p95HER2 and breast cancer

Exploratory analysis of serum HER2 extracellular domain for HER2 positive gastric cancer treated with SOX plus trastuzumab

BACKGROUND

The aim of this study was to explore the clinical utility of serum HER2 extracellular domain (sHER2 ECD) using data from a clinical trial evaluating trastuzumab combined S-1 plus oxaliplatin (SOX) in HER2 positive gastric cancer.

METHODS

sHER2 ECD were prospectively measured at baseline and subsequent treatment courses. Based on each quantile point of baseline sHER2 ECD levels and its early changes, patients were divided into two groups and compared clinical outcomes.

RESULTS

43 patients were enrolled, and 17 patients (39.5%) were positive for baseline sHER2 ECD. Higher baseline sHER2 ECD levels tended to have lower hazard ratios (HRs). When divided into two groups by baseline sHER2 ECD of 19.1 ng/ml, median progression-free survival (PFS) and overall survival (OS) was longer in the higher group (mPFS: 16.8 vs 8.7 months, p = 0.359. mOS: 35.5 vs 20.6 months, p = 0.270), respectively. After initiation of treatment, sHER2 ECD significantly decreased up until the third cycle. Higher reduction rates of sHER2 ECD within 3 cycles also tended to have lower HRs. When divided into two groups by reduction rate of 42.5%, mPFS and mOS was longer in the higher reduced group (mPFS: 17.2 vs 8.7 months, p = 0.095. mOS: 65.0 vs 17.8 months, p = 0.047), respectively. Furthermore, higher reduction rates could surrogate higher objective response rates (ORR) (ORR: 90% vs 63.2% for 29.5%, p = 0.065. 100% vs 70% for 42.5%, p = 0.085), respectively.

CONCLUSIONS

Baseline sHER2 ECD levels and its early decline may be useful biomarkers for SOX plus trastuzumab efficacy in HER2 positive gastric cancer.

LINC02535 + miR-30a-5p combination enhances proliferation and inhibits apoptosis in metastatic breast Cancer cells

Current clinical therapies for metastatic breast cancer (MBC) have limited therapeutic efficacy and induce significant systemic side effects, leading to poor patient compliance. To address this challenge, this investigation focuses on the design of LINC02535 + miR-30a-5p for treating breast cancer. In vitro cytotoxicity studies confirmed that LINC02535 + miR-30a-5p was more effective in 4 T1 cells, with reduced toxicity in NIH3T3 cells. Further verification of cellular morphology was achieved through various biochemical staining methods. Additionally, the antimetastatic attributes of LINC02535 + miR-30a-5p have been evaluated using both migration scratch and Transwell migration assays, which have collectively revealed excellent antimetastatic potential. The DNA fragmentation of the 4 T1 cells was assessed using a comet assay. LINC02535 + miR-30a-5p improved ROS levels and caused mitochondrial membrane potential alterations and DNA damage, which resulted in apoptosis. Therefore, we propose that LINC02535 + miR-30a-5p could be an alternative therapeutic strategy for breast cancer therapy.

Three-dimensional cell culture of chimeric antigen receptor T cells originated from peripheral blood mononuclear cells towards cellular therapies

BACKGROUND AIMS

With the objective of improving the ex vivo production of therapeutic chimeric antigen receptor (CAR) T cells, we explored the addition of three-dimensional (3D) polystyrene scaffolds to standard suspension cell cultures.

METHODS

We aimed to mimic the structural support given by the lymph nodes during in vivo lymphocyte expansion.

RESULTS

We observed an increase in cell proliferation compared with standard suspension systems as well as an enhanced cytotoxicity toward cancer cells. Moreover, we directly obtained the CAR T cells from peripheral blood mononuclear cells, thus minimizing the ex vivo manipulation of the therapeutic cells and opening the way to synergies among different cell populations.

CONCLUSIONS

We propose the use of commercially available 3D polystyrene systems to improve the current immune cell cultures and resulting cell products for emerging cellular (immuno)therapies.

R. H, Liu J, B. M. N, Zhao D, Vishwanath P, B. M. G, Fan R. Screening fructosamine-3-kinase (FN3K) inhibitors, a deglycating enzyme of oncogenic Nrf2: Human FN3K homology modelling, docking and molecular dynamics simulations

Fructosamine-3-kinase (FN3K) is involved in the deglycation of Nrf2, a significant regulator of oxidative stress in cancer cells. However, the intricate functional aspects of FN3K and Nrf2 in breast cancers have not been explored vividly. The objectives of this study are to design the human FN3K protein using homology modeling followed by the screening of several anticancer molecules and examining their efficacy to modulate FN3K activity, Nrf2-mediated antioxidant signalling. Methods pertinent to homology modeling, virtual screening, molecular docking, molecular dynamics simulations, assessment of ADME properties, cytotoxicity assays for anticancer molecules of natural/synthetic origin in breast cancer cells (BT-474, T-47D), and Western blotting were used in this study. The screened anticancer molecules including kinase inhibitors of natural and synthetic origin interacted with the 3-dimensional structure of the catalytic domain in human FN3K protein designed through homology modeling by significant CDOCKER interaction energies. Subsequently, gefitinib, sorafenib, neratinib, tamoxifen citrate, and cyclosporine A enhanced the expression of FN3K in BT-474 cell lines with simultaneous alteration in Nrf2-driven antioxidant signalling. Oxaliplatin significantly downregulated FN3K expression and modulated Nrf2-driven antioxidant signalling when compared to cisplatin and other anticancer drugs. Hence, the study concluded the potential implications of existing anticancer drugs to modulate FN3K activity in breast cancers.

Emerging insights into mechanisms of trastuzumab resistance in HER2-positive cancers

HER2 is an established therapeutic target in breast, gastric, and gastroesophageal junction carcinomas with HER2 overexpression or genomic alterations. The humanized monoclonal antibody trastuzumab targeting HER2 has substantially improved the clinical outcomes of HER2-positive patients, yet the inevitable intrinsic or acquired resistance to trastuzumab limits its clinical benefit, necessitating the elucidation of resistance mechanisms to develop alternate therapeutic strategies. This review presents an overview of trastuzumab resistance mechanisms involving signaling pathways, cellular metabolism, cell plasticity, and tumor microenvironment, particularly discussing the prospects of developing rational combinations to improve patient outcomes.

Hierarchically Structured Molecularly Imprinted Nanotransducers for Truncated HER2-Targeted Photodynamic Therapy of Therapeutic Antibody-Resistant Breast Cancer

Antibodies have been a mainstream class of therapeutics for clinical treatment of various diseases, especially cancers. However, mutation in cancer cells leads to resistance to therapeutic antibodies, hyperactivity of proliferation of cancer cells, and difficulty in the development of therapeutic antibodies. Herein, we present a strategy termed molecularly imprinted nanotransducer (MINT) for targeted photodynamic therapy (PDT) of mutated cancers. The MINT is a rationally engineered nanocomposite featuring a core of an upconversion nanoparticle, a shell of a thin layer of molecularly imprinted polymer, and a photosensitizer modified on the surface. As a proof-of-principle, truncated HER2 (P95HER2) overexpressed breast cancer, a challenging cancer lacking effective targeted therapeutics, was used as the cancer model. The designed structure, properties, functions, and anticancer efficacy of MINT were systematically investigated and experimentally confirmed. The MINT could not only specifically target P95HER2+ cancer cells in vitro and in vivo but also efficiently transfer the irradiated light and generate excited-state oxygen, resulting in efficient targeted cancer killing. Therefore, the MINT strategy provides a promising therapeutic for targeted PDT of drug-resistant cancers caused by target mutation.

Mammalian orthoreovirus infection in human epidermal growth factor receptor 2 positive (HER2+) breast cancer cells

Mammalian orthoreovirus (MRV) is a clinically benign oncolytic virus which has been investigated for use in multiple cancer types, including breast cancer (BC). In human clinical trials, MRV has been shown to be safe, and multiple BC patients have shown partial responses to intratumoral and intravenous virus delivery. Combination therapies inclusive of MRV and current FDA approved BC chemotherapies are being investigated to target metastatic, early BC, and triple negative BC. Though MRV is being tested clinically, we still do not fully understand the highly variable patient responses to MRV therapy. One of the most aggressive BC subtypes is HER2+ BC, in which human epidermal growth factor receptor 2 (HER2) is dysregulated, resulting in increased growth, survival, and metastasis of cancer cells. FDA approved therapies, trastuzumab and pertuzumab, target HER2 to prevent signaling of the phosphoinositide 3-kinase (PI3K) pathway. However, recent findings show that accumulation of hypoxia inducible factor-1 alpha (HIF-1α) in HER2+ BC cells contributes to trastuzumab resistance. In this work, we provide evidence that MRV infects, replicates in, and kills HER2 overexpressing cells. MRV infection is also found to have variable effects on signaling pathways that activate or are activated by HER2 expression. Finally, we show that MRV reduces HIF-1α accumulation in all the cell lines tested, including a HER2+ BC cell line. These studies provide further evidence that MRV holds promise for use in conjunction with trastuzumab to treat HER2+ BC patients.

Detailed curriculum vitae of HER2-targeted therapy

With the booming development of precision medicine, molecular targeted therapy has been widely used in clinical oncology treatment due to a smaller number of side effects and its superior accuracy compared to that of traditional strategies. Among them, human epidermal growth factor receptor 2 (HER2)-targeted therapy has attracted considerable attention and has been used in the clinical treatment of breast and gastric cancer. Despite excellent clinical effects, HER2-targeted therapy remains in its infancy due to its resulting inherent and acquired resistance. Here, a comprehensive overview of HER2 in numerous cancers is presented, including its biological role, involved signaling pathways, and the status of HER2-targeted therapy.

"A Review of HER2 overexpression and somatic mutations in cancers"

The Human Epidermal Growth Factor Receptor (HER) proteins family, which includes HER2, are membrane-bound receptors that activate many intracellular pathways associated with growth and development. When there are mutations in HER2, or when it becomes overexpressed, it can cause oncogenesis and offer differential prognosis and treatment across almost all cancer types. Both mutations in HER2 and its overexpression have distinct mechanisms by which they can cause these effects in cancers. This review outlines how HER2's normal pathway is altered in both overexpression and mutation and compiles all the well-known mechanisms by which HER2 can cause oncogenesis. Finally, this review briefly outlines how HER2 mutants and HER2 overexpression is detected, and how their detection can lead to different prognosis and treatment in cancers.

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.

Resistance to Antibody-Drug Conjugates Targeting HER2 in Breast Cancer: Molecular Landscape and Future Challenges

The treatment of HER2-positive metastatic breast cancer (mBC) with Trastuzumab emtansine (T-DM1) and Trastuzumab deruxtecan (T-DXd), two antibody-drug conjugates (ADCs) targeting HER2, is burdened by progression of disease related to the acquisition of mechanisms of resistance. Resistance to T-DM1 is caused by the decrease of HER2 expression, the alteration of intracellular trafficking, the impairment of lysosome functions, the drug expulsion through efflux pumps and the activation of alternative signal pathways. Instead, the decrease of HER2 expression and SLX4 loss of function mutations represent the first evidences of mechanisms of resistance to T-DXd, according to the results of DAISY trial. Several strategies are under evaluation to overcome resistances to anti-HER2 ADCs and improve clinical outcomes in patients progressing on these agents: combinations with tyrosine kinase inhibitors, statins, immune checkpoint inhibitors and synthetic DNA-damaging agents are emerging as promising approaches. Furthermore, novel anti-HER2 ADCs with innovative structures and mechanisms of action are in development, in the attempt to further improve the activity and tolerability of currently available agents.

Immunotherapies against HER2-Positive Breast Cancer

Breast cancer is the leading cause of cancer-related deaths among women worldwide. HER2-positive breast cancer, which represents 15-20% of all cases, is characterized by the overexpression of the HER2 receptor. Despite the variety of treatments available for HER2-positive breast cancer, both targeted and untargeted, many patients do not respond to therapy and relapse and eventually metastasize, with a poor prognosis. Immunotherapeutic approaches aim to enhance the antitumor immune response to prevent tumor relapse and metastasis. Several immunotherapies have been approved for solid tumors, but their utility for HER2-positive breast cancer has yet to be confirmed. In this review, we examine the different immunotherapeutic strategies being tested in HER2-positive breast cancer, from long-studied cancer vaccines to immune checkpoint blockade, which targets immune checkpoints in both T cells and tumor cells, as well as the promising adoptive cell therapy in various forms. We discuss how some of these new approaches may contribute to the prevention of tumor progression and be used after standard-of-care therapies for resistant HER2-positive breast tumors, highlighting the benefits and drawbacks of each. We conclude that immunotherapy holds great promise for the treatment of HER2-positive tumors, with the potential to completely eradicate tumor cells and prevent the progression of the disease.

A Review of Margetuximab-Based Therapies in Patients with HER2-Positive Metastatic Breast Cancer

Breast cancer (BC) is the most commonly diagnosed cancer globally, with high mortality rates. Targeted drug therapies have revolutionized cancer treatment. For example, treatment with human epidermal receptor 2 (HER2) antagonists has markedly improved the prognosis of patients with HER2-positive BC (HER2 + BC). However, HER2+ metastatic BC (MBC) remains prevalent owing to its resistance to conventional anti-HER2 drugs. Therefore, novel agents are needed to overcome the limitations of existing cancer treatments and to enhance the progression-free and overall survival rates. Progress has been made by optimizing the fragment crystallizable (Fc) domain of trastuzumab, an IgG1 monoclonal, chimeric anti-HER2 antibody, to develop margetuximab. The modified Fc domain of margetuximab enhances its binding affinity to CD16A and decreases its binding affinity to CD32B, thereby promoting its antitumor activity. This review summarizes studies on the efficacy of margetuximab, discusses its utility as an anti-HER2 monoclonal antibody drug for the treatment of HER2 + BC, and presents the latest advances in the treatment of BC. This review provides insights into the clinical implication of margetuximab in HER2 + MBC treatment.

Resistance to Trastuzumab

Simple Summary

Trastuzumab is a humanized antibody that has significantly improved the management and treatment outcomes of patients with cancers that overexpress HER2. Many research groups, both in academia and industry, have contributed towards understanding the various mechanisms engaged by trastuzumab to mediate its anti-tumor effects. Nevertheless, data from several clinical studies have indicated that a significant proportion of patients exhibit primary or acquired resistance to trastuzumab therapy. In this article, we discuss underlying mechanisms that contribute towards to resistance. Furthermore, we discuss the potential strategies to overcome some of the mechanisms of resistance to enhance the therapeutic efficacy of trastuzumab and other therapies based on it.

Abstract

One of the most impactful biologics for the treatment of breast cancer is the humanized monoclonal antibody, trastuzumab, which specifically recognizes the HER2/neu (HER2) protein encoded by the ERBB2 gene. Useful for both advanced and early breast cancers, trastuzumab has multiple mechanisms of action. Classical mechanisms attributed to trastuzumab action include cell cycle arrest, induction of apoptosis, and antibody-dependent cell-mediated cytotoxicity (ADCC). Recent studies have identified the role of the adaptive immune system in the clinical actions of trastuzumab. Despite the multiple mechanisms of action, many patients demonstrate resistance, primary or adaptive. Newly identified molecular and cellular mechanisms of trastuzumab resistance include induction of immune suppression, vascular mimicry, generation of breast cancer stem cells, deregulation of long non-coding RNAs, and metabolic escape. These newly identified mechanisms of resistance are discussed in detail in this review, particularly considering how they may lead to the development of well-rationalized, patient-tailored combinations that improve patient survival.

Upregulation of Receptor Tyrosine Kinase Activity and Stemness as Resistance Mechanisms to Akt Inhibitors in Breast Cancer

The PI3K/Akt pathway is frequently deregulated in human cancers, and multiple Akt inhibitors are currently under clinical evaluation. Based on the experience from other molecular targeted therapies, however, it is likely that acquired resistance will be developed in patients treated with Akt inhibitors. We established breast cancer models of acquired resistance by prolonged treatment of cells with allosteric or ATP-competitive Akt inhibitors. Phospho-Receptor tyrosine kinase (Phospho-RTK) arrays revealed hyper-phosphorylation of multiple RTKS, including EGFR, Her2, HFGR, EhpB3 and ROR1, in Akt-inhibitor-resistant cells. Importantly, resistance can be overcome by treatment with an EGFR inhibitor. We further showed that cancer stem cells (CSCs) are enriched in breast tumor cells that have developed resistance to Akt inhibitors. Several candidates of CSC regulators, such as ID4, are identified by RNA sequencing. Cosmic analysis indicated that sensitivity of tumor cells to Akt inhibitors can be predicted by ID4 and stem cell/epithelial-mesenchymal transition pathway targets. These findings indicate the potential of targeting the EGFR pathway and CSC program to circumvent Akt inhibitor resistance in breast cancer.

Discordance of positive immunohistochemical results among different primary HER2 antibodies used in breast cancer: A comparison between Histofine® HER2 Kit (MONO) SV2-61γ antibody and Ventana I-VIEW PATHWAY™ HER2 4B5 antibody

INTRODUCTION

Immunohistochemical (IHC) testing for human epidermal growth factor receptor 2 (HER2) expression status renders variable scores among different primary antibodies.

MATERIALS AND METHODS

We assessed HER2 expression status by IHC score using two types of kits, i.e., Roche Ventana I-VIEW PATHWAY™ HER2 using the 4B5 antibody that recognizes the intracellular domain (ICD) and Nichirei Biosciences Histofine® HER2 Kit (MONO) using the SV2-61γ antibody that recognizes the extracellular domain (ECD). In addition, we determined the presence or absence of the ECD in samples by Western blotting (WB) and examined its relationship with the IHC score.

RESULTS

Of 101 samples, 44 and 9 samples received a score of 2+/3+ by IHC with 4B5 and SV2-61γ, respectively. A verification by WB in samples with a discrepancy of IHC scores found that samples with the score of 2+/3+ with SV2-61γ showed a significantly higher protein intensity of p185HER2 with the ECD, whereas samples with a score of 2+/3+ with 4B5 but as 0/1+ with SV2-61γ showed a significantly higher protein intensity of p95HER2 without the ECD.

CONCLUSION

The nature of primary antibodies used for IHC and the presence or absence of the ECD in samples may contribute to different positive rates between 4B5 and SV2-61γ.

Novel Therapies and Strategies to Overcome Resistance to Anti-HER2-Targeted Drugs

The prognosis and quality of life of HER2 breast cancer patients have significantly improved due to the crucial clinical benefit of various anti-HER2 targeted therapies. However, HER2 tumors can possess or develop several resistance mechanisms to these treatments, thus leaving patients with a limited set of additional therapeutic options. Fortunately, to overcome this problem, in recent years, multiple different and complementary approaches have been developed (such as antibody-drug conjugates (ADCs)) that are in clinical or preclinical stages. In this review, we focus on emerging strategies other than on ADCs that are either aimed at directly target the HER2 receptor (i.e., novel tyrosine kinase inhibitors) or subsequent intracellular signaling (e.g., PI3K/AKT/mTOR, CDK4/6 inhibitors, etc.), as well as on innovative approaches designed to attack other potential tumor weaknesses (such as immunotherapy, autophagy blockade, or targeting of other genes within the HER2 amplicon). Moreover, relevant technical advances such as anti-HER2 nanotherapies and immunotoxins are also discussed. In brief, this review summarizes the impact of novel therapeutic approaches on current and future clinical management of aggressive HER2 breast tumors.

Inactivating amplified HER2: challenges, dilemmas, and future directions

The pharmaceutical inactivation of driver oncogenes has revolutionized the treatment of cancer replacing cytotoxic chemotherapeutic approaches with kinase inhibitor therapies for many types of cancers. This approach has not yet been realized for the treatment of HER2-amplified cancers. The monotherapy activities associated with HER2-targeting antibodies and kinase inhibitors are modest, and their clinical use has been in combination with, and not in replacement of cytotoxic chemotherapies. This stands in sharp contrast to achievements in the treatment of many other oncogene-driven cancers. The mechanism-based treatment hypothesis regarding the inactivation of HER2 justifies expectations far beyond what is currently realized. Overcoming this barrier requires mechanistic insights that can fuel new directions for pursuit, but scientific investigation of this treatment hypothesis, particularly with regards to trastuzumab, has been complicated by conflicting and confusing data sets, ironclad dogma, and mechanistic conclusions that have repeatedly failed to translate clinically. We are now approaching a point of convergence regarding the challenges and resiliency in this tumor driver, and I will provide here a review and opinion to inform where we currently stand with this treatment hypothesis and where the future potential lies.

Discovery of SPH5030, a Selective, Potent, and Irreversible Tyrosine Kinase Inhibitor for HER2-Amplified and HER2-Mutant Cancer Treatment

Small-molecule irreversible tyrosine kinase inhibitors as high potent agents have led to improvements in disease-free and overall survival in patients with HER2-amplified cancer. The approved irreversible HER2 inhibitors, neratinib and pyrotinib, both lack HER2 selectivity, leading to off-target adverse events in patients. The development of HER2 mutation during treatment also hampers the progress of the treatment. We used a molecular hybridization strategy for structural optimizations, in conjunction with in vitro and in vivo drug-like property screening, to obtain a clinical candidate SPH5030. Overall, SPH5030 showed excellent activities against four frequent kinds of HER2 mutants and high relative HER2 selectivity compared with neratinib and pyrotinib, good pharmacokinetic characteristics with desirable bioavailabilities, and significant in vivo antitumor efficacy in xenograft mouse models, especially in a HER2 mutation A775_G776insYVMA xenograft mouse model with its potency much higher than those of neratinib and pyrotinib.

Evolution of HER2-positive mammary carcinoma: HER2 loss reveals claudin-low traits in cancer progression

HER2-positive breast cancers may lose HER2 expression in recurrences and metastases. In this work, we studied cell lines derived from two transgenic mammary tumors driven by human HER2 that showed different dynamics of HER2 status. MamBo89HER2^stable cell line displayed high and stable HER2 expression, which was maintained upon in vivo passages, whereas MamBo43HER2^labile cell line gave rise to HER2-negative tumors from which MamBo38HER2^loss cell line was derived. Both low-density seeding and in vitro trastuzumab treatment of MamBo43HER2^labile cells induced the loss of HER2 expression. MamBo38HER2^loss cells showed a spindle-like morphology, high stemness and acquired in vivo malignancy. A comprehensive molecular profile confirmed the loss of addiction to HER2 signaling and acquisition of an EMT signature, together with increased angiogenesis and migration ability. We identified PDGFR-B among the newly expressed determinants of MamBo38HER2^loss cell tumorigenic ability. Sunitinib inhibited MamBo38HER2^loss tumor growth in vivo and reduced stemness and IL6 production in vitro. In conclusion, HER2-positive mammary tumors can evolve into tumors that display distinctive traits of claudin-low tumors. Our dynamic model of HER2 status can lead to the identification of new druggable targets, such as PDGFR-B, in order to counteract the resistance to HER2-targeted therapy that is caused by HER2 loss.

Case Report: Effective Treatment With Pyrotinib and Capecitabine in a Heavily Pretreated Locally Advanced Breast Cancer Harboring Both HER2 Overexpression and Mutant

The prognosis for female patients with locally advanced breast cancer (LABC) has improved with the emergence of novel drugs, especially for those who have HER2 overexpression or ERBB-2 amplification. Trastuzumab-based regimen has been the paradigm in guidelines as first-line therapy, whereas many patients got progressive disease after several cycles of treatment or rapidly progress because of primary resistance. Point mutations of ERBB2 gene occur in both HER2-amplication and non-amplification patients, with a 2% ratio in HER2 non-amplification cohort and 1.48% in HER2 amplication population. The acquired mutation ratio of ERBB2 substantially raised to 16.7%–17.7% in patients prior to trastuzumab treatment. ERBB2 mutation may be a critical reason of resistance and disease progression among the patients treated with anti-HER2 monoclonal trastuzumab or dual anti-HER2 antibodies with trastuzumab and pertuzumab, or tyrosine-kinase inhibitor. ERBB-2 mutation with L755S and V842I indicates resistance to trastuzumab, while that with L755S and K753I indicates resistance to lapatinib; these mutations maybe sensitive to pan-HER tyrosine-kinase inhibitors. A 48-year woman diagnosed with HER2-positive LABC developed trastuzumab resistance after three lines of trastuzumab cross-line treatment with partial response (PR) as the best response. The tissue was performed by next-generation sequencing (NGS), and the results discovered L755S in ERBB2 gene. Then, she received effective treatment with pyrotinib plus capecitabine and underwent mastectomy after six cycles of combined treatment with PR. Subsequently, breast mastectomy was performed, and she took pyrotinib plus capecitabine for 1 year and pyrotinib monotherapy for another 1 year as adjuvant therapy and achieved a long-term clinical benefit. In conclusion, pyrotinib is a potential neoadjuvant agent for patients who are heavily pretreated and harbor both ERBB2 amplification and ERBB2 mutant in locally advanced breast cancer.

HER2 Signaling and Breast Cancer Stem Cells: The Bridge behind HER2-Positive Breast Cancer Aggressiveness and Therapy Refractoriness

Simple Summary

Breast cancer (BC) is not a single disease, but a group of different tumors, and altered HER2 expression defines a particularly aggressive subtype. Although HER2 pharmacological inhibition has dramatically improved the prognosis of HER2-positive BC patients, there is still an urgent need for improved knowledge of HER2 biology and mechanisms underlying HER2-driven aggressiveness and drug susceptibility. Emerging data suggest that the clinical efficacy of molecularly targeted therapies is related to their ability to target breast cancer stem cells (BCSCs), a population that is not only self-sustaining and able to differentiate into distinct lineages, but also contributes to tumor growth, aggressiveness, metastasis and treatment resistance. The aim of this review is to provide an overview of how the full-length HER2 receptor, the d16HER2 splice variant and the truncated p95HER2 variants are involved in the regulation and maintenance of BCSCs.

Abstract

HER2 overexpression/amplification occurs in 15–20% of breast cancers (BCs) and identifies a highly aggressive BC subtype. Recent clinical progress has increased the cure rates of limited-stage HER2-positive BC and significantly prolonged overall survival in patients with advanced disease; however, drug resistance and tumor recurrence remain major concerns. Therefore, there is an urgent need to increase knowledge regarding HER2 biology and implement available treatments. Cancer stem cells (CSCs) represent a subset of malignant cells capable of unlimited self-renewal and differentiation and are mainly considered to contribute to tumor onset, aggressiveness, metastasis, and treatment resistance. Seminal studies have highlighted the key role of altered HER2 signaling in the maintenance/enrichment of breast CSCs (BCSCs) and elucidated its bidirectional communication with stemness-related pathways, such as the Notch and Wingless/β-catenin cascades. d16HER2, a splice variant of full-length HER2 mRNA, has been identified as one of the most oncogenic HER2 isoform significantly implicated in tumorigenesis, epithelial-mesenchymal transition (EMT)/stemness and the response to targeted therapy. In addition, expression of a heterogeneous collection of HER2 truncated carboxy-terminal fragments (CTFs), collectively known as p95HER2, identifies a peculiar subgroup of HER2-positive BC with poor prognosis, with the p95HER2 variants being able to regulate CSC features. This review provides a comprehensive overview of the current evidence regarding HER2-/d16HER2-/p95HER2-positive BCSCs in the context of the signaling pathways governing their properties and describes the future prospects for targeting these components to achieve long-lasting tumor control.

Mechanisms of Therapeutic Antitumor Monoclonal Antibodies

Monoclonal antibodies (mAb) are a major component of cancer therapy. In this review, we summarize the different therapeutic mAbs that have been successfully developed against various tumor-expressed antigens and examine our current understanding of their different mechanisms of antitumor action. These mechanisms of action (MOA) largely center on the stimulation of different innate immune effector processes, which appear to be principally responsible for the efficacy of most unconjugated mAb therapies against cancer. This is evident in studies of mAbs targeting antigens for hematologic cancers, with emerging data also demonstrating the critical nature of innate immune-mediated mechanisms in the efficacy of anti-HER2 mAbs against solid HER2+ cancers. Although HER2-targeted mAbs were originally described as inhibitors of HER2-mediated signaling, multiple studies have since demonstrated these mAbs function largely through their engagement with Fc receptors to activate innate immune effector functions as well as complement activity. Next-generation mAbs are capitalizing on these MOAs through improvements to enhance Fc-activity, although regulation of these mechanisms may vary in different tumor microenvironments. In addition, novel antibody-drug conjugates have emerged as an important means to activate different MOAs. Although many unknowns remain, an improved understanding of these immunologic MOAs will be essential for the future of mAb therapy and cancer immunotherapy.

Epigenetic Silencing of HER2 Expression during Epithelial-Mesenchymal Transition Leads to Trastuzumab Resistance in Breast Cancer

HER2 receptor tyrosine kinase (encoded by the ERBB2 gene) is overexpressed in approximately 25% of all breast cancer tumors (HER2-positive breast cancers). Resistance to HER2-targeting therapies is partially due to the loss of HER2 expression in tumor cells during treatment. However, little is known about the exact mechanism of HER2 downregulation in HER2-positive tumor cells. Here, by analyzing publicly available genomic data we investigate the hypothesis that epithelial-mesenchymal transition (EMT) abrogates HER2 expression by epigenetic silencing of the ERBB2 gene as a mechanism of acquired resistance to HER2-targeted therapies. As result, HER2 expression was found to be positively and negatively correlated with the expression of epithelial and mesenchymal phenotype marker genes, respectively. The ERBB2 chromatin of HER2-high epithelial-like breast cancer cells and HER2-low mesenchymal-like cells were found to be open/active and closed/inactive, respectively. Decreased HER2 expression was correlated with increased EMT phenotype, inactivated chromatin and lower response to lapatinib. We also found that induction of EMT in the HER2-positive breast cancer cell line BT474 resulted in downregulated HER2 expression and reduced trastuzumab binding. Our results suggest that ERBB2 gene silencing by epigenetic regulation during EMT may be a mechanism of de novo resistance of HER2-positive breast cancer cells to trastuzumab and lapatinib.

Trastuzumab Mechanism of Action; 20 Years of Research to Unravel a Dilemma

Trastuzumab as a first HER2-targeted therapy for the treatment of HER2-positive breast cancer patients was introduced in 1998. Although trastuzumab has opened a new avenue to treat patients with HER2-positive breast cancer and other types of cancer, some patients are not responsive or become resistant to this treatment. So far, several mechanisms have been suggested for the mode of action of trastuzumab; however, the findings regarding these mechanisms are controversial. In this review, we aimed to provide a detailed insight into the various mechanisms of action of trastuzumab.

Multiplexed Ion Beam Imaging Readout of Single-Cell Immunoblotting

Improvements in single-cell protein analysis are required to study the cell-to-cell variation inherent to diseases, including cancer. Single-cell immunoblotting (scIB) offers proteoform detection specificity, but often relies on fluorescence-based readout and is therefore limited in multiplexing capability. Among rising multiplexed imaging methods is multiplexed ion beam imaging by time-of-flight (MIBI-TOF), a mass spectrometry imaging technology. MIBI-TOF employs metal-tagged antibodies that do not suffer from spectral overlap to the same degree as fluorophore-tagged antibodies. We report for the first-time MIBI-TOF of single-cell immunoblotting (scIB-MIBI-TOF). The scIB assay subjects single-cell lysate to protein immunoblotting on a microscale device consisting of a 50- to 75-μm thick hydrated polyacrylamide (PA) gel matrix for protein immobilization prior to in-gel immunoprobing. We confirm antibody-protein binding in the PA gel with indirect fluorescence readout of metal-tagged antibodies. Since MIBI-TOF is a layer-by-layer imaging technique, and our protein target is immobilized within a 3D PA gel layer, we characterize the protein distribution throughout the PA gel depth by fluorescence confocal microscopy and confirm that the highest signal-to-noise ratio is achieved by imaging the entirety of the PA gel depth. Accordingly, we report the required MIBI-TOF ion dose strength needed to image varying PA gel depths. Lastly, by imaging ∼42% of PA gel depth with MIBI-TOF, we detect two isoelectrically separated TurboGFP (tGFP) proteoforms from individual glioblastoma cells, demonstrating that highly multiplexed mass spectrometry-based readout is compatible with scIB.

Nectin-4 and p95-ErbB2 cooperatively regulate Hippo signaling-dependent SOX2 gene expression, enhancing anchorage-independent T47D cell proliferation

Nectin-4, upregulated in various cancer cells, cis-interacts with ErbB2 and its trastuzumab-resistant splice variants, p95-ErbB2 and ErbB2∆Ex16, enhancing DNA synthesis through the PI3K-AKT signaling in human breast cancer T47D cells in an adherent culture. We found here that nectin-4 and p95-ErbB2, but not nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively enhanced SOX2 gene expression and cell proliferation in a suspension culture. This enhancement of T47D cell proliferation in a suspension culture by nectin-4 and p95-ErbB2 was dependent on the SOX2 gene expression. In T47D cells, nectin-4 and any one of p95-ErbB2, ErbB2, or ErbB2∆Ex16 cooperatively activated the PI3K-AKT signaling, known to induce the SOX2 gene expression, to similar extents. However, only a combination of nectin-4 and p95-ErbB2, but not that of nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively enhanced the SOX2 gene expression. Detailed studies revealed that only nectin-4 and p95-ErbB2 cooperatively activated the Hippo signaling. YAP inhibited the SOX2 gene expression in this cell line and thus the MST1/2-LATS1/2 signaling-mediated YAP inactivation increased the SOX2 gene expression. These results indicate that only the combination of nectin-4 and p95-ErbB2, but not that of nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively regulates the Hippo signaling-dependent SOX2 gene expression, enhancing anchorage-independent T47D cell proliferation.

Activation of PI3K/AKT/mTOR Pathway Causes Drug Resistance in Breast Cancer

Although chemotherapy, targeted therapy and endocrine therapy decrease rate of disease recurrence in most breast cancer patients, many patients exhibit acquired resistance. Hyperactivation of the PI3K/AKT/mTOR pathway is associated with drug resistance and cancer progression. Currently, a number of drugs targeting PI3K/AKT/mTOR are being investigated in clinical trials by combining them with standard therapies to overcome acquired resistance in breast cancer. In this review, we summarize the critical role of the PI3K/AKT/mTOR pathway in drug resistance, the development of PI3K/AKT/mTOR inhibitors, and strategies to overcome acquired resistance to standard therapies in breast cancer.

HER2 Kinase-Targeted Breast Cancer Therapy: Design, Synthesis, and In Vitro and In Vivo Evaluation of Novel Lapatinib Congeners as Selective and Potent HER2 Inhibitors with Favorable Metabolic Stability

HER2 kinase as a well-established target for breast cancer (BC) therapy is associated with aggressive clinical outcomes; thus, herein we present structural optimization for HER2-selective targeting. HER2 profiling of the developed derivatives demonstrated potent and selective inhibitions (IC₅₀: 5.4-12 nM) compared to lapatinib (IC₅₀: 95.5 nM). Favorably, 17d exhibited minimum off-target kinase activation. NCI-5-dose screening revealed broad-spectrum activities (GI₅₀: 1.43-2.09 μM) and 17d had a remarkable selectivity toward BC. Our compounds revealed significant selective and potent antiproliferative activities (∼20-fold) against HER2+ (AU565, BT474) compared to HER2(-) cells. At 0.1 IC₅₀, 15i, 17d, and 25b inhibited pERK1/2 and pAkt by immunoblotting. Furthermore, 17d demonstrated potent in vivo tumor regression against the BT474 xenograft model. Notably, a metastasis case was observed in the vehicle but not in the test mice groups. CD-1 mice metabolic stability assay revealed high stability and low intrinsic clearance of 17d (T_1/2 > 145 min and CL_int(mic) < 9.6 mL/min/kg).

3D projection electrophoresis for single-cell immunoblotting

Immunoassays and mass spectrometry are powerful single-cell protein analysis tools; however, interfacing and throughput bottlenecks remain. Here, we introduce three-dimensional single-cell immunoblots to detect both cytosolic and nuclear proteins. The 3D microfluidic device is a photoactive polyacrylamide gel with a microwell array-patterned face (xy) for cell isolation and lysis. Single-cell lysate in each microwell is “electrophoretically projected” into the 3^rd dimension (z-axis), separated by size, and photo-captured in the gel for immunoprobing and confocal/light-sheet imaging. Design and analysis are informed by the physics of 3D diffusion. Electrophoresis throughput is > 2.5 cells/s (70× faster than published serial sampling), with 25 immunoblots/mm² device area (>10× increase over previous immunoblots). The 3D microdevice design synchronizes analyses of hundreds of cells, compared to status quo serial analyses that impart hours-long delay between the first and last cells. Here, we introduce projection electrophoresis to augment the heavily genomic and transcriptomic single-cell atlases with protein-level profiling.

Single-cell immunoblotting previously separated proteins on a polyacrylamide slab in the xy direction and was limited by throughput and sample consumption. Here the authors adapt the system to separate proteins in the z direction, allowing for closer spacing of sample wells and improved sample consumption.

ERBB2b mRNA isoform encodes a nuclear variant of the ERBB2 oncogene in breast cancer

The presence of nuclear ERBB2 receptor-type tyrosine kinase is one of the causes of the resistance to membrane ERBB2-targeted therapy in breast cancers. It has been previously reported that this nuclear location arises through at least two different mechanisms: proteolytic shedding of the extracellular domain of the full-length receptor and translation of the messenger RNA (mRNA)-encoding ERBB2 from internal initiation codons. Here, we report a new mechanism and function where a significant portion of nuclear ERBB2 results from the translation of the variant ERBB2 mRNA under the transcriptional control of a distal promoter that is actively used in breast cancer cells. We show that both membrane ERBB2a and nuclear ERBB2b isoforms are prevalently expressed in breast cancer cell lines and carcinoma samples. The ERBB2b isoform, which is translated from mRNA variant 2, can directly translocate into the nucleus due to the lack of the signal peptide which is required for an intermediate membrane location. Small interfering RNA-mediated gene silencing showed that ERBB2b can repress ERBB2a expression, encoded by variant 1, whereas ERBB2a activates ERBB2b. Nuclear ERBB2 binding to its own promoter was revealed by chromatin immunoprecipitation assay. Altogether, our results provide new insights into the origin and function of nuclear ERBB2 where it can participate at the same time in a positive or a negative feedback autoregulatory loop, dependent on which of its promoters this bona fide transcription factor is acting. They also provide a new understanding for the resistance to therapies targeting the membrane-anchored ERBB2 in breast cancer.

Selected updates in molecular and genomic pathology of esophageal cancer

Recent years have seen rapid advances in the field of molecular and genomic pathology that have not only improved understanding of esophageal carcinogenesis and tumor immune environment in general but also have reshaped pathology practice and clinical management. In this article, we provide updates on three topics (1) human epidermal growth factor receptor 2, the first and most important biomarker in targeted therapy of esophageal cancer; (2) programmed death 1/programmed death ligand 1, recent biomarkers that have shown promise in treating both esophageal adenocarcinoma and esophageal squamous cell carcinoma; and (3) human papillomavirus involvement in esophageal carcinogenesis, one of the most debated topics in the field, discussed here with a renewed understanding from recent genomic and molecular data.

β2-AR activation promotes cleavage and nuclear translocation of Her2 and metastatic potential of cancer cells

Prolonged hypersecretion of catecholamine induced by chronic stress may correlate with malignant progression of cancer. β2‐adrenergic receptor (β2‐AR) overexpressed in certain cancer cells may translate the signals from neuroendocrine system to malignant signals by interacting with oncoproteins, such as Her2. In the present study, we demonstrate that catecholamine stimulation activates the expression and proteolytic activity of ADAM10 by modulating the expression of miR‐199a‐5p and SIRT1 and also confirm that catecholamine induction triggers the activities of γ‐secretase, leading to shedding of Her2 extracellular domain (ECD) by ADAM10 and subsequent intramembranous cleavage of Her2 intracellular domain (ICD) by presenilin‐dependent γ‐secretase, nuclear translocation of Her2 ICD, and enhanced transcription of tumor metastasis‐associated gene COX‐2. Chronic stimulation of catecholamine strongly promotes the invasive activities of cancer cells in vitro and spontaneous tumor lung metastasis in mice. Furthermore, nuclear localization of Her2 was significantly correlated with overexpression of β2‐AR in human breast cancer tissues, indicating that catecholamine‐induced β2‐AR activation plays decisive roles in tumor metastasis. Our data also reveal that an unknown mechanism by which the regulated intramembrane proteolysis (RIP) initiated by β2‐AR‐mediated signaling controls a novel Her2‐mediated signaling transduction.

The root cause of drug resistance in HER2-positive breast cancer and the therapeutic approaches to overcoming the resistance

HER2 is a well-known oncogenic receptor tyrosine kinase. HER2 gene amplification occurs in about 20% of breast cancer (BC), which leads to overexpression of HER2 protein, known as HER2-positive BC. Inhibitors of HER2 have significantly improved the prognosis of patients with this subset of BC. Since 1998, seven HER2 inhibitors have been developed to treat this disease. However, drug resistance is common and remains a major unresolved clinical problem. Patients typically show disease progression after some time on treatment. This review discusses the complexity and diversified nature of HER2 signaling, the mechanisms of actions and therapeutic activities of all HER2 inhibitors, the roles of HER2 and other signaling proteins in HER2-positive BC resistant to the inhibitors, the non-cell-autonomous mechanisms of drug resistance, and the heterogeneity of tumor HER2 expression. The review presents the concept that drug resistance in HER2-positive BC results primarily from the inability of HER2 inhibitors to deplete HER2. Emerging therapeutics that are promising for overcoming drug resistance are also discussed.

Characterization of T-DM1-resistant breast cancer cells

The development of targeted therapies has drastically improved the outcome of patients with different types of cancer. T-DM1 (trastuzumab-emtansine) is an antibody-drug conjugate used for the treatment of HER2-positive breast cancer combining the FDA approved mAb (monoclonal antibody) trastuzumab and the microtubule cytotoxic agent DM1 (emtansine). Despite clinical successes achieved by targeted therapies, a large number of patients develop resistance during treatment. To explore mechanisms of resistance to T-DM1, the MDA-MB-361 HER2-positive breast cancer cell line was exposed in vitro to T-DM1 in the absence or presence of ciclosporin A. Previously reported mechanisms of resistance such as trastuzumab-binding alterations, MDR1 upregulation, and SLC46A3 downregulation were not observed in these models. Despite a decrease in HER2 expression at the cell surface, both resistant cell lines remained sensitive to HER2 targeted therapies such as mAbs and tyrosine kinase inhibitors. In addition, sensitivity to DNA damaging agents and topoisomerase inhibitors were unchanged. Conversely resistance to anti-tubulin agents increased. Resistant cells displayed a decreased content of polymerized tubulin and a decreased content of βIII tubulin although the downregulation of βIII tubulin by siRNA in the parental cell line did not modified the sensitivity to T-DM1. Both cell lines resistant to T-DM1 also presented giant aneuploid cells. Several SLC (solute carrier) transporters were found to be differentially expressed in the resistant cells in comparison to parental cells. These results suggest that some characteristics such as increased baseline aneuploidy and altered intracellular drug trafficking might be involved in resistance to T-DM1.

Enhanced Immunogenicity of Engineered HER2 Antigens Potentiates Antitumor Immune Responses

For cancer vaccines, the selection of optimal tumor-associated antigens (TAAs) that can maximize the immunogenicity of the vaccine without causing unwanted adverse effects is challenging. In this study, we developed two engineered Human epidermal growth factor receptor 2 (HER2) antigens, K965 and K1117, and compared their immunogenicity to a previously reported truncated HER2 antigen, K684, within a B cell and monocyte-based vaccine (BVAC). We found that BVAC-K965 and BVAC-K1117 induced comparable antigen-specific antibody responses and antigen-specific T cell responses to BVAC-K684. Interestingly, BVAC-K1117 induced more potent antitumor activity than the other vaccines in murine CT26-HER2 tumor models. In addition, BVAC-K1117 showed enhanced antitumor effects against truncated p95HER2-expressing CT26 tumors compared to BVAC-K965 and BVAC-K684 based on the survival analysis by inducing T cell responses against intracellular domain (ICD) epitopes. The increased ICD epitope-specific T cell responses induced by BVAC-K1117 compared to BVAC-K965 and BVAC-K684 were recapitulated in human leukocyte antigen (HLA)-untyped human PBMCs and HLA-A*0201 PBMCs. Furthermore, we also observed synergistic antitumor effects between BVAC-K1117 and anti-PD-L1 antibody treatment against CT26-HER2 tumors. Collectively, our findings demonstrate that inclusion of a sufficient number of ICD epitopes of HER2 in cellular vaccines can improve the antitumor activity of the vaccine and provide a way to optimize the efficacy of anticancer cellular vaccines targeting HER2.

Acetyltanshinone IIA is more potent than lapatinib in inhibiting cell growth and degrading HER2 protein in drug-resistant HER2-positive breast cancer cells

High expression of human epidermal factor receptor 2 (HER2) is directly related to tumor progression, malignancy and drug resistance in HER2-positive breast cancer (HER2-PBC). The major limitation of current anti-HER2 therapies is that they cannot reduce the levels of HER2 protein. Here, we investigated the effect of acetyltanshinone IIA (ATA) in lapatinib-resistant HER2-PBC cells. Our data showed that ATA exhibited more potent effects than lapatinib against drug-resistant HER2-PBC cells in terms of (1) inhibiting cell growth, (2) reducing phosphorylated and total HER2 levels, (3) inhibiting tumor xenograft growth in nude mice, and (4) reducing HER2 protein levels in tumor xenografts. A mechanistic study revealed that ATA promoted HER2 degradation via increasing c-Cbl and CHIP-mediated HER2 ubiquitination and subsequent HER2 degradation by the proteasome or lysosome. ATA also reduced the levels of other tyrosine kinase receptors (TKRs), such as HER3, IGF-1R and MET, in lapatinib-resistant cells. Our findings suggest that direct degradation of HER2 and other TKRs can be an effective strategy for combatting drug resistance. They also indicate the potential utilization of ATA in treating breast cancer that is resistant or nonresponsive to current HER2-targeted therapies.

Evaluating Trastuzumab in the treatment of HER2 positive breast cancer

The transmembrane oncoprotein HER2 is encoded by ERBB2 gene and overexpressed in around 20% of invasive breast cancers. It can be specifically targeted by Trastuzumab (Herceptin®), a humanised IgG1 antibody. Trastuzumab has been regarded as one of the most effective therapeutic drugs targeted to HER2 positive cancers. However, there are drawbacks, notably cardiotoxicity and resistance, which have raised awareness in clinical use. Therefore, understanding the mechanism of action is vital to establish improved therapeutic strategies. Here we evaluate Trastuzumab application in the treatment of HER2 positive breast cancer, focusing on its mechanistic actions and clinical effectiveness. Alternative therapies targeting the HER2 receptor and its downstream anomalies will also be discussed, as these could highlight further targets that could be key to improving clinical outcomes.

Mechanisms of Resistance to NK Cell Immunotherapy

Immunotherapy has recently been a major breakthrough in cancer treatment. Natural killer (NK) cells are suitable targets for immunotherapy owing to their potent cytotoxic activity that may target cancer cells in a major histocompatibility complex (MHC) and antigen-unrestricted manner. Current therapies targeting NK cells include monoclonal antibodies that promote NK cell antibody-dependent cell-mediated cytotoxicity (ADCC), hematopoietic stem cell transplantation (HSCT), the adoptive transfer of NK cells, the redirection of NK cells using chimeric antigen receptor (CAR)-NK cells and the use of cytokines and immunostimulatory drugs to boost the anti-tumor activity of NK cells. Despite some encouraging clinical results, patients receiving these therapies frequently develop resistance, and a myriad of mechanisms of resistance affecting both the immune system and cancer cells have been reported. A first contributing factor that modulates the efficacy of the NK cell therapy is the genetic profile of the individual, which regulates all aspects of NK cell biology. Additionally, the resistance of cancer cells to apoptosis and the immunoediting of cancer cells, a process that decreases their immunogenicity and promotes immunosuppression, are major determinants of the resistance to NK cell therapy. Consequently, the efficacy of NK cell anti-tumor therapy is specific to each patient and disease. The elucidation of such immunosubversive mechanisms is crucial to developing new procedures and therapeutic strategies to fully harness the anti-tumor potential of NK cells.

Nectin-4 cis-interacts with ErbB2 and its trastuzumab-resistant splice variants, enhancing their activation and DNA synthesis

Nectin-4 cell adhesion molecule and ErbB2 tyrosine kinase receptor are upregulated in many cancers, including breast cancer, and promote cancer cell proliferation and metastasis. Using human breast cancer cell lines T47D and SUM190-PT, in which both nectin-4 and ErbB2 were upregulated, we showed here that nectin-4 cis-interacted with ErB2 and enhanced its dimerization and activation, followed by the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. The third immunoglobulin-like domain of nectin-4 cis-interacted with domain IV of ErbB2. This region differs from the trastuzumab-interacting region but is included in the trastuzumab-resistant splice variants of ErbB2, p95-ErbB2 and ErbB2ΔEx16. Nectin-4 also cis-interacted with these trastuzumab-resistant splice variants and enhanced the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. In addition, nectin-4 enhanced the activation of the p95-ErbB2-induced JAK-STAT3 signalling pathway, but not the ErbB2- or ErbB2ΔEx16-induced JAK-STAT3 signalling pathway. These results indicate that nectin-4 cis-interacts with ErbB2 and its trastuzumab-resistant splice variants and enhances the activation of these receptors and downstream signalling pathways in a novel mechanism.

Molecular Targeting Therapy against EGFR Family in Breast Cancer: Progress and Future Potentials

The epidermal growth factor receptor (EGFR) family contains four transmembrane tyrosine kinases (EGFR1/ErbB1, Her2/ErbB2, Her3/ErbB3 and Her4/ErbB4) and 13 secreted polypeptide ligands. EGFRs are overexpressed in many solid tumors, including breast, pancreas, head-and-neck, prostate, ovarian, renal, colon, and non-small-cell lung cancer. Such overexpression produces strong stimulation of downstream signaling pathways, which induce cell growth, cell differentiation, cell cycle progression, angiogenesis, cell motility and blocking of apoptosis.The high expression and/or functional activation of EGFRs correlates with the pathogenesis and progression of several cancers, which make them attractive targets for both diagnosis and therapy. Several approaches have been developed to target these receptors and/or the EGFR modulated effects in cancer cells. Most approaches include the development of anti-EGFRs antibodies and/or small-molecule EGFR inhibitors. This review presents the state-of-the-art and future prospects of targeting EGFRs to treat breast cancer.

HER2-targeted therapies - a role beyond breast cancer

HER2 is an established therapeutic target in a large subset of women with breast cancer; a variety of agents including trastuzumab, pertuzumab, lapatinib, neratinib and trastuzumab emtansine (T-DM1) have been approved for the treatment of HER2-positive breast cancer. HER2 is also overexpressed in subsets of patients with other solid tumours. Notably, the addition of trastuzumab to first-line chemotherapy has improved the overall survival of patients with HER2-positive gastric cancer, and has become the standard-of-care treatment for this group of patients. However, trials involving pertuzumab, lapatinib and T-DM1 have failed to provide significant improvements in the outcomes of patients with HER2-positive gastric cancer. HER2-targeted therapies are also being tested in patients with other solid tumours harbouring HER2 overexpression, and/or amplifications or other mutations of the gene encoding HER2 (ERBB2), including biliary tract, colorectal, non-small-cell lung and bladder cancers. The experience with gastric cancer suggests that the successes observed in HER2-positive breast cancer might not be replicated in these other tumour types, owing to differences in the level of HER2 overexpression and other aspects of disease biology. In this Review, we describe the current role of HER2-targeted therapies beyond breast cancer and also highlight the potential of novel HER2-targeted agents that are currently in clinical development.

Could quantitative real-time polymerase chain reaction assay serve as an alternative test method to evaluate human epidermal growth factor receptor 2 status of gastric carcinoma in the South Asian setting?

BACKGROUND

Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification are/is linked to a dismal outcome of gastric carcinoma (GCa). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are key methods to identify patients for HER2 targeted therapy. Drawbacks of both the methods warrant novel tests. Hence, we evaluated the value of quantitative real-time polymerase chain reaction (qPCR) as an alternative test method, relative to IHC to detect HER2 status of GCa and to find relationship between these  results with demographic/clinicopathological data.

METHOD

Twenty GCa patients with known IHC HER2 scores were evaluated. qPCR was performed for the HER2 gene and amyloid precursor protein (reference gene) in formalin-fixed paraffin-embedded GCa tissue. Cycle threshold values (Ct) were analyzed using the Pfaffl method to detect HER2 gene amplification.

RESULTS

HER2 positivity rates by IHC and qPCR were 20% and 35%, respectively. The sensitivity and specificity of qPCR were 67% and 76%, respectively, relative to IHC. qPCR results were reproducible. The diagnostic consistency between IHC and qPCR (κ = 0.146) was slightly agreeable (0.01 < k < 0.20), with a 65% concordance. Based on McNemar's test, there was no significant difference between the results of the two tests. IHC HER2 protein expression had relationship with the tumor (TNM) stage and Lauren histological type (p < 0.05). Positive HER2 gene expression by qPCR showed relationship with depth of invasion, lymph node involvement, and degree of differentiation (p < 0.05).

CONCLUSION

Cost-effective qPCR could serve as an alternative test method for detection of HER2 status of GCa. Both HER2 overexpression by IHC and gene amplification by qPCR are associated with adverse clinicopathological features.

A toolkit for studying cell surface shedding of diverse transmembrane receptors

Proteolysis of transmembrane receptors is a critical cellular communication mechanism dysregulated in disease, yet decoding proteolytic regulation mechanisms of hundreds of shed receptors is hindered by difficulties controlling stimuli and unknown fates of cleavage products. Notch proteolytic regulation is a notable exception, where intercellular forces drive exposure of a cryptic protease site within a juxtamembrane proteolytic switch domain to activate transcriptional programs. We created a Synthetic Notch Assay for Proteolytic Switches (SNAPS) that exploits the modularity and unequivocal input/response of Notch proteolysis to screen surface receptors for other putative proteolytic switches. We identify several new proteolytic switches among receptors with structural homology to Notch. We demonstrate SNAPS can detect shedding in chimeras of diverse cell surface receptors, leading to new, testable hypotheses. Finally, we establish the assay can be used to measure modulation of proteolysis by potential therapeutics and offer new mechanistic insights into how DECMA-1 disrupts cell adhesion.

Preclinical Characteristics of the Irreversible Pan-HER Kinase Inhibitor Neratinib Compared with Lapatinib: Implications for the Treatment of HER2-Positive and HER2-Mutated Breast Cancer

An estimated 15–20% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2/ERBB2/neu). Two small-molecule tyrosine kinase inhibitors (TKIs), lapatinib and neratinib, have been approved for the treatment of HER2-positive (HER2+) breast cancer. Lapatinib, a reversible epidermal growth factor receptor (EGFR/ERBB1/HER1) and HER2 TKI, is used for the treatment of advanced HER2+ breast cancer in combination with capecitabine, in combination with trastuzumab in patients with hormone receptor-negative metastatic breast cancer, and in combination with an aromatase inhibitor for the first-line treatment of HER2+ breast cancer. Neratinib, a next-generation, irreversible pan-HER TKI, is used in the US for extended adjuvant treatment of adult patients with early-stage HER2+ breast cancer following 1 year of trastuzumab. In Europe, neratinib is used in the extended adjuvant treatment of adult patients with early-stage hormone receptor-positive HER2+ breast cancer who are less than 1 year from the completion of prior adjuvant trastuzumab-based therapy. Preclinical studies have shown that these agents have distinct properties that may impact their clinical activity. This review describes the preclinical characterization of lapatinib and neratinib, with a focus on the differences between these two agents that may have implications for patient management.

Personalized medicine in breast cancer: pharmacogenomics approaches

Abstract: Breast cancer is the fifth cause of cancer death among women worldwide and represents a global health concern due to the lack of effective therapeutic regimens that could be applied to all disease groups. Nowadays, strategies based on pharmacogenomics constitute novel approaches that minimize toxicity while maximizing drug efficacy; this being of high importance in the oncology setting. Besides, genetic profiling of malignant tumors can lead to the development of targeted therapies to be included in effective drug regimens. Advances in molecular diagnostics have revealed that breast cancer is a multifaceted disease, characterized by inter-tumoral and intra-tumoral heterogeneity and, unlike the past, molecular classifications based on the expression of individual biomarkers have led to devising novel therapeutic strategies that improve patient survival. In this review, we report and discuss the molecular classification of breast cancer subtypes, the heterogeneity resource, and the advantages and disadvantages of current drug regimens with consideration of pharmacogenomics in response and resistance to treatment.