Abstract 2690: Loss of E-cadherin induces IGF1R activation revealing a targetable pathway in invasive lobular breast carcinoma

Invasive Ductal Carcinoma (IDC) and Invasive Lobular Carcinoma (ILC) are two major subtypes of breast cancer with significant differences in their histological and molecular underpinnings. ILC has a unique loss of E-cadherin (CDH1) which we have previously demonstrated as a negative regulator of the Insulin-like Growth Factor 1 receptor (IGF1R) through a comprehensive analysis of cell line models and tumor samples. We propose that loss of E-cadherin in ILC sensitizes cells to growth factor signaling and thus alters their sensitivity to growth factor signaling inhibitors. To investigate this, we used CRISPR to generate CDH1 knockout (KO) IDC cell lines (MCF7, T47D, ZR75.1) to uncover the mechanism by which E-cadherin loss activates the IGF pathway while also assessing its targetability. CDH1 KO cells exhibited anchorage independent growth in suspension culture and altered p120 catenin localization as observed in ILC tumors. Through in vitro studies, we show increased signaling sensitivity to IGF/insulin ligands and enhanced signaling duration in CDH1 KO cells. In addition, we observed a higher migratory potential of CDH1 KO cells compared to wild type (WT) cells, which was further enhanced as a chemotactic response to IGF1 or serum. Further, this phenotype could be reversed with an IGF1R inhibitor, BMS-754807. We additionally identified an increase in Collagen I haptotaxis in the CDH1 KO cells, which was also translated into a novel invasive phenotype towards serum in the T47D CDH1 KO cells. Despite no significant differences in membranous IGF1R levels between WT and CDH1 KO cells, higher ligand-receptor interaction was observed with CDH1 KO cells, demonstrating an increased ligand-receptor complex formation upon stimulation. Our results suggest that loss of CDH1 results in an increase in IGF1 receptor availability for ligand binding which in turn allows for an enhanced downstream signaling activation. Interestingly, a physical repression of E-cadherin on IGF1R could not be demonstrated, suggesting spatial changes on the membrane following E-cadherin loss may control ligand binding. Critically, increased sensitivity to IGF1R, PI3K, AKT and MEK inhibitors was observed in CDH1 KO cells suggesting that these targets should be further explored in ILC and that CDH1 loss may be exploited as a biomarker of response, or for patient stratification to inhibitors targeting these pathways.

Citation Format: Ashuvinee Elangovan, Laura Savariau, Megan E. Yates, Jagmohan Hooda, Alison M. Nagle, Steffi Oesterreich, Jennifer M. Atkinson, Adrian V. Lee. Loss of E-cadherin induces IGF1R activation revealing a targetable pathway in invasive lobular breast carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2690.

Recurrent hyperactive ESR1 fusion proteins in endocrine therapy-resistant breast cancer

Background

Estrogen receptor-positive (ER-positive) metastatic breast cancer is often intractable due to endocrine therapy resistance. Although ESR1 promoter switching events have been associated with endocrine-therapy resistance, recurrent ESR1 fusion proteins have yet to be identified in advanced breast cancer.

Patients and methods

To identify genomic structural rearrangements (REs) including gene fusions in acquired resistance, we undertook a multimodal sequencing effort in three breast cancer patient cohorts: (i) mate-pair and/or RNAseq in 6 patient-matched primary-metastatic tumors and 51 metastases, (ii) high coverage (>500×) comprehensive genomic profiling of 287-395 cancer-related genes across 9542 solid tumors (5216 from metastatic disease), and (iii) ultra-high coverage (>5000×) genomic profiling of 62 cancer-related genes in 254 ctDNA samples. In addition to traditional gene fusion detection methods (i.e. discordant reads, split reads), ESR1 REs were detected from targeted sequencing data by applying a novel algorithm (copyshift) that identifies major copy number shifts at rearrangement hotspots.

Results

We identify 88 ESR1 REs across 83 unique patients with direct confirmation of 9 ESR1 fusion proteins (including 2 via immunoblot). ESR1 REs are highly enriched in ER-positive, metastatic disease and co-occur with known ESR1 missense alterations, suggestive of polyclonal resistance. Importantly, all fusions result from a breakpoint in or near ESR1 intron 6 and therefore lack an intact ligand binding domain (LBD). In vitro characterization of three fusions reveals ligand-independence and hyperactivity dependent upon the 3' partner gene. Our lower-bound estimate of ESR1 fusions is at least 1% of metastatic solid breast cancers, the prevalence in ctDNA is at least 10× enriched. We postulate this enrichment may represent secondary resistance to more aggressive endocrine therapies applied to patients with ESR1 LBD missense alterations.

Conclusions

Collectively, these data indicate that N-terminal ESR1 fusions involving exons 6-7 are a recurrent driver of endocrine therapy resistance and are impervious to ER-targeted therapies.

Loss of E-cadherin Enhances IGF1-IGF1R Pathway Activation and Sensitizes Breast Cancers to Anti-IGF1R/InsR Inhibitors

Purpose: Insulin-like growth factor 1 (IGF1) signaling regulates breast cancer initiation and progression and associated cancer phenotypes. We previously identified E-cadherin (CDH1) as a repressor of IGF1 signaling and in this study examined how loss of E-cadherin affects IGF1R signaling and response to anti-IGF1R/insulin receptor (InsR) therapies in breast cancer.Experimental Design: Breast cancer cell lines were used to assess how altered E-cadherin levels regulate IGF1R signaling and response to two anti-IGF1R/InsR therapies. In situ proximity ligation assay (PLA) was used to define interaction between IGF1R and E-cadherin. TCGA RNA-seq and RPPA data were used to compare IGF1R/InsR activation in estrogen receptor-positive (ER+) invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC) tumors. ER+ ILC cell lines and xenograft tumor explant cultures were used to evaluate efficacy to IGF1R pathway inhibition in combination with endocrine therapy.Results: Diminished functional E-cadherin increased both activation of IGF1R signaling and efficacy to anti-IGF1R/InsR therapies. PLA demonstrated a direct endogenous interaction between IGF1R and E-cadherin at points of cell-cell contact. Increased expression of IGF1 ligand and levels of IGF1R/InsR phosphorylation were observed in E-cadherin-deficient ER+ ILC compared with IDC tumors. IGF1R pathway inhibitors were effective in inhibiting growth in ER+ ILC cell lines and synergized with endocrine therapy and similarly IGF1R/InsR inhibition reduced proliferation in ILC tumor explant culture.Conclusions: We provide evidence that loss of E-cadherin hyperactivates the IGF1R pathway and increases sensitivity to IGF1R/InsR targeted therapy, thus identifying the IGF1R pathway as a potential novel target in E-cadherin-deficient breast cancers. Clin Cancer Res; 24(20); 5165-77. ©2018 AACR.

Controlled dimerization of insulin-like growth factor-1 and insulin receptors reveals shared and distinct activities of holo and hybrid receptors

Breast cancer development and progression are influenced by insulin-like growth factor receptor 1 (IGF1R) and insulin receptor (InsR) signaling, which drive cancer phenotypes such as cell growth, proliferation, and migration. IGF1R and InsR form IGF1R/InsR hybrid receptors (HybRs) consisting of one molecule of IGF1R and one molecule of InsR. The specific signaling and functions of HybR are largely unknown, as HybR is activated by both IGF1 and insulin, and no cellular system expresses HybR in the absence of holo-IGF1R or holo-InsR. Here we studied the role of HybR by constructing inducible chimeric receptors and compared HybR signaling with that of holo-IGF1R and holo-InsR. We cloned chemically inducible chimeric IGF1R and InsR constructs consisting of the extracellular domains of the p75 nerve growth factor receptor fused to the intracellular β subunit of IGF1R or InsR and a dimerization domain. Dimerization with the drugs AP20187 or AP21967 allowed specific and independent activation of holo-IGF1R, holo-InsR, or HybR, resulting in activation of the PI3K pathway. Holo-IGF1R and HybR both promoted cell proliferation and glucose uptake, whereas holo-InsR only promoted glucose uptake, and only holo-IGF1R showed anti-apoptotic effects. We also found that the three receptors differentially regulated gene expression: holo-IGF1R and HybR up-regulated EGR3; holo-InsR specifically down-regulated JUN and BCL2L1; holo-InsR down-regulated but HybR up-regulated HK2; and HybR specifically up-regulated FHL2, ITGA6, and PCK2. Our findings suggest that, when expressed and activated in mammary epithelial cells, HybR acts in a manner similar to IGF1R and support further investigation of the role of HybR in breast cancer.

Abstract B158: Exploiting IGF1R pathway activation as a therapeutic strategy for E-cadherin deficient breast cancers

Insulin-like growth factor I (IGF1) plays an important role in breast cancer initiation and progression due to its regulation of cell proliferation, migration, and invasion. These characteristics make IGF1R an attractive therapeutic target; however, only a subset of patients show beneficial response to IGF1R inhibitors in clinical trials. To identify putative biomarkers of response to IGF1, we performed a proteomic screen in 21 breast cancer cell lines stimulated with IGF1. Using a novel integrated computational and experimental approach, we identified levels of E-cadherin (CDH1), a major component of the adherens junction (AJ), as a repressor of IGF1R signaling. CDH1 is genetically lost in invasive lobular breast cancer (ILC), a subtype of breast cancer that accounts for ~10-15% of total cases. E-cadherin is also downregulated in estrogen receptor (ER)-negative breast cancers that have undergone epithelial to mesenchymal transition. Consistent with the proteomic screen, knockdown of E-cadherin enhanced IGF1-induced activation of IGF1R and downstream Akt and ERK1/2 phosphorylation, and this enhanced cell cycle progression. Disruption of the AJ alone with an E-cadherin monoclonal antibody also enhanced IGF1R signaling. Further, we have shown a direct interaction of IGF1R and E-cadherin using in situ proximity ligation assay indicating a physical regulation of E-cadherin on IGF1R signaling. Supporting the clinical relevance of our observations, we found increased expression of IGF1 ligand and increased IGF1R phosphorylation in E-cadherin deficient ER+ ILC tumors in The Cancer Genome Atlas (TCGA) compared to ER+ invasive ductal carcinomas (IDC). We also discovered a correlation between mRNA expression and the activation of the IGF gene signature in (1) a cohort of ER+ ILC tumors compared to ER+ IDC and (2) a subset of ER-negative tumors within TCGA. We have previously published that IGF1R inhibitors are effective in inhibiting growth of ER-negative breast cancer cell lines and xenograft models in combination with chemotherapy. Thus, we focused our studies on understanding the utility of IGF1R pathway inhibition in ER+ ILC as a therapeutic strategy. Our data indicate that IGF1R and Akt pathway inhibitors are effective in inhibiting growth in ER+ ILC cell lines and ex vivo tumor culture, and synergize with standard-of-care anti-ER targeted therapy. Therefore, we hypothesize that loss of E-cadherin potentiates IGF1R signaling to enhance breast cancer progression and that loss of E-cadherin expression in ILC and ER-negative tumors may highlight those susceptible to IGF1R inhibition.

Citation Format: Alison M. Nagle, Cemal Erdem, Kevin Levine, Christos Sotiriou, Otto Metzger, D Lans Taylor, Timothy Lezon, Steffi Oesterreich, Adrian V. Lee. Exploiting IGF1R pathway activation as a therapeutic strategy for E-cadherin deficient breast cancers [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B158.

Proteomic Screening and Lasso Regression Reveal Differential Signaling in Insulin and Insulin-like Growth Factor I (IGF1) Pathways

Insulin and insulin-like growth factor I (IGF1) influence cancer risk and progression through poorly understood mechanisms. To better understand the roles of insulin and IGF1 signaling in breast cancer, we combined proteomic screening with computational network inference to uncover differences in IGF1 and insulin induced signaling. Using reverse phase protein array, we measured the levels of 134 proteins in 21 breast cancer cell lines stimulated with IGF1 or insulin for up to 48 h. We then constructed directed protein expression networks using three separate methods: (i) lasso regression, (ii) conventional matrix inversion, and (iii) entropy maximization. These networks, named here as the time translation models, were analyzed and the inferred interactions were ranked by differential magnitude to identify pathway differences. The two top candidates, chosen for experimental validation, were shown to regulate IGF1/insulin induced phosphorylation events. First, acetyl-CoA carboxylase (ACC) knock-down was shown to increase the level of mitogen-activated protein kinase (MAPK) phosphorylation. Second, stable knock-down of E-Cadherin increased the phospho-Akt protein levels. Both of the knock-down perturbations incurred phosphorylation responses stronger in IGF1 stimulated cells compared with insulin. Overall, the time-translation modeling coupled to wet-lab experiments has proven to be powerful in inferring differential interactions downstream of IGF1 and insulin signaling, in vitro.

Abstract 1880: Determining the role of E-cadherin in regulating IGF1 signaling in breast cancer: An interaction predicted by large-scale modeling

Insulin-like growth factor I (IGF1) plays an important role in breast cancer initiation and progression due to its regulation of cell proliferation, migration, and invasion. These characteristics make IGF1R an attractive therapeutic target. While numerous clinical trials have sought to inhibit IGF1R action, these were largely unsuccessful due to a lack of biomarkers for positive therapeutic response, poor patient selection, and potential compensatory signaling by the highly similar insulin receptor (InsR). To identify biomarkers of response, our laboratory identified a set of genes regulated by IGF1 (IGF-sig) that revealed a correlation between activation of the IGF-sig and poor prognosis in estrogen receptor (ER)-negative breast cancer. Further, we showed that ER-negative breast cancer cells are sensitive to IGF1R inhibition both in vitro and in vivo. In an effort to better understand the IGF1 and insulin signaling networks in breast cancer, we performed a reverse phase protein array (RPPA) using 134 antibodies on lysates from twenty-one breast cancer cell lines stimulated with a six point time-course of IGF1 or insulin. We developed a time-dependent model to predict differential mediators of IGF1 and insulin signaling using perturbation analysis. The model predicted that alterations in levels of E-cadherin (CDH1), a major component of the adherens junction, affect IGF1 induced Akt activation. In breast cancer, E-cadherin is genetically lost in invasive lobular cancer (ILC), a subtype that accounts for ∼10-15% of breast cancers. Alternatively, invasive ductal cancers may lose E-cadherin via EMT. I confirmed this in silico prediction, showing that shRNA reduction of E-cadherin enhances the ability of IGF1 to induce Akt signaling, and additionally IGF1R, ERK and S6 ribosomal protein activation. Supporting the clinical relevance of our observations, we found a correlation between loss of E-cadherin (CDH1) mRNA expression and the activation of the IGF-sig in ER-negative tumors within The Cancer Genome Atlas (TCGA). Therefore, we hypothesize that loss of E-cadherin potentiates IGF1 signaling to enhance breast cancer progression, and that loss of E-cadherin expression in ILC and ER-negative tumors may highlight those susceptible to IGF1R inhibition. These studies will investigate how E-cadherin modulates IGF1 signaling and the interaction with EMT with the goal of better defining breast cancers that may respond to IGF1R inhibitors.

Citation Format: Alison M. Nagle, Cemal Erdem, YuFen Wang, Kevin Levine, Tiffany Katz, D. Lansing Taylor, Adrian V. Lee, Timothy R. Lezon. Determining the role of E-cadherin in regulating IGF1 signaling in breast cancer: An interaction predicted by large-scale modeling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1880.

Dietary supplementation of β-guanidinopropionic acid (βGPA) reduces whole-body and skeletal muscle growth in young CD-1 mice

Increased AMP-activated protein kinase (AMPK) activity leads to enhanced fatty acid utilization, while also promoting increased ubiquitin-dependent proteolysis (UDP) in mammalian skeletal muscle. β-guanidinopropionic acid (βGPA) is a commercially available dietary supplement that has been shown to promote an AMPK-dependent increase in fatty acid utilization and aerobic capacity in mammals by compromising creatine kinase function. However, it remains unknown if continuous βGPA supplementation can negatively impact skeletal muscle growth in a rapidly growing juvenile. The current study was conducted to examine the effect of βGPA supplementation on whole-body and skeletal muscle growth in juvenile and young adult mice. Three-week old, post weanling CD-1 mice were fed a standard rodent chow that was supplemented with either 2% (w/w) α-cellulose (control) or βGPA. Control and βGPA-fed mice (n = 6) were sampled after 2, 4, and 8 weeks. Whole-body and hindlimb muscle masses were significantly (P < 0.05) reduced in βGPA-fed mice by 2 weeks. The level of AMPK (T172) phosphorylation increased significantly (P < 0.05) in the gastrocnemius of βGPA-fed versus control mice at 2 weeks, but was not significantly different at the 4- and 8-week time points. Further analysis revealed a significant (P < 0.05) increase in the skeletal muscle-specific ubiquitin ligase MAFbx/Atrogin-1 protein and total protein ubiquitination in the gastrocnemius of βGPA versus control mice at the 8-week time point. Our data indicate that feeding juvenile mice a βGPA-supplemented diet significantly reduced whole-body and skeletal muscle growth that was due, at least in part, to an AMPK-independent increase in UDP.

Does occupational stereotyping still exist?

We surveyed 113 college students regarding their views of certain occupational stereotypes. Our results indicated that in this population gender was related to the subjects' views of occupations as either male, female, or neutral, and that the father's primary occupation significantly affected the subjects' views of only one occupation--clinical sociologist. The mother's occupational seemed to have no effect.