The Epidermal Growth Factor Receptor (EGFR) is frequently mutated and overexpressed in metastatic cancer. Although EGFR is a transmembrane tyrosine kinase localized to the basolateral membrane in normal epithelium, it is frequently found intracellularly localized in transformed cells. We have previously demonstrated the epithelial adaptor protein mucin 1 (MUC1) alters trafficking of EGFR, inhibiting its degradation and promoting its translocation to the nucleus, where it can directly modulate gene transcription. Here, we demonstrate that MUC1 promotes the retention of EGF-bound EGFR in Early Endosome Antigen1 (EEA1)-positive vesicles while preventing its trafficking to the lysosome. These events result in the accumulation of endosomal vesicles harboring active receptor throughout the cell and a reorganization of the actin cytoskeleton. EGF-dependent cell migration and filopodia formation is reliant upon this altered trafficking, and can be prevented by blocking retrograde trafficking. Together, these results indicate that intracellular EGFR may play an essential role in cancer metastasis and a potential mechanism for the failure of therapeutic antibodies in EGFR-driven metastatic breast cancer.

Background The human epidermal growth factor receptor (HER) family of transmembrane tyrosine kinases is overexpressed and correlates with poor prognosis and decreased survival in many cancers. The receptor family has been therapeutically targeted, yet tyrosine kinase inhibitors (TKIs) do not inhibit kinase-independent functions and antibody-based targeting does not affect internalized receptors. We have previously demonstrated that a peptide mimicking the internal juxtamembrane domain of HER1 (EGFR; EJ1) promotes the formation of non-functional HER dimers that inhibit kinase-dependent and kinase-independent functions of HER1 (ERBB1/EGFR), HER2 (ERBB2) and HER3 (ERBB3). Despite inducing rapid HER-dependent cell death in vitro, EJ1 peptides are rapidly cleared in vivo, limiting their efficacy. Method To stabilize EJ1 activity, hydrocarbon staples (SAH) were added to the active peptide (SAH-EJ1), resulting in a 7.2-fold increase in efficacy and decreased in vivo clearance. Viability assays were performed across HER1 and HER2 expressing cell lines, therapeutic-resistant breast cancer cells, clinically relevant HER1-mutated lung cancer cells, and patient-derived glioblastoma cells, in all cases demonstrating improved efficacy over standard of care pan-HER therapeutics. Tumor burden studies were also performed in lung, glioblastoma, and inflammatory breast cancer mouse models, evaluating tumor growth and overall survival. Results When injected into mouse models of basal-like and inflammatory breast cancers, EGFRvIII-driven glioblastoma, and lung adenocarcinoma with Erlotinib resistance, tumor growth is inhibited and overall survival is extended. Studies evaluating the toxicity of SAH-EJ1 also demonstrate a broad therapeutic window. Conclusions Taken together, these data indicate that SAH-EJ1 may be an effective therapeutic for HER-driven cancers with the potential to eliminate triple negative inflammatory breast cancer. Electronic supplementary material The online version of this article (10.1186/s12967-019-1939-7) contains supplementary material, which is available to authorized users.

Retrograde trafficking is a well-regulated, multi-component pathway that can result in endosomal trafficking to the trans-Golgi network, the perinuclear space, or the nucleus. Either clathrin or the retromer complex can travel with proteins endocytosed from the plasma membrane, guided by Rabs (including 5, 6, 7, 9, 22A), interacting with a host of sorting nexin proteins, and fusing with Golgi-specific anchors to allow transport of activated receptor tyrosine kinases to a potential end within the nucleus. Amplification in these constituents is common in cancer, leading to increased retrotranslocation and a reduction in degradation of receptor tyrosine kinases, an event highly associated with cancer metastasis. Here, we review the role of retrograde trafficking in altering transmembrane receptor localization and activity and the relationship to metastasis, focusing on all four members of the ErbB family, with comparison to other receptor tyrosine kinases including the insulin receptor and fibroblast growth factor receptor, as well as other transmembrane proteins dysregulated in metastasis. By examining how these receptors are being alternatively trafficked and the cancer-associated events resulting from this process, we hope to identify novel therapeutic targets.

We have previously demonstrated that Llgl1 loss results in a gain of mesenchymal phenotypes and a loss of apicobasal and planar polarity. We now demonstrate that these changes represent a fundamental shift in cellular phenotype. Llgl1 regulates the expression of multiple cell identity markers, including CD44, CD49f, and CD24, and the nuclear translocation of TAZ and Slug. Cells lacking Llgl1 form mammospheres, where survival and transplantability is dependent upon the Epidermal Growth Factor Receptor (EGFR). Additionally, Llgl1 loss allows cells to grow in soft-agar and maintain prolonged survival as orthotopic transplants in NOD-SCIDmice. Lineage tracing and wound healing experiments demonstrate that mammosphere survival is due to enhanced EGF-dependent migration. The loss of Llgl1 drives EGFR mislocalization and an EGFR mislocalization point mutation (P667A) drives these same phenotypes, including activation of AKT and TAZ nuclear translocation. Together, these data indicate that the loss of Llgl1 results in EGFR mislocalization, promoting pre-neoplastic changes.

BACKGROUND: Metastatic disease in ovarian cancer is difficult to treat and patients often exhaust standard-of-care regimens. To gain a better understanding of potential treatments, genomic data can be used. However, the interpretation of the genomic data for ovarian cancer is challenging given complex mutation patterns and the absence of recurrent druggable alterations beyond DNA repair deficiency. Here we present the first CLIA certified high-throughput functional assay employing organoid cultures derived from primary patient specimens to directly aid oncologists for personalized treatment selection in combination with genomic data (P.A.R.I.S® Assay, SEngine Precision Medicine, Seattle, WA). EXPERIMENTAL PROCEDURES: Organoids are exposed to a library of 123 clinically relevant drugs. The library was developed to include chemotherapies and FDA approved drugs currently used in the clinic, as well as promising drugs undergoing clinical trials. Compounds are evaluated at a multi-dose response curve and ranked by SPM™ score, which weighs both the sensitivity (degree of cell death) and specificity, which compares the response of the patient's tumor cells to the drug relative to all prior patients. In addition to single agent screens, optimal combinations can also be tested. The results are further integrated with genomic data when available, and drug-responses are reported to the clinician. SEngine has performed >200 drug screens across >20 different tumor types and established high reproducibility of the high-throughput platform. Ovarian samples were derived from either ascites or biopsies. RESULTS: Of the 7 samples directly derived from patients, 1 was from ascites, 4 were from biopsies or surgical excisions, and 2 had both. In addition, 13 cell lines were screened with the SEngine drug library. While every patient exhibited a unique pattern of response consistent with the heterogeneity of the complex genetic landscape of ovarian cancer, sensitivities for certain drugs such as HDAC, PI3K and tyrosine-kinase inhibitors were frequently found. Several n=1 cases will be presented to highlight correlations with retrospective clinical responses as well as with genomic alterations. These results highlight how genomic data and functional testing can be combined to optimize personalized cancer care. To identify optimal drug combinations with PARP inhibitors, we have performed an unbiased screen where patient derived ovarian cancer cell lines were challenged with SEngine drug library in the presence of rucaparib. The screen indicated multiple drugs, such as bromodomain, BCL2 and cyclin dependent kinase (CDK) inhibitors as well as dasatinib as potential sensitizers to rucaparib. Confirmation of these results in additional patient derived organoids and PDX models are in progress. IMPACT: We developed a robust ex vivo screening platform to objectively quantify patient specific sensitivity to a panel of more than 123 oncology drugs and potential novel combinations. SEngine is compiling a registry capturing clinical data, outcome following the P.A.R.I.S® test, and genomic data. Combining the power of high-throughput technology and organoid isolation with genomic data will enable the rapid selection of optimal individualized therapies as single agents or in combination and guide design of future clinical trials. Citation Format: Franz X Schaub, Sabrina Maisel, Reid Shaw, Rachele Rosati, Caroline Bridgwater, Michael Churchill, Robert Diaz, Stephanie Tatem Murphy, Shalini Pereira, Christopher Kemp, VK Gadi, and Carla Grandori. A CLIA-CERTIFIED HIGH-THROUGHPUT DRUG SCREENING PLATFORM FOR OVARIAN CANCER TO INFORM PERSONALIZED CANCER CARE AND DISCOVER NOVEL COMBINATIONS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-051.

The Epidermal Growth Factor Receptor family of transmembrane tyrosine kinases (ErbB) is over-expressed, correlates with poor prognosis and negatively correlates with disease free survival in many cancer types.  EGFR, HER2 and ErbB3 are known to be highly expressed and active, and have been targeted by both kinase inhibitors and monoclonal antibodies, both with disappointing results.  Importantly, though, these therapeutics only target either a single receptor or the kinase domain alone. It is well known that these receptors function as heterodimers, and blocking of a single receptor will only promote the hetero-dimerization of the remaining family members. Furthermore, while the tyrosine kinase activity of these receptors is well known, less appreciated are the kinase-independent mechanisms by which they drive cancer progression. These include the modulation of calcium signaling and mitochondrial and nuclear translocation and activity as transcriptional co-factors.  The highly conserved juxta-membrane domain (JD) of the ErbB receptors regulates these kinase-independent functions, as well as receptor homo- and hetero-dimerization.   Upon ligand binding, the JD forms anti-parallel dimers between the receptors, resulting in receptor dimerization and intracellular trafficking. These protein-protein interactions result in cell growth, survival, migration and invasion.             We have previously shown that peptides mimicking this JD can act in a dominant-negative fashion, promoting the formation of non-functional ErbB dimers (consisting of EGFR, HER2 and ErbB3) that induce rapid, ErbB-dependent cell death.  Using Cell Penetrating Peptides synthesized in tandem with the JD, these peptides (called EJ1) rapidly cross the plasma membrane, bind the ErbB receptors, and induce cell death in cell lines and PDX lines grown in culture.  Death results from a combination of apoptotic and necrotic mechanisms, due to inactivation of mitochondrial function and calcium signaling (as well as kinase inhibition).  Although EJ1 peptides display rapid ErbB-dependent cell death in vitro, they are rapidly cleared in vivo, limiting their efficacy.  To stabilize in vivo activity, the active peptide (which is an alpha-helix) was stabilized with hydrocarbon staples. Based on this, we hypothesized that SAH-EJ1 would be an effective targeted therapeutic for the treatment of ErbB-dependent cancer. We therefore tested SAH-EJ1 in 3 different ErbB-dependent models of cancer, including EGFRvIII-driven glioblastoma, a PDX model of basal-like breast cancer with EGFR and ErbB3 amplification, and a PDX model of lung cancer with EGFR kinase domain mutations driven by Erlotinib treatment. In each of these models, substantial inhibition of tumor growth was observed, as well as extended survival. Citation Format: Joyce A. Schroeder, Sabrina Maisel, Derrick Broka. Pan-ERBB inhibitor blocks tumor growth and metastasis [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 1346. doi:10.1158/1538-7445.AM2017-1346