Targeting ErbB3 Research Articles

A monoclonal antibody targeting ErbB2 domain III inhibits ErbB2 signaling and suppresses the growth of ErbB2-overexpressing breast tumors.

The anti-ErbB2 antibodies trastuzumab and pertuzumab in combination have recently been approved for the treatment of patients with ErbB2-positive metastatic breast cancer. Pertuzumab, which binds to ErbB2 near the center of domain II, and trastuzumab, which binds to the juxtamembrane region of ErbB2 domain IV, directly interfere with domain II- and domain IV-mediated heterodimerization contacts, respectively. In this study, we report a novel anti-ErbB2 antibody, 3E10, which binds to an epitope in domain III that appears to be located opposite to the dimerization interfaces in domain II and domain IV of ErbB2. Our data show that the 3E10 antibody inhibits ErbB2 heterodimerization via a mechanism that strikingly differs from trastuzumab and pertuzumab. It could be speculated that the 3E10 antibody may affect ErbB2 heterodimerization by causing major conformational changes of ErbB2. Furthermore, 3E10 provides synergistic inhibition of ErbB2 heterodimerization and signaling in combination with either trastuzumab or pertuzumab. The combination of these three anti-ErbB2 antibodies that have complementary mechanisms of action appears to be an extremely potent ErbB2 heterodimerization blocker. Compared with trastuzumab plus pertuzumab, the combination of trastuzumab, pertuzumab and 3E10 provides a more potent blockade of ErbB2 signaling. Consistent with this, trastuzumab plus pertuzumab plus 3E10 results in greater in vitro and in vivo antitumor activity in ErbB2-overexpressing breast tumor models, suggesting its potential use for treating ErbB2-overexpressing breast cancer.

Abstract B14: Molecular characterization of mucinous ovarian carcinoma.

Abstract Mucinous ovarian carcinoma (MOC) is a rare, chemoresistant tumor known to share pathologic features with tumors of the gastrointestinal and pancreaticobiliary tracts. To better understand the genomic and proteomic landscapes of invasive MOCs, we identified somatic mutations and proteins expression in a single institution cohort and compared these results with data from TCGA tumor projects. Twenty-six tumors consistent with primary invasive MOC after expert pathology review and with available paired tumor and normal tissue were identified from institutional databases between July 2001 and July 2012. DNA extracted from FFPE or fresh frozen samples underwent next generation sequencing with a combination of a candidate gene assay (37 genes), the MSK-IMPACT assay (341 genes), transcriptome sequencing, and whole exome sequencing. Copy number alterations were identified using data from the MSK-IMPACT assay, whole exome sequencing or Affymetrix SNP 6.0 arrays. Immunohistochemistry (IHC) was performed using optimized antibodies for six proteins to confirm the diagnosis of MOC (ER, PR, CK7, CK20, CDX-2, PAX8) and seven proteins to correlate with mutation status and copy number alterations (p53, ARID1A[Baf250a], PTEN, PMS2, MSH6, HER2, p16). Mutation data for other TCGA tumor types was obtained from the cBio Cancer Genomics Portal (cbioportal.org). The median age of the cohort was 58 years (range 20-86 years). Most (19/26, 73%) of the tumors were stage I. Somatic TP53 and KRAS mutations were the most common seen and were identified in 18 (69%) cases each, with a co-mutation rate of 50% (13/26). Other commonly mutated genes include ARID1A, PTEN, and PIK3CA. Homozygous deletions of CDKN2A were found in 27% (7/26). ERBB2 alterations were identified in 19% (5/26) and consisted of three amplifications and two mutations. Mutations in at least one potentially targetable gene were identified in 42% (11/26) of tumors. IHC was concordant with sequencing results in 154/182 (85%) of stained cases. Pancreatic, colorectal, lung adenocarcinoma, endometrial, and stomach cancers have the highest frequency of KRAS mutations. Co-mutations of KRAS and TP53 occur most commonly in pancreatic (59%) and colorectal (21%) carcinomas. CDKN2A homozygous deletions are also found at a similar frequency in pancreatic adenocarcinomas (28%). When evaluating the mutation rates of the five most commonly mutated genes in our MOC cohort with colorectal, pancreatic, gastric and high-grade serous ovarian carcinomas (HGSOC) in the TCGA datasets, pancreatic adenocarcinoma showed the most similarity. HGSOC showed little similarity to the MOCs. KRAS and TP53 co-mutation are common in invasive MOCs. Other commonly mutated genes include ARID1A, PTEN, and PIK3CA. Potentially targetable ERBB2 alterations were identified in several cases. Despite anatomic distinctions, the mutational landscape of MOC shares similarities with that of pancreatic adenocarcinoma including frequent CDKN2A deletions and KRAS/TP53 co-mutation. The suggested shared molecular pattern with pancreatic adenocarcinoma offers potential to guide future developmental therapeutics. Citation Format: Brooke Schlappe, Jennifer J. Mueller, Narciso Olvera, Fanny Dao, Cyriac Kandoth, Faina Bogomolniy, Agnes Viale, Kety Huberman, Gouri Nanjangud, Yaser Hussein, Barry Taylor, Robert Soslow, Douglas A. Levine. Molecular characterization of mucinous ovarian carcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B14.

Abstract 2681: Stromal neuregulin-1 promotes adaptive resistance in mutant BRAF melanoma

Abstract RAF inhibitors are first-line treatments for melanomas that harbor BRAF V600E/K mutations; however, patients invariably progress on these targeted therapies. While durable resistance is mediated frequently by stable alterations intrinsic to the tumor cells leading to ERK1/2 pathway reactivation, the compensatory activation of growth factor receptor tyrosine kinases (RTKs) modulates the level of initial response. The composition of the tumor microenvironment likely plays a key role in these compensatory/adaptive responses to targeted inhibitors. In this study, we demonstrate that NRG1 is expressed in fibroblasts, as well as cancer associated fibroblasts (CAFs) isolated from a mutant BRAF melanoma. Fibroblast derived-NRG1 was able to mediate the enhanced ErbB3 pathway activation in RAF-inhibited mutant BRAF melanoma cells. Furthermore, conditioned medium from fibroblasts and CAFs limits RAF inhibitor cytotoxicity in V600 BRAF-harboring melanomas. Importantly, ErbB3 and ErbB2 targeting antibodies partially reverse the protective effects of fibroblast-derived medium on ErbB3 pathway activation and cell growth properties of mutant BRAF-inhibited melanoma cells. Together, these data demonstrate a requirement for a paracrine-produced factor in the tumor microenvironment to promote resistance to RAF inhibitor in mutant BRAF melanoma and reinforce the idea that targeting ErbB3/ErbB2 signaling may improve the efficacy of RAF inhibitors. Citation Format: Claudia Capparelli, Sheera Rosenbaum, Adam Berger, Andrew E. Aplin. Stromal neuregulin-1 promotes adaptive resistance in mutant BRAF melanoma. [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 2681. doi:10.1158/1538-7445.AM2015-2681

The dual targeting of EGFR and ErbB2 with the inhibitor Lapatinib corrects high glucose-induced apoptosis and vascular dysfunction by opposing multiple diabetes-induced signaling changes

The epidermal growth factor receptors, EGFR and EGFR2 (ErbB2), appear important mediators of diabetes-induced vascular dysfunction. We investigated whether targeted dual inhibition of EGFR and ErbB2 with Lapatinib would be effective in treating diabetes-induced vascular dysfunction in a rat model of type 1 diabetes. In streptozotocin-induced diabetes, chronic 4-week oral or acute, ex vivo, administration of Lapatinib prevented the development of vascular dysfunction as indicated by the attenuation of the hyper-reactivity of the diabetic mesenteric vascular bed (MVB) to norephinephrine without correcting hyperglycemia. Chronic in vivo or acute ex vivo Lapatinib treatment also significantly attenuated diabetes-induced increases in phosphorylation of EGFR, ErbB2, ERK1/2, AKT, ROCK2 and IkB-alpha as well as normalized the reduced levels of phosphorylated FOXO3A, and eNOS (Ser1177) in the diabetic MVB. Similar results were observed in vascular smooth muscle cells (VSMCs) cultured in high glucose (25 mM) treated with Lapatinib or small interfering RNA (siRNA) targeting the ErbB2 receptor. Lapatinib also prevented high glucose-induced apoptosis in VSMC. Thus, Lapatinib corrects hyperglycemia-induced apoptosis and vascular dysfunction with concomitant reversal of diabetes or high glucose-induced signaling changes in EGFR/ErbB2 and downstream signaling pathways implying that targeted dual inhibition of EGFR/ErbB2 might be an effective vasculoprotective treatment strategy in diabetic patients.

ErbB-3 activation by NRG-1β sustains growth and promotes vemurafenib resistance in BRAF-V600E colon cancer stem cells (CSCs).

Approximately 5-10% of metastatic colorectal cancers harbor a BRAF-V600E mutation, which is correlated with resistance to EGFR-targeted therapies and worse clinical outcome. Vice versa, targeted inhibition of BRAF-V600E with the selective inhibitor PLX 4032 (Vemurafenib) is severely limited due to feedback re-activation of EGFR in these tumors. Mounting evidence indicates that upregulation of the ErbB-3 signaling axis may occur in response to several targeted therapeutics, including Vemurafenib, and NRG-1β-dependent re-activation of the PI3K/AKT survival pathway has been associated with therapy resistance.Here we show that colon CSCs express, next to EGFR and ErbB-2, also significant amounts of ErbB-3 on their membrane. This expression is functional as NRG-1β strongly induces AKT/PKB and ERK phosphorylation, cell proliferation, clonogenic growth and promotes resistance to Vemurafenib in BRAF-V600E mutant colon CSCs. This resistance was completely dependent on ErbB-3 expression, as evidenced by knockdown of ErbB-3. More importantly, resistance could be alleviated with therapeutic antibody blocking ErbB-3 activation, which impaired NRG-1β-driven AKT/PKB and ERK activation, clonogenic growth in vitro and tumor growth in xenograft models. In conclusion, our findings suggest that targeting ErbB-3 receptors could represent an effective therapeutic approach in BRAF-V600E mutant colon cancer.

Multiple Bacteriophage Selection Strategies for Improved Affinity of a Peptide Targeting ERBB2.

Due to the heterogeneity of ERBB2-expression between tumors and over the course of treatment, a non-invasive molecular imaging agent is needed to accurately detect overall ERBB2 status. Peptides are a highly advantageous platform for molecular imaging, since they have excellent tumor penetration and rapid pharmacokinetics. One limitation of peptides however, is their traditionally low target affinity, and consequently, tumor uptake. The peptide KCCYSL was previously selected from a bacteriophage (phage) display library to bind ERBB2 and did so with moderate affinity of 295 nM. In order to enhance tumor uptake and clinical utility of the peptide, a novel phage microlibrary was created by flanking the parent sequence with random amino acids, followed by reselection using parallel strategies for high affinity and specific ERBB2 binding in an attempt to affinity maturate the peptide. One limitation of traditional phage display selections is difficulty in releasing the highest affinity phages from the target by incubation of acidic buffer. In an attempt to recover high affinity second-generation peptides from the ERBB2 microlibrary, two elution strategies, sonication and target elution, were undertaken. Sonication resulted in an approximately 50-fold enhancement in recovered phage per round of selection in comparison to target elution. Despite the differences in elution efficiency, the affinities of phage-displayed peptides selected from either strategy were relatively similar. Although both selections yielded peptides with significantly improved affinity in comparison to KCCYSL, the improvements were modest, most likely because the parental peptide binding cannot be improved by additional amino acids.

Abstract P6-07-04: Targeting ErbB2 with human PEPD

Abstract ErbB2, also known as Her2 or Neu, belongs to the ErbB family of plasma membrane-bound receptor tyrosine kinases, which also include ErbB1, ErbB3 and ErbB4. ErbB2 is best known for its involvement in human breast cancer. ErbB2 gene amplification occurs in ∼20% of breast cancer, and ErbB2 amplification or overexpression is a strong predictor of poor disease prognosis. ErbB2-targeted therapies, particularly humanized monoclonal antibody trastuzumab (Ttzm) in combination with chemotherapy, have shown considerable clinical efficacy. However, primary and secondary resistance remains a clinical challenge, and Ttzm, produced in mammalian cells, is very expensive. We have found that human prolidase, also known as peptidase D (PEPD) among several other names, binds to ErbB2 with high affinity (Kd = ∼7 nM) and binds as a homodimer (493 amino acids per subunit) to subdomain 3 in the extracellular domain of ErbB2. Each monomer of PEPD binds to one copy of ErbB2. However, PEPD is a weak ErbB1 binder (Kd = ∼5 μM) and does not bind to ErbB3 or ErbB4. PEPD is the first-ever natural ligand of ErbB2, and unlike the other ligands of ErbB receptors, it is devoid of an EGF motif. PEPD has been long known to hydrolyze dipeptides with proline or hydroxylproline at the carboxy terminus, but the dipeptidase activity of PEPD is not involved in ErbB2/ErbB1 modulation. In cells overexpressing ErbB2, where both activated dimers and inactive monomers of ErbB2 exist, as ErbB2 overexpression causes spontaneous dimerization, auto-tyrosine phosphorylation and recruitment and activation of downstream signals, PEPD rapidly binds to ErbB2 homodimers (<∼10 min) and silences the existing ErbB2-SRC signaling, a key oncogenic pathway of ErbB2, by disrupting SRC association with ErbB2. In contrast, PEPD binds to ErbB2 monomers relatively slowly (>∼30 min), but this binding causes ErbB2 dimerization, ErbB2 phosphorylation and downstream signaling. PEPD binding to ErbB2 subsequently causes pronounced ErbB2 depletion, resulting from its internalization and degradation. PEPD also strongly inhibits the DNA synthesis, anchorage-independent growth and invasion of cells that overexpress ErbB2, but has no effect on cells without overexpression of ErbB2. In fact, cells become sensitized to inhibition by PEPD upon achieving stable ErbB2 overexpression. Thus, the overall impact of PEPD on ErbB2 is inhibitory, and PEPD targets cells addicted to ErbB2. In ErbB2-overexpressing cells, at equimolar concentrations, PEPD was more effective than Ttzm in driving ErbB2 depletion, but is weaker than Ttzm in stimulating ErbB2 phosphorylation. In mouse tumor models, PEPD administered by intraperitoneal injection (Monday, Wednesday, Friday) at 0.2-2 mg/kg body weight strongly inhibited the growth of ErbB2-overexpressing tumors, but had no impact on tumors without ErbB2 overexpression, and the PEPD-treated mice showed no adverse effects. Given that the findings described above were made using human PEPD generated in bacteria, there is a distinct possibility that recombinant human PEPD may be a low cost alternative to Ttzm. Further investigation of the antitumor activity of PEPD and its modulation of ErbB2 signaling is warranted. Citation Format: Lu Yang, Yun Li, Arup Bhattacharya, Yuesheng Zhang. Targeting ErbB2 with human PEPD [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-04.

First-in-human study of MM-141: A novel tetravalent monoclonal antibody targeting IGF-1R and ErbB3.

384 Background: MM-141 is a novel tetravalent bispecific monoclonal antibody that binds IGF-1R and ErbB3 and blocks both ligand dependent and independent IGF-1R/ErbB3/PI3K/AKT/mTOR signaling. MM-141 potentiated gemcitabine, nab-paclitaxel, docetaxel, irinotecan, tamoxifen, and everolimus in preclinical models. A multi-arm Phase 1 study is ongoing and the monotherapy dose-escalation portion of the study is completed. Hepatocellular carcinoma (HCC) patients were enrolled to an expansion cohort of Arm A to receive MM-141 as a monotherapy. Another arm of treatment combined MM-141 with gemcitabine and nab-paclitaxel. Methods: This is a Phase 1 dose-escalation study evaluating safety, tolerability, pharmacokinetic (PK), and pharmacodynamic (PD) properties of MM-141 as monotherapy (n=15) and in combination with everolimus (Arm B) or with nab-paclitaxel and gemcitabine (Arm C). Three HCC patients in the Arm A expansion cohort received MM-141 as a monotherapy at a weekly dose of 20 mg/kg. These patients underwent mandatory pre-treatment and optional post-treatment biopsies. Patients in the dose-escalation portion of Arm C received MM-141 at a weekly dose of 12 or 20 mg/kg or a bi-weekly dose of 40 mg/kg in combination with gemcitabine (1000 mg/m2) and nab-paclitaxel (125 mg/m2). Results: 15 patients with advanced solid tumors were enrolled into the dose escalation portion of Arm A. No dose-limiting toxicities were observed at any of the studied doses. The safety, tolerability, PK and PD profile support weekly and bi-weekly MM-141 dosing. The Arm A expansion enrolled 3 patients with sorafenib-refractory HCC. The analysis of pre- and post-treatment biopsies confirmed that IGF-1R and ErbB3 are expressed in patients previously exposed to sorafenib, and their levels are decreased after MM-141 exposure. Arm C, combining MM-141, gemcitabine, and nab-paclitaxel in a “3+3” dose-escalation design is on-going. Conclusions: MM-141 was well tolerated as a monotherapy and translational analysis of pharmacodynamic parameters suggest appropriate target engagement. Combination data with gemcitabine/nab-paclitaxel will be presented and preparations for a randomized Phase 2 study in front-line pancreatic cancer are underway. Clinical trial information: NCT01733004.

Systemic Delivery of Stable siRNA-Encapsulating Lipid Vesicles: Optimization, Biodistribution, and Tumor Suppression

Lipid-based nanoparticles are considered as promising candidates for delivering siRNA into the cytoplasm of targeted cells. However, in vivo efficiency of these nanoparticles is critically dependent on formulation strategies of lipid-siRNA complexes. Adsorption of serum proteins to lipid-siRNA complexes and its charge determine siRNA degradation and serum half-life, thus significantly altering the bioavailability of siRNA. To address these challenges, we developed a formulation comprising dihydroxy cationic lipid, N,N-di-n-hexadecyl-N,N-dihydroxyethylammonium chloride (DHDEAC), cholesterol, and varying concentrations of 1,2-distearoryl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol-2000)] (DSPE-PEG 2000). Using an ethanol dilution method, addition of these lipids to siRNA solution leads to formation of stable and homogeneous population of siRNA-encapsulated vesicles (SEVs). Biodistribution of these SEVs, containing 5 mol % of DSPE-PEG 2000 in xenograft mice, as monitored by live animal imaging and fluorescence microscopy, revealed selective accumulation in the tumor. Remarkably, four intravenous injections of the modified vesicles with equimolar amounts of siRNA targeting ErbB2 and AURKB genes led to significant gene silencing and concomitant tumor suppression in the SK-OV-3 xenograft mouse model. Safety parameters as evaluated by various markers of hepatocellular injury indicated the nontoxic nature of this formulation. These results highlight improved pharmacokinetics and effective in vivo delivery of siRNA by DHDEAC-based vesicles.

ERBB2 Deficiency Alters an E2F-1-Dependent Adaptive Stress Response and Leads to Cardiac Dysfunction

The tyrosine kinase receptor ERBB2 is required for normal development of the heart and is a potent oncogene in breast epithelium. Trastuzumab, a monoclonal antibody targeting ERBB2, improves the survival of breast cancer patients, but cardiac dysfunction is a major side effect of the drug. The molecular mechanisms underlying how ERBB2 regulates cardiac function and why trastuzumab is cardiotoxic remain poorly understood. We show here that ERBB2 hypomorphic mice develop cardiac dysfunction that mimics the side effects observed in patients treated with trastuzumab. We demonstrate that this phenotype is related to the critical role played by ERBB2 in cardiac homeostasis and physiological hypertrophy. Importantly, genetic and therapeutic reduction of ERBB2 activity in mice, as well as ablation of ERBB2 signaling by trastuzumab or siRNAs in human cardiomyocytes, led to the identification of an impaired E2F-1-dependent genetic program critical for the cardiac adaptive stress response. These findings demonstrate the existence of a previously unknown mechanistic link between ERBB2 and E2F-1 transcriptional activity in heart physiology and trastuzumab-induced cardiac dysfunction.

Abstract 5437: Dual targeting of ErbB-2 and ErbB-3: A new potential strategy for the treatment of pancreatic cancer

Abstract Background: Pancreatic cancer (PC) is one of the most lethal cancers and there is an urgent need to find out new therapeutic approaches. Deregulated signaling through ErbB-1 and ErbB-2, members of the epidermal growth factor receptor family, frequently occurs in PC. However, attempts aiming at inhibiting ErbB-1 and ErbB-2 have revealed only a modest impact on disease outcome. A growing body of evidence suggests that ErbB-3 and its ligand NRG-1β are key players in driving oncogenic signaling and resistance to targeted therapy in PC. We have recently developed a novel humanized ErbB-3 antibody, named EV20, which displayed a potent antitumor activity by promoting receptor downregulation in vitro and in vivo. Here we hypothesized that targeting of ErbB-3 with EV20 would enhance the therapeutic effect of ErbB-2 inhibitors in PC. Materials and Methods: Three different PC cell lines (BxPC-3, HPAF II and SW1990) were chosen based on their metastatic origin, genetic background (KRAS status) and responsiveness to erlotinib. The expression of ErbB-1, ErbB-2 and ErbB-3 was analyzed by FACS and WB. The effects of trastuzumab, cetuximab, EV20 and their combinations on NRG-1β-induced activation of the ErbB3/PI3K/Akt axis, cell proliferation, and in vivo tumor growth were evaluated by standard procedures. Results: ErbB-1 was overexpressed by all the cell lines, whereas the expression levels of ErbB-2 and ErbB-3 were moderate in HPAFII cells and low in BxPC-3 and SW1990 cells. NRG-1β was more effective than EGF (an ErbB-1 ligand) in activating ErbB-3 downstream signaling, which was not inhibited by cetuximab, despite a high ErbB-1 expression in the cells. Conversely, inhibition of ErbB-2 and/or ErbB-3 resulted in a marked suppression of NRG-1β-driven Akt activation. Finally, EV20 in combination with trastuzumab exerted a superior antitumor activity compared to single agent alone in terms of cell proliferation and growth of PC xenografts in nude mice. Conclusions: Dual targeting of ErbB-2 and ErbB-3 could represent a newer therapeutic approach in PC. Note: This abstract was not presented at the meeting. Citation Format: Gianluca Sala, Reza Ghasemi, Emily Capone, Ilario Giovanni Rapposelli, Sara Traini, Cosmo Rossi, Pier Giorgio Natali, Stefano Iacobelli. Dual targeting of ErbB-2 and ErbB-3: A new potential strategy for the treatment of pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5437. doi:10.1158/1538-7445.AM2014-5437

Abstract 2611: Function blocking ERBB3 antibody inhibits adaptive response to RAF inhibitor

Abstract ERBB3/HER3 is a member of the EGFR family of receptor tyrosine kinase. Our lab recently showed that treating melanoma cells with the FDAapproved small molecule BRAF inhibitor vemurafenib leads to an increase in ERBB3 signaling when grown in the presence of its ligand neuregulin (NRG1). Here, we show that targeting ERBB3 with a monoclonal antibody inhibits its activation and downstream signaling in the presence of vemurafenib and NRG1. This inhibition of ERBB3 led to a decrease in proliferation and increase in apoptosis in vitro as measured by EdU and AnnexinV/PI staining. Targeting ERBB3 in combination with mutant BRAF in vivo resulted in a delay of tumor re-growth in immune deficient mice compared to targeting mutant BRAF alone. Taken together, these results indicate that targeting ERBB3 in combination with mutant BRAF in melanoma may help enhance the initial effects of vemurafenib in the clinic. Citation Format: Curtis Harrison Kugel, Edward J. Hartsough, Michael A. Davies, Andrew E. Aplin. Function blocking ERBB3 antibody inhibits adaptive response to RAF inhibitor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2611. doi:10.1158/1538-7445.AM2014-2611

Abstract 1390: Interferon-gamma potentiates the targeted phenotypic reversion of erbb2/her2/neu transformed human tumor cells

Abstract Oncogenic erbB2/HER2 is a major transforming determinant of human breast cancer and its amplification is prognostic of poor survival. Monoclonal antibody (mAb)-based therapy to specifically target erbB2/HER2 has been effective in patients with HER2-positive breast cancer; however, some patients do not respond and those who do frequently relapse despite ongoing therapy. The evolution of tumors that resist targeted therapy is complex and involves the emergence of complex transcriptional functions. Snail is overexpressed in recurrent tumors of transgenic HER2/neu mice and snail expression participates in tumor recurrence. Previous studies from our laboratory and others have revealed that targeted therapy requires cooperation with elements of the endogenous immune system for optimal tumor regression activity. The cytokine interferon-gamma (IFN-γ) is relevant to the regression process although the mechanism by which IFN operates on targeted cells remains undefined and the effects of IFN on the transformed cell have not been studied during phenotypic reversion. In the present study, we utilized cell biological and biochemical-based assays to define if targeted therapy could be improved through the addition of IFN-γ and unexpectedly defined a unique mechanism operative to achieve this end. Cell culture model systems were used to examine the co-treatment of erbB2/HER2 targeting with IFN-γ to eliminate issues such as aberrant immune responses, which arise as a consequence of adding IFN-γ to cells. We defined that while mAb targeting of erbB2 reversed the transformed phenotype of HER2-positive breast cancer cells reversion of phenotype was increased upon inclusion of IFN-γ. Co-treatment with the erbB2 mAb and IFN-γ resulted in a greater reduction of snail protein levels compared to either modality alone. Snail degradation was dependent on GSK3-β and active proteasome dependent elimination processes. Furthermore, IFN-γ activated GSK3-β in mAb treated cells to the extent of that observed in cells treated with specific small molecule inhibitors to erbB receptors. Our findings provide a mechanistic explanation as to how to use IFN-γ to optimize mAb-mediated tumor regression. The implication of this study is improvement of targeted efficacy could lead to more comprehensive therapy options that may eliminate tumor recurrence. Citation Format: Edwin Aaron Runkle, Peter Young, Yasuhiro Nagai, Hiromichi Tsuchiya, Hongtao Zhang, Mark I. Greene. Interferon-gamma potentiates the targeted phenotypic reversion of erbb2/her2/neu transformed human tumor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1390. doi:10.1158/1538-7445.AM2014-1390

Abstract 1823: Novel regulation of Jagged1 by ErbB2 in breast cancer: implications for anti-ErbB2 therapy

Abstract We have demonstrated that Notch1 is required for trastuzumab resistance in ErbB2 positive breast cancer. This indicates that ErbB2 suppresses Notch1 in breast cancer and therapeutic intervention targeting ErbB2 might have an unintended consequence which is aberrant up regulation of Notch1 which is a breast oncogene. However, the mechanism of action by which ErbB2 restricts Notch1 activation is unknown. In this current study, we investigated the role of cis- and trans-activation of Notch signaling by Notch ligands which are developmentally conversed to tightly regulate Notch activation. To address this hypothesis, we performed co-culture studies using fibroblasts expressing no Notch ligands or over-expressing human Jagged1 or Deltalike1 and ErbB2 positive breast cancer cells. We performed flow cytometry to isolate breast cancer cells after co-culture and extracted RNA to measure expression of Notch gene targets as a measure of Notch activity. The results showed that trastuzumab, Lapatinib, or ErbB2 knockdown increased overall Notch activition. Similarly, Co-culture with Jagged1-expressing fibroblasts increased overall Notch activation. However, Knocked down of Jagged1 in the breast cancer cells had little effect on ligand-induced Notch activation relieving the possibility of cis-inhibition. In contrast, Jagged1 knocked down abrogated trastuzumab-induced Notch activation in the breast cancer cells. These results suggest that ErbB2 might restrict Notch activation by preventing Jagged1-mediated trans activation of Notch and not by promoting cis-inhibition. Confocal immunofluorescence showed that Jagged1 is localized with Notch1 when ErbB2 is hyperactive but is trafficked to the cell surface in response to trastuzumab. K44ADynamin abrogated Jagged1 expression on the cell surface as measured by IF and surface biotinylation studies. Furthermore, K44ADynamin expression abrogated trastuzumab-induced Notch1 activation. Importantly, we measured growth consequences of Jagged1-mediated Notch activation in response to trastuzumab and found that Jagged1 is necessary for survival of ErbB2 positive breast cancer cells and trastuzumab resistance as measured by cell cycle analysis and Annexin V staining. These results taken together indicate that ErbB2 restricts Notch by limiting Jagged1-mediated trans-activation. Citation Format: Clodia Osipo, Kinnari Pandya, Debra Wyatt. Novel regulation of Jagged1 by ErbB2 in breast cancer: implications for anti-ErbB2 therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1823. doi:10.1158/1538-7445.AM2014-1823

MiR-143 and miR-145 synergistically regulate ERBB3 to suppress cell proliferation and invasion in breast cancer.

IntroductionERBB3, one of the four members of the ErbB family of receptor tyrosine kinases, plays an important role in breast cancer etiology and progression. In the present study, we aimed to identify novel miRNAs that can potentially target ERBB3 and their biological functions.MethodThe expression levels of miR-143/145 and target mRNA were examined by relative quantification RT-PCR, and the expression levels of target protein were detected by Western blot. We used bioinformatic analyses to search for miRNAs that can potentially target ERBB3. Luciferase reporter plasmids were constructed to confirm direct targeting. Furthermore, the biological consequences of the targeting of ERBB3 by miR-143/145 were examined by cell proliferation and invasion assays in vitro and by the mouse xenograft tumor model in vivo.ResultsWe identified an inverse correlation between miR-143/145 levels and ERBB3 protein levels, but not between miR-143/145 levels and ERBB3 mRNA levels, in breast cancer tissue samples. We identified specific targeting sites for miR-143 and miR-145 (miR-143/145) in the 3’-untranslated region (3’-UTR) of the ERBB3 gene and regulate ERBB3 expression. We demonstrated that the repression of ERBB3 by miR-143/145 suppressed the proliferation and invasion of breast cancer cells, and that miR-143/145 showed an anti-tumor effect by negatively regulating ERBB3 in the xenograft mouse model. Interestingly, miR-143 and miR-145 showed a cooperative repression of ERBB3 expression and cell proliferation and invasion in breast cancer cells, such that the effects of the two miRNAs were greater than with either miR-143 or miR-145 alone.ConclusionTaken together, our findings provide the first clues regarding the role of the miR-143/145 cluster as a tumor suppressor in breast cancer through the inhibition of ERBB3 translation. These results also support the idea that different miRNAs in a cluster can synergistically repress a given target mRNA.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-220) contains supplementary material, which is available to authorized users.

A Zebrafish Drug Screen Repositions FDA-Approved Compounds for Radiochemotherapy

The apoptosic response to ionizing radiation (IR) is dependent on functional p53. As up to 50% of tumors harbor mutations in TP53, many cancer types are thought to be resistant to chemoradiation treatments. Small molecules that specifically radiosensitize tumors to IR while maintaining minimal toxicity in normal cells may enhance the efficacy of radiation therapy while minimizing adverse side effects. However, radiosensitization must occur in the context of mutant TP53 in order to target therapeutically resistant tumor cells. To identify novel targeted strategies for restoring radiosensitivity in TP53 mutant tumors, we exploited the high-throughput screening capability of zebrafish to perform a blinded phenotypic radiosensitization screen of 640 FDA-approved compounds. Our screen identified 13 compounds that demonstrate specific radiosensitizing effects in irradiated p53 mutant embryos after 15 Gy IR while showing no toxicity in non-irradiated embryos. Acridine orange staining to label apoptotic or necrotic cells identified 2 compounds that induced cell death specifically in combination with radiation. The putative targets of these candidate radiosensitizers were assembled using a combination of Similarity Ensemble Approach (SEA) searches with Structure Activity Relationship (SAR) analysis. To determine if the compounds identified in fish have relevance to human tumors, they were screened for survival after IR using a resazurin cell viability assay in a panel of cell lines, specifically focusing on HNSCC. Two compounds specifically led to increased cell death in p53 mutant fish after radiation. Compound A is a veterinary antihelminth with multiple analogs that are approved for human use. This compound is particular amenable to target prediction with SEA and SAR, yielding putative targets PIN1, ERBB2, and NMDZ1. Compound B is an aromatase inhibitor whose current indication includes ER-positive breast cancer. Neither compound has been previously indicated as a radiosensitizer and both have shown minimal toxicity to embryos in the absence of radiation. In addition, compound B has showed efficacy as a radiosensitizer in HeLa and CAL27 cell lines. We have identified two candidate radiosensitizers in p53 mutant zebrafish to IR with a large therapeutic window, indicating promising repurposing possibilities. Further study is required to identify the mechanism of action of how these compounds sensitize in the context of TP53 mutation.

Targeting ErbB-2 nuclear localization and function inhibits breast cancer growth and overcomes trastuzumab resistance.

Membrane overexpression of ErbB-2/HER2 receptor tyrosine kinase (membrane ErbB-2 (MErbB-2)) has a critical role in breast cancer (BC). We and others have also shown the role of nuclear ErbB-2 (NErbB-2) in BC, whose presence we identified as a poor prognostic factor in MErbB-2-positive tumors. Current anti-ErbB-2 therapies, as with the antibody trastuzumab (Ttzm), target only MErbB-2. Here, we found that blockade of NErbB-2 action abrogates growth of BC cells, sensitive and resistant to Ttzm, in a scenario in which ErbB-2, ErbB-3 and Akt are phosphorylated, and ErbB-2/ErbB-3 dimers are formed. Also, inhibition of NErbB-2 presence suppresses growth of a preclinical BC model resistant to Ttzm. We showed that at the cyclin D1 promoter, ErbB-2 assembles a transcriptional complex with Stat3 (signal transducer and activator of transcription 3) and ErbB-3, another member of the ErbB family, which reveals the first nuclear function of ErbB-2/ErbB-3 dimer. We identified NErbB-2 as the major proliferation driver in Ttzm-resistant BC, and demonstrated that Ttzm inability to disrupt the Stat3/ErbB-2/ErbB-3 complex underlies its failure to inhibit growth. Furthermore, our results in the clinic revealed that nuclear interaction between ErbB-2 and Stat3 correlates with poor overall survival in primary breast tumors. Our findings challenge the paradigm of anti-ErbB-2 drug design and highlight NErbB-2 as a novel target to overcome Ttzm resistance.

Dual targeting of ErbB-2/ErbB-3 results in enhanced antitumor activity in preclinical models of pancreatic cancer.

ErbB-3 and its ligand NRG-1β are key players in driving oncogenic signaling and resistance to therapy through the activation of the PI3K/Akt pathway. We have recently reported that EV20, a humanized anti-ErbB3 antibody, possesses a marked antitumor activity in a variety of human tumor models, including pancreatic cancer (PC). Here, we report that despite epidermal growth factor receptor overexpression, PC cells are more sensitive to NRG-1β than EGF in terms of Akt activation and cell proliferation. Using stable ErbB-3-knocked down cells and EV20 in combination with trastuzumab, we showed that dual targeting of ErbB-2 and ErbB-3 was necessary to completely abrogate ErbB-3 signaling and to impair cell proliferation. Similarly, enhanced therapeutic efficacy of the antibody combination was seen in xenografts originating from K-Ras-mutated HPAF-II and SW1990 cells, without increasing the toxicity. These results indicate that dual targeting of ErbB-2 and ErbB-3 could represent a new therapeutic approach in PC.

ERBB3 knockdown induces cell cycle arrest and activation of Bak and Bax-dependent apoptosis in colon cancer cells.

ERBB3 is an emerging target for cancer therapy among the EGFR family. Contrary to resistance against EGFR and ERBB2 targeting, the genetic inhibition of ERBB3 results in anti-tumorigenic in HCT116 colon cancer cells harboring constitutively active KRAS and PIK3CA mutations. Still, the anti-tumorigenic molecular mechanism has not been defined. We demonstrated in this study that ERBB3 knockdown resulted in cell cycle arrest and activation of Bak and Bax-dependent apoptosis. Apoptosis was irrelevant to the majority of BH3-only pro-apoptotic proteins and correlated with the transcriptional upregulation of Bak and p53-dependent Bax translocation. Treatment with LY294002, a PI3K inhibitor, resulted in cell cycle arrest without apoptosis and a concomitant down-regulation of cap-dependent translation by the suppression of the PI3K/AKT/mTOR pathway. However, the inhibition of cap-dependent translation by ERBB3 knockdown occurred without altering the PI3K/AKT/mTOR pathway. In addition, ERBB3 knockdown-induced cell cycle arrest was observed in most colon cancer cells but was accompanied by apoptosis in p53 wild-type cells. These results indicate that ERBB3 is a potential target for EGFR- and ERBB2-resistant colon cancer therapy.

Therapeutic targeting of ERBB2 in breast cancer: understanding resistance in the laboratory and combating it in the clinic.

ERBB2 gene amplification occurs in about one quarter of breast carcinomas (BCs) and identifies a distinct clinical subset of BC. The introduction in the clinic of Trastuzumab, a humanized monoclonal antibody (mAb) directed to the ERBB2 extracellular domain, has had a great impact on the therapeutic management of ERBB2+ BC. Yet, not all patients respond to Trastuzumab and resistance develops also among patients that initially benefit from Trastuzumab-based regimens. Pre-clinical studies have discovered several mechanisms through which tumor cells may escape from Trastuzumab-mediated ERBB2 inhibition. These include rewiring of the ErbB signaling network, loss of ERBB2 expression, expression of ERBB2 isoforms refractory to Trastuzumab inhibition, vicarious signaling by non-ErbB tyrosine kinases and constitutive activation of downstream signaling routes, such as the PI3K pathway. While the relative contribution of each of these mechanisms to establishing Trastuzumab resistance in the clinical setting is not fully understood, much attention has been focused on abating resistance by achieving complete blockade of ERBB2-containing dimers. This approach, propelled by the development of novel anti-ERBB2 therapeutics, has led to the recent approval of Lapatinib, Pertuzumab and T-DM1 as additional anti-ERBB2 therapeutics in BC. However, full success is far from being achieved and resistance to ERBB2 targeting remains a relevant problem in the clinical management of BC. Herein, we provide an overview of biological and molecular bases underpinning resistance to ERBB2 therapeutics in BC, discuss outstanding issues in the field of ERBB2 therapeutic targeting and elaborate on future directions of translational research on ERBB2+ breast cancer.