Heregulin-expressing HER2-positive breast and gastric cancer exhibited heterogeneous susceptibility to the anti-HER2 agents lapatinib, trastuzumab and T-DM1

Establishment of a trastuzumab-resistant extramammary Paget disease model: loss of PTEN as a potential mechanism

BACKGROUND/OBJECTIVES

Extramammary Paget disease (EMPD) is a rare, cutaneous intraepithelial adenocarcinoma typically treated with wide local excision. Unfortunately, a number of patients with metastases show poor responses to chemotherapy. While some studies have explored trastuzumab's effectiveness against EMPD positive for human epidermal growth factor receptor 2 (HER2), trastuzumab resistance (TR) may emerge after anti-HER2 therapy.

METHODS/SUBJECTS

In this study, we established TR EMPD patient-derived xenografts (PDX) that replicated the histological and HER2 expression traits of naive EMPD tumours.

RESULTS

Cancer gene analyses revealed a loss of the PTEN gene in TR tumours, which was further confirmed by immunohistochemical staining and immunoblotting to test for protein expression levels. Reduced PTEN levels correlated with increased protein kinase B (Akt) phosphorylation and p27 downregulation, suggesting a potential mechanism for trastuzumab resistance in EMPD cells. In the trastuzumab-sensitive EMPD-PDX mouse model, PTEN inhibitors partially restored trastuzumab-mediated tumour regression. The TR EMPD-PDX responded favourably to targeted therapy (lapatinib, abemaciclib, palbociclib) and chemotherapy (eribulin, docetaxel, trastuzumab deruxtecan).

CONCLUSIONS

This study demonstrates an innovative TR EMPD-PDX model and introduces promising antineoplastic effects with various treatments for TR EMPD tumours.

Mechanisms of resistance to trastuzumab in HER2-positive gastric cancer

Gastric cancer is one of the most prevalent cancers worldwide, and human epidermal growth factor receptor 2 (HER2)-positive cases account for approximately 20% of the total cases. Currently, trastuzumab + chemotherapy is the recommended first-line treatment for patients with HER2-positive advanced gastric cancer, and the combination has exhibited definite efficacy in HER2-targeted therapy. However, the emergence of drug resistance during treatment considerably reduces its effectiveness; thus, it is imperative to investigate the potential mechanisms underlying resistance. In the present review article, we comprehensively introduce multiple mechanisms underlying resistance to trastuzumab in HER2-positive gastric cancer cases, aiming to provide insights for rectifying issues associated with resistance to trastuzumab and devising subsequent treatment strategies.

Quantitative systems pharmacology modeling of HER2-positive metastatic breast cancer for translational efficacy evaluation and combination assessment across therapeutic modalities

HER2-positive (HER2+) metastatic breast cancer (mBC) is highly aggressive and a major threat to human health. Despite the significant improvement in patients' prognosis given the drug development efforts during the past several decades, many clinical questions still remain to be addressed such as efficacy when combining different therapeutic modalities, best treatment sequences, interindividual variability as well as resistance and potential coping strategies. To better answer these questions, we developed a mechanistic quantitative systems pharmacology model of the pathophysiology of HER2+ mBC that was extensively calibrated and validated against multiscale data to quantitatively predict and characterize the signal transduction and preclinical tumor growth kinetics under different therapeutic interventions. Focusing on the second-line treatment for HER2+ mBC, e.g., antibody-drug conjugates (ADC), small molecule inhibitors/TKI and chemotherapy, the model accurately predicted the efficacy of various drug combinations and dosing regimens at the in vitro and in vivo levels. Sensitivity analyses and subsequent heterogeneous phenotype simulations revealed important insights into the design of new drug combinations to effectively overcome various resistance scenarios in HER2+ mBC treatments. In addition, the model predicted a better efficacy of the new TKI plus ADC combination which can potentially reduce drug dosage and toxicity, while it also shed light on the optimal treatment ordering of ADC versus TKI plus capecitabine regimens, and these findings were validated by new in vivo experiments. Our model is the first that mechanistically integrates multiple key drug modalities in HER2+ mBC research and it can serve as a high-throughput computational platform to guide future model-informed drug development and clinical translation.

HER2-Positive Gastric Cancer and Antibody Treatment: State of the Art and Future Developments

Despite a decreasing incidence in Western countries, gastric cancer is among the most common cancer subtypes globally and is associated with one of the highest tumor-related mortality rates. Biomarkers play an increasing role in the treatment against gastric cancer. HER2 was one of the first biomarkers that found its way into clinical practice. Since the ToGA trial, trastuzumab has been part of first-line palliative chemotherapy in metastatic or unresectable gastric cancer. HER2-targeting agents, such as the tyrosine kinase inhibitor lapatinib, the antibody drug conjugate (ADC) trastuzumab-emtansine or dual HER2 inhibition (pertuzumab and trastuzumab), have been investigated in the second-line setting but led to negative study results. More recently, the ADC trastuzumab-deruxtecan was authorized after the failure of trastuzumab-based treatment. However, further improvements in HER2-directed therapy are required as resistance mechanisms and HER2 heterogeneity limit the existing treatment options. This review aims to give an overview of the current standard-of-care HER2-directed therapy in gastric cancer, as well as its challenges and future developments.

Preclinical and Clinical Characterization of Fibroblast-derived Neuregulin-1 on Trastuzumab and Pertuzumab Activity in HER2-positive Breast Cancer

PURPOSE

To characterize expression of neuregulin-1 (NRG1), an HER3 ligand, in HER2-positive breast cancer and its relation with the efficacy of trastuzumab with or without pertuzumab.

EXPERIMENTAL DESIGN

Characterization of NRG1 expression in tumor cell lines, in tumor specimens, and in cancer-associated fibroblasts (CAFs). Patient-derived CAFs were used to investigate NRG1 impact on the activity of trastuzumab with or without pertuzumab in HER2-positive breast cancer cells. The relationship between NRG1 expression and pathologic response to anti-HER2-based neoadjuvant therapy was assessed in a retrospective patient cohort and in the NeoSphere trial.

RESULTS

NRG1 was expressed in HER2-positive breast cancer-derived fibroblasts at significantly higher levels than in cancer cells. NRG1 and the conditioned media (CM) from CAFs phosphorylated HER3 and AKT in cancer cells and mediated trastuzumab resistance. Stable genetic depletion of NRG1 from CAFs overcame trastuzumab resistance. Pertuzumab effectively suppressed trastuzumab resistance mediated by either NRG1 or CAF's CM. NRG1 engaged an epithelial-to-mesenchymal transition that was prevented by trastuzumab and pertuzumab. In clinical samples, stromal and/or tumor cell expression of NRG1 determined by immunohistochemistry was uncommon (13.2%) yet significantly linked with residual disease following trastuzumab-based neoadjuvant therapy. In the NeoSphere trial, the magnitude of the difference of pathologic complete response rates favoring the pertuzumab arm was higher in the NRG1-high group.

CONCLUSIONS

CAF-derived NRG1 mediates trastuzumab resistance through HER3/AKT, which might be reverted by pertuzumab. In patients with HER2-positive breast cancer, high expression of NRG1 was associated to poor response to trastuzumab, but not in combination with pertuzumab.

HER2-/HER3-Targeting Antibody-Drug Conjugates for Treating Lung and Colorectal Cancers Resistant to EGFR Inhibitors

Epidermal growth factor receptor (EGFR) is one of the anticancer drug targets for certain malignancies, including nonsmall cell lung cancer (NSCLC), colorectal cancer (CRC), and head and neck squamous cell carcinoma. However, the grave issue of drug resistance through diverse mechanisms persists, including secondary EGFR-mutation and its downstream RAS/RAF mutation. Since the discovery of the role of human epidermal growth factor receptor 2 (HER2) and HER3 in drug resistance, HER2- or HER3-targeting treatment strategies using monoclonal antibodies have been intensively examined and have demonstrated impressive responsiveness and limitations. Finally, an innovative targeted therapy called antibody drug conjugates (ADC) has provided a solution to overcome this resistance. Specifically, a new cleavable linker-payload system enables stable drug delivery to cancer cells, causing selective destruction. HER2-targeting ADC trastuzumab deruxtecan demonstrated promising responsiveness in patients with HER2-positive CRC, in a phase 2 clinical trial (objective response rate = 45.3%). Furthermore, HER3-targeting patritumab deruxtecan, another ADC, exhibited impressive tumor shrinkage in pretreated patients with EGFR-mutated NSCLC, in a phase 1 clinical trial. This manuscript presents an overview of the accumulated evidence on HER2- and HER3-targeting therapy, especially ADCs, and discussion of remaining issues for further improving these treatments in cancers resistant to EGFR inhibitors.

A novel tumor inhibitory hybridoma monoclonal antibody with dual specificity for HER3 and HER2

BACKGROUND

The human epidermal growth factor receptor (HER/ErbB) family-targeted therapies result in a significant improvement in cancer immunotherapy. Monoclonal antibodies (MAb) against HER2 demonstrated a survival benefit for patients; however, drug resistance unavoidably occurs due to the overexpression of HER3, which leads to treatment failure. Effective inhibition of HER3 besides HER2 is thought to be required to overcome resistance and enhance therapeutic efficacy.

OBJECTIVE

The present study describes the production and characterization of a novel MAb, designated 1G5D2, which acts as a natural bispecific antibody targeting extracellular domains (ECD) of both HER2 and HER3.

METHODS

In this study, 1G5D2 was produced by hybridoma technology against HER3-ECD, and its structural and functional characteristics were studied by various methodologies, including enzyme linked-immunosorbent assays, flow cytometry, immunoblotting, cell signaling, and cell proliferation assays.

RESULTS

1G5D2 specifically binds to both HER2 (subdomain III + IV) and HER3 (subdomain I + II) expressed on tumor cells, and these receptors compete with each other for binding to this MAb. Competition flow cytometry experiments demonstrated that 1G5D2 does not compete with heregulin and recognizes an epitope out of HER3 ligand-binding site. Evaluation of 1G5D2 inhibitory effects in tumor cell lines co-expressing HER2 and HER3 showed that 1G5D2 synergizes with trastuzumab to inhibit both PI3K/AKT and MAPK/ERK pathways and potently downregulates the proliferation of these tumor cells more efficiently than each MAb alone.

CONCLUSION

1G5D2 is the first reported hybridoma antibody, which acts as a natural HER2/HER3 bispecific antibody. It might potentially be a suitable therapeutic candidate for HER2/HER3 overexpressing cancer types.

Heregulin-induced cell migration is prevented by trastuzumab and trastuzumab-emtansine in HER2+ breast cancer

PURPOSE

Heregulin (HRG) signaling has been implicated in the development of an aggressive phenotype in breast cancer (BC) cells, and HER2 overexpression has been associated with a worse prognosis in BC patients. Nevertheless, the molecular mechanisms through which HRG affects the efficiency of anti-HER2 therapies such as trastuzumab (Tz) and trastuzumab-emtansine (T-DM1) are currently unknown.

METHODS

In the present study, we evaluate the molecular action of HRG toward fundamental scaffold proteins and several kinases in the signal transduction pathways triggered via HER2/HER3, which integrate precise and sequential steps to promote changes in cell morphology to impulse BC cell migration. In addition, we evaluate the effectiveness of Tz and T-DM1 on the control of key proteins involved in BC cell motility, since the acquisition of a migratory phenotype is essential to promote invasion and metastasis.

RESULTS

We show that HRG induces actin cytoskeleton reorganization and focal adhesion complex formation, and promotes actin nucleation in BT-474 BC cells. This signaling is triggered by HER2/HER3 to c-Src, FAK and paxillin. When paxillin is phosphorylated, it recruits PAK1, which then phosphorylates cortactin. In parallel, paxillin signals to N-WASP, and both signalings regulate Arp2/3 complex, leading to the local reorganization of actin fibers.

CONCLUSIONS

Our findings reveal an original mechanism by which HRG increases HER2+ BC cell motility, and show that the latter can be abolished by Tz and T-DM1 treatments. These results provide evidence for the molecular mechanisms involved in cell motility and drug resistance. They will be useful to develop new and more specific therapeutic schemes that interfere with the progression and metastasis of HER2+ BC.

Extramammary Paget's disease patient-derived xenografts harboring ERBB2 S310F mutation show sensitivity to HER2-targeted therapies

Although the prognosis of advanced extramammary Paget's disease (EMPD) is poor, there have been no preclinical research models for the development of novel therapeutics. This study aims to establish a preclinical research model for EMPD. We transplanted EMPD tissue into immunodeficient NOD/Scid mice. Histopathological and genetic analyses using a comprehensive cancer panel were performed. For in vivo preclinical treatments, trastuzumab, lapatinib, docetaxel, or eribulin were administered to patient-derived xenograft (PDX) models. Tissue transplanted from the EMPD patient was enlarged in NOD/Scid mice and was transplanted into further generations. Both the transplantation of PDX into nu/nu mice and the reanimation of the cryopreserved xenografted tumors in NOD/Scid mice were successful. We also established an EMPD-PDX-derived primary cell culture. Histopathologically, the xenografted tumors were positive for CK7, which was consistent with the patient's tumors. Genetically, the pathogenic mutation ERBB2 S310F was detected in the patient's tumors (primary intraepidermal lesion, metastatic lymph node) and was observed in the xenografted tumors even after continued passages. The xenografted tumors responded well to trastuzumab and lapatinib therapy. Also, cytotoxic agents (docetaxel and eribulin) were effective against the xenografted tumors. This PDX model (EMPD-PDX-H1) could be a powerful tool for the research and development of EMPD treatments.

Emerging Targeted Therapies for HER2 Positive Gastric Cancer That Can Overcome Trastuzumab Resistance

Trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), has improved survival in patients with HER2-positive advanced gastric or gastroesophageal junction cancer (AGC). The inevitable development of resistance to trastuzumab remains a problem, however, with several treatment strategies that have proven effective in breast cancer having failed to show clinical benefit in AGC. In this review, we summarize the mechanisms underlying resistance to HER2-targeted therapy and outline past and current challenges in the treatment of HER2-positive AGC refractory to trastuzumab. We further describe novel agents such as HER2 antibody-drug conjugates that are under development and have shown promising antitumor activity in early studies.

[Pharmacological effects of site specific conjugated anti-human epidermal growth factor receptor 2-antibody drug conjugate using unnatural amino acid technology]

OBJECTIVE

To investigate inhibitory activities of a homogenous anti-human epidermal growth factor receptor 2 (HER2)-antibody drug conjugate (ADC) on the proliferation of nine tumor cell lines with different levels of HER2 expressions, and its activities on the tumor growth of five xenograft mouse models.

METHODS

The HER2 expression levels of BT-474, Calu-3, MCF-7, MDA-MB-231, MDA-MB-468, SK-BR-3, SK-OV-3, HCC1954, NCI-N87 tumor cell lines were measured using QIFI KIT. For the in vitro anti-proliferation assay, serial diluted anti-HER2-ADC, ado-trastuzumab emtansine, AS269, pAF-AS269 and paclitaxel were added to the seeded cells, and after 72 or 96 hours of incubation, the cell proliferation was analyzed. For the in vivo activity, 5-6 weeks old mice were inoculated with four HER2 positive tumor cell lines HCC1954, BT-474, SK-OV-3, NCI-N87 or one HER2 negative tumor cell line MDA-MB-468. Different amounts of anti-HER2-ADC, ado-trastuzumab emtansine, trastuzumab, paclitaxel and phosphate buffered saline control were injected after the tumor volume reached a certain size, then the tumor growth inhibition was analyzed.

RESULTS

The expression levels of the six high HER2-expression cell lines SK-OV-3, NCI-N87, SK-BR-3, Calu-3, HCC1954, BT-474 were between 430 000 to 800 000 receptors per cell, which were 50 times higher than those of the other three low HER2 expression tumor cell lines MDA-MB-231, MCF-7, MDA-MB-468. Anti-HER2-ADC had inhibition effects on cell lines with high level of HER2 expression in the in vitro anti-proliferation assay. The half maximal inhibitory concentrations of anti-HER2-ADC on SK-OV-3, NCI-N87, SK-BR-3, Calu-3, HCC1954, BT-474 tumor cell lines were 46 pmol/L, 17 pmol/L, 17 pmol/L, 161 pmol/L, 125 pmol/L, 50 pmol/L, respectively. Anti-HER2-ADC had a dose dependent antitumor activity in vivo in all the HER2 positive xenograft mouse models. In NCI-N87 xenograft tumor model, the same dose of anti-HER2-ADC showed better anti-tumor activity compared with trastuzumab and ado-trastuzumab emtansine, and its relative tumor proliferation rates were about 1/30 to 1/20 of the two. In HCC1954 xenograft tumor model, the complete regression of the tumor was observed. As expected, anti-HER2-ADC had no tumor inhibitory effects on MDA-MB-468 xenograft models with low HER2 expression. The antitumor activities of anti-HER2-ADC in HER2 positive xenograft tumor models were the same as or better than the activities of ado-trastuzumab emtansine.

CONCLUSION

The homogenous site-specific anti-HER2-ADC obtained using unnatural amino acid technology can inhibit the growth of high HER2-expression tumor cells with high potency both in vivo and in vitro.

[Pharmacological effects of site specific conjugated anti-human epidermal growth factor receptor 2-antibody drug conjugate using unnatural amino acid technology]

OBJECTIVE

To investigate inhibitory activities of a homogenous anti-human epidermal growth factor receptor 2 (HER2)-antibody drug conjugate (ADC) on the proliferation of nine tumor cell lines with different levels of HER2 expressions, and its activities on the tumor growth of five xenograft mouse models.

METHODS

The HER2 expression levels of BT-474, Calu-3, MCF-7, MDA-MB-231, MDA-MB-468, SK-BR-3, SK-OV-3, HCC1954, NCI-N87 tumor cell lines were measured using QIFI KIT. For the in vitro anti-proliferation assay, serial diluted anti-HER2-ADC, ado-trastuzumab emtansine, AS269, pAF-AS269 and paclitaxel were added to the seeded cells, and after 72 or 96 hours of incubation, the cell proliferation was analyzed. For the in vivo activity, 5-6 weeks old mice were inoculated with four HER2 positive tumor cell lines HCC1954, BT-474, SK-OV-3, NCI-N87 or one HER2 negative tumor cell line MDA-MB-468. Different amounts of anti-HER2-ADC, ado-trastuzumab emtansine, trastuzumab, paclitaxel and phosphate buffered saline control were injected after the tumor volume reached a certain size, then the tumor growth inhibition was analyzed.

RESULTS

The expression levels of the six high HER2-expression cell lines SK-OV-3, NCI-N87, SK-BR-3, Calu-3, HCC1954, BT-474 were between 430 000 to 800 000 receptors per cell, which were 50 times higher than those of the other three low HER2 expression tumor cell lines MDA-MB-231, MCF-7, MDA-MB-468. Anti-HER2-ADC had inhibition effects on cell lines with high level of HER2 expression in the in vitro anti-proliferation assay. The half maximal inhibitory concentrations of anti-HER2-ADC on SK-OV-3, NCI-N87, SK-BR-3, Calu-3, HCC1954, BT-474 tumor cell lines were 46 pmol/L, 17 pmol/L, 17 pmol/L, 161 pmol/L, 125 pmol/L, 50 pmol/L, respectively. Anti-HER2-ADC had a dose dependent antitumor activity in vivo in all the HER2 positive xenograft mouse models. In NCI-N87 xenograft tumor model, the same dose of anti-HER2-ADC showed better anti-tumor activity compared with trastuzumab and ado-trastuzumab emtansine, and its relative tumor proliferation rates were about 1/30 to 1/20 of the two. In HCC1954 xenograft tumor model, the complete regression of the tumor was observed. As expected, anti-HER2-ADC had no tumor inhibitory effects on MDA-MB-468 xenograft models with low HER2 expression. The antitumor activities of anti-HER2-ADC in HER2 positive xenograft tumor models were the same as or better than the activities of ado-trastuzumab emtansine.

CONCLUSION

The homogenous site-specific anti-HER2-ADC obtained using unnatural amino acid technology can inhibit the growth of high HER2-expression tumor cells with high potency both in vivo and in vitro.

ErbB3 Phosphorylation as Central Event in Adaptive Resistance to Targeted Therapy in Metastatic Melanoma: Early Detection in CTCs during Therapy and Insights into Regulation by Autocrine Neuregulin

In recent years the introduction of target therapies with BRAF and MEK inhibitors (MAPKi) and of immunotherapy with anti-CTLA-4 and anti-PD-1 monoclonal antibodies have dramatically improved survival of metastatic melanoma patients. Despite these changes drug resistance remains a major hurdle. Several mechanisms are at the basis of drug resistance. Particular attention has been devoted over the last years to unravel mechanisms at the basis of adaptive/non genetic resistance occurring in BRAF mutated melanomas upon treatment with to MAPKi. In this paper we focus on the involvement of activation of ErbB3 receptor following early exposure of melanoma cells to BRAF or MEK inhibitors, and the following induction of PI3K/AKT pathway. Although different mechanisms have been invoked in the past at the basis of this activation we show here with a combination of approaches that autocrine production of neuregulin by melanoma cells is a major factor responsible for ErbB3 phosphorylation and downstream AKT activation. Interestingly the kinetic of neuregulin production and of the ensuing ErbB3 phosphorylation is different in different melanoma cell lines which underscores the high degree of tumor heterogeneity. Moreover, heterogeneity is further highlighted by the evidence that in different cell lines neuregulin upregulation can occur at the transcriptional or at the post-transcritpional level. Finally we complement our study by showing with a liquid biopsy assay that circulating tumor cells (CTCs) from melanoma patients undergo upregulation of ErbB3 phosphorylation in vivo shortly after initiation of therapy.

Targeting of the HER2/HER3 signaling axis overcomes ligand-mediated resistance to trastuzumab in HER2-positive breast cancer

HER2‐targeted therapy, especially the anti‐HER2 antibody trastuzumab, is standard for HER2‐positive breast cancer; however, its efficacy is limited in a subpopulation of patients. HER3 ligand (heregulin)‐dependent HER2‐HER3 interactions play a critical role in the evasion of apoptosis and are therefore a target for oncotherapy to treat HER2‐positive breast cancer. The anti‐HER2 antibody pertuzumab and anti‐HER3 antibody patritumab both target this heregulin–HER3‐HER2 complex in different ways. This study examined the anticancer efficacy of dual HER2 and HER3 blockade in trastuzumab‐resistant HER2‐positive breast cancer. HER2‐positive SKBR3 or BT474 cells overexpressing heregulin (SKBR3‐HRG, BT474‐HRG) were used to evaluate the efficacy of trastuzumab, pertuzumab, and patritumab in vitro by performing cell viability, immunoblotting, and clonogenic assays. The effects of these agents were then evaluated in vivo using BT474‐HRG and an intrinsic heregulin‐expressing and HER2‐positive JIMT‐1 xenograft models. SKBR3‐HRG and BT474‐HRG cells lost sensitivity to trastuzumab, which was accompanied by Akt activation. Unexpectedly, trastuzumab in combination with pertuzumab or patritumab also showed limited efficacy toward these cells. In contrast, trastuzumab/pertuzumab/patritumab triple treatment demonstrated potent anticancer efficacy, concomitant with strong repression of Akt. Finally, in heregulin‐expressing BT474‐HRG and JIMT‐1 xenograft models, the addition of pertuzumab and patritumab to trastuzumab also enhanced antitumor efficacy leading to tumor regression. The current study found that triple blockade of HER2 and HER3 using trastuzumab, pertuzumab, and patritumab could overcome resistance to trastuzumab therapy in heregulin‐expressing and HER2‐positive breast cancer, which could be exploited clinically.

Unbiased Combinatorial Screening Identifies a Bispecific IgG1 that Potently Inhibits HER3 Signaling via HER2-Guided Ligand Blockade

HER2-driven cancers require phosphatidylinositide-3 kinase (PI3K)/Akt signaling through HER3 to promote tumor growth and survival. The therapeutic benefit of HER2-targeting agents, which depend on PI3K/Akt inhibition, can be overcome by hyperactivation of the heregulin (HRG)/HER3 pathway. Here we describe an unbiased phenotypic combinatorial screening approach to identify a bispecific immunoglobulin G1 (IgG1) antibody against HER2 and HER3. In tumor models resistant to HER2-targeting agents, the bispecific IgG1 potently inhibits the HRG/HER3 pathway and downstream PI3K/Akt signaling via a "dock & block" mechanism. This bispecific IgG1 is a potentially effective therapy for breast cancer and other tumors with hyperactivated HRG/HER3 signaling.

HER2 genomic amplification in circulating tumor DNA and estrogen receptor positivity predict primary resistance to trastuzumab emtansine (T-DM1) in patients with HER2-positive metastatic breast cancer

Background

Trastuzumab emtansine (T-DM1) is approved for the treatment of patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (ABC), and has high efficacy. However, some patients exhibit primary resistance to T-DM1, and thus methods that can predict resistance in clinical practice are needed. Genomic analysis of circulating tumor DNA (ctDNA) in plasma is a non-invasive and reproducible method. This study aimed to predict primary resistance to T-DM1 by combining genomic analysis of ctDNA and other clinicopathological features of patients with HER2-positive ABC.

Methods

The study population comprised 34 patients with HER2-positive ABC who had been treated with T-DM1. Correlations between clinicopathological characteristics of patients and primary resistance to T-DM1 were examined, and HER2 gene copy number and PIK3CA gene mutations were analyzed using plasma ctDNA samples obtained from 16 patients before T-DM1 administration.

Results

Among the 34 patients, nine (26.5%) had progressive disease at the first efficacy analysis; these patients were considered to have primary resistance to T-DM1. No significant difference was found in the rate of primary resistance to T-DM1 between groups. Among 16 patients whose ctDNA was analyzed, four showed primary resistance to T-DM1. These four patients showed negative HER2 gene amplification in ctDNA and were ER-positive and/or PR-positive by immunohistochemistry.

Conclusions

HER2 gene amplification in ctDNA and ER and PR status may predict primary resistance to T-DM1. A liquid biopsy before the initiation of T-DM1 treatment could be a non-invasive way to predict whether a patient would exhibit primary resistance to T-DM1.

Identification of key pathways and genes in response to trastuzumab treatment in breast cancer using bioinformatics analysis

Breast cancer (BC) is one of the leading causes of death among women worldwide. The gene expression profile GSE22358 was downloaded from the Gene Expression Omnibus (GEO) database, which included 154 operable early-stage breast cancer samples treated with neoadjuvant capecitabine plus docetaxel, with (34) or without trastuzumab (120), to identify gene signatures during trastuzumab treatment and uncover their potential mechanisms. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed, and a protein–protein interaction (PPI) network of the differentially expressed genes (DEGs) was constructed by Cytoscape software. There were 2284 DEGs, including 1231 up-regulated genes enriched in DNA replication, protein N-linked glycosylation via asparagine, and response to toxic substances, while 1053 down-regulated genes were enriched in axon guidance, protein localization to plasma membrane, protein stabilization, and protein glycosylation. Eight hub genes were identified from the PPI network, including GSK3B, RAC1, PXN, ERBB2, HSP90AA1, FGF2, PIK3R1 and RAC2. Our experimental results showed that GSK3B was also highly expressed in breast cancer tissues and was associated with poor survival, as was β-catenin. In conclusion, the present study indicated that the identified DEGs and hub genes further our understanding of the molecular mechanisms underlying trastuzumab treatment in BC and highlighted GSK3B, which might be used as a molecular target for the treatment of BC.

Current therapeutic landscape for advanced gastroesophageal cancers

Treatment of advanced gastroesophageal cancers remains challenging for clinicians, patients, and caregivers alike. Despite considerable research, the therapeutic armamentarium is restricted and hardly personalized. In the first-line setting, trastuzumab with a fluoropyrimidine and platinum agent is the standard-of-care in patients with HER2-positive tumor. For the others, a platinum-based doublet (preferably with oxaliplatin) is recommended. Three-drug cytotoxic regimens should be reserved for exceptional cases where patients have good performance status. Triple combinations produce higher toxicity and provide marginal advantage. In the second line setting, the combination of paclitaxel and ramucirumab is preferred over all others. Currently, nothing is approved in the 3rd or later line. Nivolumab has resulted in an improved benefit in an Asian trial. Early trials of TAS-102, STAT3 inhibitors, anti-claudin 18.2 and other immune checkpoint inhibitors (alone or in combination) are ongoing. However, development of reproducible biomarkers for patient enrichment is critical for future progress.

H19 functions as a competing endogenous RNA to regulate human epidermal growth factor receptor expression by sequestering let‑7c in gastric cancer

Long non‑coding RNA (lncRNA) H19 has been suggested to serve important roles in the progression of gastric cancer (GC); however, the mechanism involved is largely unknown. The present study aimed to investigate the mechanism underlying the effect of H19 on human epidermal growth factor receptor (HER2) expression. Let‑7c belongs to the let‑7 family, which has been reported to be downregulated in cancers and considered to serve as a tumor suppressor. Let‑7c has been negatively associated with the expression of human epidermal growth factor receptor 2 (HER2). Reverse transcription‑quantitative polymerase chain reaction was used to examine the expression levels of H19 and let‑7c in GC tissues and cell lines. HER2 protein expression levels were examined using immunohistochemistry and western blot analyses. The effect of H19 on let‑7c and HER2 expression was analyzed following transfection of small interfering RNA targeting H19 in GC cells. The results indicated that the expression levels of H19 lncRNA in GC tissue samples were significantly higher when compared with that in matched benign adjacent tissue samples (P<0.001). H19‑silenced GC cells exhibited significantly increased let‑7c expression and decreased HER2 protein expression levels. Assessment of tumor diameter and pathological tumor stage suggested that increased H19 expression was associated with a poorer prognosis in patients with GC. The results of the present study suggest that H19 may function as a competing endogenous RNA to regulate HER2 expression by sequestering let‑7c in GC cells. The present study has aided the understanding of the mechanism of H19 lncRNA in GC, and has provided evidence for the application of lncRNA‑based diagnostic and therapeutic strategies for GC.

DS-8201a, a new HER2-targeting antibody-drug conjugate incorporating a novel DNA topoisomerase I inhibitor, overcomes HER2-positive gastric cancer T-DM1 resistance

Anti-HER2 therapies are beneficial for patients with HER2-positive breast or gastric cancer. T-DM1 is a HER2-targeting antibody-drug conjugate (ADC) comprising the antibody trastuzumab, a linker, and the tubulin inhibitor DM1. Although effective in treating advanced breast cancer, all patients eventually develop T-DM1 resistance. DS-8201a is a new ADC incorporating an anti-HER2 antibody, a newly developed, enzymatically cleavable peptide linker, and a novel, potent, exatecan-derivative topoisomerase I inhibitor (DXd). DS-8201a has a drug-to-antibody-ratio (DAR) of 8, which is higher than that of T-DM1 (3.5). Owing to these unique characteristics and unlike T-DM1, DS-8201a is effective against cancers with low-HER2 expression. In the present work, T-DM1-resistant cells (N87-TDMR), established using the HER2-positive gastric cancer line NCI-N87 and continuous T-DM1 exposure, were shown to be susceptible to DS-8201a. The ATP-binding cassette (ABC) transporters ABCC2 and ABCG2 were upregulated in N87-TDMR cells, but HER2 overexpression was retained. Furthermore, inhibition of ABCC2 and ABCG2 by MK571 restored T-DM1 sensitivity. Therefore, resistance to T-DM1 is caused by efflux of its payload DM1, due to aberrant expression of ABC transporters. In contrast to DM1, DXd payload of DS-8201a inhibited the growth of N87-TDMR cells in vitro. This suggests that either DXd may be a poor substrate of ABCC2 and ABCG2 in comparison to DM1, or the high DAR of DS-8201a relative to T-DM1 compensates for increased efflux. Notably, N87-TDMR xenograft tumor growth was prevented by DS-8201a. In conclusion, the efficacy of DS-8201a as a treatment for patients with T-DM1-resistant breast or gastric cancer merits investigation.

Chimeric antigen receptor T cells: a novel therapy for solid tumors

The chimeric antigen receptor T (CAR-T) cell therapy is a newly developed adoptive antitumor treatment. Theoretically, CAR-T cells can specifically localize and eliminate tumor cells by interacting with the tumor-associated antigens (TAAs) expressing on tumor cell surface. Current studies demonstrated that various TAAs could act as target antigens for CAR-T cells, for instance, the type III variant epidermal growth factor receptor (EGFRvIII) was considered as an ideal target for its aberrant expression on the cell surface of several tumor types. CAR-T cell therapy has achieved gratifying breakthrough in hematological malignancies and promising outcome in solid tumor as showed in various clinical trials. The third generation of CAR-T demonstrates increased antitumor cytotoxicity and persistence through modification of CAR structure. In this review, we summarized the preclinical and clinical progress of CAR-T cells targeting EGFR, human epidermal growth factor receptor 2 (HER2), and mesothelin (MSLN), as well as the challenges for CAR-T cell therapy.