Target In HER2-positive Breast Cancer Research Articles

Hsa-miR-221-3p promotes proliferation and migration in HER2-positive breast cancer cells by targeting LASS2 and MBD2.

Human epidermal growth factor receptor (HER2)-positive breast cancers account for nearly 20% of all breast cancer cases and microRNAs (miRNAs) play crucial roles in disease progression. The study was aimed to explore the role of miR-221-3p in HER2-positive breast cancer. Differentially expressed miRNAs were identified by high-throughput sequencing. Quantitative real-time PCR was used to evaluate mRNA levels of corresponding genes. CKK8 and transwell assays were performed to evaluate cell viability and migration. The translation binding was assessed by luciferase assay. Hsa-miR-221-3p was highly upregulated in HER2-positive breast cancer samples, particularly in patients with advanced or metastatic disease, as compared to healthy controls. miR-221-3p upregulation using mimics promoted cell proliferation and migration in HER2-positive cell lines, whereas miR-221-3p suppression had the opposite effect. Additionally, miR-221-3p mimics reduced the expression levels of LASS2 and MBD2 in HER2-positive breast cancer cells; conversely, miR-221-3p inhibition upregulated LASS2 and MBD2. miR-221-3p inhibited the translation of LASS2 and MBD2 by directly binding to their 3'-untranslated regions. Forced expression of LASS2 and MBD2 significantly attenuated the ability of miR-221-3p mimics to enhance cell growth and migration in HER2-positive but not in HER2-negative breast cancer cells. In HER-2-positive breast cancer patients, the levels of miR-221-3p were negatively correlated with the mRNA levels of LASS2 and MBD2. Upregulation of hsa-miR-221-3 in HER2-positive breast cancer contributes to cancer cell proliferation and migration by directly targeting the tumor suppressors LASS2 and MBD2. Therefore, the hsa-miR-221-3 may serve as a promising and actionable therapeutic target in HER2-positive breast cancer.

YES1 as a Therapeutic Target for HER2-Positive Breast Cancer after Trastuzumab and Trastuzumab-Emtansine (T-DM1) Resistance Development.

Trastuzumab-emtansine (T-DM1) is a therapeutic agent molecularly targeting human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC), and it is especially effective for MBC with resistance to trastuzumab. Although several reports have described T-DM1 resistance, few have examined the mechanism underlying T-DM1 resistance after the development of acquired resistance to trastuzumab. We previously reported that YES1, a member of the Src family, plays an important role in acquired resistance to trastuzumab in HER2-amplified breast cancer cells. We newly established a trastuzumab/T-DM1-dual-resistant cell line and analyzed the resistance mechanisms in this cell line. At first, the T-DM1 effectively inhibited the YES1-amplified trastuzumab-resistant cell line, but resistance to T-DM1 gradually developed. YES1 amplification was further enhanced after acquired resistance to T-DM1 became apparent, and the knockdown of the YES1 or the administration of the Src inhibitor dasatinib restored sensitivity to T-DM1. Our results indicate that YES1 is also strongly associated with T-DM1 resistance after the development of acquired resistance to trastuzumab, and the continuous inhibition of YES1 is important for overcoming resistance to T-DM1.

Abstract P6-20-17: Targeting SHP2 for the treatment of HER2-positive breast cancer

Abstract Approximately 20% of breast cancer (BC) is caused by overexpression of the human epidermal growth factor receptor 2 (HER2). As a result, several antibody-based and small molecule-based anti-HER2 therapies have been developed. These drugs have benefited BC patients by improving overall survival and quality of life. However, development of resistance and disease recurrence have been the major clinical challenges. One way to overcome these clinical problems is to develop alternative therapeutic strategies. Multiple lines of evidence show that targeting the Src homology phosphotyrosyl phosphatase 2 (SHP2) in HER2-positive BC may prove beneficial both in treatment-naïve and anti-HER2 therapy-resistant forms of the disease. For instance, silencing SHP2 expression in HER2-positive breast cancer cells or conditional knockout in ErbB2 transgenic mice blocks HER2 overexpression and associated signaling, leading to loss of cell transformation and tumorigenesis. To test the clinical translational significance of SHP2 targeting, we have invented a specific small molecule SHP2 inhibitor named WGMDY (US 9,932,288) that has shown promising anti-cancer effects. The results obtained so far show that inhibition of SHP2 with WGMDY blocks HER2 expression, suppresses cell proliferation and anchorage independent growth, and induces regression of preformed xenograft tumors. These findings suggest that SHP2 might be an excellent drug target for HER2-positive BC and WGMDY has a promising potential to serve as a lead compound for developing anti-SHP2 drugs. Citation Format: Agazie Y, Hartman Z. Targeting SHP2 for the treatment of HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-17.

Downregulation of LncRNA GAS5 causes trastuzumab resistance in breast cancer.

Therapeutic resistance to trastuzumab caused by dysregulation of long noncoding RNAs (lncRNAs) is a major obstacle to clinical management of HER2-positive breast cancer. To investigate which lncRNAs contribute to trastuzumab resistance, we screened a microarray of lncRNAs involved in the malignant phenotype of trastuzumab-resistant SKBR-3/Tr cells. Expression of the lncRNA GAS5 was decreased in SKBR-3/Tr cells and in breast cancer tissue from trastuzumab-treated patients. Inhibition of GAS5 promoted SKBR-3 cell proliferation, and GAS5 knockdown partially reversed lapatinib-induced inhibition of SKBR-3/Tr cell proliferation. GAS5 suppresses cancer proliferation by acting as a molecular sponge for miR-21, leading to the de-repression of phosphatase and tensin homologs (PTEN), the endogenous target of miR-21. Moreover, mTOR activation associated with reduced GAS5 expression was required to suppress PTEN. This work identifies GAS5 as a novel prognostic marker and candidate drug target for HER2-positive breast cancer.

Design and Optimization of Peptide Ligands to Target Breast Cancer-Positive HER2 by Grafting and Truncation of MIG6 Peptide

The human epidermal growth factor receptor 2 (EGFR2 or HER2) has been established as a therapeutic target for HER2-positive breast cancer. Although a number of small-molecule agents have been developed to target HER2, many adverse drug reactions (ADRs) such as side effects and drug resistance are frequently observed in the chemotherapeutics. Previously, peptides derived from MIG6 protein, a natural negative regulator of EGFR and HER2, have been shown to destabilize EGFR dimerization (Zhang et al. 2007). Here, we grafted a MIG6 fragment (336KSLPSYLNGVMPPTQSFAPDPKYVSS361) in crystal interaction site from EGFR to HER2, truncated the fragment to obtain a short segment (346MPPTQSFA353) with reserved binding capability (K d = 121.6 ± 14.5 μM) to HER2 kinase domain, and optimized the segment to improve its affinity for the domain. Consequently, three peptides (MLPNQSFA, MFPNQSFA and MFPYQSFA) were successfully designed to exhibit moderate or high potency (K d = 78.0 ± 9.8, 28.7 ± 3.9 and 65.1 ± 7.2 μM, respectively) towards HER2 kinase domain, which are expected to destabilize HER2 dimerization and then suppress the kinase activation in breast cancer.

Effect of Her2 Overexpression on Cancer Stem-Like Characteristics of Triple-Negative Breast Cancer Cells

ABSTRACT Aim: Cancer stem cells (CSCs) have been proposed to constitute a subpopulation of undifferentiated tumor cells that are resistant to both radio- and chemotherapy. The population exhibiting CD44+/CD24- is generally accepted to be human breast CSCs. However the overexpression of CD24 in breast cancer is associated with a poor patient prognosis. HER2-positive breast cancers are predominantly positive for CD24, which has been identified as a marker of differentiated normal mammary epithelial cells. We aimed to investigate the relationship between HER2 and CD24. Methods: We established stable HER2-expressing cell lines by introducing a wild type HER2 gene into 231-Luc triple-negative (ER- PgR- HER2-) breast cancer cells, having stem-like characteristics. Then, we determined the functional relevance of CD24 expression in HER2-positive breast cancer cells. We also investigated the expression of CD44, CD24 and HER2 by flow cytometry analysis. Results: Overexpression of HER2 decreased representative CSC properties, such as the sphere-forming ability and ALDH1 activity, and did not affect the tumorigenicity of 231-Luc triple-negative breast cancer cells. Flow cytometry analysis revealed that stable overexpression of HER2 up-regulates CD24 in triple-negative breast cancer. Positive relationship between HER2 and CD24 expression was also confirmed in HER2-positive breast cancer cell lines: BT-474, HCC202, SKBR3, and HCC1569. Given that overexpression of HER2 increases the level of Akt phosphorylation, we examined if CD24 depletion might suppress Akt phosphorylation in HER2-expressing cells. Successfully, the phosphorylation of Akt was down-regulated by CD24 depletion in the HER2-expressing cells. Moreover, knockdown of CD24 increased the sensitivity of HER2-expressing cells to lapatinib, a dual tyrosine kinase inhibitor for both EGFR and HER2. Conclusions: HER2 may have some contribution to stem-like characteristics of breast cancer cells but other factors are required to regulate CSC functions. CD24 supports both the expression of HER2 and the consequent activation of the PIK3/AKT signaling pathway so as to promote cell survival. CD24 appears to contribute to the resistance to HER2-targeted therapy and is itself a potential therapeutic target in HER2-positive breast cancer. Disclosure: All authors have declared no conflicts of interest.

Expression of CD24 is associated with HER2 expression and supports HER2‐Akt signaling in HER2‐positive breast cancer cells

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is treated with HER2-targeted agents, such as trastuzumab and lapatinib, that suppress signaling by phosphatidylinositol 3-kinase (PI3K)-Akt and MAPK pathways. However, resistance to HER2-targeted therapy remains a major clinical problem. Overexpression of CD24 has been detected in many cancers and is associated with a poor prognosis in women with breast cancer. HER2-positive breast tumors are predominantly positive for CD24, suggesting that the expression of the two molecules is related. To investigate the relation between HER2 and CD24, we overexpressed HER2 in breast cancer cells that were triple-negative for the estrogen receptor, progesterone receptor and HER2. We found that expression of CD24 was increased by stable overexpression of HER2. Flow cytometry thus revealed that the percentage of CD24-positive cells was markedly higher in the HER2-positive fraction than in the HER2-negative fraction. Knockdown of CD24 in breast cancer cells positive for endogenous HER2 downregulated HER2 expression, whereas knockdown of HER2 did not affect the expression of CD24. Knockdown of CD24 also suppressed the phosphorylation of Akt, which functions downstream of HER2 and PI3K to promote cell survival. Moreover, knockdown of CD24 increased the sensitivity of HER2-positive breast cancer cells to lapatinib treatment. Our results thus indicate that CD24 supports both the expression of HER2 and the consequent activation of PI3K-Akt signaling. Furthermore, CD24 may contribute to resistance to HER2-targeted therapy and, therefore, is itself a potential therapeutic target in HER2-positive breast cancer.

MiR‐199b‐5p targets HER2 in breast cancer cells

HER2 (ErbB2) has been reported to be overexpressed in 20-30% of breast cancer and confers poor survival because of high proliferation and metastasis rates. MicroRNAs are small noncoding RNAs that are responsible for the post-transcriptional regulation of target genes. We found miR-199b-5p inhibited HER2 expression by direct targeting its 3'-untranslated region (3'UTR) in breast cancer cells. In addition, miR-199b-5p inhibited HER2 downstream signaling by ERK1/2 and AKT pathways in breast cancer cells. Besides, transwell migration, wound healing, and clonogenicity were obviously inhibited by overexpression of miR-199b-5p in HER2-positive breast cancer cells. We also found that miR-199b-5p could enhance the suppression of trastuzumab on cell migration and clonogenicity. These results suggest that miR-199b-5p may have the potential to be a novel important alternative therapeutic target for HER2-positive breast cancer.

ADAM17 as a novel therapeutic target for HER2-positive breast cancer.

622 Background: Although the HER2 gene is amplifiend/overexpressed in 15-20% of breast cancers, only a proportion of these patients benefit from anti-HER2 therapy. Clearly additional biomarkers and/or therapeutic targets are necessary to enhance efficacy and improve outcome in these patients. Here, we tested the hypothesis that inhibition of ADAM17-mediated release of HER ligands may enhance response to trastuzumab and lapatinib. Methods: The ADAM17-selective inhibitor, PF-5480090 (Pfizer) both alone and in combination with lapatinib, trastuzumab or 5FU was tested for potential growth inhibitory effects on a panel of 4 HER2-positive breast cancer cell lines (BT474, MDA-MB-453, SKBR3 and JIMT-1). Results: Using the MTT viability assay, treatment with 1 µM TMI-2 resulted in a significant reduction in cell proliferation compared to vehicle control in BT474 (p=0.01), MDA-MB-453 (p < 0.005), JIMT-1 (p=0.002) and SKBR3 cells (p < 0.005). Addition of PF-5480090 to lapatinib resulted in a significant reduction in cell growth compared to lapatinib alone (JIMT-1: p < 0.005; SKBR3: p < 0.005; MDA-MB-453: p < 0.005), while addition of PF-5480090 to trastuzumab resulted in significant reduction in cell growth compared to trastuzumab alone (JIMT-1: p < 0.005; SKBR3: p < 0.005; MDA-MB-453: p=0.001). Addition of PF-5480090 to 5FU resulted in significant reduction in growth compared to 5FU alone (JIMT-1: p < 0.005; SKBR3: p < 0.005; MDA-MB-453: p=0.001). Consistent with its ability to block proliferation, addition of PF-5480090 significantly reduced release of TGFalpha (BT474: p=0.003; JIMT1: p=0.023; SKBR3: p=0.036 and MDA-MB-453: p=0.014). Conclusions: Inhibitionof ADAM17 resulted in growth inhibitory responses in HER2-positive breast cancer cell lines. Furthermore, addition of PF-5480090 to lapatinib, trastuzumab or 5FU resulted in significant growth inhibition compared to these agents alone. We propose that inhibition of ADAM17 may be used in combination with existing treatments for HER2-positive breast cancer. Acknowledgement. The authors thank SFI (SRC award, 08/SRC/B1410 to MTCI) for funding this work.

Dual mTORC1/2 and HER2 Blockade Results in Antitumor Activity in Preclinical Models of Breast Cancer Resistant to Anti-HER2 Therapy

The PI3K/Akt/mTOR pathway is an attractive target in HER2-positive breast cancer that is refractory to anti-HER2 therapy. The hypothesis is that the suppression of this pathway results in sensitization to anti-HER2 agents. However, this combinatorial strategy has not been comprehensively tested in models of trastuzumab and lapatinib resistance. We analyzed in vitro cell viability and induction of apoptosis in five different cell lines resistant to trastuzumab and lapatinib. Inhibition of HER2/HER3 phosphorylation, PI3K/Akt/mTOR, and extracellular signal-regulated kinase (ERK) signaling pathways was evaluated by Western blotting. Tumor growth inhibition after treatment with lapatinib, INK-128, or the combination of both agents was evaluated in three different animal models: two cell-based xenograft models refractory to both trastuzumab and lapatinib and a xenograft derived from a patient who relapsed on trastuzumab-based therapy. The addition of lapatinib to INK-128 prevented both HER2 and HER3 phosphorylation induced by INK-128, resulting in inhibition of both PI3K/Akt/mTOR and ERK pathways. This dual blockade produced synergistic induction of cell death in five different HER2-positive cell lines resistant to trastuzumab and lapatinib. In vivo, both cell line-based and patient-derived xenografts showed exquisite sensitivity to the antitumor activity of the combination of lapatinib and INK-128, which resulted in durable tumor shrinkage and exhibited no signs of toxicity in these models. The simultaneous blockade of both PI3K/Akt/mTOR and ERK pathways obtained by combining lapatinib with INK-128 acts synergistically in inducing cell death and tumor regression in breast cancer models refractory to anti-HER2 therapy.

Serum CD44 levels and overall survival in patients with HER2-positive breast cancer

CD44 is an adhesion molecule involved in tumor cell invasion and metastasis. The function of CD44 in breast cancer is not understood completely, or is its role as a predictive or prognostic factor. In this study, we tested for the hypothesis that the concentration of soluble CD44 (sCD44) in serum is correlated with clinicopathological factors, especially HER2, and survival in patients with breast cancer. We retrospectively identified 110 patients with breast cancer who had been treated at The University of Texas MD Anderson Cancer Center (MDACC) from September 2001 to May 2004. Sera were collected before definitive surgery in patients with stage I or II breast cancer, before initiation of neoadjuvant chemotherapy (if indicated) for patients with stage I-III breast cancer, and before initiation of systemic therapy in patients with stage IV breast cancer. sCD44 levels were determined using an enzyme-linked immunosorbent assay. The median age at diagnosis was 51 years (range, 28.6-87.1 years). sCD44 concentration was correlated with tumor stage (P = 0.0308). sCD44 serum concentration did not predict pathological response in patients treated with neoadjuvant chemotherapy. Among patients with distant metastases, sCD44 levels were significantly higher in patients with liver involvement than in patients with metastases at other sites. The overall survival rate did not differ between patients with high sCD44 concentration and patients with low sCD44 concentration. However, sCD44 concentration was a significant predictor of overall survival for patients with HER2-positive breast cancer, while no difference in overall survival rates was observed in patients with HER2-negative breast cancer. To the best of our knowledge, this is the first study to show an association between circulating sCD44 levels and survival in HER2-positive breast cancer patients. Our results suggest a role for sCD44 as a prognostic marker. Furthermore, sCD44 level may offer a new clinical therapeutic target in HER2-positive breast cancer.

Calpain regulates sensitivity to trastuzumab and survival in HER2-positive breast cancer

Resistance to anti-HER2 (human epithelial growth factor receptor 2) trastuzumab therapy occurs commonly in HER2-positive breast cancer and involves overactivation of HER2 and/or AKT1. Using the model of trastuzumab-sensitive or trastuzumab-resistant HER2-positive cells with wild-type PTEN, negative regulator of AKT1, we explore the involvement of cysteine protease calpain in mechanisms of trastuzumab resistance. Overexpression of calpain1 or activation of endogenous calpain during adhesion or trastuzumab treatment of trastuzumab-sensitive cells induces cleavage of cytoplasmic domains of HER2/phospho-HER2; cleavage occurs in HER2-positive tumors. Expression of the catalytically inactive mutant of calpain1 reduces the cleavage to enhance the activity of HER2, inactivates PTEN to enhance the activation of AKT1, induces desensitization to trastuzumab and promotes survival of trastuzumab-sensitive cells. In the model of trastuzumab resistance, constitutive overactivation of HER2 and AKT1 correlates with reduced activation of calpain. Moreover, inhibitors of the catalytic site of calpain reduce the increase in constitutive activity of AKT1 and survival of trastuzumab-resistant cells selectively. Together, by regulating the activation of HER2 and PTEN/AKT1, calpain regulates trastuzumab sensitivity and survival, and the deregulation of the activation of calpain promotes trastuzumab resistance. Trastuzumab-resistant cells activate AKT1 in a mechanism dependent on the residual calpain activity, inhibition of which restores trastuzumab sensitivity and rescues resistance. These data identify calpain as a new therapeutic target in HER2-positive breast cancer.