HER2-positive Breast Cancer Cells Research Articles

Macrolide and Ketolide Antibiotics Inhibit the Cytotoxic Effect of Trastuzumab Emtansine in HER2-Positive Breast Cancer Cells: Implication of a Potential Drug-ADC Interaction in Cancer Chemotherapy.

Macrolides are widely used for the long-term treatment of infections and chronic inflammatory diseases. The pharmacokinetic features of macrolides include extensive tissue distribution because of favorable membrane permeability and accumulation within lysosomes. Trastuzumab emtansine (T-DM1), a HER2-targeting antibody-drug conjugate (ADC), is catabolized in the lysosomes, where Lys-SMCC-DM1, a potent cytotoxic agent, is processed by proteinase degradation and subsequently released from the lysosomes to the cytoplasm through the lysosomal membrane transporter SLC46A3, resulting in an antitumor effect. We recently demonstrated that erythromycin and clarithromycin inhibit SLC46A3 and attenuate the cytotoxicity of T-DM1; however, the effect of other macrolides and ketolides has not been determined. In this study, we evaluated the effect of macrolide and ketolide antibiotics on T-DM1 cytotoxicity in a human breast cancer cell line, KPL-4. Macrolides used in the clinic, such as roxithromycin, azithromycin, and josamycin, as well as solithromycin, a ketolide under clinical development, significantly attenuated T-DM1 cytotoxicity in addition to erythromycin and clarithromycin. Of these, azithromycin was the most potent inhibitor of T-DM1 efficacy. These antibiotics significantly inhibited the transport function of SLC46A3 in a concentration-dependent manner. Moreover, these compounds extensively accumulated in the lysosomes at the levels estimated to be 0.41-13.6 mM when cells were incubated with them at a 2 μM concentration. The immunofluorescence staining of trastuzumab revealed that azithromycin and solithromycin inhibit the degradation of T-DM1 in the lysosomes. These results suggest that the attenuation of T-DM1 cytotoxicity by macrolide and ketolide antibiotics involves their lysosomal accumulation and results in their greater lysosomal concentrations to inhibit the SLC46A3 function and T-DM1 degradation. This suggests a potential drug-ADC interaction during cancer chemotherapy.

Electrochemical Modification of Polypeptides at Selenocysteine.

Mild strategies for the selective modification of peptides and proteins are in demand for applications in therapeutic peptide and protein discovery, and in the study of fundamental biomolecular processes. Herein, we describe the development of an electrochemical selenoetherification (e-SE) platform for the efficient site-selective functionalization of polypeptides. This methodology utilizes the unique reactivity of the 21st amino acid, selenocysteine, to effect formation of valuable bioconjugates through stable selenoether linkages under mild electrochemical conditions. The power of e-SE is highlighted through late-stage C-terminal modification of the FDA-approved cancer drug leuprolide and assembly of a library of anti-HER2 affibody conjugates bearing complex cargoes. Following assembly by e-SE, the utility of functionalized affibodies for in vitro imaging and targeting of HER2 positive breast and lung cancer cell lines is also demonstrated.

Electrochemical Modification of Polypeptides at Selenocysteine

AbstractMild strategies for the selective modification of peptides and proteins are in demand for applications in therapeutic peptide and protein discovery, and in the study of fundamental biomolecular processes. Herein, we describe the development of an electrochemical selenoetherification (e‐SE) platform for the efficient site‐selective functionalization of polypeptides. This methodology utilizes the unique reactivity of the 21st amino acid, selenocysteine, to effect formation of valuable bioconjugates through stable selenoether linkages under mild electrochemical conditions. The power of e‐SE is highlighted through late‐stage C‐terminal modification of the FDA‐approved cancer drug leuprolide and assembly of a library of anti‐HER2 affibody conjugates bearing complex cargoes. Following assembly by e‐SE, the utility of functionalized affibodies for in vitro imaging and targeting of HER2 positive breast and lung cancer cell lines is also demonstrated.

Development of High-Loading Trastuzumab PLGA Nanoparticles: A Powerful Tool Against HER2 Positive Breast Cancer Cells.

Trastuzumab, a therapeutic monoclonal antibody directed against HER2, is routinely used to treat HER2-positive breast cancer with a good response rate. However, concerns have arisen in the clinical practice due to adverse side effects. One way to overcome these limitations is to encapsulate trastuzumab in nanoparticles to improve cytotoxic activity, increase intracellular drug concentrations, escape the immune system and avoid systemic degradation of the drug in vivo. A double emulsion method was used to encapsulate trastuzumab into poly(lactic-co-glycolic) nanoparticles, effective for their biocompatibility and biodegradability. These nanocarriers, hereafter referred to as TZPs, were characterised in terms of size, homogeneity, zeta potential and tested for their stability and drug release kinetics. Finally, the TZPs cytotoxicity was assessed in vitro on the HER2 positive SKBR3 breast cancer cell line and compared to free trastuzumab. The TZPs were stable, homogeneous in size, with a reduced zeta potential. They showed higher encapsulation efficiency and drug loading, a prolonged trastuzumab release kinetics that retained its physicochemical properties and functionality. TZPs showed a stronger cytotoxicity and increased apoptosis than similar doses of free trastuzumab in the cell line analysed. Confocal microscopy and flow cytometry assessed TZPs and trastuzumab cellular uptake while Western blot evaluated downstream signalling, overall HER2 content and shedding. TZPs exert more robust effects than free trastuzumab via a dual mode of action: TZPs are taken up by cells through an endocytosis mechanism and release the drug intracellularly for longer time. Additionally, the TZPs that remain in the extracellular space release trastuzumab which binds to the cognate receptor and impairs downstream signalling. This is the sole modality used by free trastuzumab. Remarkably, half dose of TZPs is as efficacious as the highest dose of free drug supporting their possible use for drug delivery in vivo.

225Ac]Ac- and [111In]In-DOTA-trastuzumab theranostic pair: cellular dosimetry and cytotoxicity in vitro and tumour and normal tissue uptake in vivo in NRG mice with HER2-positive human breast cancer xenografts

BackgroundTrastuzumab (Herceptin) has improved the outcome for patients with HER2-positive breast cancer (BC) but brain metastases (BM) remain a challenge due to poor uptake of trastuzumab into the brain. Radioimmunotherapy (RIT) with trastuzumab labeled with α-particle emitting, 225Ac may overcome this challenge by increasing the cytotoxic potency on HER2-positive BC cells. Our first aim was to synthesize and characterize [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab as a theranostic pair for imaging and RIT of HER2-positive BC, respectively. A second aim was to estimate the cellular dosimetry of [225Ac]Ac-DOTA-trastuzumab and determine its cytotoxicity in vitro on HER2-positive BC cells. A third aim was to study the tumour and normal tissue uptake of [225Ac]Ac-DOTA-trastuzumab using [111In]In-DOTA-trastuzumab as a radiotracer in vivo in NRG mice with s.c. 164/8-1B/H2N.luc+ human BC tumours that metastasize to the brain.ResultsTrastuzumab was conjugated to 12.7 ± 1.2 DOTA chelators and labeled with 111In or 225Ac. [111In]In-DOTA-trastuzumab exhibited high affinity specific binding to HER2-positive SK-BR-3 human BC cells (KD = 1.2 ± 0.3 × 10–8 mol/L). Treatment with [225Ac]Ac-DOTA-trastuzumab decreased the surviving fraction (SF) of SK-BR-3 cells dependent on the specific activity (SA) with SF < 0.001 at SA = 0.74 kBq/µg. No surviving colonies were noted at SA = 1.10 kBq/µg or 1.665 kBq/µg. Multiple DNA double-strand breaks (DSBs) were detected in SK-BR-3 cells exposed to [225Ac]Ac-DOTA-trastuzumab by γ-H2AX immunofluorescence microscopy. The time-integrated activity of [111In]In-DOTA-trastuzumab in SK-BR-3 cells was measured and used to estimate the absorbed doses from [225Ac]Ac-DOTA-trastuzumab by Monte Carlo N-Particle simulation for correlation with the SF. The dose required to decrease the SF of SK-BR-3 cells to 0.10 (D10) was 1.10 Gy. Based on the D10 reported for γ-irradiation of SK-BR-3 cells, we estimate that the relative biological effectiveness of the α-particles emitted by 225Ac is 4.4. Biodistribution studies in NRG mice with s.c. 164/8-1B/H2N.luc+ human BC tumours at 48 h post-coinjection of [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab revealed HER2-specific tumour uptake (10.6 ± 0.6% ID/g) but spleen uptake was high (28.9 ± 7.4% ID/g). Tumours were well-visualized by SPECT/CT imaging using [111In]In-DOTA-trastuzumab.ConclusionWe conclude that [225Ac]Ac-DOTA-trastuzumab exhibited potent and HER2-specific cytotoxicity on SK-BR-3 cells in vitro and HER2-specific uptake in s.c. 164/8-1B/H2N.luc+ human BC tumours in NRG mice, and these tumours were imaged by SPECT/CT with [111In]In-DOTA-trastuzumab. These results are promising for combining [111In]In-DOTA-trastuzumab and [225Ac]Ac-DOTA-trastuzumab as a theranostic pair for imaging and RIT of HER2-positive BC.

Recombinant anti-human epidermal growth factor receptor type 2 single-chain variable fragment-alpha-luffin fusion protein as a putative immunotoxin against human epidermal growth factor receptor type 2-positive breast cancer cells: an experimental research.

Breast cancer is one of the most frequent causes of cancer death in women. The application of immunotoxins to target overexpressed biomarkers on the surface of cancer cells and delivery of the toxin molecules into these cells has attracted too much attention during the last decade. This study was conducted to investigate the possible in-vitro cytotoxic and apoptotic activity of previously designed recombinant immunotoxin compromising anti-HER2 single-chain variable fragment (scFv) and alpha-luffin protein in human epidermal growth factor receptor type 2 (HER2)-positive and HER2-negative breast cancer cell lines. The previously designed recombinant immunotoxin and alpha-luffin protein were expressed in E. coli host cells and purified using Ni-affinity chromatography. The cytotoxicity of the proteins was tested through MTT and apoptosis studies on HER2-positive and HER2-negative breast cancer cell lines. Treatment of SKBR3 and MDA-MB-468 cells with the immunotoxin caused differential cytotoxicity and apoptotic events. Flow cytometry analysis indicated that the immunotoxin could arrest SKBR3 cells at the G0/G1 phase and induce apoptosis and cell death which were not observed in HER2-negative MDA-MB-468 cells. Annexin V/PI staining revealed late apoptotic events in SKBR3 cells treated with the immunotoxin which was different from the early apoptosis induced by the alpha-luffin protein alone. This immunotoxin could be a promising tool in developing new targeted therapeutic agents against HER2-positive cancer cells. Animal experiments are needed before making firmed conclusions.

Peptides Targeting HER2-Positive Breast Cancer Cells and Applications in Tumor Imaging and Delivery of Chemotherapeutics.

Breast cancer represents the most common cancer type and one of the major leading causes of death in the female worldwide population. Overexpression of HER2, a transmembrane glycoprotein related to the epidermal growth factor receptor, results in a biologically and clinically aggressive breast cancer subtype. It is also the primary driver for tumor detection and progression and, in addition to being an important prognostic factor in women diagnosed with breast cancer, HER2 is a widely known therapeutic target for drug development. The aim of this review is to provide an updated overview of the main approaches for the diagnosis and treatment of HER2-positive breast cancer proposed in the literature over the past decade. We focused on the different targeting strategies involving antibodies and peptides that have been explored with their relative outcomes and current limitations that need to be improved. The review also encompasses a discussion on targeted peptides acting as probes for molecular imaging. By using different types of HER2-targeting strategies, nanotechnology promises to overcome some of the current clinical challenges by developing novel HER2-guided nanosystems suitable as powerful tools in breast cancer imaging, targeting, and therapy.

Ex vivo dual gene therapy using human adipocytes secreting anti-HER2 antibody on HER2-positive xenograft tumor models.

Although targeted treatments against human epidermal growth factor receptor 2 (HER2) have improved survival in patients with metastatic HER2-positive breast cancer, long and repeated treatment is time-consuming and costly for patients. To reduce these burdens, we developed ex vivo gene-transduced adipocytes that secrete anti-HER2 antibodies and evaluated their anti-tumor effects. Ceiling culture-derived proliferative adipocytes (ccdPA) secreting anti-HER2 antibody against domain IV receptors: TRA-ccdPA, and domain II receptors: PER-ccdPA, were constructed using a plasmid lentivirus. Delivery of secreted antibody and its specific binding to HER2 breast cancer were evaluated in vitro and in vivo. To optimize antibody production from ccdPA, different conditions of ccdPA implantation were examined. Anti-tumor efficacy was evaluated in HER2-positive-cancer-inoculated nude mice. Anti-HER2 antibody against domain II was identified in supernatants from PER-ccdPAs. The optimal method to achieve the highest concentration of antibody in mouse sera was injecting differentiated ccdPA cells into the mammary fat pad. Antibody in supernatants from PER-ccdPAs bound to the surface of HER2-positive breast cancer cells similar to pertuzumab. Antibodies in mouse sera were delivered to HER2-positive breast cancer tumors and tumor necrosis was observed microscopically. One-time administration of combined TRA-ccdPAs and PER-ccdPAs produced antibody continuously in mouse sera, and anti-tumor effects were maintained for the duration of this study in xenograft models. Furthermore, combination therapy significantly suppressed tumor growth compared with a single administration. Ex vivo gene-transduced adipocytes might be useful for cell-based gene therapy. This system may be a platform for various antibody therapies.

Coiled-Coil-Based Biofunctionalization of 100 nm Gold Nanoparticles with the Trastuzumab Antibody for the Detection of HER2-Positive Cancer Cells.

We compared different biofunctionalization strategies for immobilizing trastuzumab, an IgG targeting the HER2 biomarker, onto 100 nm spherical gold nanoparticles because of the E/K coiled-coil peptide heterodimer. First, Kcoil peptides were grafted onto the gold surface while their Ecoil partners were genetically encoded at the C-terminus of trastuzumab's Fc region, allowing for a strong and specific interaction between the antibodies and the nanoparticles. Gold nanoparticles with no Kcoil peptides on their surface were also produced to immobilize Ecoil-tagged trastuzumab antibodies via the specific adsorption of their negatively charged Ecoil tags on the positively charged gold surface. Finally, the nonspecific adsorption of wild-type trastuzumab on the gold surface was also assessed, with and without Kcoil peptides grafted on it beforehand. We developed a thorough workflow to systematically compare the immobilization strategies regarding the stability of nanoparticles, antibody coverage, and ability to specifically bind to HER2-positive breast cancer cells. All nanoparticles were highly monodisperse and retained their localized surface plasmon resonance properties after biofunctionalization. A significant increase in the amount of immobilized antibodies was observed with the two oriented coil-based strategies compared to nonspecific adsorption. Finally, all biofunctionalization strategies allowed for the detection of HER2-positive breast cancer cells, but among the investigated approaches, we recommend using the E/K coiled-coil-based strategy for gold nanoparticle biofunctionalization because it allows for the qualitative and quantitative detection of HER2-positive cells with a higher contrast compared to HER2-negative cells.

Anthocyanins extract as a non-toxic and green fluorescent label for bioimaging of HER2-positive breast cancer cells

Breast cancer is one of the most common causes of death among women. Fluorescent labeling is an essential research and diagnostic tool in the detection of cancer cells. The development of inexpensive and easily accessible fluorescent probes for the detection of cancerous cells is of great importance. Herein we report a green and inexpensive method for extraction of natural anthocyanin fluorophore from Red Cabbage and demonstrate its application for fluorescent bioimaging of human epidermal growth factor receptor 2 (HER2) positive breast cancer cells using non-covalent conjugation of anthocyanin fluorophores to Trastuzumab antibody. In this work, the extracted anthocyanins were characterized by Fourier transform infrared spectroscopy (FTIR), Ultraviolet–Visible (UV–Vis) and fluorescent spectroscopy. The anthocyanin extract showed proper fluorescent intensity for microscopic fluorescent cell imaging, negligible photobleaching and no sign of cytotoxicity (more than 90% viability). The presence of hydroxy and carboxyl functional groups in the structure of anthocyanins provided the opportunity for the non-covalent conjugation of anthocyanins to antibodies. The fluorescent probe made by non-covalent conjugation of the anthocyanin fluorophores to Trastuzumab antibody was used for specific fluorescent imaging of HER2 receptors on HER2 positive breast cancer cells. This green fluorescent probe may have several future applications in biological diagnosis and bio-imaging techniques.

Aminosteroid RM-581 Decreases Cell Proliferation of All Breast Cancer Molecular Subtypes, Alone and in Combination with Breast Cancer Treatments.

Breast cancer (BC) is a heterogenous disease classified into four molecular subtypes (Luminal A, Luminal B, HER2 and triple-negative (TNBC)) depending on the expression of the estrogen receptor (ER), the progesterone receptor (PR) and the human epidermal receptor 2 (HER2). The development of effective treatments for BC, especially TNBC, remains a challenge. Aminosteroid derivative RM-581 has previously shown an antiproliferative effect in multiple cancers in vitro and in vivo. In this study, we evaluated its effect in BC cell lines representative of BC molecular subtypes, including metastatic TNBC. We found that RM-581 has an antiproliferative effect on all BC molecular subtypes, especially on Luminal A and TNBC, in 2D and 3D cultures. The combination of RM-581 and trastuzumab or trastuzumab-emtansine enhanced the anticancer effect of each drug for HER2-positive BC cell lines, and the combination of RM-581 and taxanes (docetaxel or paclitaxel) improved the antiproliferative effect of RM-581 in TNBC and metastatic TNBC cell lines. We also confirmed that RM-581 is an endoplasmic reticulum (EnR)-stress aggravator by inducing an increase in EnR-stress-induced apoptosis markers such as BIP/GRP78 and CHOP and disrupting lipid homeostasis. This study demonstrates that RM-581 could be effective for the treatment of BC, especially TNBC.

Immunomagnetic Isolation of HER2-Positive Breast Cancer Cells Using a Microfluidic Device.

Analysis of circulating tumor cells (CTCs) as a tool for monitoring metastatic cancers, early diagnosis, and evaluation of disease prognosis paves the way toward personalized cancer treatment. Developing an effective, feasible, and low-cost method to facilitate CTC isolation is, therefore, vital. In the present study, we integrated magnetic nanoparticles (MNPs) with microfluidics and used them for the isolation of HER2-positive breast cancer cells. Iron oxide MNPs were synthesized and functionalized with the anti-HER2 antibody. The chemical conjugation was verified by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and dynamic light scattering/zeta potential analysis. The specificity of the functionalized NPs for the separation of HER2-positive from HER2-negative cells was demonstrated in an off-chip test setting. The off-chip isolation efficiency was 59.38%. The efficiency of SK-BR-3 cell isolation using a microfluidic chip with a S-shaped microchannel was considerably enhanced to 96% (a flow rate of 0.5 mL/h) without chip clogging. Besides, the analysis time for the on-chip cell separation was 50% faster. The clear advantages of the present microfluidic system offer a competitive solution in clinical applications.

Precision Therapyof Recurrent Breast Cancer throughTargeting Different MalignantTumor Cells witha HER2/CD44-Targeted Hydrogel Nanobot.

Heterogeneity and drug resistance of tumor cells are the leading causes of incurability and poor survival for patients with recurrent breast cancer. In order to accurately deliver the biological anticancer drugs to different subtypes of malignant tumor cells for omnidirectional targeted treatment of recurrent breast cancer, a distinct design is demonstrated by embedding liposome-based nanocomplexes containing pro-apoptotic peptide and survivin siRNA drugs (LPR) into Herceptin/hyaluronic acid cross-linked nanohydrogels (Herceptin-HA) to fabricate a HER2/CD44-targeted hydrogel nanobot (named as ALPR). ALPR delivered cargoes to the cells overexpressing CD44 and HER2, followed by Herceptin-HA biodegradation, subsequently, the exposed lipid component containing DOPE fused with the endosomal membrane and released peptide and siRNA into the cytoplasm. These experiments indicated that ALPR can specifically deliver Herceptin, peptide, and siRNA drugs to HER2-positive SKBR-3, triple-negative MDA-MB-231, and HER2-negative drug-resistant MCF-7 human breast cancer cells. ALPR completely inhibited the growth of heterogeneous breast tumors via multichannel synergistic effects: disrupting mitochondria, downregulating the survivin gene, and blocking HER2 receptors on the surface of HER2-positive cells. The present design overcomes the chemical drug resistance and opens a feasible route for the combinative treatment of recurrent breast cancer, even other solid tumors, utilizing different kinds of biological drugs.

One-step multiplex analysis of breast cancer exosomes using an electrochemical strategy assisted by gold nanoparticles.

Exosomes, as a non-invasive biomarker, perform an important role in breast cancer screening and prognosis monitoring. However, establishing a simple, sensitive, and reliable exosome analysis technique remains challenging. Herein, a one-step multiplex analysis electrochemical aptasensor based on a multi-probe recognition strategy was constructed to analyze breast cancer exosomes. HER2-positive breast cancer cell (SK-BR-3) exosomes were selected as the model targets and three aptamers including CD63, HER2 and EpCAM aptamers were used as the capture units. Methylene blue (MB) functionalized HER2 aptamer and ferrocene (Fc) functionalized EpCAM aptamer, which were modified on gold nanoparticles (Au NPs), i.e. MB-HER2-Au NPs and Fc-EpCAM-Au NPs, were used as signal units. When the mixture of target exosomes, MB-HER2-Au NPs and Fc-EpCAM-Au NPs were added on the CD63 aptamer modified gold electrode, two Au NPs modified by MB and Fc could be specifically captured on the electrode by the recognition of three aptamers with target exosomes. Then one-step multiplex analysis of exosomes was achieved by detecting two independent electrochemical signals. This strategy can not only distinguish breast cancer exosomes from other exosomes (including normal exosomes and other tumor exosomes) but also HER2-positive breast cancer exosomes and HER2-negative breast cancer exosomes. Besides, it had high sensitivity and can detect SK-BR-3 exosomes with a concentration as low as 3.4×103 particles mL-1. Crucially, this method can be applicable to the examination of exosomes in complicated samples, which is anticipated to afford assistance for the screening and prognosis of breast cancer.

Abstract 3998: Metronomic gemcitabine plus neratinib effectively inhibits the growth of human Her-2 positive breast cancer cells intracranially implanted into immunodeficient mice

Abstract Metastatic breast cancer is a major cause of death for women in the US, and breast cancers that metastasize to the brain have a particularly poor prognosis. To treat brain metastases of Her-2 positive breast cancers a number of Her-2 targeting drugs are now clinically available, including lapatinib, neratinib and tucatinib, among others. However, in part as a consequence of poor penetration of many drugs into the brain, combinations of standard chemotherapy plus targeted agent have only modest impact on progression free survival for such patients. We have developed preclinical models of human Her-2 positive breast cancer brain metastases to help address these issues. We selected human MDA-MD-361 and BT474 breast cancer cells lines by in vivo passaging in SCID mice, followed by molecular tagging of the derived variants (MDA361R and BT474R respectively), and then the stereotactic implantation of such cells into the brain of female SCID mice. Using luciferase-tagged BT474R we implanted 75,000 cells into the brains of the mice, and thereafter confirmed by luminescence the growth of the cells, which allowed for randomization of the mice to receive control saline (n=7), metronomic gemcitabine (100mg/kg/3days; i.p.; n=8), neratinib (40mg/kg/3 days; p.o.; n=7), or the combination of gemcitabine plus neratinib (n=8), which continued for 5 months largely in the absence of overt toxicity. The gemcitabine plus neratinib combination prolonged survival over the controls (150 days vs 65 days, p&amp;lt;0.5), although eventually all mice succumbed to disease. Tumors cells have been isolated from these therapy-administered mice for further characterization. Neratinib alone did not result in an increase in survival compared to controls, whereas metronomic gemcitabine improved survival but was inferior to the combination. We confirmed these findings using MDA361R tagged with human chorionic gonadotropin (hCG), which allows for the growth of cells to be monitored by assessment of hCG in the mouse urine, and these cells were implanted intracranially into female SCID mice. After urine hCG levels confirmed the presence of growing cells in the brain, the mice were randomized to the above 4 therapies (n=4/group), which showed an increase in survival of the combination compared to controls. These results point to intriguing effects of chemotherapy when used at continuous low (metronomic) doses, that in these studies involved gemcitabine administration every 3 days, and which in these models can be effectively combined with neratinib to suppress the growth of Her-2 positive breast cancer cells implanted into the mouse brain. These results highlight promising combination that could be used to suppress Her-2 positive breast cancer brain metastatic growth, and the developed models should facilitate the study of this subset of breast cancers. Citation Format: Serina Batson, Alejandro Sanchez, Hector M. Padilla, Diana L. Prospero, Brenda Lugo, Valeria V. Lopez, Daniella E. Estrada, Nydia De Avila, Saeedeh Darvishi, Arlene Levario, Shan Man, Ping Xu, Robert S. Kerbel, Guido Bocci, Giulio Francia. Metronomic gemcitabine plus neratinib effectively inhibits the growth of human Her-2 positive breast cancer cells intracranially implanted into immunodeficient mice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3998.

Abstract 6121: UCP2 inhibitor eradicates cancer stem-like population in trastuzumab-resistant HER2-positive breast cancer

Abstract Purpose: Uncoupling protein 2 (UCP2) is a member of the mitochondrial anion carrier protein family that plays an important role in stabilizing the inner mitochondrial membrane potential (MMP, ΔΨm) and controlling reactive oxygen species (ROS) production. A selective UCP2 inhibitor, genipin is known to elicit cytotoxicity in several cancers, however, its effects on cancer stem cells (CSCs)-like properties and trastuzumab resistance in HER2-positive breast cancer cells have not been fully elucidated. In the present study, we sought to investigate the mechanism of action of genipin responsible for the induction of apoptosis and its effects on CSC-like features, expression of HER family member and trastuzumab resistance in HER2-positive breast cancer cells in vitro and in vivo. Experimental Designs: The effects of genipin on trastuzuamb-sensitive [BT474 and SKBR3] and trastuzumab-resistant [JIMT-1 and MDA-MB-453] HER2-positive breast cancer cell lines in vitro were evaluated for cell viability, Sub-G1, ROS, MMP, ALDH1 activity, CD44+/CD24- subpopulation and mammosphere formation. To confirm the physiological relevance of our in vitro observations, we explored the impact of genipin on tumor growth and angiogenesis and expression of p95HER2 and ALDH1A1 in trastuzumab-resistant xenograft model in vivo. Results: HER2-positive breast cancer cells harbored a higher level of UCP2, when compared to their counterparts. Genipin significantly downregulated UCP2 and mitochondrial dysfunction coinciding with increased ROS generation and disruption of MMP. These phenomena were accompanied with upregulation of the Bax/Bcl-2 ratio and activation of caspase-3 and caspase-7. Genipin treatment led to significant reduction in levels of truncated p95HER2, p-HER2, p-HER3 and p-Akt levels in both trastuzumab-sensitive and -resistant lines. Marked decline of CD44 and ALDH1A1 expression by genipin treatment was associated with attenuation of mammosphere-forming ability. UCP2 level is predominantly upregulated in CSC-enriched populations, while its knockdown significantly suppressed CSC-like characteristics concomitant with decreased ALDH1A1 and CD44 expression as well as impairment of ALDH1 activity. Genipin administration significantly retarded tumor growth and angiogenesis in trastuzumab-resistant JIMT-1 xenograft tumors. The antitumor effect occurred concomitantly with a decrease in Ki-67 proliferating index and enhancement of apoptosis. Furthermore, individuals receiving genipin exhibited markedly lower levels of p95HER2, full-length p185HER2, CD44 and ALDH1A1 expression compared to their control counterparts. Conclusion: To our knowledge, our findings are the first reported instance of genipin-induced suppression of CSC-like properties and HER2/HER3/Akt axis, implying that genipin treatment may have application in addressing trastuzumab resistance. Citation Format: Minsu Park, Soeun Park, Juyeon Seo, Dongmi Ko, Seongjae Kim, Yong Koo Kang, Kee Dal Nam, So Ra Seuk, Tae-Min Cho, Eunsun Jung, Yoon-Jae Kim, Ji Young Kim, Jae Hong Seo. UCP2 inhibitor eradicates cancer stem-like population in trastuzumab-resistant HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6121.

Abstract 423: β-Escin eradicates cancer stem-like population in HER2-positive breast cancer with trastuzumab resistance

Abstract Purpose: Trastuzumab resistance is a multifactorial phenomenon arising from the steric effects of p95HER2, activation of HER2 downstream signaling pathways, and the existence of cancer stem cells. We sought to examine the capacity of β-escin, an anti-inflammatory drug, to address trastuzumab resistance in HER2-positive breast cancer cells. Experimental designs: The effects of β-escin in trastuzumab-sensitive and -resistant cell lines were evaluated for apoptosis, HER2 expression, calpain activation and CSC-like properties. In vivo trastuzumab-resistant xenograft mice model was used to examine tumor growth, angiogenesis and organ toxicity of β-escin. Results: β-escin induced mitochondrial-mediated apoptosis accompanied by reactive oxygen species (ROS) production and increased active p18Bax fragmentation, leading to caspase-3/-7 activation. β-escin downregulated p95HER2, HER2 and HER3 as well as their phosphorylation. β-escin-induced HER2 degradation appears to be mediated by calpain activation. We observed that treatment with β-escin induced cleavage of HER2 and p95HER2 (at 75, 50 and 42 kDa fragments) in HER2 overexpressing MDA-MB-231 cells. Attenuation of CSC-related features by β-escin challenge was accompanied by marked reductions in CD44high/CD24low stem-like cells and aldehyde dehydrogenase 1 (ALDH1) activity as well as hindrance of mammosphere formation. β-escin administration also significantly retarded tumor growth and angiogenesis in a trastuzumab-resistant JIMT-1 xenograft model via downregulation of CSC-associated markers and intracellular domain HER2. Importantly, β-escin selectively inhibited malignant cells and was less toxic to normal mammary cells, and no toxic effects were found in liver and kidney function in animals. Conclusion: Herein, for the first time, we report the potent efficacy of β-escin, a drug repurposing candidate with an exceptional safety profile in addressing trastuzumab-resistant HER2-positive breast cancer. Citation Format: Soeun Park, Minsu Park, Dongmi Ko, Seongjae Kim, Juyeon Seo, Kee Dal Nam, Eunsun Jung, Yong koo Kang, Seojin Jang, So Ra Seock, Yoon-Jae Kim, Ji Young Kim, Jae Hong Seo, Jaeyoun Park. β-Escin eradicates cancer stem-like population in HER2-positive breast cancer with trastuzumab resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 423.

Abstract 2489: Study the efficacy of hypomethylating agent in treating regular and brain metastasized HER2-positive breast cancer

Abstract Breast cancer is the second leading cause of cancer with the highest mortality rate in females in the United States. Late stage breast cancer can metastasize to different locations of the body, and patients with brain metastasis have a poor prognosis and short survival time. HER2-positive breast cancer, composed of ~15-20% of total cases, is aggressive with unfavorable clinical outcomes. Although HER2-targeted therapies are available, they are mostly ineffective against brain metastasis. To study tumor metastasis, we had established the breast cancer brain metastasis preclinical cell and mouse models. Our previous study has shown that the hypomethylating agent azacitidine (AZA) is effective in treating brain metastasis triple-negative breast cancer using in vitro cell and in vivo mouse models. Thus, we hypothesized that AZA will be effective to treat HER2-positive breast cancer. To test our hypothesis, we treated regular (JIMT-1) and brain metastasized (JIMT-1 Br) HER2-positive breast cancer cell lines with various concentrations of AZA, and the IC50 values, cell proliferation, and apoptosis were measured. Our results showed that train metastasized HER2-positive breast cancer JIMT-1 Br cells have similar growth rate compared to their parental regular breast cancer JIMT-1 cells. Regular breast cancer cells are more sensitive to AZA treatment, supported by (1) The IC50 value of AZA in JIMT-1 cells is significantly lower than that in JIMT-1 Br cells; (2) 72 hours of AZA treatment significantly inhibited cell grow in both cell lines, and the inhibition of JIMT-1 growth is greater than that of JIMT-1 Br cells; (3) AZA triggered apoptosis in both cell lines in a dose-dependent manner; (4) Higher concentrations of AZA induced a higher percentage of cell apoptosis in JIMT-1 compared to JIMT-1 Br cells. AZA treatment does not significantly change the expression of metastasis protein markers in either cell line. Epithelial-mesenchymal transition promotes cancer cell invasion and metastasis. Epithelial markers include cytokeratins and E-cadherin, and mesenchymal markers include N-cadherin and vimentin. We measured the expression of those markers in both cell lines after AZA treatment by Western blotting, and found that the expression of pan-cytokeratins and keratin 18 were equivalent between both cell lines upon AZA treatment. However, the expression of keratin 19, E-cadherin, N-cadherin, and vimentin were not detected in either cell line. In conclusion, in this study, we tested the in vitro effects of the hypomethylating agent AZA in both regular and brain metastasized HER2-positive breast cancer cells. We found that AZA inhibits cell growth and promotes apoptosis in both cell types, but the regular breast cancer cells are more sensitive to AZA treatment compared to brain metastasized cells, shown by the differences in IC50 values and extents of cell growth inhibition and apoptosis induction. Citation Format: Tuoen Liu, Christopher Butler, Kelsey Donoughe, Lauren Forchette, William Sebastian, Gabor Szalai, Paul Lockman. Study the efficacy of hypomethylating agent in treating regular and brain metastasized HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2489.

Abstract 1998: Characterization of immunoliposomes for HER2-targeted delivery of the dual Rac/Cdc42 inhibitor MBQ-167

Abstract Breast cancer is the second leading cause of mortality among women in the US. Among the various subtypes, human epidermal growth factor receptor 2 (HER2) positive breast cancer shows a very aggressive and invasive phenotype. This subtype is characterized by the overexpression of HER2 receptor on the cell surface that upon ligand binding and dimerization, leads to overactive cell signaling that promotes cell proliferation and metastasis. Even though therapies have been developed to treat this type of breast cancer by targeting HER2 and preventing dimerization (eg. Trastuzumab), patients can present with acquired or intrinsic therapy resistance. One of the mechanisms of resistance is the compensation of intracellular signaling from other receptors. This signaling converges on guanine nucleotide exchange factors (GEFs) that activate Rac and Cdc42 by exchanging GDP for GTP, thus activating downstream effectors that modulate the actin cytoskeleton to promote cell migration and invasion. Therefore, targeting Rac and Cdc42 activation selectively in HER2 positive breast cancer is a promising strategy for overcoming HER2-targeted therapy resistance. Previously, we characterized the dual Rac/Cdc42 inhibitor MBQ-167 that inhibits Rac and Cdc42 activity with IC50s of 103nM and 78nM, respectively. However, there is a need to develop selective delivery systems that transport MBQ-167 directly into HER2-positive breast cancer cells. Our objective is to deliver MBQ-167 selectively into HER2-positive cells using liposomes coated with Trastuzumab, a clinically used monoclonal antibody that targets HER2. We conjugated Trastuzumab to a lipid linker (DSPE-PEG-Maleimide) by reacting Trastuzumab with 2-iminothiolane (Traut’s reagent) under nitrogenated (low oxygen) conditions and then mixing with the lipid linker overnight. This reaction was characterized by measuring the thiol groups formed after the reaction with Traut’s reagent and after mixing with the lipid, followed by mixing the Trastuzumab-lipid conjugate with liposomes containing MBQ-167. To quantify the amount of MBQ-167 in the liposomes, we determined the excitation/emission parameters of the molecule and measured the concentration of MBQ-167 by fluorescence. We found an increase in thiol groups after the reaction with Traut’s reagent, which decreased after mixing with the lipids, suggesting the formation of the DSPE-PEG-Trastuzumab conjugate. Additionally, we determined the excitation/emission parameters (320nm/430nm), quantified a lower limit of detection (LLOD) at 0.1mM, and calculated an encapsulation efficiency of 97% (530μM). Future studies include testing our formulation in vitro and in vivo in HER2+ breast cancer models. Citation Format: Luis E. Velazquez, Suranganie Dharmawardhane. Characterization of immunoliposomes for HER2-targeted delivery of the dual Rac/Cdc42 inhibitor MBQ-167 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1998.

MiR-146a-5p Promotes Angiogenesis and Confers Trastuzumab Resistance in HER2+ Breast Cancer

Trastuzumab treatment has significantly improved the prognosis of HER2-positive breast cancer patients. Despite this, resistance to therapy still remains the main clinical challenge. In order to evaluate the implication of microRNAs in the trastuzumab response, we performed a microRNA array in parental and acquired trastuzumab-resistant HER2-positive breast cancer cell lines. Our results identified miR-146a-5p as the main dysregulated microRNA. Interestingly, high miR-146a-5p expression in primary tumor tissue significantly correlated with shorter disease-free survival in HER2-positive breast cancer patients. The gain- and loss-of-function of miR-146a-5p modulated the response to trastuzumab. Furthermore, the overexpression of miR-146a-5p increased migration and angiogenesis, and promoted cell cycle progression by reducing CDKN1A expression. Exosomes from trastuzumab-resistant cells showed a high level of miR-146a-5p expression compared with the parental cells. In addition, the co-culture with resistant cells' exosomes was able to decrease in sensitivity and increase the migration capacities in trastuzumab-sensitive cells, as well as angiogenesis in HUVEC-2 cells. Collectively, these data support the role of miR-146a-5p in resistance to trastuzumab, and demonstrate that it can be transferred by exosomes conferring resistance properties to other cells.