MicroRNA-125a influences breast cancer stem cells by targeting leukemia inhibitory factor receptor which regulates the Hippo signaling pathway

Cancer stem cells (CSC) are the main driving force behind cancer initiation and progression. The molecular mechanisms that regulate CSC properties are poorly understood. MicroRNAs (miRNAs) play a significant role in normal and cancer tissues. Here, we show that miRNA-125a indirectly regulates TAZ, an effector molecule in the Hippo pathway, through the leukemia inhibitory factor receptor (LIFR). The miR-125a→LIFR axis affected the homeostasis of nonmalignant and malignant breast epithelial stem cells through the Hippo signaling pathway. Inhibition of miR-125a in breast cancer cells led to a significant reduction in the CSC pool. In contrast, enhanced expression of miR-125a in nonmalignant breast epithelial cells resulted in significant expansion of the stem cell pool. Gain of function and loss of function of LIFR directly correlated with the inhibition and overexpression of miR-125a, respectively. Modulation of miR-125a led to a change in the activity of TAZ and its subcellular localization. We further demonstrated that miR-125a influenced stem cells by regulating Hippo signaling through LIFR in human primary breast cancer cells confirming the data obtained from established cell lines. We suggest that miR-125a could be a potential target against CSCs that maybe used along with the existing conventional therapies.

Role of Growth Hormone in Breast Cancer

Breast cancer is one of the most common cancers diagnosed in women. Approximately two-thirds of all breast cancers diagnosed are classified as hormone dependent, which indicates that hormones are the key factors that drive the growth of these breast cancers. Ovarian and pituitary hormones play a major role in the growth and development of normal mammary glands and breast cancer. In particular, the effect of the ovarian hormone estrogen has received much attention in regard to breast cancer. Pituitary hormones prolactin and growth hormone have also been associated with breast cancer. Although the role of these pituitary hormones in breast cancers has been studied, it has not been investigated extensively. In this review, we attempt to compile basic information from most of the currently available literature to understand and demonstrate the significance of growth hormone in breast cancer. Based on the available literature, it is clear that growth hormone plays a significant role in the development, progression, and metastasis of breast cancer by influencing tumor angiogenesis, stemness, and chemoresistance.

Progesterone receptor membrane component 1 promotes the growth of breast cancers by altering the phosphoproteome and augmenting EGFR/PI3K/AKT signalling

BACKGROUND

Increased expression of the progesterone receptor membrane component 1 (PGRMC1) has been linked to multiple cancers, including breast cancer. Despite being a regulatory receptor and a potential therapeutic target, the oncogenic potential of PGRMC1 has not been studied.

METHODS

The impact of PGRMC1 on breast cancer growth and progression was studied following chemical inhibition and alteration of PGRMC1 expression, and evaluated by using online-based gene expression datasets of human breast cancer tissue. MTS, flow cytometry, qPCR, Western blotting, confocal microscopy and phosphoproteome analysis were performed.

RESULTS

We observed higher PGRMC1 levels in both ER-positive ZR-75-1 and TNBC MDA-MB-468 cells. Both chemical inhibition and silencing decreased cell proliferation, induced cell-cycle arrest, promoted apoptosis and reduced the migratory and invasive capabilities of ZR-75-1 and MDA-MB-468 cells. Further, phosphoproteome analysis demonstrated an overall decrease in activation of proteins involved in PI3K/AKT/mTOR and EGFR signalling pathways. In contrast, overexpression of PGRMC1 in non-malignant MCF10A cells resulted in increased cell proliferation, and enhanced activity of PI3K/AKT/mTOR and EGFR signalling pathways.

CONCLUSIONS

Our data demonstrate that PGRMC1 plays a prominent role in regulating the growth of cancer cells by altering the PI3K/AKT/mTOR and EGFR signalling mechanisms in both ER-positive and TNBC cells.

Chemotherapy Coupled to Macrophage Inhibition Induces T-cell and B-cell Infiltration and Durable Regression in Triple-Negative Breast Cancer

Immunosuppressive elements within the tumor microenvironment, such as tumor-associated macrophages (TAM), can present a barrier to successful antitumor responses by cytolytic T cells. Here we employed preclinical syngeneic p53 null mouse models of triple-negative breast cancer (TNBC) to develop a treatment regimen that harnessed the immunostimulatory effects of low-dose cyclophosphamide coupled with the pharmacologic inhibition of TAMs using either a small-molecule CSF1R inhibitor or an anti-CSF1R antibody. This therapeutic combination was effective in treating several highly aggressive TNBC murine mammary tumor and lung metastasis models. Single-cell RNA sequencing characterized tumor-infiltrating lymphocytes including Th cells and antigen-presenting B cells that were highly enriched in responders to combination therapy. In one model that exhibited long-term posttreatment tumor regression, high-dimensional imaging techniques identified the close spatial localization of B220+/CD86+-activated B cells and CD4+ T cells in tertiary lymphoid structures that were present up to 6 weeks posttreatment. The transcriptional and metabolic heterogeneity of TAMs was also characterized in two closely related claudin-low/mesenchymal subtype tumor models with differential treatment responses. A murine TAM signature derived from the T12 model was highly conserved in human claudin-low breast cancers, and high expression of the TAM signature correlated with reduced overall survival in patients with breast cancer. This TAM signature may help identify human patients with claudin-low breast cancer that will benefit from the combination of cyclophosphamide and anti-CSF1R therapy. These studies illustrate the complexity of the tumor immune microenvironment and highlight different immune responses that result from rational immunotherapy combinations.

SIGNIFICANCE

Immunostimulatory chemotherapy combined with pharmacologic inhibition of TAMs results in durable treatment responses elicited by Th cells and B cells in claudin-low TNBC models.

A socioenvironmental composite index as a tool for identifying urban areas at risk of lymphatic filariasis

OBJECTIVE

To describe the spatial distribution of lymphatic filariasis and its relationship with the socioenvironmental risk indicator, thus identifying priority localities for interventions in endemic urban areas.

METHODS

The study area was the municipality of Jaboatão dos Guararapes, State of Pernambuco, Brazil. The data sources were a parasitological survey and the 2000 demographic census. From these data, a socioenvironmental composite risk indicator was constructed using the 484 census tracts (CT) as the analysis units, based on the score-formation technique. Census tracts with higher indicator values presented higher risk of occurrences of filariasis.

RESULTS

Six thousand five hundred and seven households were surveyed and 23 673 individuals were examined, among whom 323 cases of microfilaremia were identified. The mean prevalence rate for the municipality was 1.4%. The indicator showed that 73% (237/323) of the cases of microfilaremia were in high-risk areas (third and fourth quartiles) with worse socioenvironmental conditions (RR = 4.86, CI = 3.09-7.73, P < 0.05).

CONCLUSIONS

The socioenvironmental composite risk indicator demonstrated sensitivity, since it was able to identify the localities with greater occurrence of infection. Because it can stratify spaces by using official and available data, it constitutes an important tool for use in the worldwide program for eliminating lymphatic filariasis.

Mechanisms of cell death by deprivation of depolarizing conditions during cerebellar granule neurons maturation

Cerebellar granule cells (CGC) cultured under 5mM KCl (K5) undergo apoptosis after 5 days in vitro (DIV). CGC death is reduced by chronic treatment with 25 mM KCl (K25) or NMDA. Also, when CGC cultured for 6-8 DIV in K25 are transferred to a K5 medium, cells die apoptotically. Moreover, Bcl-2 and Bcl-xL protect neurons from apoptosis, while Bax and Bcl-xS may act as proapototic proteins. It is suggested that these members of the Bcl-2 family may be involved in the cytochrome-c (cyt-c) release to the cytosol. Cytochrome-c is able to form a complex with other proteins to activate a cascade of proteases. In this work, we found that Bcl-2 levels in K5 cells did not show any change during 2-7 days in vitro (DIV); but cells grown with NMDA and K25 displayed an increase (55% approximately) of Bcl-2 from 4 DIV, as compared to control. Under these conditions, Bax levels showed a tendency to decrease with age under control cells and NMDA/K25 induced a reduction of approximately 10% in Bax levels from 4 DIV. On the other hand, in cells maintained in K25 during 7 DIV and then switched to a K5 medium, the levels of Bax showed a consistent decrease (30% after 8h). Under these conditions, the Bcl-2 levels did not show any significant change after 24h. Cytochrome-c levels were unaffected under K5, NMDA and K25 and only a marginal increase of cytochrome-c in the cytosol was detected at 6h after switching. We also found that caspase-9 was only activated under K25-deprivation meanwhile caspase-3 was involved in both protocols. These results suggest that the Bcl-2 family members, caspases activation and cytochrome-c release are involved in CGC death induced by K5 and their participation in this process could be different depending on neuronal maturation in culture.

Crosstalk between progesterone receptor membrane component 1 and estrogen receptor α promotes breast cancer cell proliferation

Progesterone (P4) and estradiol (E2) have been shown to stimulate and regulate breast cancer proliferation via classical nuclear receptor signaling through progesterone receptor (PR) and estrogen receptor α (ERα), respectively. However, the basis of communication between PR/ERα and membrane receptors remains largely unknown. Here, we aim to identify classical and nonclassical endocrine signaling mechanisms that can alter cell proliferation through a possible crosstalk between PR, ERα, and progesterone receptor membrane component 1 (PGRMC1), a membrane receptor frequently observed in breast cancer cells. While P4 and E2 treatment increased cell proliferation of ER+/PR+/PGRMC1 overexpressing breast cancer cells, silencing ERα and PR or treatment with selective estrogen receptor modulator (SERM) tamoxifen, or (PR-antagonist) RU-486 decreased cell proliferation. All four treatments rapidly altered PGRMC1 mRNA levels and protein expression. Furthermore, P4 and E2 treatments rapidly activated EGFR a known interacting partner of PGRMC1 and its downstream signaling. Interestingly, downregulation of ERα by tamoxifen and ERα silencing decreased the expression levels of PGRMC1 with no repercussions to PR expression. Strikingly PGRMC1 silencing decreased ERα expression irrespective of PR. METABRIC and TCGA datasets further demonstrated that PGRMC1 expression was comparable to that of ERα in Luminal A and B breast cancers. Targeting of PR, ERα, and PGRMC1 confirmed that a crosstalk between classical and nonclassical signaling mechanisms exists in ER+ breast cancer cells that could enhance the growth of ER+/PR+/PGRMC1 overexpressing tumors.

Effect of naloxone on serum testosterone in adult male rabbits

Considerable evidence suggests that endogenous opioids may play an important role in the hypothalamic LH-releasing hormone. Administration of high doses of naloxone, an opiate antagonist, produces an increase in plasma concentration of LH. Naltrexone administration to healthy males produces an increase in both immunoactive and bioactive LH. The objective of the present work was to assess the effect of low doses of naloxone during 10 consecutive days on testosterone serum levels in rabbit. Three groups of five rabbits were injected with naloxone or saline. Naloxone was tested at 0.1 and 0.01 mg/kg day-1. Blood samples were taken at 90 min and 1, 2, 4, 7, 10, and 14 days after starting naloxone administration. Plasma testosterone (T) levels were measured by RIA. T levels increased progressively through the study in the experimental groups. The differences were significant after days 4 and 7 for 0.01-mg/kg and 0.1-mg/kg doses, respectively. T levels in both groups peaked at day 10 and decreased at day 14 (4 days after treatment).

Role of heat shock proteins in the effect of NMDA and KCl on cerebellar granule cells survival

Cerebellar granule cells (CGC) die apoptotically after five days in culture (DIV) at physiological concentrations of potassium (5 mM; K5). When CGC are depolarized (K25) or treated with NMDA (150 microM) cell survival is increased. CGC changed from K25 to K5 die after 24-48 h. It is known that heat shock protein (HSP) may protect from cell death. Here, we found that cells in K5 showed an increase in HSP-70 levels after 3 DIV. Similarly, in cells changed from K25 to K5, HSP-70 levels were increased after 6 h. Neither NMDA nor K25 treatment affected HSP-70 levels from 2-7 DIV. Ethanol or thermal stress induced HSP-70, but cell survival was not affected in K5 medium. These results suggest that HSP, particularly HSP-70, are not involved in the mechanisms by which NMDA and KCl promote cell survival.

The cytotoxic effect of 2-acylated-1,4-naphthohydroquinones on leukemia/lymphoma cells

Here, we tested seven 2-acylated-1,4-hydronaphthoquinones for their cytotoxic effects on a panel of cancer lymphoma/leukemia cells and compared to a non-cancer origin cell line. Several naphthohydroquinones exhibited selective cytotoxic effects on lymphoma/leukemia cells with lowest activity on non-cancer cells. The mode of cell death induced by an acylated naphthohydroquinone, which has a long alkyl chain, was found to be via apoptosis. Furthermore, the naphthohydroquinone provoked mitochondria depolarization and activation of its downstream effector, caspase-3, thus implicating the intrinsic apoptotic pathway as its mechanism to exert cell death.

Hepatocyte nuclear factor 1 alpha influences pancreatic cancer growth and metastasis

Hepatocyte nuclear factor 1 homeobox alpha (HNF1α) is a transcription factor involved in endodermal organogenesis and pancreatic precursor cell differentiation and development. Earlier studies have reported a role for HNF1α in pancreatic ductal adenocarcinoma (PDAC) but it is controversial. The mechanism by which it impacts PDAC is yet to be explored in depth. In this study, using the online databases we observed that HNF1α is upregulated in PDAC, which was also confirmed by our immunohistochemical analysis of PDAC tissue microarray. Silencing HNF1α reduced the proliferative, migratory, invasive and colony forming capabilities of pancreatic cancer cells. Key markers involved in these processes (pPI3K, pAKT, pERK, Bcl2, Zeb, Snail, Slug) were significantly changed in response to alterations in HNF1α expression. On the other hand, overexpression of HNF1α did not induce any significant change in the aggressiveness of pancreatic cancer cells. Our results demonstrate that reduced expression of HNF1α leads to inhibition of pancreatic cancer growth and progression, which indicates that it could be a potential oncogene and target for PDAC.

miRNome and Functional Network Analysis of PGRMC1 Regulated miRNA Target Genes Identify Pathways and Biological Functions Associated With Triple Negative Breast Cancer

Background

Increased expression of the progesterone receptor membrane component 1, a heme and progesterone binding protein, is frequently found in triple negative breast cancer tissue. The basis for the expression of PGRMC1 and its regulation on cellular signaling mechanisms remain largely unknown. Therefore, we aim to study microRNAs that target selective genes and mechanisms that are regulated by PGRMC1 in TNBCs.

Methods

To identify altered miRNAs, whole human miRNome profiling was performed following AG-205 treatment and PGRMC1 silencing. Network analysis identified miRNA target genes while KEGG, REACTOME and Gene ontology were used to explore altered signaling pathways, biological processes, and molecular functions.

Results

KEGG term pathway analysis revealed that upregulated miRNAs target specific genes that are involved in signaling pathways that play a major role in carcinogenesis. While multiple downregulated miRNAs are known oncogenes and have been previously demonstrated to be overexpressed in a variety of cancers. Overlapping miRNA target genes associated with KEGG term pathways were identified and overexpression/amplification of these genes was observed in invasive breast carcinoma tissue from TCGA. Further, the top two genes (CCND1 and YWHAZ) which are highly genetically altered are also associated with poorer overall survival.

Conclusions

Thus, our data demonstrates that therapeutic targeting of PGRMC1 in aggressive breast cancers leads to the activation of miRNAs that target overexpressed genes and deactivation of miRNAs that have oncogenic potential.

Targeting EIF4A triggers an interferon response to synergize with chemotherapy and suppress triple-negative breast cancer

Protein synthesis is frequently dysregulated in cancer and selective inhibition of mRNA translation represents an attractive cancer therapy. Here, we show that therapeutically targeting the RNA helicase eIF4A by Zotatifin, the first-in-class eIF4A inhibitor, exerts pleiotropic effects on both tumor cells and the tumor immune microenvironment in a diverse cohort of syngeneic triple-negative breast cancer (TNBC) mouse models. Zotatifin not only suppresses tumor cell proliferation but also directly repolarizes macrophages towards an M1-like phenotype and inhibits neutrophil infiltration, which sensitizes tumors to immune checkpoint blockade. Mechanistic studies revealed that Zotatifin reprograms the tumor translational landscape, inhibits the translation of Sox4 and Fgfr1, and induces an interferon response uniformly across models. The induction of an interferon response is partially due to the inhibition of Sox4 translation by Zotatifin. A similar induction of interferon-stimulated genes was observed in breast cancer patient biopsies following Zotatifin treatment. Surprisingly, Zotatifin significantly synergizes with carboplatin to trigger DNA damage and an even heightened interferon response resulting in T cell-dependent tumor suppression. These studies identified a vulnerability of eIF4A in TNBC, potential pharmacodynamic biomarkers for Zotatifin, and provide a rationale for new combination regimens comprising Zotatifin and chemotherapy or immunotherapy as treatments for TNBC.

Targeting eIF4A triggers an interferon response to synergize with chemotherapy and suppress triple-negative breast cancer

Protein synthesis is frequently dysregulated in cancer and selective inhibition of mRNA translation represents an attractive cancer therapy. Here, we show that therapeutically targeting the RNA helicase eIF4A with zotatifin, the first-in-class eIF4A inhibitor, exerts pleiotropic effects on both tumor cells and the tumor immune microenvironment in a diverse cohort of syngeneic triple-negative breast cancer (TNBC) mouse models. Zotatifin not only suppresses tumor cell proliferation but also directly repolarizes macrophages toward an M1-like phenotype and inhibits neutrophil infiltration, which sensitizes tumors to immune checkpoint blockade. Mechanistic studies revealed that zotatifin reprograms the tumor translational landscape, inhibits the translation of Sox4 and Fgfr1, and induces an interferon (IFN) response uniformly across models. The induction of an IFN response is partially due to the inhibition of Sox4 translation by zotatifin. A similar induction of IFN-stimulated genes was observed in breast cancer patient biopsies following zotatifin treatment. Surprisingly, zotatifin significantly synergizes with carboplatin to trigger DNA damage and an even heightened IFN response, resulting in T cell-dependent tumor suppression. These studies identified a vulnerability of eIF4A in TNBC, potential pharmacodynamic biomarkers for zotatifin, and provide a rationale for new combination regimens consisting of zotatifin and chemotherapy or immunotherapy as treatments for TNBC.

Biguanides antithetically regulate tumor properties by the dose-dependent mitochondrial reprogramming-driven c-Src pathway

The biguanide metformin attenuates mitochondrial oxidation and is proposed as an anti-cancer therapy. However, recent clinical studies suggest increased proliferation and fatty acid β-oxidation (FAO) in a subgroup of patients with breast cancer (BC) after metformin therapy. Considering that FAO can activate Src kinase in aggressive triple-negative BC (TNBC), we postulate that low-dose biguanide-driven AMPK-ACC-FAO signaling may activate the Src pathway in TNBC. The low bioavailability of metformin in TNBC xenografts mimics metformin's in vitro low-dose effect. Pharmacological or genetic inhibition of FAO significantly enhances the anti-tumor properties of biguanides. Lower doses of biguanides induce and higher doses suppress Src signaling. Dasatinib and metformin synergistically inhibit TNBC patient-derived xenograft growth, but not in high-fat diet-fed mice. This combination also suppresses TNBC metastatic progression. A combination of biguanides with Src inhibitors provides synergy to target metastatic TNBC suffering with limited treatment options.

CREB-binding protein/P300 bromodomain inhibition reduces neutrophil accumulation and activates antitumor immunity in triple-negative breast cancer

Tumor-associated neutrophils (TANs) have been shown to promote immunosuppression and tumor progression, and a high TAN frequency predicts poor prognosis in triple-negative breast cancer (TNBC). Dysregulation of CREB-binding protein (CBP)/P300 function has been observed with multiple cancer types. The bromodomain (BRD) of CBP/P300 has been shown to regulate its activity. In this study, we found that IACS-70654, a selective CBP/P300 BRD inhibitor, reduced TANs and inhibited the growth of neutrophil-enriched TNBC models. In the bone marrow, CBP/P300 BRD inhibition reduced the tumor-driven abnormal differentiation and proliferation of neutrophil progenitors. Inhibition of CBP/P300 BRD also stimulated the immune response by inducing an IFN response and MHCI expression in tumor cells and increasing tumor-infiltrated cytotoxic T cells. Moreover, IACS-70654 improved the response of a neutrophil-enriched TNBC model to docetaxel and immune checkpoint blockade. This provides a rationale for combining a CBP/P300 BRD inhibitor with standard-of-care therapies in future clinical trials for neutrophil-enriched TNBC.

Abstract 1461: miR-424-cdc42, key signaling axis in hyperglycemic regulation of stemness in triple negative breast cancer

Introduction: Meta-analysis shows women with diabetes have a 20% increased risk of breast cancer. Diabetes increases the risk of breast cancer mortality. Additionally, patients with breast cancer and preexisting diabetes have an increased risk for distant metastasis compared with non-diabetic counterparts. The molecular mechanisms for distant metastasis in breast cancer patients with diabetes are not very well understood. Our preliminary data suggested that hyperglycemia enhances stem cell activity in triple negative breast cancer (TNBC) cells. Here, we report miR-424 to be a key regulator of breast cancer stem cell pool dynamics under hyperglycemic environment.

Materials and Methods: MDA-MB-231, TNBC cell line was maintained under euglycemic (5mM) and hyperglycemic (10mM) culture conditions. RT-PCR based microRNA array was performed followed by validation of significantly altered microRNA to confirm the effect of hyperglycemia on the global microRNA profile. Flow cytometric analysis for CD44+/CD24- was performed to assess the alterations in breast cancer stem cell population. In addition, sphere-forming assay were also performed. Mir-424 over-expressing or knocked down cell lines were established from parental MDA-MB-231 cells and maintained in hyperglycemic or euglycemic condition respectively. Promoter analysis for PR/SET domain 14 (prdm14) was done. Western blotting and immunofluorescence assays were performed for cdc42 (cell division control 42), pStat5 (phospho signal transducer and activator of transcription factor 5) and prdm14.

Results: Loss of miR-424 in TNBC cells under euglycemic conditions led to enhanced stem cell activity; whereas over expression of miR- 424 under hyperglycemic conditions resulted in suppressed stem cell activity. Introduction of cdc42, (a miR-424 target gene) in miR-424 over expressing TNBC cells under hyperglycemic conditions leads to increased stem cell activity demonstrating the significance of miR-424-cdc42 signaling in hyperglycemia. Over-expression of miR-424 in TNBC dramatically reduced its metastatic abilities in vivo. Mechanistically, we found that miR-424-cdc42 signaling in hyperglycemia promotes Prdm14 activation, a stem cell regulator through increased phosphorylation of Stat5.

Conclusions: Our findings establish a key molecular signaling cascade (miR-424→cdc42→prdm14) that promotes TNBC stem cell activity under hyperglycemic conditions.

Citation Format: Sushmita B. Nandy, Alexis Orozco, Gautham Prabhakar, Viktoria Stewart, Stephanie Jones, Paloma Munoz, Ramadevi Subramani, Diego Pedroza, Rajkumar Lakshmanaswamy. miR-424-cdc42, key signaling axis in hyperglycemic regulation of stemness in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1461. doi:10.1158/1538-7445.AM2017-1461

Abstract P5-05-12: Progesterone drives ER-positive and triple negative breast cancer cell proliferation through progesterone receptor membrane component 1

Introduction: The role of progesterone and its receptors in breast cancer progression continue to be studied but remain controversial. Progesterone membrane receptors with the ability to regulate kinase signals, mediating breast cancer proliferation have been demonstrated. Increased expression of the Progesterone Receptor Membrane Component 1 (PGRMC1), a heme – binding protein with the ability to interact and stabilize epidermal growth factor receptor (EGFR) is frequently found in breast cancer tissue. Some evidence suggests that progesterone can stimulate and regulate breast cancer cell proliferation. The basis of the signaling mechanisms by which Progesterone exerts its function remains largely unknown. Both the nuclear and membrane progesterone receptors could play a significant role in the development and progression of breast cancer and both could become viable therapeutic options. We, aim to investigate the role of PGRMC1 in progesterone driven breast cancers.

Materials and Methods: Human breast tissues were utilized to identify PGRMC1 expression along with a panel of normal and breast cancer cell lines. Two breast cancer cell lines (ZR-75-1 and MDA-MB-468) were selected and treated with progesterone and AG-205 (PGRMC1 inhibitor) at different concentrations to assess optimum dosage. We performed MTS assay, qRT-PCR, Western blot, immunofluorescence, immunohistochemistry and flow cytometry for measuring cell proliferation, apoptosis and key markers involved in these processes. We also performed an in silico analysis to compare the expression of PGRMC1 in various cell lines and breast cancer tissues.

Results: Immunohistochemistry demonstrated strong staining for PGRMC1 in human breast cancer tissue compared to normal tissue. Increased PGRMC1 expression was observed specifically in ZR-75-1 and MDA-MB-468 cells by qRT-PCR, western blot and immunofluorescence, these results were validated and compared to microarray-based gene expression analysis of breast cell lines and breast tumor data sets. Progesterone treatment increased cell proliferation in a dose dependent manner while AG-205 decreased cell proliferation in a dose dependent manner in ZR-75-1 and MDA-MB-468. Minimal effects of AG-205 were observed in normal breast epithelial cells. AG-205 also, induced apoptosis in both ZR-75-1 and MDA-MB-468 cell lines. Furthermore, short-term treatment of progesterone increased both mRNA and protein expression of PGRMC1. Key markers of cell proliferation (pAKT, CCND1, pEGFR, pmTOR) and apoptosis (PTEN, Bcl2, Bax, Bim) revealed that PGRMC1 facilitated the proliferative effect of progesterone. Interestingly progesterone increases phosphorylation of EGFR and treatment of AG-205 alters EGFR expression in a dose dependent manner.

Conclusion: Our data demonstrates that PGRMC1 plays a prominent role in regulating progesterone driven cell proliferation in both ER-positive and triple negative breast cancer cells. These initial findings uncover the potential of PGRMC1 as a therapeutic target for breast cancers.

Citation Format: Pedroza DA, Subramani R, Galvez A, Lakshmanaswamy R. Progesterone drives ER-positive and triple negative breast cancer cell proliferation through progesterone receptor membrane component 1 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-12.

Abstract P1-12-02: Growth hormone and prolactin influences mammary epithelial and stromal interactions in early parity induced protection against breast cancer

Introduction: Early pregnancy has been shown to decrease the life-time risk of mammary cancer. Further, systemic alterations in circulating levels of growth hormone (GH) and prolactin (PRL) have been associated with the decreased risk. GH and PRL have been shown to affect the mammary stroma and epithelium. Carcinogenesis is a multistep process and there are several ways in which the host environment can affect progression of initiated cells to neoplasia. During normal and tumor development complex interactions occur between epithelial cells and stromal cells in the tissue microenvironment. These epithelial-stromal interactions in the microenvironment play a crucial role in the progression of mammary tumors. Determining the epithelial-stromal regulation by GH and PRL in the mammary gland of early parous rats is expected to improve our understanding of the dynamics of the epithelium and stromal interactions in mammary carcinogenesis. Materials and Methods: The inguinal mammary fat pad was cleared of the host mammary gland in 3-4-week-old female Lewis rats. One group (n=20) of rats were exposed to MNU at 7 weeks of age, and another group (n=20) of rats were not exposed to MNU. A subset (n=10) of rats from each of these experimental groups were mated at 9 weeks and allowed to go through a full-term pregnancy. The mothers were allowed to lactate for 3 weeks and weaned. All animals were terminated 6 weeks post-weaning. Mammary epithelial cells (MECs) were isolated using a standard collagenase cell dissociation procedure. The isolated MECs (5 × 105) were transplanted into the gland-free fat pads of respective hosts (n=30). MECs isolated from control and carcinogen treated age-matched nulliparous (AMNP) rats were transplanted into the gland-free fat pads of parous hosts and similarly MECs from control and carcinogen treated parous were transplanted into gland-free fats pads of AMNP hosts. In brief, we studied the following groups to understand the influence of early parity on epithelial-stromal interactions involved in mammary carcinogenesis: 1) carcinogen treated MECs from AMNP rats was transplanted into untreated parous rats; 2) carcinogen treated MECs from parous rats was transplanted into untreated AMNP rats; 3) untreated MECs from AMNP rats was transplanted into carcinogen treated parous rats and 4) untreated MECs from parous rats was transplanted into carcinogen treated AMNP rats. In another experiment, we treated a subset of the above mentioned groups with GH or PRL (n=10). Mammary carcinogenesis was monitored weekly for incidence, multiplicity, and latency. The cancerous nature of the palpable tumors was confirmed by histopathological analysis. Results: Our results demonstrate that when MECs from AMNP rats were transplanted to parous hosts they did not grow further to make palpable cancers. In contrast when MECs from parous rats were transplanted to AMNP they formed palpable cancers. Further, administration of GH or PRL increased carcinogenesis in parous rats. Conclusion: These findings indicate that the epithelial stromal interactions are important for mammary carcinogenesis and they are influenced significantly by GH and PRL.

Citation Format: Ramadevi Subramani, Adriana Galvez, Diego Pedroza, Alejandro Bencomo, Madeline Dixon, Rajkumar Lakshmanaswamy. Growth hormone and prolactin influences mammary epithelial and stromal interactions in early parity induced protection against breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-12-02.

Abstract P5-05-15: Pregnancy inhibits mammary carcinogenesis by persistently altering the hypothalamic-pituitary axis

Pregnancy, carried to term at an early age, is probably the best natural protection against breast cancer development. The relative life-long breast cancer risk for women that give birth to their first child before the age of 20 years is approximately half that of nulliparous women. In contrast, if a woman undergoes her first full-term pregnancy after the age of 35, her risk for breast cancer is increased even more than nulliparous women. In the current generation many women are career oriented and have children later in life. Universally the average age at first birth is on the rise. It is critical to understand the underlying mechanism of this protective effect of pregnancy against breast cancer to develop novel prevention strategies to reduce the risk of breast cancer without women having to undergo pregnancy early in life. Earlier, we and others have demonstrated that post-pregnancy there were persistent changes in circulating levels of hormones. In order to understand the significance of these systemic changes we determined alterations in the hypothalamic-pituitary axis in parous rats. In particular, we examined the static and dynamic alterations in the hypothalamic-pituitary axis in response to pregnancy. Seven weeks old female Lewis rats were injected with the chemical carcinogen N-methyl-N-nitrosourea (MNU) at a dose of 50mg/kg body weight intraperitoneally. Two weeks post-carcinogen treatment these rats were housed with a male rat. On the observation of the vaginal plug the male was removed from the cage. Once the rats gave birth they nursed the pups for three weeks and were weaned after that period. Mammary tumorigenesis was monitored through weekly palpation for a period of nine months. A subset of rats at 6, 12 and 24 weeks post-weaning were used to study static and dynamic changes in the level of hormones. We investigated the static alterations in the hypothalamic-pituitary axis in response to pregnancy by measuring the levels of thyrotropin releasing hormone (TRH), growth hormone releasing hormone (GHRH), somatostatin (SS), dopamine (DA), growth hormone (GH) and prolactin (PRL). Next we investigated if the dynamic alterations in the hypothalamic-pituitary axis in response to pregnancy. Control and parous animals were subjected to secretogogue treatments (Growth Hormone Related Peptide 6 for GH and Perphenazine for PRL) and the levels of GH and PRL were measured. We also isolated the pituitary and treated them with the secretogogues and measured the levels of GH and PRL. Our data demonstrated that pregnancy resulted in persistent static and dynamic alterations in circulating levels of hormones. Parous rats response to the secretogogues was severely blunted compared to the control nulliparous rats. The levels of TRH, GHRH, GH and PRL were significantly lowered in parous rats while DA and SS levels were higher in nulliparous rats. As expected mammary carcinogenesis was significantly inhibited in parous rats. Overall, these preliminary results suggest that pregnancy induces persistent changes in hypothalamic-pituitary axis, which results in a lowered hormonal promotion environment resulting in inhibition of mammary carcinogenesis.

Citation Format: Subramani R, Galvez A, Pedroza D, Lakshmanaswamy R. Pregnancy inhibits mammary carcinogenesis by persistently altering the hypothalamic-pituitary axis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-15.

Abstract P6-05-08: Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers

Introduction: Increased expression of progesterone receptor membrane component 1 (PGRMC1), has been linked to breast cancer cell proliferation and tumor growth via epidermal growth factor receptor (EGFR) dependent interaction. As estrogen receptor positive breast cancers receive endocrine therapy and triple negative breast cancers (TNBC) rely on chemotherapeutic agents and or small molecule inhibitors. PGRMC1 could be a potential therapeutic target for both estrogen receptor positive and TNBCs, however its mechanism of action remains elusive. We, aim to understand the signaling mechanism behind PGRMC1 and its potential as viable target for the treatment of breast cancers. Materials and Methods: A panel of non-malignant and malignant breast cell lines were cultured and screened for PGRMC1 expression. PGRMC1 overexpressing breast cancer cell lines were treated with AG-205 (PGRMC1 inhibitor) and PGRMC1 targeting siRNAs. MTS, qRT-PCR, Western blot, immunofluorescence, flow cytometry assays and phospho explorer antibody array analysis were performed. Results: Increased PGRMC1 mRNA and protein levels were observed in estrogen receptor positive ZR-75-1 and TNBC MDA-MB-468 cells, these results were validated and compared to online RNA-seq based gene expression analysis of breast cell lines and breast tumor data sets. Data from online databases also demonstrated PGRMC1 overexpression in multiple breast cancer subtypes (Luminal, Basal B and Basal A). Immunohistochemistry demonstrated strong staining for PGRMC1 in human breast cancer tissue compared to normal tissue. Both AG-205 treatment and PGRMC1 silencing decreased cell proliferation, induced cell cycle arrest at the G0/G1 phase, promoted apoptosis and reduced the capability of the cells to migrate and invade. Phospho-specific antibody array data demonstrated overall downregulation of the EGFR/PI3K/AKT signaling mechanisms following AG-205 and PGRMC1 silencing. Alteration in the expression of key markers of cell proliferation, apoptosis and cell cycle revealed that PGRMC1 inhibition decreases breast cancer proliferation. Conclusion: Our data demonstrate that PGRMC1 plays a prominent role in regulating breast cancer growth and progression by altering the EGFR/PI3K/AKT signaling mechanisms.

Citation Format: Diego A Pedroza, Alejandra Bencomo, Adriana Galvez, Ramadevi Subramani, Venkatesh Rajamanickam, Rajkumar Lakshmanaswamy. Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-05-08.

Leveraging preclinical models of metastatic breast cancer

Women that present to the clinic with established breast cancer metastases have limited treatment options. Yet, the majority of preclinical studies are actually not directed at developing treatment regimens for established metastatic disease. In this review we will discuss the current state of preclinical macro-metastatic breast cancer models, including, but not limited to syngeneic GEMM, PDX and xenografts. Challenges within these models which are often overlooked include fluorophore-immunogenic neoantigens, differences in experimental vs spontaneous metastasis and tumor heterogeneity. Furthermore, due to cell plasticity in the tumor immune microenvironment (TIME) of the metastatic landscape, the treatment efficacy of newly approved immune checkpoint blockade (ICB) may differ in metastatic sites as compared to primary localized tumors.

Abstract 645: Pregnancy inhibits mammary carcinogenesis by altering the mammary epithelial and stromal interactions

A full-term pregnancy before the age of 20 is the only known natural phenomenon that can drastically reduce the risk of breast cancer in women of all ethnic backgrounds worldwide. This universal protective effect of early pregnancy is clearly of major consideration in devising prevention strategies against breast cancer. It is well known that parous subjects have an altered systemic hormonal milieu with a significant decrease in circulating GH and PRL. Determining how these hormonal alterations impact the mammary gland of early parous rats is expected to improve our understanding of the dynamics of mammary carcinogenesis. The inguinal mammary fat pad was cleared of the host mammary gland in 3-4-week-old rats. One group of rats were exposed to N-Methyl-N-Nitrosourea (MNU) at 7 weeks of age, and another group of rats were not exposed to MNU. A subset of rats from each of these experimental groups were mated at 9 weeks and allowed to go through a full-term pregnancy. All animals were terminated 6 weeks post-weaning. Mammary epithelial cells (MECs) were isolated using the collagenase cell dissociation procedure. The isolated MECs (5 × 105) were transplanted into the gland-free fat pads of respective hosts. In brief, we studied the following groups to understand the influence of early parity on epithelial-stromal interactions involved in mammary carcinogenesis: 1) carcinogen treated MECs from Age-matched nulliparous (AMNP) rats were transplanted into untreated parous rats; 2) carcinogen treated MECs from parous rats were transplanted into untreated AMNP rats; 3) untreated MECs from AMNP rats were transplanted into carcinogen treated parous rats and 4) untreated MECs from parous rats were transplanted into carcinogen treated AMNP rats. All experimental animals were palpated weekly for the presence of mammary cancers. The cancerous nature of the palpable tumors was confirmed by histopathological analysis. Digital images of immunocytochemistry result was analyzed using Image Pro Plus software. Carcinogenesis experiments were terminated nine months after carcinogen administration. Incidence, multiplicity, and latency of mammary cancers was determined for each group and analyzed for significance by the appropriate statistical test. Our data demonstrated that transplantation of MECs from AMNP rats into parous hosts did not develop into palpable tumors while MECs from parous rats when transplanted to AMNP hosts developed mammary tumors. Analysis of the mammary gland wholemounts and molecular markers clearly indicated that parity alters key signaling mechanisms and inhibits progression of mammary lesions. These findings suggests that the mammary epithelial-stromal interactions in the parous rats is altered making it resistant to mammary carcinogenesis.

Citation Format: Ramadevi Subramani Reddy, Adriana Galvez, Diego A. Pedroza, Animesh Chatterjee, Courtney Perry, Elizabeth Penner, Rajkumar Lakshmanaswamy. Pregnancy inhibits mammary carcinogenesis by altering the mammary epithelial and stromal interactions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 645.

Abstract 846: Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers

Introduction: The role of progesterone and its receptors in breast cancer progression continue to be studied but remain controversial. Progesterone membrane receptors with the ability to regulate kinase signals, mediating breast cancer proliferation have been demonstrated. Increased expression of the progesterone receptor membrane component 1 (PGRMC1), a heme - binding protein with the ability to interact and stabilize epidermal growth factor receptor (EGFR) is frequently found in breast cancer tissue. The basis of the signaling mechanisms of progesterone membrane receptors remain largely unknown. Both the nuclear and membrane progesterone receptors could play a significant role in the development and progression of breast cancers and both could become viable therapeutic options. We, aim to investigate the molecular circuitry of PGRMC1 in both ER-positive and Triple Negative Breast Cancers (TNBCs).

Materials and Methods: Human breast tissues were utilized to identify the expression of PGRMC1 along with a panel of normal and breast cancer cell lines. PGRMC1 overexpressing ZR-75-1 and MDA-MB-468 breast cancer cell lines were selected and treated with AG-205 (PGRMC1 inhibitor) and PGRMC1 siRNAs, while PGRMC1 was overexpressed in MCF10A non-malignant breast epithelial cells. MTS, qRT-PCR, Western blot, immunofluorescence, immunohistochemistry and flow cytometry were performed to study cell proliferation, apoptosis and key markers involved in these processes. In silico analysis utilizing publicly available gene expression datasets were also performed.

Results: Immunohistochemistry demonstrated strong staining for PGRMC1 in human breast cancer tissue compared to normal breast tissue. Increased PGRMC1 expression was observed specifically in ZR-75-1 and MDA-MB-468 cells by qRT-PCR, Western blot and immunofluorescence, these results were validated and compared to microarray-based gene expression analysis of breast cell lines and breast tumor data sets. Both AG-205 and PGRMC1 targeted siRNAs decreased cell proliferation in ZR-75-1 and MDA-MB-468. Minimal effects of AG-205 were observed in MCF10A non-malignant breast epithelial cells. AG-205 treatment and silencing of PGRMC1 induced apoptosis in both cancer cell lines. Furthermore, PGRMC1 overexpression transformed MCF10A cells into a malignant phenotype. Key markers of cell proliferation (pAKT, CCND1, pEGFR, pmTOR) and apoptosis (PTEN, Bcl2, Bax,) revealed that PGRMC1 inhibition decreases proliferation while overexpression promotes tumorigenesis.

Conclusion: Our data demonstrates that PGRMC1 plays a prominent role in both ER-positive and TNBCs. These initial findings uncover the potential of PGRMC1 as an oncogene and therapeutic target for breast cancer patients who overexpress this gene.

Citation Format: Diego A. Pedroza, Ramadevi Subramani Reddy, Adriana Galvez, Rajkumar Lakshmanaswamy. Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 846.

Abstract 2725: Progesterone promotes estrogen induced mammary tumorigenesis through the activation of nodal and notch signaling

Nodal and Notch are considered to be important embryonic morphogens, regulating cell - cell communication, determining left - right asymmetry and in formation of the mesoderm. Cellular processes in embryogenesis can be compared to processes occurring during tumorigenesis. Nodal has been shown to re emerge in aggressive triple negative breast carcinomas, and Notch is known to promote breast cancer. The role of Nodal and Notch in breast carcinomas is being studied; however hormonal regulation of theses two cancer-promoting genes is unknown. Ovarian hormones Estrogen (E) and Progesterone (P) play a vital role in the normal development and function of breast tissue, while extensive exposure to these hormones increases the risk of breast cancer. Studies conducted by the Women's Health Initiative (WHI) have demonstrated that combined Hormone Replacement Therapy (HRT) increases breast cancer risk. The objective of this study is to determine whether P promotes E induced mammary tumorigenesis through the activation of Nodal and Notch signaling. To study the molecular mechanism, MCF-7 cells were cultured and treated with hormones: E, P, E+P and E+Mifepristone (MP - a progesterone antagonist). MTS assay for cellular proliferation, PCR array for gene expression, and western blot for protein expression, were performed. MTS assay showed increased cell proliferation of MFC-7 hormone treatment E+P when compared to control. PCR array analysis showed significant alteration of genes associated with Nodal signaling, specifically Lefty in E+MP treatment, protein expression analysis showed activation of Notch and up - regulation of its downstream targets HES1 and HEY1 with E and P individual and combination treatments while it was down regulated in E+MP treatment. Based on our findings, we suggest that P mediates E induced mammary tumorigenesis through the activation of Nodal and Notch signaling, proposing a possible crosstalk between both pathways in the development and progression of breast cancer.

Citation Format: Diego A. Pedroza, Arunkumar Arumugam, Sushmita Nandy, Ramadevi Subramani, Thiyagarajan Boopalan, Rajkumar Lakshmanaswamy. Progesterone promotes estrogen induced mammary tumorigenesis through the activation of nodal and notch signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2725. doi:10.1158/1538-7445.AM2015-2725