells were detected by flow cytometry in the same experimental groups suggesting that an increased vascular network is responsible, at least partially, of increasing the nano-chemotherapeutic drug concentration within these tumors. On the other hand, the T47D-YA and T47D-YB xenografts showed a similar responsiveness as the MMC: PEG-DL (0.9 mg/Kg/week) or Abraxane (10 mg/Kg; three doses every 4 days) combined with MFP (10 mg/Kg/Day) were more effective than the single treatments decreasing tumor size, only in the T47D-YA xenografts (p&lt;0.05). We propose that antiprogestins have the potential to enhance the efficacy of nano-chemotherapeutic formulations in patients with breast cancer showing higher levels of PR-A than PR-B by increasing their access to the tumor cells.

Citation Format: Gonzalo R. Sequeira, Silvia I. Vanzulli, Maria May, Paola Rojas, Caroline A. Lamb, Alfredo Molinolo, Claudia Lanari. Antiprogestins induce tumor vessels remodeling and increase the effects of albumin-bound paclitaxel or doxorubicin-pegylated liposomes in PR-A (+) but not in PR-B (+) T47D xenografts. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B126.

Abstract P4-06-15: Mifepristone modifies the tumor microenvironment increasing the therapeutic efficiency of low doses of Doxorubicin liposomes or paclitaxel-albumin nanoparticles in a murine model of breast cancer

Chemotherapy is the standard treatment for metastatic breast cancer today. To overcome undesired side effects and improve drug efficacy in tumor cells, different nanoparticle formulations have been developed. Paclitaxel has been bound with human albumin (Nab-paclitaxel), and pegylated liposomes have been developed for doxorubicin delivery (PEG-LD). The aim of our study was to evaluate the effect of these therapeutic agents in experimental mammary carcinomas expressing different ratios of progesterone receptor (PR) isoforms and to evaluate the effect of combined treatments of chemotherapeutic agents with the antiprogestin mifepristone (MFP). Nab-paclitaxel (Abraxane, Abraxis), at a dosage of 30 and 60 mg/kg body weight administered in three doses every four days, completely inhibited the growth of the antiprogestin-resistant C4-2-HI mouse mammary carcinoma, which is associated with high levels of PR isoform B (PR-B) expression. C4-HI, an antiprogestin-responsive mouse tumor that shows high levels of PR isoform A (PR-A) expression, was not inhibited by the low Nab-paclitaxel dose. However, the combination of MFP (6 mg silastic pellet) with Nab-paclitaxel improved the efficacy of both single treatments. Similar experiments were conducted using PEG-LD (Doxopeg; Laboratorios Raffo). In this case, all tumors tested (C4-HI, CC4-3-HI, 59–2-HI and C4-2-HI) were all highly responsive to high (18 mg/kg/week) or low (9 mg/kg/week) PEG-LD doses. When PEG-LD concentrations were lowered to 4.5 mg/kg/week and they were combined with MFP, an improved response was observed with combined treatments only in tumors with high PR-A levels (p &lt;0.001). Using BALB/c-GFP mice, we demonstrated that MFP treatment induced tissue remodeling in PR-A positive tumors, increasing the stromal/tumor cell ratio and the number of vessels (as shown by CD31 positive cells; p &lt; 0.001). Taking advantage of doxorubicin's red autofluorescence, we showed increased levels of drug accumulation in tumor cells surrounding the stromal tissue. Using a human albumin antibody we demonstrated nab-paclitaxel accumulation in similar locations. However, because increased areas (p &lt; 0.001) of stromal tissue were observed in the antiprogestin-treated mice, the total amount of PEG-LD or Nab-paclitaxel was much higher in the combined-treated tumors. We propose that antiprogestins have the potential to enhance the efficacy of nanotherapeutics in patients with breast tumors with a high PR-A/PR-B ratio.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-15.

Regression of the murine LM3 tumor by repeated photodynamic therapy with meso-tetrakis-(4-N,N,N-trimethylanilinium)porphine

Photodynamic therapy (PDT) of cancer is based on the cytotoxicity induced by a photosensitizer (PS) in the presence of oxygen and visible light, with formation of reactive oxygen species which cause cell death and tumor destruction. This work describes the response of the murine mammary adenocarcinoma, LM3, to repeated PDT using meso-tetrakis(4-N,N,N-trimethylanilinium)porphine (TMAP), a PS that has been overlooked for PDT applications. Intradermal LM3 tumors in BALB/c mice (controls) were left untreated, only treated with light, only injected with 0.9% NaCl solution or with TMAP alone (10 μg/0.1 ml). For PDT, the intratumoral PS injection was followed 1 h later by blue-red light irradiation (290 J.cm-2). In all cases, control and PDT treatments were performed on the depilated and glycerol-covered skin which covers the tumor of anesthetized animals, and repeated 4 times (every 2 days). No significant differences were found in the growth rate of all control tumors. PDT-treated tumors showed complete and long-term regression in 4 out of 5 mice, and cure in one animal. The survival of PDT-mice was significantly longer than that of controls (TMAP alone), showing a lower number of tumor-draining lymph node metastasis. The PDT protocol applied in the present work (intratumoral PS injection, repeated photosensitizing treatments, and reduction of tissue light scattering by glycerol) could be a useful strategy in studies on PDT of cancer.

[The role of estrogen receptor alpha in breast cancer cell proliferation mediated by progestins]

In C4-HD murine mammary carcinomas and in human breast cancer T47D cells, we showed that medroxyprogesterone acetate (MPA) induces a nuclear physical association between estrogen receptor alpha (ERa) and progesterone receptors (PR). The blockade of ERa inhibits cell proliferation mediated by progestins. We hypothesized that this nuclear association between ERa/PR is necessary to trigger progestin-induced cell proliferation and tumor growth. We demonstrated that fulvestrant (FUL, ICI182.780) induced complete regression of C4-HD tumors growing with progestins. MPA treatment induced an early increase in both CCND1 and MYC expression in T47D cells. The blockade of ERa prevented the MPA-dependent transcription of both genes. Specific binding of PR/ERa was observed at the same MPA-sensitive regions at the CCND1 and MYC gene promoters after chromatin immunoprecipitation (ChIP) analysis. ICI inhibited binding of ERa to both gene regulatory sequences while PR binding was unaffected. The nuclear colocalization between both receptors in T47D cells was confirmed by: confocal microscopy, Duolink assays and co-immunoprecipitation assays. In breast cancer samples we also observed a nuclear interaction between both steroid receptors. Our results indicate that the presence of ERa interacting with activated PR at the CCND1 and MYC promoters is required to trigger progestin-induced gene transcription and cell proliferation in breast cancer cells.

Abstract 1319: Early tumor regression after endocrine and kinase inhibitor treatments in mammary carcinomas with different hormonal requirements

Two-thirds of diagnosed breasts cancers express either estrogen receptors (ER), progesterone receptors (PR) or both. Unlike most experimental breast cancer models, in the medroxyprogesterone acetate (MPA) model, MPA induces mammary carcinomas that express high levels of ER and PR. In this model we developed a tumor variant that depends on MPA to grow (C4-HD), and another one that grows without it (C4-HI). Previous studies showed that both types of tumors represent a useful tool to study mechanisms of regression after endocrine therapy, since both regress, albeit differently, after prolonged treatment (10 days) with the antiprogestin mifepristone. While regressive C4-HD tumors display extensive apoptosis, C4-HI tumors regress showing increased glandular differentiation. In order to investigate specific mechanisms of regression and to determine if these mechanisms are tumor specific or antitumor agent specific, we evaluated early steps of tumor regression caused by different agents in C4-HD and C4-HI tumors. We evaluated mifepristone (12mg/kg/day), ER modulators such as ICI182780 (25mg/kg) and tamoxifen (5mg/kg/day), and the PI3K/AKT inhibitor wortmannin (1 mg/kg/day). Mice carrying C4-HD or C4-HI tumors were treated for 48 hours and then sacrificed. Tumors were measured, excised and processed for histopathological and immunohistochemical studies as well as western blotting.

We found that after 48 hs of treatment the size of C4-HD tumors was only reduced with mifepristone (p&lt;0.001). However, even a short exposure of these tumors to any of the treatments increased apoptosis and necrosis index and stromal area, with mifepristone and tamoxifen being the most effective (p&lt;0.001 and 0.01 respectively). In C4-HI tumors, we did not observe an increase in apoptosis or necrosis index neither a significant stromal reaction after 48 hs with any treatment tested. However, all treatments caused tissular reorganization and differentiation, being the most effective mifepristone and wortmannin. To study tissue reorganization we evaluated the expression of differentiation markers such as the apical marker MUC-1 and the luminal cell marker cytoqueratin 8 and found that these markers are increased in C4-HI tumors treated with wortmannin and mifepristone (p&lt;0.01).

Taken together, these results suggest that each tumor variant has its own mechanism of regression in response to endocrine or kinase inhibitor treatments. Such different mechanism of regression in each tumor type may arise as a result of specific tumor-stromal interactions. Understanding the particular cellular mechanisms that lead to each tumor type regression could provide the basis to develop more specific and selective new antitumor therapies or potentiate therapies that already exist.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1319. doi:10.1158/1538-7445.AM2011-1319

Interaction between FGFR-2, STAT5, and progesterone receptors in breast cancer

Fibroblast growth factor (FGF) receptor 2 (FGFR-2) polymorphisms have been associated with an increase in estrogen receptor and progesterone receptor (PR)-positive breast cancer risk; however, a clear mechanistic association between FGFR-2 and steroid hormone receptors remains elusive. In previous works, we have shown a cross talk between FGF2 and progestins in mouse mammary carcinomas. To investigate the mechanisms underlying these interactions and to validate our findings in a human setting, we have used T47D human breast cancer cells and human cancer tissue samples. We showed that medroxyprogesterone acetate (MPA) and FGF2 induced cell proliferation and activation of ERK, AKT, and STAT5 in T47D and in murine C4-HI cells. Nuclear interaction between PR, FGFR-2, and STAT5 after MPA and FGF2 treatment was also showed by confocal microscopy and immunoprecipitation. This effect was associated with increased transcription of PRE and/or GAS reporter genes, and of PR/STAT5-regulated genes and proteins. Two antiprogestins and the FGFR inhibitor PD173074, specifically blocked the effects induced by FGF2 or MPA respectively. The presence of PR/FGFR-2/STAT5 complexes bound to the PRE probe was corroborated by using NoShift transcription and chromatin immunoprecipitation of the MYC promoter. Additionally, we showed that T47D cells stably transfected with constitutively active FGFR-2 gave rise to invasive carcinomas when transplanted into NOD/SCID mice. Nuclear colocalization between PR and FGFR-2/STAT5 was also observed in human breast cancer tissues. This study represents the first demonstration of a nuclear interaction between FGFR-2 and STAT5, as PR coactivators at the DNA progesterone responsive elements, suggesting that FGFRs are valid therapeutic targets for human breast cancer treatment.

Inoculated mammary carcinoma-associated fibroblasts: contribution to hormone independent tumor growth

Background

Increasing evidence has underscored the role of carcinoma associated fibroblasts (CAF) in tumor growth. However, there are controversial data regarding the persistence of inoculated CAF within the tumors. We have developed a model in which murine metastatic ductal mammary carcinomas expressing estrogen and progesterone receptors transit through different stages of hormone dependency. Hormone dependent (HD) tumors grow only in the presence of progestins, whereas hormone independent (HI) variants grow without hormone supply. We demonstrated previously that CAF from HI tumors (CAF-HI) express high levels of FGF-2 and that FGF-2 induced HD tumor growth in vivo. Our main goal was to investigate whether inoculated CAF-HI combined with purified epithelial (EPI) HD cells can induce HD tumor growth.

Methods

Purified EPI cells of HD and HI tumors were inoculated alone, or together with CAF-HI, into female BALB/c mice and tumor growth was evaluated. In another set of experiments, purified EPI-HI alone or combined with CAF-HI or CAF-HI-GFP were inoculated into BALB/c or BALB/c-GFP mice. We assessed whether inoculated CAF-HI persisted within the tumors by analyzing inoculated or host CAF in frozen sections of tumors growing in BALB/c or BALB/c-GFP mice. The same model was used to evaluate early stages of tumor development and animals were euthanized at 2, 7, 12 and 17 days after EPI-HI or EPI-HI+CAF-HI inoculation. In angiogenesis studies, tumor vessels were quantified 5 days after intradermal inoculation.

Results

We found that admixed CAF-HI failed to induce epithelial HD tumor growth, but instead, enhanced HI tumor growth (p < 0.001). Moreover, inoculated CAF-HI did not persist within the tumors. Immunofluorescence studies showed that inoculated CAF-HI disappeared after 13 days. We studied the mechanisms by which CAF-HI increased HI tumor growth, and found a significant increase in angiogenesis (p < 0.05) in the co-injected mice at early time points.

Conclusions

Inoculated CAF-HI do not persist within the tumor mass although they play a role during the first stages of tumor formation promoting angiogenesis. This angiogenic environment is unable to replace the hormone requirement of HD tumors that still need the hormone to recruit the stroma from the host.

Association of estrogen receptor-alpha and progesterone receptor A expression with hormonal mammary carcinogenesis: role of the host microenvironment

Introduction

Medroxyprogesterone acetate (MPA) induces estrogen receptor (ER)-positive and progesterone receptor (PR)-positive ductal invasive mammary carcinomas in BALB/c mice. We sought to reproduce this MPA cancer model in C57BL/6 mice because of their widespread use in genetic engineering. Within this experimental setting, we studied the carcinogenic effects of MPA, the morphologic changes in mammary glands that are induced by MPA and progesterone, and the levels of ER and PR expression in MPA-treated and progesterone-treated mammary glands. Finally, we evaluated whether the differences found between BALB/c and C57BL/6 mouse strains were due to intrinsic differences in epithelial cells.

Methods

The carcinogenic effect of MPA was evaluated in C57BL/6 mice using protocols proven to be carcinogenic in BALB/c mice. In addition, BALB/c and C57BL/6 females were treated with progesterone or MPA for 1 or 2 months, and mammary glands were excised for histologic studies and for immunohistochemical and Western blot evaluation of ER and PR. Hormone levels were determined by radioimmunoassay. Isolated mammary epithelial cells were transplanted into cleared fat pads of 21-day-old female Swiss nu/nu mice or control congenic animals.

Results

MPA failed to induce mammary carcinomas or significant morphologic changes in the mammary glands of C57BL/6 mice. The expression of ER-α and PR isoform A in virgin mice was surprisingly much higher in BALB/c than in C57BL/6 mammary glands, and both receptors were downregulated in progestin-treated BALB/c mice (P < 0.05). PR isoform B levels were low in virgin control mice and increased after progestin treatment in both strains. ER-β expression followed a similar trend. No differences in hormone levels were found between strains. Surprisingly, the transplantation of the epithelial mammary gland cells of both strains into the cleared fat pads of Swiss (nu/nu) mice abolished the mammary gland morphologic differences and the ER and PR differences between strains.

Conclusion

C57BL/6 mammary glands are resistant to MPA-induced carcinogenesis and to hormone action. MPA and progesterone have different effects on mammary glands. Low ER-α and PR-A levels in untreated mammary glands may be associated with a low-risk breast cancer profile. Although we cannot at this time rule out the participation of other, untested factors, our findings implicate the stroma as playing a crucial role in the strain-specific differential hormone receptor expression and hormone responsiveness.

Antisense oligonucleotides targeting the progesterone receptor inhibit hormone-independent breast cancer growth in mice

Introduction

Previous data from our laboratory suggested that progesterone receptors (PRs) are involved in progestin-independent growth of mammary carcinomas. To investigate this possibility further, we studied the effects of PR antisense oligodeoxynucleotides (asPR) on in vivo tumor growth.

Method

BALB/c mice with subcutaneous 25 mm² mammary carcinomas expressing estrogen receptor-α and PR were either injected intraperitoneally with 1 mg asPR every 24 or 12 hours for 5–10 days, or subcutaneously with RU 486 (6.5 mg/kg body weight) every 24 hours. Control mice received vehicle or scPR.

Results

Significant inhibition of tumor growth as well as a significant decrease in bromodeoxyuridine uptake was observed in asPR-treated mice, which correlated with histological signs of regression and increased apoptosis. Mice treated with RU 486 experienced almost complete tumor regression. No differences were detected between vehicle-treated and scPR-treated mice. Anti-progestin-treated and asPR-treated mice were in a continuous estrous/meta-estrous state. Decreased phosphorylated extracellular signal-regulated kinase (ERK)1 and ERK2 levels and estrogen receptor-α expression were observed as late events in RU 486-treated and asPR-treated mice with regressing tumors.

Conclusion

We demonstrate, for the first time, inhibition of tumor growth in vivo using asPR. Our results provide further evidence for a critical and hierarchical role of the PR pathway in mammary carcinomas.

Long-term regression of the murine mammary adenocarcinoma, LM3, by repeated photodynamic treatments using meso-tetra (4-N-methylpyridinium) porphine

Photodynamic therapy (PDT) is based on the cytotoxic effect induced by a photosensitizer in the presence of light and molecular oxygen, with production of reactive oxygen species which cause cell death and tumor destruction. Here we describe the response of the murine mammary adenocarcinoma, LM3, to repeated PDT treatments using the synthetic porphyrin derivative, meso-tetra (4-N-methylpyridinium) porphine (TMPyP). Intradermal LM3 tumors in BALB/c mice were left untreated, only treated with light, only injected with 0.9% NaCl solution, or with TMPyP alone (10 microg in 0.1 ml of 0.9% NaCl). For PDT, the intratumoral TMPyP injection was followed 1 h later by blue-red light irradiation for 50 min (80 mW/cm2 total dose: 240 J/cm2). In all cases, control and PDT treatments were performed on the depilated and glycerol-covered skin over the tumor of anesthetized mice and repeated four times (every two days). In a pilot experiment, no significant differences were found in the growth rate of untreated tumors (n=4) and tumors only treated with light (n=4), 0.9% NaCl (n=3) or TMPyP (n=3). PDT-treated tumors (n=3) showed transitory regression and growth delay. In a second approach, the average diameter (mean, mm +/- SEM) of control (drug alone, n=15) vs PDT tumors (n=17) was 2.13+/-0.11 vs 2.02+/-0.10 at day 0, and 4.00+/-0.17 vs 0.20+/-0.07 at day 9, p<0.0001. At day 37 the average diameter of tumors from control vs the PDT group was 10.98+/-0.59 vs 6.31+/-0.82, p<0.0001. PDT caused partial regression of tumors in one from a total of 17 mice, long-term regression in 15, and cure in one animal. Significant differences in the survival and tumor size at death were found between control and PDT-treated mice. Histopathological analysis of LM3 tumors one day after a unique PDT treatment showed extensive hemorrhage and necrotic areas. These results indicate the considerable potential of intratumoral injection of photosensitizers and repeated PDT protocols.

Estrogen or antiprogestin treatment induces complete regression of pulmonary and axillary metastases in an experimental model of breast cancer progression

In this paper we demonstrate, using the C7-2-HI metastatic transplantable ductal mammary tumor, that endocrine therapy can induce complete regression of spontaneous lymph node and lung metastases in a mouse model of breast cancer progression. This tumor expresses high levels of estrogen and progesterone receptors and shows a high incidence of early axillary lymph nodes and lung metastases; using this model we had previously shown complete tumor regression of subcutaneous implants. Interestingly, although the metastases showed a more differentiated histology as compared with the primary growth, they underwent complete regression when treated with estrogens or antiprogestins. This phenomenon was associated with sustained cytostasis and apoptosis accompanied by increases in p21 and p27 expression and early tissue remodeling. These results highlight the essential role of PR in regulating cell proliferation in this model as well as its possible use as therapeutic target.

Embryonal mass and hormone-associated effects of pregnancy inducing a differential growth of four murine tumors

A differential effect of pregnancy on the growth of subcutaneous implants of four murine tumors has been observed. Two tumors lacking receptors for progesterone and estrogen [methylcholanthrene-induced fibrosarcoma (MC-C) and spontaneous lymphoid leukemia (LB)] exhibited slow kinetics throughout the course of pregnancy, although inhibition was stronger beyond day 10. On the other hand, one of two tumors bearing receptors for progesterone and estrogen [medroxyprogesterone (MPA)-induced mammary adenocarcinoma (C7HI)] exhibited three phases: up to days 8-10 of gestation the tumor grew faster than in virgins, between days 8-10 and 15 it reached a plateau, and beyond day 15 a sharp reduction in tumor mass was observed. The other tumor [mouse mammary tumor virus (MMTV)-induced mammary carcinoma(T2280)] behaved as a typical pregnancy-dependent tumor (i.e., it grew in pregnant but not in virgin mice, regressed soon after delivery, and reassumed its growth at the middle of a second round of pregnancy). Neither MPA nor estrogen affected MC-C and LB tumor growth. On the other hand, MPA-treated mice enhanced C7HI tumor and reciprocally C7HI tumor-bearing mice treated with estrogen strongly inhibited tumor growth. As for T2280, neither MPA nor estrogen alone could promote tumor growth and, in consequence, no tumor developed. However, when MPA plus estrogen was administered in a schedule simulating the successive appearance of these hormones in pregnancy, T2280 grew even faster than in pregnant mice. When the four tumors were implanted in mice bearing grafts of embryonal tissues (teratomas), all of them were inhibited. This antitumor effect was similar to that observed in pregnancy when tumors unresponsive to progesterone and estrogen were tested. On the other hand, with tumors bearing progesterone and estrogen receptors, differences in tumor growth were detected in pregnant and teratoma-bearing mice. This suggested the existence during pregnancy of two factors potentially acting on tumor growth. First, a progesterone and estrogen-mediated hormonal component, which would exert either inhibitory or stimulatory effects only evidenced with tumors bearing hormonal receptors. Secondly, an antitumor effect proportional to the growing embryonal mass, inhibiting all tumors independently of their origin or hormone responsiveness. This antitumor effect could be attributed to a beat-resistant serum factor (1,000-1,200 Da molecular weight) presumably associated with the pathway of the arachidonic acid metabolism. The interplay between the hormonal component and the serum factor associated with embryonal mass could account for some of the largely heterogeneous and otherwise unexplained effects of pregnancy on tumor growth reported in the literature and illustrated by the four tumors studied here.

Adenomas of the colon: overexpression of p53 protein and risk factors

BACKGROUND AND STUDY AIMS

p53 gene mutation and the ensuing overexpression of its protein is one of the steps related to colorectal carcinogenesis. This study analyzed the relationships between immunohistochemically detected p53 protein accumulation in colonic adenomas and morphological and clinical indicators of risk of malignant transformation and relapse.

PATIENTS AND METHODS

A total of 100 endoscopically resected sporadic colonic adenomas (nonpolyposis) from 79 patients were retrospectively studied by using archival paraffin tissue blocks. p53 protein immunohistochemically detected was related to morphological adenoma risk factors (size, histological type and dysplasia) and in patients to neoplastic colonic pathology (NCP), such as previous adenomas/carcinomas or coexistent adenomas.

RESULTS

There was a correlation between p53 expression and the grade of dysplasia but not with size or histological type in adenomas. NCP data was present in 52.5% of patients with p53 positive adenomas, and only in 25.6% of patients with p53 negative adenomas. This difference remains even in those with low-grade dysplastic lesions. When coexistent adenoma and previous adenoma/carcinoma data were analyzed separately, similar results were obtained.

CONCLUSIONS

The presence of previous and/or coexistent NCP was more frequent in patients with p53 expressing adenomas, even in low-grade dysplastic lesions, which probably could be a high risk subpopulation. Its follow-up may be eventually reviewed.