ErbB2-positive Breast Cancer Cells Research Articles

SON is an essential RNA splicing factor promoting ErbB2 and ErbB3 expression in breast cancer.

In breast cancer, ErbB receptors play a critical role, and overcoming drug resistance remains a major challenge in the clinic. However, intricate regulatory mechanisms of ErbB family genes are poorly understood. Here, we demonstrate SON as an ErbB-regulatory splicing factor and a novel therapeutic target for ErbB-positive breast cancer. SON and ErbB expression analyses using public database, patient tissue microarray, and cell lines were performed. SON knockdown assessed its impact on cell proliferation, apoptosis, kinase phosphorylation, RNA splicing, and in vivo tumour growth. RNA immunoprecipitation was performed to measure SON binding. SON is highly expressed in ErbB2-positive breast cancer patient samples, inversely correlating with patient survival. SON knockdown induced intron retention in selective splice sites within ErbB2 and ErbB3 transcripts, impairing effective RNA splicing and reducing protein expression. SON disruption suppressed downstream kinase signalling of ErbB2/3, including the Akt, p38, and JNK pathways, with increased vulnerability in ErbB2-positive breast cancer cells compared to ErbB2-negative cells. SON silencing in ErbB2-positive breast cancer xenografts led to tumour regression in vivo. We identified SON as a novel RNA splicing factor that plays a critical role in regulating ErbB2/3 expression, suggesting SON is an ideal therapeutic target in ErbB2-positive breast cancers.

Abstract 203: Promotion of metastasis of ERBB2-positive breast cancer by mesenchymal stem cells via exosomes-mediated activation of ERBB2/ERBB3→PI3K/Akt singaling pathway

Abstract Elevated expression of ERBB3 receptor correlates with increased distant metastasis of breast cancers with amplification and/or overexpression of ERBB2 (HER2/neu), which the underlying molecular mechanism remains unclear. In recent years, cumulative studies have demonstrated that mesenchymal stem cells (MSCs), one of the important cellular components in tumor microenvironment, play important roles in multiple hallmarks of cancer including invasion and metastasis. However, its role in metastasis of ERBB2-positive breast cancer as well as the precise mechanisms are largely unrevealed. In our current study, we found that co-culture with MSCs or treatment with exosomes derived from MSCs can significantly promote the epithelial-mesenchymal transition (EMT), migration and invasion of ERBB2-positive breast cancer cells. MSCs exhibited significantly higher expression of NRG-1, a known ligand of ERBB3, as compared with ERBB2-positive breast cancer cells. The presence of NRG-1 in exosomes derived from MSCs was also evidenced. Mechanistically, co-culture with MSCs or treatment with exosomes derived from MSCs induced upregulation of ZEB1 and Slug via activation of downstream PI3K/Akt singaling to promote EMT of ERBB2-positive breast cancer cells. In addition, the expression of MMP2 was also upregulated by treatment with MSCs-derived exosomes, which enhanced the migration and invasion of ERBB2-positive breast cancer cells simultaneously. Interestingly, our study further demonstrated that treatment with MSCs-derived exosomes could significantly downregulate the expression of PTEN, the key negative regulator of PI3K/Akt singaling, via transferring three PTEN-targeting miRNAs (miR-21-5p, miR-23a-3p, and miR-148a-3p). Taken together, we presented here that MSCs may, on the one hand, directly activate the ERBB2/ERBB3→PI3K/Akt signaling pathway in ERBB2-positive breast cancer cells through the expression and secretion of NRG-1 via exosomes. Meanwhile, miR-21-5p, miR-23a-3p, and miR-148a-3p targeted delivery by exosomes specifically downregulated the expression of PETN, thus reliefs the negative regulation of PI3K/Akt signaling in ERBB2-positive breast cancer cells. These effects of MSCs act in concert to promote the metastasis of ERBB2-positive breast cancer. Our study lays a theoretical foundation and preliminary experimental basis for the development of novel combined therapies for patient with ERBB2-positive breast cancer through co-targeting MSC-derived NRG-1 and miR-21-5p, miR23a-3p, miR148a-3p/PTEN axis in tumor microenvironment in the future. Citation Format: Yating Wu, Li Chen, Yue Cao, Qinfeng Huang, Huimin Niu, Xiaofeng Lai, Meng Zhao, Huihui Yan, Hui Lyu, Bolin Liu, Shenghang Zhang, Shuiliang Wang. Promotion of metastasis of ERBB2-positive breast cancer by mesenchymal stem cells via exosomes-mediated activation of ERBB2/ERBB3→PI3K/Akt singaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 203.

CAR-mediated targeting of NK cells overcomes tumor immune escape caused by ICAM-1 downregulation

BackgroundThe antitumor activity of natural killer (NK) cells can be enhanced by specific targeting with therapeutic antibodies that trigger antibody-dependent cell-mediated cytotoxicity (ADCC) or by genetic engineering to express chimeric...

Effect of Calcitriol in Inhibiting the Cancer Cell Growth and Promoting Apoptosis in ErbB2-positive Breast Cancer Cells.

Targeted therapies, specifically ErbB family tyrosine kinase inhibitors, have demonstrated potential for improving outcomes in patients with ErbB2-positive breast cancer. Despite their effectiveness, these therapies are associated with limitations, including high costs, side effects, drug resistance, lack of specificity, and toxicity. To overcome these challenges, drug repurposing has emerged as a promising strategy in breast cancer treatment. The aim of this investigation was to assess the influence of calcitriol on breast cancer cell lines expressing ErbB2 and comparing its effects with the conventional treatment, neratinib. We employed an MTT test to determine cell viability and utilized staining techniques to assess cell apoptosis. Flow cytometry was used to evaluate cell cycle arrest, while a scratch wound healing test was performed to examine cancer cell migration ability. Additionally, gene expression studies were conducted for calcitriol and neratinib to support our hypothesis regarding the ErbB2 gene. The repurposing of calcitriol demonstrated enhanced efficacy in suppressing cancer cell growth in ErbB2- positive breast cancer. Proportionally, calcitriol significantly reduced the viability of SK-BR-3 cells, similar to neratinib. Furthermore, calcitriol exhibited significant cytotoxicity against neratinib and substantially reduced breast cancer cell growth. These findings were corroborated by the wound healing assay, cell cycle arrest analysis, and gene expression studies, demonstrating comparable efficacy to the standard treatment, neratinib. The findings from this investigation offer compelling proof that highlights the promising role of calcitriol as an adjuvant drug with antiproliferative and antitumoral effects in the management of ErbB2-positive breast carcinoma patients. Therefore, we recommend further evaluation of calcitriol in clinical settings, particularly for the treatment of ErbB2-positive breast cancer, as it shows promise as a valuable therapeutic option.

ErbB2/Her2-dependent downregulation of a cell death-promoting protein BLNK in breast cancer cells is required for 3D breast tumor growth

A significant proportion of breast cancers are driven by ErbB2/Her2 oncoprotein that they overexpress. These malignancies are typically treated with various ErbB2-targeted drugs, but many such cancers develop resistance to these agents and become incurable. Conceivably, treatment of ErbB2-positive cancers could be facilitated by use of agents blocking oncogenic signaling mechanisms downstream of ErbB2. However, current understanding of these mechanisms is limited. The ability of solid tumor cells to resist anoikis, cell death triggered by cell detachment from the extracellular matrix (ECM), is thought to be critical for 3D tumor growth. In an effort to understand the mechanisms of ErbB2-driven breast cancer cell anoikis resistance we found that detachment of non-malignant breast epithelial cells from the ECM upregulates a cell death-promoting tumor suppressor adapter protein BLNK and that ErbB2 blocks this upregulation by reducing tumor cell levels of transcription factor IRF6. We further observed that trastuzumab, a therapeutic anti-ErbB2 antibody, upregulates BLNK in human trastuzumab-sensitive but not trastuzumab-resistant ErbB2-positive breast cancer cells. Moreover, we established that BLNK promotes anoikis by activating p38 MAP kinase and that ErbB2-dependent BLNK downregulation blocks breast cancer cell anoikis. In search for pharmacological approaches allowing to upregulate BLNK in tumor cells we found that clinically approved proteasome inhibitor bortezomib upregulates IRF6 and BLNK in human breast cancer cells and inhibits their 3D growth in a BLNK-dependent manner. In addition, we found that BLNK upregulation in human ErbB2-positive breast cancer cells blocks their ability to form tumors in mice. Furthermore, we used publicly available data on mRNA levels in multiple breast cancers to demonstrate that increased BLNK mRNA levels correlate with increased relapse-free survival in a cohort of approximately 400 patients with ErbB2-positive breast cancer. In summary, we discovered a novel mechanism of ErbB2-driven 3D breast tumor growth mediated by ErbB2-dependent BLNK downregulation.

Tumor levels of the mediators of ErbB2-driven anoikis resistance correlate with breast cancer relapse in patients receiving trastuzumab-based therapies.

Patients with ErbB2/Her2 oncoprotein-positive breast cancers often receive neoadjuvant therapies (NATs) containing the anti-ErbB2 antibody trastuzumab. Tumors that are still present after NATs are resected, and patients continue receiving trastuzumab. These cancers are associated with high relapse risk. Whether relapse will occur cannot be presently reliably predicted. The ability to make such predictions could improve disease management. We found previously that ErbB2 blocks breast tumor cell anoikis, apoptosis induced by cell detachment from the extracellular matrix, by downregulating the pro-apoptotic protein Irf6 and upregulating the anti-apoptotic protein Epidermal Growth Factor Receptor (EGFR) in the cells and, thus, promotes their three-dimensional growth. We now tested whether tumor levels of these proteins before and after NATs correlate with patients' relapse-free survival (RFS) and overall survival (OS). We selected archival breast tumor samples collected from 37 women with ErbB2-positive stages II and III breast cancer before and after NATs. We used immunohistochemistry to test whether levels of the indicated proteins in respective tumors correlate with RFS and OS. We observed that the presence of high Irf6 levels in the tumors following NATs correlated with reduced RFS and OS. Perhaps not by coincidence, we noticed that trastuzumab-sensitive ErbB2-positive breast cancer cells selected for the ability to overproduce exogenous Irf6 in culture acquired trastuzumab resistance. Finally, EGFR presence in patients' tumors before or after NATs was associated with decreased RFS and OS. This study could help identify patients with ErbB2-positive tumors that are at increased risk of disease relapse following NATs.

Erb-b2 Receptor Tyrosine Kinase 2 (ERBB2) Promotes ATG12-Dependent Autophagy Contributing to Treatment Resistance of Breast Cancer Cells

Simple SummaryExpression of the tyrosine kinase receptor ERBB2 in cancer cells leads to drug resistance. Autophagy, a “self-eating” process inside the cell, is a mechanism for drug resistance in cancer cells. It has been shown that ERBB2 activation leads to increased autophagy in breast cancer cells, but the underlying mechanisms remains unclear. In this study, we demonstrated that ERBB2 promotes autophagy by increasing the protein levels of the autophagy gene ATG12 (autophagy-related 12), contributing to the resistance of breast cancer cells to chemotherapy drugs or ERBB2-targeted antibody treatments. We further showed that ATG12 expression in breast tumors containing ERBB2 correlated with a worse patient survival outcome. Finally, lapatinib is an inhibitor for both EGFR and ERBB2 tyrosine kinases in the EGFR protein family and promotes autophagy in cells containing only EGFR but inhibits autophagy in cells containing only ERBB2. Taken together, this suggests that ERBB2 promotes autophagy through upregulation of ATG12.The epidermal growth factor receptor (EGFR) family member erb-b2 receptor tyrosine kinase 2 (ERBB2) is overexpressed in many types of cancers leading to (radio- and chemotherapy) treatment resistance, whereas the underlying mechanisms are still unclear. Autophagy is known to contribute to cancer treatment resistance. In this study, we demonstrate that ERBB2 increases the expression of different autophagy genes including ATG12 (autophagy-related 12) and promotes ATG12-dependent autophagy. We clarify that lapatinib, a dual inhibitor for EGFR and ERBB2, promoted autophagy in cells expressing only EGFR but inhibited autophagy in cells expressing only ERBB2. Furthermore, breast cancer database analysis of 35 genes in the canonical autophagy pathway shows that the upregulation of ATG12 and MAP1LC3B is associated with a low relapse-free survival probability of patients with ERBB2-positive breast tumors following treatments. Downregulation of ERBB2 or ATG12 increased cell death induced by chemotherapy drugs in ERBB2-positive breast cancer cells, whereas upregulation of ERBB2 or ATG12 decreased the cell death in ERBB2-negative breast cancer cells. Finally, ERBB2 antibody treatment led to reduced expression of ATG12 and autophagy inhibition increasing drug or starvation-induced cell death in ERBB2-positive breast cancer cells. Taken together, this study provides a novel approach for the treatment of ERBB2-positive breast cancer by targeting ATG12-dependent autophagy.

Inability of granule polarization by NK cells defines tumor resistance and can be overcome by CAR or ADCC mediated targeting

BackgroundOn encountering a susceptible target, natural killer (NK) cells mediate cytotoxicity through highly regulated steps of directed degranulation. Cytotoxic granules converge at the microtubule organizing center and are polarized toward...

DEPTOR stabilizes ErbB2 to promote the proliferation and survival of ErbB2-positive breast cancer cells.

Rationale: Dysregulation of the PI3K/AKT/mTOR pathway occurs frequently in cancers, providing an attractive therapeutic target for anticancer treatments. DEPTOR plays essential roles in regulation of cell proliferation and survival by directly modulating mTOR activity. However, whether DEPTOR regulates the growth of ErbB2-positive breast cancer cells remains unknown.Methods: DEPTOR expression was determined by TCGA data analysis and immunohistochemistry of human breast tissue microarrays. The membrane localization of DEPTOR was demonstrated by immunofluorescence and subcellular fractionation. The interaction of DEPTOR with ErbB2 was determined by immunoprecipitation. Furthermore, the biological significance of this interaction was assessed by ATPlite cell growth, clonogenic survival, and flow cytometry-based apoptosis assays.Results: DEPTOR promoted the proliferation and survival of ErbB2-positive breast cancer cells by directly interacting with and stabilizing ErbB2. Specifically, DEPTOR translocates to cell membrane and interacts with ErbB2 to disrupt ErbB2 polyubiquitination and degradation promoted by β-TrCP, an E3 ubiquitin ligase. DEPTOR knockdown destabilizes ErbB2 by shortening its protein half-life to inactivate ErbB2-PI3K-AKT-mTOR signaling, leading to the suppression of cell proliferation and survival by inducing apoptosis. Ectopic expression of a constitutively active ErbB2 mutant completely rescued the reduction in cell proliferation and survival by DEPTOR knockdown. Importantly, DEPTOR expression is increased in human breast cancer tissues and its overexpression correlates with poor patient survival. Moreover, DEPTOR is located on the cell membrane in ErbB2-positive breast cancer tissues, but not in tumor-adjacent normal tissues, indicating that DEPTOR may contribute to the oncogenic characteristics of ErbB2.Conclusions: Our study reveals a novel mechanism by which DEPTOR promotes breast cancer cell proliferation and survival by stabilizing ErbB2.

Trastuzumab-induced upregulation of a protein set in extracellular vesicles emitted by ErbB2-positive breast cancer cells correlates with their trastuzumab sensitivity

BackgroundErbB2/HER2 oncoprotein often drives breast cancers (BCs) which are treated with the anti-ErbB2 antibody trastuzumab. The efficacy of trastuzumab-based metastatic BC therapies is routinely assessed by imaging studies. Trastuzumab typically becomes ineffective in the case of this disease and is then replaced by other drugs. Biomarkers of BC trastuzumab response could allow imaging studies and the switch to other drugs to occur earlier than is now possible. Moreover, bone-only BC metastases can be hard to measure, and biomarkers of their trastuzumab response could facilitate further treatment decisions. Such biomarkers are presently unavailable. In this study, we searched for proteins whose levels in BC cell-emitted extracellular vesicles (EVs) potentially correlate with BC trastuzumab sensitivity.MethodsWe isolated EVs from cultured trastuzumab-sensitive and trastuzumab-resistant human BC cells before and after trastuzumab treatment and characterized these EVs by nanoparticle tracking analysis and electron microscopy. We found previously that ErbB2 drives BC by downregulating a pro-apoptotic protein PERP. We now tested whether trastuzumab-induced PERP upregulation in EVs emitted by cultured human BC cells correlates with their trastuzumab sensitivity. We also used mass spectrometry to search for additional proteins whose levels in such EVs reflect BC cell trastuzumab sensitivity. Once we identified proteins whose EV levels correlate with this sensitivity in culture, we explored the feasibility of testing whether their levels in the blood EVs of trastuzumab-treated metastatic BC patients correlate with patients’ response to trastuzumab-based treatments.ResultsWe found that neither trastuzumab nor acquisition of trastuzumab resistance by BC cells affects the size or morphology of EVs emitted by cultured BC cells. We established that EV levels of proteins PERP, GNAS2, GNA13, ITB1, and RAB10 correlate with BC cell trastuzumab response. Moreover, these proteins were upregulated during trastuzumab-based therapies in the blood EVs of a pilot cohort of metastatic BC patients that benefited from these therapies but not in those derived from patients that failed such treatments.ConclusionsUpregulation of a protein set in EVs derived from cultured breast tumor cells correlates with tumor cell trastuzumab sensitivity. It is feasible to further evaluate these proteins as biomarkers of metastatic BC trastuzumab response.

Live cell imaging of lytic granule motility in anti-ErbB2 CAR NK cells and FcR NK cells plus Herceptin towards ErbB2+ breast cancer cells

Background & Aim Upon encountering a susceptible target, NK cells mediate directed cytotoxicity by exocytosis of lytic effector molecules such as perforin and granzymes. The steps leading to NK cell granule exocytosis are highly regulated. Granule exocytosis is preceded by convergence of granules to the microtubule organizing center (MTOC) and subsequent polarization of the MTOC and granules to the immunological synapse (IS). In case of antibody-dependent cell-mediated cytotoxicity (ADCC), it has been shown that signaling through the Fc receptor is critical to polarize MTOC and granules to the IS with otherwise resistant targets. Methods, Results & Conclusion Here we used spinning disk confocal microscopy for live cell imaging to analyze granule-mediated NK cell cytotoxicity in ErbB2-targeted CAR expressing NK-92 cells (NK-92/5.28.z) and research-grade high affinity FcR expressing NK-92 cells plus Herceptin™ towards ErbB2-positive breast cancer cells (MDA-MB-453), which are resistant to parental NK-92. Interestingly, unmodified NK-92 cells in combination with MDA-MB-453 cells showed granule convergence to the MTOC, but failed to polarize MTOC and granules to the IS. In contrast, retargeting by either CAR or mAb/FcR towards the ErbB2 antigen on MDA-MB-453 enabled granule polarization to the IS resulting in highly effective cytotoxicity. Granule polarization was rapid in both the CAR and high affinity FcR expressing NK-92 cells after cell-cell contact was initiated. These observations suggest that retargeting of NK-92 cells by either transgenic CAR or high affinity FcR expression in combination with tumor-specific antibodies confers tumor cell lysis by enabling the otherwise impaired MTOC and granule polarization to the IS which resembles the physiological exocytosis cascade observed in naturally occurring ADCC.

The deubiquitylase USP2 maintains ErbB2 abundance via counteracting endocytic degradation and represents a therapeutic target in ErbB2-positive breast cancer

ErbB2 overexpression identifies a subclass of breast cancer as ErbB2-positive that is frequently associated with poor prognosis. Current ErbB2-targeted therapies have profoundly improved patient outcomes, but mutations occurring in ErbB2 have been shown to confer drug resistance. Induction of ErbB2 degradation was proposed as an intriguing strategy to battle with ErbB2-positive breast cancer and reduced mutation-incurred drug resistance. Although multiple HSP90 inhibitors have been demonstrated to effectively trigger ErbB2 degradation, none succeeded in the clinical evaluations. To develop novel ErbB2-targeting strategies, we investigated the endocytic degradation and reversible ubiquitylation of ErbB2 in breast cancer. In this study, we reveal that HSP90 inhibition leads to efficient ubiquitylation and endocytic degradation of ErbB2 through the canonical endo-lysosomal route. USP2 associates with internalized ErbB2 and prevents its lysosomal sorting and degradation via exerting deubiquitylase activity. Accordingly, the USP2 inhibitor ML364 is capable of inducing ErbB2 ubiquitylation and accelerating its turnover. ML364 potentiates the pro-degradation effects of HSP90 inhibitors on ErbB2 and hence sensitizes ErbB2-positive breast cancer cells to HSP90 inhibition. The combination of USP2 and HSP90 inhibitors effectively restrains ErbB2-positive breast cancer xenograft growth in vivo. Based on these observations, we conclude that USP2 safeguards ErbB2 surface levels by antagonizing its ubiquitylation-mediated endocytic degradation, which can be exploited to design novel therapeutic strategies against ErbB2-driven malignancies as combinatorial treatment with HSP90 inhibitors.

Dissecting the Shared and Context-Dependent Pathways Mediated by the p140Cap Adaptor Protein in Cancer and in Neurons.

The p140Cap adaptor protein is a scaffold molecule physiologically expressed in few epithelial tissues, such as the mammary gland, and in differentiated neurons. While the role of p140Cap in mammary gland epithelia is not still understood, we already know that a significant subset of breast cancers express p140Cap. In the subgroup of ERBB2-amplified breast cancers, a high p140Cap status predicts a significantly lower probability of developing a distant event and a clear difference in survival. p140Cap is causal in dampening ERBB2-positive tumor cell progression, impairing tumor onset and growth, and counteracting epithelial mesenchymal transition, resulting in decreased metastasis formation. Since only a few p140Cap interacting proteins have been identified in breast cancer and the molecular complexes and pathways underlying the cancer function of p140Cap are largely unknown, we generated a p140Cap interactome from ERBB2-positive breast cancer cells, identifying cancer specific components and those shared with the synaptic interactome. We identified 373 interacting proteins in cancer cells, including those with functions relevant to cell adhesion, protein homeostasis, regulation of cell cycle and apoptosis, which are frequently deregulated in cancer. Within the interactome, we identified 15 communities (clusters) with topology-functional relationships. In neurons, where p140Cap is key in regulating synaptogenesis, synaptic transmission and synaptic plasticity, it establishes an extensive interactome with proteins that cluster to sub complexes located in the postsynaptic density. p140Cap interactors converge on key synaptic processes, including synaptic transmission, actin cytoskeleton remodeling and cell-cell junction organization. Comparing the breast cancer to the synaptic interactome, we found 39 overlapping proteins, a relatively small overlap. However, cell adhesion and remodeling of actin cytoskeleton clearly emerge as common terms in the shared subset. Thus, the functional signature of the two interactomes is primarily determined by organ/tissue and functional specificity, while the overlap provides a list of shared functional terms, which might be linked to both cancer and neurological functions.

Cholesterol content in cell membrane maintains surface levels of ErbB2 and confers a therapeutic vulnerability in ErbB2-positive breast cancer

BackgroundErbB2 overexpression identifies a subset of breast cancer as ErbB2-positive and is frequently associated with poor clinical outcomes. As a membrane-embedded receptor tyrosine kinase, cell surface levels of ErbB2 are regulated dynamically by membrane physical properties. The present study aims to investigate the influence of membrane cholesterol contents on ErbB2 status and cellular responses to its tyrosine kinase inhibitors.MethodsThe cholesterol abundance was examined in ErbB2-positive breast cancer cells using filipin staining. Cellular ErbB2 localizations were investigated by immunofluorescence with altered membrane cholesterol contents. The inhibitory effects of the cholesterol-lowering drug lovastatin were assessed using cell proliferation, apoptosis, immunoblotting and immunofluorescence assays. The synergistic effects of lovastatin with the ErbB2 inhibitor lapatinib were evaluated using an ErbB2-positive breast cancer xenograft mouse model.ResultsMembrane cholesterol contents positively correlated with cell surface distribution of ErbB2 through increasing the rigidity and decreasing the fluidity of cell membranes. Reduction in cholesterol abundance assisted the internalization and degradation of ErbB2. The cholesterol-lowering drug lovastatin significantly potentiated the inhibitory effects of ErbB2 kinase inhibitors, accompanied with enhanced ErbB2 endocytosis. Lovastatin also synergized with lapatinib to strongly suppress the in vivo growth of ErbB2-positive breast cancer xenografts.ConclusionThe cell surface distribution of ErbB2 was closely regulated by membrane physical properties governed by cholesterol contents. The cholesterol-lowering medications can hence be exploited for potential combinatorial therapies with ErbB2 kinase inhibitors in the clinical treatment of ErbB2-positive breast cancer.

MiR-183-5p Inhibits Occurrence and Progression of Acute Myeloid Leukemia via Targeting Erbin.

Erbin has been shown to have significant effects on the development of solid tumors. However, little is known about its function and regulatory mechanism in hematological malignancies. The biological function of Erbin on cell proliferation was measured in vitro and in vivo. The predicted target of Erbin was validated by dual-luciferase reporter assay and rescue experiment. We found that overexpression of Erbin could inhibit the cell proliferation and promote the cell differentiation of acute myeloid leukemia (AML) cells, whereas depletion of Erbin could enhance the cell proliferation and block the cell differentiation in AML cells in vitro and in vivo. Besides, miR-183-5p was identified as the upstream regulator that negatively regulated the Erbin expression. The results were confirmed by dual-luciferase reporter and RNA pull-down assay. Furthermore, we found that miR-183-5p negatively regulated Erbin, resulting in enhanced cell proliferation of AML cells via activation of RAS/RAF/MEK/ERK and PI3K/AKT/FoxO3a pathways. The activation of RAS/RAF/MEK/ERK and PI3K/AKT/FoxO3a pathways was mediated by Erbin interacting with Grb2. These results were also validated by rescue experiments in vitro and in vivo. All above-mentioned findings indicated that the miR-183-5p/Erbin signaling pathway might represent a novel prognostic biomarker or therapeutic target for treatment of AML.

ErbB2-driven downregulation of the transcription factor Irf6 in breast epithelial cells is required for their 3D growth

BackgroundThe ability of solid tumor cells to resist anoikis, apoptosis triggered by cell detachment from the extracellular matrix (ECM), is thought to be critical for 3D tumor growth. ErbB2/Her2 oncoprotein is often overproduced by breast tumor cells and blocks their anoikis by partially understood mechanisms. In our effort to understand them better, we observed that detachment of nonmalignant human breast epithelial cells from the ECM upregulates the transcription factor Irf6. Irf6 is thought to play an important role in mammary gland homeostasis and causes apoptosis by unknown mechanisms. We noticed that ErbB2, when overproduced by detached breast epithelial cells, downregulates Irf6.MethodsTo test whether ErbB2 downregulates Irf6 in human ErbB2-positive breast cancer cells, we examined the effect of ErbB2 inhibitors, such as the anti-ErbB2 antibody trastuzumab or the ErbB2/epidermal growth factor receptor small-molecule inhibitor lapatinib, on Irf6 in these cells. Moreover, we performed Irf6 IHC analysis of tumor samples derived from the locally advanced ErbB2-positive breast cancers before and after neoadjuvant trastuzumab-based therapies. To examine the role of Irf6 in anoikis of nonmalignant and ErbB2-overproducing breast epithelial cells, we studied anoikis after knocking down Irf6 in the former cells by RNA interference and after overproducing Irf6 in the latter cells. To examine the mechanisms by which cell detachment and ErbB2 control Irf6 expression in breast epithelial cells, we tested the effects of genetic and pharmacological inhibitors of the known ErbB2-dependent signaling pathways on Irf6 in these cells.ResultsWe observed that trastuzumab and lapatinib upregulate Irf6 in ErbB2-positive human breast tumor cells and that neoadjuvant trastuzumab-based therapies tend to upregulate Irf6 in human breast tumors. We found that detachment-induced Irf6 upregulation in nonmalignant breast epithelial cells requires the presence of the transcription factor ∆Np63α and that Irf6 mediates their anoikis. We showed that ErbB2 blocks Irf6 upregulation in ErbB2-overproducing cells by activating the mitogen-activated protein kinases that inhibit ∆Np63α-dependent signals required for Irf6 upregulation. Finally, we demonstrated that ErbB2-driven Irf6 downregulation in ErbB2-overproducing breast epithelial cells blocks their anoikis and promotes their anchorage-independent growth.ConclusionsWe have demonstrated that ErbB2 blocks anoikis of breast epithelial cells by downregulating Irf6.

A rational and iterative process for targeted nanoparticle design and validation.

The lack of understanding of fundamental nano-bio interactions, and difficulties in designing particles stable in complex biological environments are major limitations to their translation into biomedical clinical applications. Here we present a multi-parametric approach to fully characterize targeted nanoparticles, and emphasizes the significant effect that each detail in the synthetic process can have on downstream in vitro results. Through an iterative process, particles were designed, synthesized and tested for physico-chemical and bio-interactive properties which allowed the optimization of nanoparticle functionality. Taken together all interative steps demonstrate that we have synthesized a multifunctional gold nanoparticles that can detect ERBB2-positive breast cancer cells while showing stealth-like behavior toward ERBB2-negative cells and excellent physicochemical stability.

Molecular and Transcriptional Signatures for ErbB2-Induced Invasion

Invasion and metastasis are the most fatal activities connected to ErbB2. Current ErbB2-targeting therapies are highly efficient against early stage breast cancer, but often fail to cure the advanced cases. It is estimated that the majority of ErbB2-positive, invasive breast cancers are either intrinsically resistant to the current antibody-based therapy or can develop into resistant disease with high risk of metastasis. Local invasion is a prerequisite for metastatic dissemination. Here, we introduce and summarize the latest mechanistic knowledge of how ErbB2 activation can lead to invasion and spreading of breast cancer cells. In this review, we focus on the recent research in the molecular and cellular changes that initiate and maintain ErbB2-induced invasion. These comprise mechanisms that can promote cell migration and those that activate the extracellular degradome, as well as the involvement of lysosomes. We also discuss epithelial-to-mesenchymal transition and circulating tumor cells and what is currently known about their role in invasive, ErbB2-positive breast cancer. The activation of invasion in ErbB2-positive breast cancer cells is accomplished by initiation of invasion-promoting transcriptional programs, including activation of transcription factors such as myeloid zinc finger 1 (MZF1) and Ets1 that leads to changes in the expression of genes that can drive and maintain the invasive and metastatic cellular phenotype. Increasing our understanding of the downstream components of the ErbB2 signaling, especially those that regulate its invasive function, can contribute to the development of novel treatments that benefit patients with advanced and therapy-resistant ErbB2-positive breast cancer.

Abstract 5849: Valproic acid reverses trastuzumab resistance in erbB2-positive breast cancer cells via downregulation of ErbB2/ErbB3 signaling through induction of ErbB family members-targeting miRNAs

Abstract Amplification and/or overexpression of erbB2 occur in approximately 25% of invasive breast cancer and are significantly associated with a worse prognosis for breast cancer patients. Trastuzumab, a humanized monoclonal antibody against erbB2 receptor, has been successfully used in early-stage and metastatic breast cancer therapy of patients with erbB2-overexpressing tumors as monotherapy and in combination with other agents; however, both primary and acquired resistances to trastuzumab are common and currently represent a significant clinical problem. Thus, seeking of novel therapeutic strategies/agents to overcome trastuzumab resistance is vital to improve the survival of breast cancer patients whose tumors overexpress erbB2. In our current study, we explored whether valproic acid (VPA), a clinically used anticonvulsant drug with reported HDACi activity, reverses trastuzumab resistance in erbB2-positive breast cancer cells. We have found that VPA inhibits proliferation of both trastuzumab-sensitive SKBR3 and BT474 cell lines as well as their corresponding trastuzumab-resistant SKBR3-pool2 and BT474-HR20 cell lines in a dose- and time-dependent manner, which is accompanied by significant reduction of cyclin D1 as well as induction of P21. Meanwhile, VPA also induces caspase-dependent apoptosis in all aforementioned four cell lines. More interestingly, VPA not only significantly enhances the anti-proliferative effects of trastuzumab, but also potentiates trastuzumab-induced apoptosis in trastuzumab-sensitive and resistant cells. Our further mechanistic studies revealed that VPA treatment results in significant inactivation of PI3K/Akt signaling via simultaneous down-regulation of ErbB2 and ErbB3 in erbB2-positive breast cancer cancer cells, an effect which could be mainly arrtibuted to induction of ErbB family members-targeting microRNAs including miR-125a, miR-125b and miR-205 by VPA. Taken together, we presented here that VPA reverses trastuzumab resistance in erbB2-positive breast cance cells via downregulation of ErbB2/ErbB3 signaling in a miRNAs-inducing-dependent manner. Our data suggested that further investigation regarding the in vivo therapeutic effect of VAP against trastuzumab-resistant breast cancer should be of especial interest. Citation Format: Tingting Lin, Qun Ren, Weimin Zuo, Rong Lin, Hu Zhao, Ping Wang, Jianming Tan, Hui Lyu, Bolin Liu, Shuiliang Wang. Valproic acid reverses trastuzumab resistance in erbB2-positive breast cancer cells via downregulation of ErbB2/ErbB3 signaling through induction of ErbB family members-targeting miRNAs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5849.

Heat shock factor 1 confers resistance to lapatinib in ERBB2-positive breast cancer cells

Despite success of ERBB2-targeted therapies such as lapatinib, resistance remains a major clinical concern. Multiple compensatory receptor tyrosine kinase (RTK) pathways are known to contribute to lapatinib resistance. The heterogeneity of these adaptive responses is a significant hurdle for finding most effective combinatorial treatments. The goal of this study was to identify a unifying molecular mechanism whose targeting could help prevent and/or overcome lapatinib resistance. Using the MMTV-ERBB2;mutant p53 (R175H) in vivo mouse model of ERBB2-positive breast cancer, together with mouse and human cell lines, we compared lapatinib-resistant vs. lapatinib-sensitive tumor cells biochemically and by kinome arrays and evaluated their viability in response to a variety of compounds affecting heat shock response. We found that multiple adaptive RTKs are activated in lapatinib-resistant cells in vivo, some of which have been previously described (Axl, MET) and some were novel (PDGFRα, PDGFRβ, VEGFR1, MUSK, NFGR). Strikingly, all lapatinib-resistant cells show chronically activated HSF1 and its transcriptional targets, heat shock proteins (HSPs), and, as a result, superior tolerance to proteotoxic stress. Importantly, lapatinib-resistant tumors and cells retained sensitivity to Hsp90 and HSF1 inhibitors, both in vitro and in vivo, thus providing a unifying and actionable therapeutic node. Indeed, HSF1 inhibition simultaneously downregulated ERBB2, adaptive RTKs and mutant p53, and its combination with lapatinib prevented development of lapatinib resistance in vitro. Thus, the kinome adaptation in lapatinib-resistant ERBB2-positive breast cancer cells is governed, at least in part, by HSF1-mediated heat shock pathway, providing a novel potential intervention strategy to combat resistance.