Advancing Breast Cancer Treatment: The Role of Immunotherapy and Cancer Vaccines in Overcoming Therapeutic Challenges

Breast cancer (BC) remains a significant global health challenge due to its complex biology, which complicates both diagnosis and treatment. Immunotherapy and cancer vaccines have emerged as promising alternatives, harnessing the body's immune system to precisely target and eliminate cancer cells. However, several key factors influence the selection and effectiveness of these therapies, including BC subtype, tumor mutational burden (TMB), tumor-infiltrating lymphocytes (TILs), PD-L1 expression, HER2 resistance, and the tumor microenvironment (TME). BC subtypes play a critical role in shaping treatment responses. Triple-negative breast cancer (TNBC) exhibits the highest sensitivity to immunotherapy, while HER2-positive and hormone receptor-positive (HR+) subtypes often require combination strategies for optimal outcomes. High TMB enhances immune responses by generating neoantigens, making tumors more susceptible to immune checkpoint inhibitors (ICIs); whereas, low TMB may indicate resistance. Similarly, elevated TIL levels are associated with better immunotherapy efficacy, while PD-L1 expression serves as a key predictor of checkpoint inhibitor success. Meanwhile, HER2 resistance and an immunosuppressive TME contribute to immune evasion, highlighting the need for multi-faceted treatment approaches. Current breast cancer immunotherapies encompass a range of targeted treatments. HER2-directed therapies, such as trastuzumab and pertuzumab, block HER2 dimerization and enhance antibody-dependent cellular cytotoxicity (ADCC), while small-molecule inhibitors, like lapatinib and tucatinib, suppress HER2 signaling to curb tumor growth. Antibody-drug conjugates (ADCs) improve tumor targeting by coupling monoclonal antibodies with cytotoxic agents, minimizing off-target effects. Meanwhile, ICIs, including pembrolizumab, restore T-cell function, and CAR-macrophage (CAR-M) therapy leverages macrophages to reshape the TME and overcome immunotherapy resistance. While immunotherapy, particularly in TNBC, has demonstrated promise by eliciting durable immune responses, its efficacy varies across subtypes. Challenges such as immune-related adverse events, resistance mechanisms, high costs, and delayed responses remain barriers to widespread success. Breast cancer vaccines-including protein-based, whole-cell, mRNA, dendritic cell, and epitope-based vaccines-aim to stimulate tumor-specific immunity. Though clinical success has been limited, ongoing research is refining vaccine formulations, integrating combination therapies, and identifying biomarkers for improved patient stratification. Future advancements in BC treatment will depend on optimizing immunotherapy through biomarker-driven approaches, addressing tumor heterogeneity, and developing innovative combination therapies to overcome resistance. By leveraging these strategies, researchers aim to enhance treatment efficacy and ultimately improve patient outcomes.

The Application and Molecular Mechanisms of Mitochondria-Targeted Antioxidants in Chemotherapy-Induced Cardiac Injury

Chemotherapeutic agents play a crucial role in cancer treatment. However, their use is often associated with significant adverse effects, particularly cardiotoxicity. Drugs such as anthracyclines (e.g., doxorubicin) and platinum-based agents (e.g., cisplatin) cause mitochondrial damage, which is one of the main mechanisms underlying cardiotoxicity. These drugs induce oxidative stress, leading to an increase in reactive oxygen species (ROS), which in turn damage the mitochondria in cardiomyocytes, resulting in impaired cardiac function and heart failure. Mitochondria-targeted antioxidants (MTAs) have emerged as a promising cardioprotective strategy, offering a potential solution. These agents efficiently scavenge ROS within the mitochondria, protecting cardiomyocytes from oxidative damage. Recent studies have shown that MTAs, such as elamipretide, SkQ1, CoQ10, and melatonin, significantly mitigate chemotherapy-induced cardiotoxicity. These antioxidants not only reduce oxidative damage but also help maintain mitochondrial structure and function, stabilize mitochondrial membrane potential, and prevent excessive opening of the mitochondrial permeability transition pore, thus preventing apoptosis and cardiac dysfunction. In this review, we integrate recent findings to elucidate the mechanisms of chemotherapy-induced cardiotoxicity and highlight the substantial therapeutic potential of MTAs in reducing chemotherapy-induced heart damage. These agents are expected to offer safer and more effective treatment options for cancer patients in clinical practice.

Trastuzumab-Mediated Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) Enhances Natural Killer Cell Cytotoxicity in HER2-Overexpressing Ovarian Cancer

Ovarian cancer is the deadliest gynecologic cancer. Although human epidermal growth factor receptor-2 (HER2) overexpression, a poor prognostic molecular marker in ovarian cancer, is found in almost 30% of ovarian cancer cases, there are no established therapies for HER2-overexpressing ovarian cancer. In this study, we investigated the efficacy of combined samfenet, a biosimilar compound of trastuzumab, and natural killer (NK) cells in preclinical model of HER2-overexpressing ovarian cancer. Firstly, we screened the HER2 expression in three ovarian cancer cell lines and eight ovarian cancer patient-derived tumor xenograft (PDTX) samples. Then, immunohistochemistry and silver in situ hybridization (SISH) were performed following clinical criteria. HER2-overexpressing cells exhibited the highest sensitivity to samfenet compared with low-HER2-expressing cells. In addition, the combination of samfenet with natural killer (NK) cells resulted in significantly enhanced sensitivity to HER2-overexpressing cells and showed a significant antitumor effect on PDTX mice compared with monotherapy. It is known that anti-HER2-humanized IgG1 monoclonal antibodies, including trastuzumab, induce antibody-dependent cellular cytotoxicity (ADCC). Consequently, the combination of samfenet with NK cells demonstrated NK cell-mediated ADCC, as confirmed using an in vitro NK cytotoxicity assay and in vivo antitumor efficacy. A transferase dUTP nick end labeling (TUNEL) assay using xenografted tumors further supported the ADCC effects based on the increase in the number of apoptotic cells in the combination group. Furthermore, high HER2 expression was associated with shorter progression-free survival and overall survival based on public mRNA expression data. In this study, we demonstrated that the combination of samfenet and NK cell therapy could be a promising treatment strategy for patients with HER2-overexpressing ovarian cancer, through ADCC effects. Therefore, this study supports a rationale for further clinical studies of the combination of samfenet and NK cells as a therapy for patients with HER2-overexpressing ovarian cancer.

Phase II Trial of HER-Vaxx, a B-cell Peptide-Based Vaccine, in HER2-Overexpressing Advanced Gastric Cancer Patients Under Platinum-Based Chemotherapy (HERIZON)

PURPOSE

A multicenter, randomized, open-label, phase II study (HERIZON; NCT02795988) was conducted to evaluate the clinical and immunologic efficacy of HER-Vaxx (IMU-131), a B-cell, peptide-based vaccine targeting HER2 overexpressed in 6% to 30% of gastroesophageal adenocarcinomas (GEA).

PATIENTS AND METHODS

Patients (n = 36) with GEA were treated with standard-of-care chemotherapy (n = 17) or HER-Vaxx plus chemotherapy (n = 19), using the recommended phase 2 dose for the vaccine. Overall survival (OS; primary endpoint), safety, progression-free survival (PFS), clinical response (secondary endpoints), and vaccine-induced HER2-specific antibody levels in serum and correlation with tumor response rates (exploratory endpoints) were investigated.

RESULTS

A 40% OS benefit [HR, 0.60; median OS, 13.9 months; 80% confidence interval (CI), 7.52-14.32] for patients treated with HER-Vaxx plus chemotherapy compared with OS of 8.31 months (80% CI, 6.01-9.59) in patients that received chemotherapy alone. A 20% PFS difference was obtained for the vaccination arm (HR, 0.80; 80% CI, 0.47, 1.38). No additional toxicity due to HER-Vaxx was observed. The vaccine-induced high levels of HER2-specific total IgG and IgG1 antibodies (P < 0.001 vs. controls) that significantly correlated with tumor reduction (IgG, P = 0.001; IgG1, P = 0.016), had a significant capacity in inhibiting phosphorylation of the intracellular HER2-signaling pathways, mediated antibody-dependent cellular cytotoxicity, and decreased immunosuppressive FOXP3+ regulatory T cells.

CONCLUSIONS

HER-Vaxx plus standard chemotherapy exhibits an excellent safety profile and improves OS. Furthermore, vaccine-induced immune response was significantly associated with reduced tumor size compared with standard-of-care chemotherapy. The presented vaccination approach may substitute for treatment with trastuzumab, upon unavailability or toxicity, based on further evidence of equivalent treatment efficacy.

Trastuzumab, a monoclonal anti-HER2 antibody modulates cytotoxicity against cholangiocarcinoma via multiple mechanisms

Cholangiocarcinoma (CCA) is an aggressive and fatal cancer. The prognosis is very poor and no optimal chemotherapy has been established. Human epidermal growth factor receptor 2 (HER2, neu, and erbB2) is highly-expressed in breast cancer and is expressed in many other tumors but poorly expressed in CCA. The anti-HER2 antibody, trastuzumab, has been used for the treatment of HER2-positive breast and gastric cancer. In this study, we examined the surface expression of HER2 on seven Thai liver-fluke-associated CCA cell lines by flow cytometry, and found all of these CCA cells were weakly positive for HER2. MTT assay revealed that trastuzumab directly suppressed the growth of CCA. By using FcR-bearing recombinant Jurkat T-cell-expressing firefly luciferase gene under the control of NFAT response elements, we defined the activities of antibody-dependent cytotoxicity (ADCC) and antibody-dependent cell phagocytosis (ADCP). ADCC was confirmed by using expanded NK cells. ADCP was confirmed by using mouse peritoneal macrophages and human monocyte-derived macrophages as effector cells. Rabbit serum was administered to test the complement-dependent cytotoxicity (CDC) activity of trastuzumab. Finally, we evaluated the efficacy of trastuzumab in in vivo patient-derived cell xenograft and patient-derived xenograft (PDX) models. Our results showed that a distinct population of CCA (liver-fluke-associated CCA) expressed HER2. Trastuzumab demonstrated a potent inhibitory effect on even HER2 weakly positive CCA both in vitro and in vivo via multiple mechanisms. Thus, HER2 is a promising target in anti-CCA therapy, and trastuzumab can be considered a promising antibody immunotherapy agent for the treatment of CCA.

In Vitro Assessment of 177Lu-Labeled Trastuzumab-Targeted Mesoporous Carbon@Silica Nanostructure for the Treatment of HER2-Positive Breast Cancer

This study assessed the effectiveness of a trastuzumab-targeted 177Lu-labeled mesoporous Carbon@Silica nanostructure (DOTA@TRA/MC@Si) for HER2-positive breast cancer treatment, focusing on its uptake, internalization, and efflux in breast cancer cells. The synthesized PEI-MC@Si nanocomposite was reacted with DOTA-NHS-ester, confirmed by the Arsenazo(III) assay. Following this, TRA was conjugated to the DOTA@PEI-MC@Si for targeting. DOTA@PEI-MC@Si and DOTA@TRA/MC@Si nanocomposites were labeled with 177Lu, and their efficacy was evaluated through in vitro radiolabeling experiments. According to the results, the DOTA@TRA/MC@Si nanocomposite was successfully labeled with 177Lu, yielding a radiochemical yield of 93.0 ± 2.4%. In vitro studies revealed a higher uptake of the [177Lu]Lu-DOTA@TRA/MC@Si nanocomposite in HER2-positive SK-BR-3 cells (44.0 ± 4.6% after 24 h) compared to MDA-MB-231 cells (21.0 ± 2.3%). The IC50 values for TRA-dependent uptake in the SK-BR-3 and BT-474 cells were 0.9 µM and 1.3 µM, respectively, indicating affinity toward HER-2 receptor-expressing cells. The lipophilic distribution coefficients of the radiolabeled nanocomposites were determined to be 1.7 ± 0.3 for [177Lu]Lu-DOTA@TRA/MC@Si and 1.5 ± 0.2 for [177Lu]Lu-DOTA@PEI-MC@Si, suggesting sufficient passive transport through the cell membrane and increased accumulation in target tissues. The [177Lu]Lu-DOTA@TRA/MC@Si nanocomposite showed an uptake into HER2-positive cell lines, marking a valuable step toward the development of a nanoparticle-based therapeutic agent for an improved treatment strategy for HER2-positive breast cancer.

Neratinib could be effective as monotherapy or in combination with trastuzumab in HER2-low breast cancer cells and organoid models

BACKGROUND

Previous studies have suggested that patients with HER2-low breast cancers do not benefit from trastuzumab treatment although the reasons remain unclear.

METHODS

We investigated the effect of trastuzumab monotherapy and its combination with different HER2 targeting treatments in a panel of breast cancer cell lines and patient-derived organoids (PDOs) using biochemical methods and cell viability assays.

RESULTS

Compared to sensitive HER2 over-expressing (IHC3 + ) breast cancer cells, increasing doses of trastuzumab could not achieve IC50 in MDA-MB-361 (IHC 2 + FISH + ) and MDA-MB-453 (IHC 2 + FISH-) cells which showed an intermediate response to trastuzumab. Trastuzumab treatment induced upregulation of HER ligand release, resulting in the activation of HER receptors in these cells, which could account for their trastuzumab insensitivity. Adding a dual ADAM10/17 inhibitor to inhibit the shedding of HER ligands in combination with trastuzumab only showed a modest decrease in the cell viability of HER2-low breast cancer cells and PDOs. However, the panHER inhibitor neratinib was an effective monotherapy in HER2-low breast cancer cells and PDOs, and showed additive effects when combined with trastuzumab.

CONCLUSION

This study demonstrates that neratinib in combination with trastuzumab may be effective in a subset of HER2-low breast cancers although further validation is required in a larger panel of PDOs and in future clinical studies.

Unveiling Alterations of Epigenetic Modifications and Chromatin Architecture Leading to Lipid Metabolic Reprogramming during the Evolutionary Trastuzumab Adaptation of HER2-Positive Breast Cancer

Secondary trastuzumab resistance represents an evolutionary adaptation of HER2-positive breast cancer during anti-HER2 treatment. Most current studies have tended to prioritize HER2 and its associated signaling pathways, often overlooking broader but seemingly less relevant cellular processes, along with their associated genetic and epigenetic mechanisms. Here, transcriptome data is not only characterized but also examined epigenomic and 3D genome architecture information in both trastuzumab-sensitive and secondary-resistant breast cancer cells. The findings reveal that the global metabolic reprogramming associated with trastuzumab resistance may stem from genome-wide alterations in both histone modifications and chromatin structure. Specifically, the transcriptional activities of key genes involved in lipid metabolism appear to be regulated by variant promoter H3K27me3 and H3K4me3 modifications, as well as promoter-enhancer interactions. These discoveries offer valuable insights into how cancer cells adapt to anti-tumor drugs and have the potential to impact future diagnostic and treatment strategies.

Decoding cell death signalling: Impact on the response of breast cancer cells to approved therapies

Breast cancer is a principal cause of cancer-related mortality in female worldwide. While many approved therapies have shown promising outcomes in treating breast cancer, understanding the intricate signalling pathways controlling cell death is crucial for optimizing the treatment outcome. A growing body of evidence has unveiled the aberrations in multiple cell death pathways across diverse cancer types, highlighting these pathways as appealing targets for therapeutic interventions. In this review, we provide a comprehensive overview of the current state of knowledge on the cell death signalling mechanisms with a particular focus on their impact on the response of breast cancer cells to approved therapies. Additionally, we discuss the potentials of combination therapies that exploit the synergy between approved drugs and therapeutic agents targeting modulators of cell death pathways.

Therapeutic approaches to enhance natural killer cell cytotoxicity

Enhancing the cytotoxicity of natural killer (NK) cells has emerged as a promising strategy in cancer immunotherapy, due to their pivotal role in immune surveillance and tumor clearance. This literature review provides a comprehensive overview of therapeutic approaches designed to augment NK cell cytotoxicity. We analyze a wide range of strategies, including cytokine-based treatment, monoclonal antibodies, and NK cell engagers, and discuss criteria that must be considered when selecting an NK cell product to combine with these strategies. Furthermore, we discuss the challenges and limitations associated with each therapeutic strategy, as well as the potential for combination therapies to maximize NK cell cytotoxicity while minimizing adverse effects. By exploring the wealth of research on this topic, this literature review aims to provide a comprehensive resource for researchers and clinicians seeking to develop and implement novel therapeutic strategies that harness the full potential of NK cells in the fight against cancer. Enhancing NK cell cytotoxicity holds great promise in the evolving landscape of immunotherapy, and this review serves as a roadmap for understanding the current state of the field and the future directions in NK cell-based therapies.

Management of patients with advanced-stage HER2-positive breast cancer: current evidence and future perspectives

Amplification and/or overexpression of ERBB2, the gene encoding HER2, can be found in 15-20% of invasive breast cancers and is associated with an aggressive phenotype and poor clinical outcomes. Relentless research efforts in molecular biology and drug development have led to the implementation of several HER2-targeted therapies, including monoclonal antibodies, tyrosine-kinase inhibitors and antibody-drug conjugates, constituting one of the best examples of bench-to-bedside translation in oncology. Each individual drug class has improved patient outcomes and, importantly, the combinatorial and sequential use of different HER2-targeted therapies has increased cure rates in the early stage disease setting and substantially prolonged survival for patients with advanced-stage disease. In this Review, we describe key steps in the development of the modern paradigm for the treatment of HER2-positive advanced-stage breast cancer, including selecting and sequencing new-generation HER2-targeted therapies, and summarize efficacy and safety outcomes from pivotal studies. We then outline the factors that are currently known to be related to resistance to HER2-targeted therapies, such as HER2 intratumoural heterogeneity, activation of alternative signalling pathways and immune escape mechanisms, as well as potential strategies that might be used in the future to overcome this resistance and further improve patient outcomes.

Update on current and new potential immunotherapies in breast cancer, from bench to bedside

Impressive advances have been seen in cancer immunotherapy during the last years. Although breast cancer (BC) has been long considered as non-immunogenic, immunotherapy for the treatment of BC is now emerging as a new promising therapeutic approach with considerable potential. This is supported by a plethora of completed and ongoing preclinical and clinical studies in various types of immunotherapies. However, a significant gap between clinical oncology and basic cancer research impairs the understanding of cancer immunology and immunotherapy, hampering cancer therapy research and development. To exploit the accumulating available data in an optimal way, both fundamental mechanisms at play in BC immunotherapy and its clinical pitfalls must be integrated. Then, clinical trials must be critically designed with appropriate combinations of conventional and immunotherapeutic strategies. While there is room for major improvement, this updated review details the immunotherapeutic tools available to date, from bench to bedside, in the hope that this will lead to rethinking and optimizing standards of care for BC patients.

Identification of novel anti-CD16a antibody clones for the development of effective natural killer cell engagers

Natural killer (NK) cells are key players in human innate immunity. Cell engager antibody formats that recruit and activate NK cells more effectively have emerged as a promising immunotherapy approach to target cancer cells through more effective antibody-dependent cell-mediated cytotoxicity (ADCC). Monoclonal antibody drugs with ADCC activity have shown clinical benefit and improved outcomes for patients with certain types of cancer. CD16a, a Fc gamma III receptor, is the major component that is responsible for the ADCC activity of NK cells. Screening AvantGen's yeast displayed human antibody libraries led to the isolation of 2 antibody clones, #1A2 and #2-2A2, that selectively recognize both isoforms (F and V) of CD16a on primary NK cells with high affinity, yet minimally (#1A2) or do not (#2-2A2) cross-react with both allelotypes of CD16b (NA1 and NA2) expressed by neutrophils. Epitope mapping studies revealed that they bind to an epitope dependent on residue Y158 of CD16a, since mutation of Y158 to the corresponding CD16b residue H158 completely abolishes binding to CD16a. When formatted as bispecific antibodies targeting CD16a and a tumor-associated antigen (TAA, e.g. CD19), they exhibit specific binding to NK cells and induce potent NK cell activation upon encountering tumor cells, resulting in effective tumor cell killing. Notably, these bispecific antibody engagers stimulate NK cell cytokine release during co-culture with target cells, resulting in target cell cytotoxicity. These anti-CD16a antibody clones are promising candidates for combination with any TAA of interest, offering the potential for novel NK cell engager-based cancer therapeutics that are minimally affected by the high concentrations of human IgG in the circulation.

Immune microenvironment dynamics of HER2 overexpressing breast cancer under dual anti-HER2 blockade

Introduction

The clinical prognosis of the HER2-overexpressing (HER2-OE) subtype of breast cancer (BC) is influenced by the immune infiltrate of the tumor. Specifically, monocytic cells, which are promoters of pro-tumoral immunosuppression, and NK cells, whose basal cytotoxic function may be enhanced with therapeutic antibodies. One of the standards of care for HER2+ BC patients includes the combination of the anti-HER2 antibodies trastuzumab and pertuzumab. This dual combination was a breakthrough against trastuzumab resistance; however, this regimen does not yield complete clinical benefit for a large fraction of patients. Further therapy refinement is still hampered by the lack of knowledge on the immune mechanism of action of this antibody-based dual HER2 blockade.

Methods

To explore how the dual antibody challenge influences the phenotype and function of immune cells infiltrating the HER2-OE BC microenvironment, we developed in vitro 3D heterotypic cell models of this subtype. The models comprised aggregates of HER2+ BC cell lines and human peripheral blood mononuclear cells. Cells were co-encapsulated in a chemically inert alginate hydrogel and maintained in agitation-based culture system for up to 7 days.

Results

The 3D models of the HER2-OE immune microenvironment retained original BC molecular features; the preservation of the NK cell compartment was achieved upon optimization of culture time and cytokine supplementation. Challenging the models with the standard-of-care combination of trastuzumab and pertuzumab resulted in enhanced immune cytotoxicity compared with trastuzumab alone. Features of the response to therapy within the immune tumor microenvironment were recapitulated, including induction of an immune effector state with NK cell activation, enhanced cell apoptosis and decline of immunosuppressive PD-L1+ immune cells.

Conclusions

This work presents a unique human 3D model for the study of immune effects of anti-HER2 biologicals, which can be used to test novel therapy regimens and improve anti-tumor immune function.

Alterations in immune cell phenotype and cytotoxic capacity in HER2+ breast cancer patients receiving HER2-targeted neo-adjuvant therapy

BACKGROUND

The phase II neo-adjuvant clinical trial ICORG10-05 (NCT01485926) compared chemotherapy in combination with trastuzumab, lapatinib or both in patients with HER2+ breast cancer. We studied circulating immune cells looking for alterations in phenotype, genotype and cytotoxic capacity (direct and antibody-dependent cell-mediated cytotoxicity (ADCC)) in the context of treatment response.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from pre- (n = 41) and post- (n = 25) neo-adjuvant treatment blood samples. Direct/trastuzumab-ADCC cytotoxicity of patient-derived PBMCs against K562/SKBR3 cell lines was determined ex vivo. Pembrolizumab was interrogated in 21 pre-treatment PBMC ADCC assays. Thirty-nine pre-treatment and 21 post-treatment PBMC samples were immunophenotyped. Fc receptor genotype, tumour infiltrating lymphocyte (TIL) levels and oestrogen receptor (ER) status were quantified.

RESULTS

Treatment attenuated the cytotoxicity/ADCC of PBMCs. CD3+/CD4+/CD8+ T cells increased following therapy, while CD56+ NK cells/CD14+ monocytes/CD19+ B cells decreased with significant post-treatment immune cell changes confined to patients with residual disease. Pembrolizumab-augmented ex vivo PBMC ADCC activity was associated with residual disease, but not pathological complete response. Pembrolizumab-responsive PBMCs were associated with lower baseline TIL levels and ER+ tumours.

CONCLUSIONS

PBMCs display altered phenotype and function following completion of neo-adjuvant treatment. Anti-PD-1-responsive PBMCs in ex vivo ADCC assays may be a biomarker of treatment response.

Antibody-drug conjugates in breast cancer: overcoming resistance and boosting immune response

Antibody-drug conjugates (ADCs) have emerged as a revolutionary therapeutic class, combining the precise targeting ability of monoclonal antibodies with the potent cytotoxic effects of chemotherapeutics. Notably, ADCs have rapidly advanced in the field of breast cancer treatment. This innovative approach holds promise for strengthening the immune system through antibody-mediated cellular toxicity, tumor-specific immunity, and adaptive immune responses. However, the development of upfront and acquired resistance poses substantial challenges in maximizing the effectiveness of these therapeutics, necessitating a deeper understanding of the underlying mechanisms. These mechanisms of resistance include antigen loss, derangements in ADC internalization and recycling, drug clearance, and alterations in signaling pathways and the payload target. To overcome resistance, ongoing research and development efforts are focused on urgently identifying biomarkers, integrating immune therapy approaches, and designing novel cytotoxic payloads. This Review provides an overview of the mechanisms and clinical effectiveness of ADCs, and explores their unique immune-boosting function, while also highlighting the complex resistance mechanisms and safety challenges that must be addressed. A continued focus on how ADCs impact the tumor microenvironment will help to identify new payloads that can improve patient outcomes.

The Function of NK Cells in Tumor Metastasis and NK Cell-Based Immunotherapy

Metastatic tumors cause the most deaths in cancer patients. Treating metastasis remains the primary goal of current cancer research. Although the immune system prevents and kills the tumor cells, the function of the immune system in metastatic cancer has been unappreciated for decades because tumors are able to develop complex signaling pathways to suppress immune responses, leading them to escape detection and elimination. Studies showed NK cell-based therapies have many advantages and promise for fighting metastatic cancers. We here review the function of the immune system in tumor progression, specifically focusing on the ability of NK cells in antimetastasis, how metastatic tumors escape the NK cell attack, as well as the recent development of effective antimetastatic immunotherapies.

Syngeneic mouse model of human HER2+ metastatic breast cancer for the evaluation of trastuzumab emtansine combined with oncolytic rhabdovirus

Background

Established mouse models of HER2+ cancer are based on the over-expression of rodent Neu/Erbb2 homologues, which are incompatible with human HER2 (huHER2) targeted therapeutics. Additionally, the use of immune-deficient xenograft or transgenic models precludes assessment of native anti-tumour immune responses. These hurdles have been a challenge for our understanding of the immune mechanisms behind huHER2-targeting immunotherapies.

Methods

To assess the immune impacts of our huHER2-targeted combination strategy, we generated a syngeneic mouse model of huHER2+ breast cancer, using a truncated form of huHER2, HER2T. Following validation of this model, we next treated tumour-bearing with our immunotherapy strategy: oncolytic vesicular stomatitis virus (VSVΔ51) with clinically approved antibody-drug conjugate targeting huHER2, trastuzumab emtansine (T-DM1). We assessed efficacy through tumour control, survival, and immune analyses.

Results

The generated truncated HER2T construct was non-immunogenic in wildtype BALB/c mice upon expression in murine mammary carcinoma 4T1.2 cells. Treatment of 4T1.2-HER2T tumours with VSVΔ51+T-DM1 yielded robust curative efficacy compared to controls, and broad immunologic memory. Interrogation of anti-tumour immunity revealed tumour infiltration by CD4+ T cells, and activation of B, NK, and dendritic cell responses, as well as tumour-reactive serum IgG.

Conclusions

The 4T1.2-HER2T model was used to evaluate the anti-tumour immune responses following our complex pharmacoviral treatment strategy. These data demonstrate utility of the syngeneic HER2T model for assessment of huHER2-targeted therapies in an immune-competent in vivo setting. We further demonstrated that HER2T can be implemented in multiple other syngeneic tumour models, including but not limited to colorectal and ovarian models. These data also suggest that the HER2T platform may be used to assess a range of surface-HER2T targeting approaches, such as CAR-T, T-cell engagers, antibodies, or even retargeted oncolytic viruses.

Blockade of exosome release alters HER2 trafficking to the plasma membrane and gives a boost to Trastuzumab

OBJECTIVE(S)

Exosomal HER2 has been evidenced to interfere with antibody-induced anti-tumor effects. However, whether the blockade of HER2+ exosomes release would affect antibody-mediated tumor inhibition has yet to be investigated.

METHODS

Exosomes derived from BT-474, SK-BR3 and SK-OV3 (HER2-overexpressing tumor cells) and MDA-MB-231 cells (HER2 negative) were purified and characterized by bicinchoninic acid (BCA) assay, western blotting and Transmission electron microscopy (TEM). Inhibition of exosome release was achieved by neutral sphingomyelinase-2 (nSMase-2) inhibitor, GW4869. The effects of exosome blockade on the anti-proliferative effects, apoptosis induction, and antibody-mediated cellular cytotoxicity (ADCC) activity of Trastuzumab were examined using MTT, flow cytometry, and LDH release assays. Also, the effects of exosome inhibition on the surface expression and endocytosis/internalization of HER2 were studied by flow cytometry.

RESULTS

Purified exosomes derived from HER2 overexpressing cancer cells were positive for HER2 protein. Blockade of exosome release was able to significantly improve apoptosis induction, anti-proliferative and ADCC responses of Trastuzumab dose dependently. The pretreatment of Trastuzumab/purified NK cells, but not PBMCs, with HER2+ exosomes could also decrease the ADCC effects of Trastuzumab. Exosome inhibition also remarkably downregulated surface HER2 levels in a time-dependent manner, but does not affect its endocytosis/internalization.

CONCLUSION

Based on our findings, HER2+ exosomes may benefit tumor progression by dually suppressing Trastuzumab-induced tumor growth inhibition and cytotoxicity of NK cells. It seems that concomitant blocking of exosome release might be an effective approach for improving the therapeutic effects of Trastuzumab, and potentially other HER2-directed mAbs. In addition, the exosome secretion pathway possibly contributes to the HER2 trafficking to plasma membrane, since the blockade of exosome secretion decreased surface HER2 levels.

Antigen-Dependent Inducible T-Cell Reporter System for PET Imaging of Breast Cancer and Glioblastoma

For the past several decades, chimeric antigen receptor T-cell therapies have shown promise in the treatment of cancers. These treatments would greatly benefit from companion imaging biomarkers to follow the trafficking of T cells in vivo. Methods: Using synthetic biology, we engineered T cells with a chimeric receptor synthetic intramembrane proteolysis receptor (SNIPR) that induces overexpression of an exogenous reporter gene cassette on recognition of specific tumor markers. We then applied a SNIPR-based PET reporter system to 2 cancer-relevant antigens, human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor variant III (EGFRvIII), commonly expressed in breast and glial tumors, respectively. Results: Antigen-specific reporter induction of the SNIPR PET T cells was confirmed in vitro using green fluorescent protein fluorescence, luciferase luminescence, and the HSV-TK PET reporter with 9-(4-18F-fluoro-3-[hydroxymethyl]butyl)guanine ([18F]FHBG). T cells associated with their target antigens were successfully imaged using PET in dual-xenograft HER2+/HER2- and EGFRvIII+/EGFRvIII- animal models, with more than 10-fold higher [18F]FHBG signals seen in antigen-expressing tumors versus the corresponding controls. Conclusion: The main innovation found in this work was PET detection of T cells via specific antigen-induced signals, in contrast to reporter systems relying on constitutive gene expression.

Acute thrombocytopenia induced by trastuzumab due to complement reaction: A case report

Background

The usual treatment option for HER2 breast cancer is targeted therapy with trastuzumab. The common adverse effects of trastuzumab treatment are thrombocytopenia, however, acute thrombocytopenia is rare and its mechanism is still largely unknown.

Case presentation

We reported a patient who presented with acute thrombocytopenia on two consecutive occasions, and the predisposing factor was identified on the second occasion because of trastuzumab-only treatment. Routine blood results showed a dramatic increase in white blood cell count and neutrophil count after both trastuzumab treatments. Moreover, the complement reaction results suggested that the dramatic thrombocytopenia was probably due to platelet destruction after complement activation.

Conclusion

This case suggests that it would be useful to perform a platelet complement reaction test before trastuzumab treatment in patients with HER2 breast cancer.

Drug-resistant HER2-positive breast cancer: Molecular mechanisms and overcoming strategies

Breast cancer is one of the most common malignancies and the leading cause of cancer-related death in women. HER2 overexpression is a factor for poor prognosis in breast cancer, and anti-HER2 therapy improves survival in these patients. A dual-targeted combination of pertuzumab and trastuzumab, alongside cytotoxic chemotherapy, constitutes the primary treatment option for individuals with early-stage, HER2-positive breast cancer. Antibody-drug conjugate (ADC) and tyrosine kinase inhibitors (TKI) also increase the prognosis for patients with metastatic breast cancer. However, resistance to targeted therapy eventually occurs. Therefore, it is critical to investigate how HER2-positive breast cancer is resistant to targeted therapy and to develop novel drugs or strategies to overcome the resistance simultaneously. This review aims to provide a comprehensive discussion of the HER2-targeted agents currently in clinical practice, the molecular mechanisms of resistance to these drugs, and the potential strategies for overcoming resistance.

Identification of novel prognostic risk signature of breast cancer based on ferroptosis-related genes

Ferroptosis is a type of cell regulated necrosis triggered by intracellular phospholipid peroxidation, which is more immunogenic than apoptosis. Therefore, genes controlling ferroptosis may be promising candidate biomarkers for tumor therapy. In this study, we investigate the function of genes associated with ferroptosis in breast cancer (BC) and systematically evaluate the relationship between ferroptosis-related gene expression and prognosis of BC patients from the Cancer Genome Atlas database. By using the consensus clustering method, 1203 breast cancer samples were clustered into two clearly divided subgroups based on the expression of 237 ferroptosis-related genes. Then differentially expressed analysis and least absolute shrinkage and selection operator were used to identify the prognosis-related genes. Furthermore, the genetic risk signature was constructed using the expression of prognosis-related genes. Our results showed that the genetic risk signature can identify patient subgroups with distinct prognosis in either training cohort or validation, and the genetic risk signature was associated with the tumor immune microenvironment. Finally, the Cox regression analysis indicated that our risk signature was an independent prognostic factor for BC patients and this signature was verified by the polymerase chain reaction and western blot. Within this study, we identified a novel prognostic classifier based on five ferroptosis-related genes which may provide a new reference for the treatment of BRCA patients.

Defucosylated mouse‑dog chimeric anti‑HER2 monoclonal antibody exerts antitumor activities in mouse xenograft models of canine tumors

Human epidermal growth factor receptor 2 (HER2) overexpression has been reported in various types of cancer, including breast, gastric, lung, colorectal and pancreatic cancer. A humanized anti-HER2 monoclonal antibody (mAb), trastuzumab, has been shown to improve survival of patients in HER2-positive breast and gastric cancer. An anti-HER2 mAb, H₂Mab-77 (mouse IgG₁, kappa) was previously developed. In the present study, a defucosylated version of mouse-dog chimeric anti-HER2 mAb (H77Bf) was generated. H77Bf possesses a high binding-affinity [a dissociation constant (K_D): 7.5×10⁻¹⁰ M, as determined by flow cytometric analysis] for dog HER2-overexpressed CHO-K1 (CHO/dHER2) cells. H77Bf highly exerted antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) for CHO/dHER2 cells by canine mononuclear cells and complement, respectively. Moreover, administration of H77Bf significantly suppressed the development of CHO/dHER2 ×enograft tumor in mice compared with the control dog IgG. H77Bf also possesses a high binding-affinity (K_D: 7.2×10⁻¹⁰ M) for a canine mammary gland tumor cell line (SNP), and showed high ADCC and CDC activities for SNP cells. Intraperitoneal administration of H77Bf in mouse xenograft models of SNP significantly suppressed the development of SNP xenograft tumors compared with the control dog IgG. These results indicated that H77Bf exerts antitumor activities against dHER2-positive canine cancers, and could be valuable treatment regimen for canine cancers.

Disentangling ERBB Signaling in Breast Cancer Subtypes-A Model-Based Analysis

Targeted therapies have shown striking success in the treatment of cancer over the last years. However, their specific effects on an individual tumor appear to be varying and difficult to predict. Using an integrative modeling approach that combines mechanistic and regression modeling, we gained insights into the response mechanisms of breast cancer cells due to different ligand-drug combinations. The multi-pathway model, capturing ERBB receptor signaling as well as downstream MAPK and PI3K pathways was calibrated on time-resolved data of the luminal breast cancer cell lines MCF7 and T47D across an array of four ligands and five drugs. The same model was then successfully applied to triple negative and HER2-positive breast cancer cell lines, requiring adjustments mostly for the respective receptor compositions within these cell lines. The additional relevance of cell-line-specific mutations in the MAPK and PI3K pathway components was identified via L1 regularization, where the impact of these mutations on pathway activation was uncovered. Finally, we predicted and experimentally validated the proliferation response of cells to drug co-treatments. We developed a unified mathematical model that can describe the ERBB receptor and downstream signaling in response to therapeutic drugs targeting this clinically relevant signaling network in cell line that represent three major subtypes of breast cancer. Our data and model suggest that alterations in this network could render anti-HER therapies relevant beyond the HER2-positive subtype.

Lipid-based nanoparticulate delivery systems for HER2-positive breast cancer immunotherapy

Lipid-based nanoparticulate delivery platforms such as liposomes help overcome cell and tissue barriers and allow prolonged therapeutic plasma drug concentrations, simultaneous targeting of tumor tissue, and increased bioavailability of numerous drugs used for treatment of cancer. The human epidermal growth factor receptor, HER2, is an important player in the pathogenesis of breast cancer and is considered a potential cancer biomarker for the design of immunotherapeutics. HER2-positive breast cancer is found in up to 30% of breast cancer patients. Currently, a variety of lipid nanoparticulate systems are being evaluated in preclinical settings and in clinical trials for targeting HER2-positive breast cancer. Advances in functionalized anti-HER2 lipid nanoparticulates have demonstrated promise and may lead to the development of new nano-immunotherapy protocols against HER2 positive breast cancer. Here we present a review of the most up-to-date literature, including our own research, on the use of lipid nanoparticulate carriers in immunotherapy of HER2-positive breast cancer.

Case Report: Significant Efficacy of Pyrotinib in the Treatment of Extensive Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Cutaneous Metastases: A Report of Five Cases

BACKGROUND

Breast cancer (BC) is the most common tumor to develop cutaneous metastases. Most BCs with cutaneous metastasis are human epidermal growth factor receptor 2 (HER2)-positive subtypes. Although the molecular mechanisms of breast cancer metastasis to different sites and the corresponding treatment methods are areas of in-depth research, there are few studies on cutaneous metastasis.

CASE PRESENTATION

Five HER2-positive BC patients with extensive cutaneous metastases were treated with a regimen containing pyrotinib, a novel small-molecule tyrosine kinase inhibitor that irreversibly blocks epidermal growth factor receptor (EGFR), HER2, and human epidermal growth factor receptor 4 (HER4), then their cutaneous metastases quickly resolved at an astonishing speed and their condition was well controlled during the follow-up period.

CONCLUSIONS

This case series reports the significant therapeutic effect of pyrotinib on cutaneous metastases of HER2-positive BC for the first time. Based on this, we recommend that pyrotinib can be used as a supplement to trastuzumab for HER2-positive BC patients with cutaneous metastases. In addition, we should consider that the pan-inhibitory effect of pyrotinib on EGFR, HER2, and HER4 may provide a dual therapeutic effect against HER2 and mucin 1.

Cellular-Resolution Imaging of Bystander Payload Tissue Penetration from Antibody-Drug Conjugates

After several notable clinical failures in early generations, antibody-drug conjugates (ADCs) have made significant gains with seven new FDA-approvals within the last 3 years. These successes have been driven by a shift towards mechanistically informed ADC design, where the payload, linker, drug-to-antibody ratio, and conjugation are increasingly tailored to a specific target and clinical indication. However, fundamental aspects needed for design, such as payload distribution, remain incompletely understood. Payloads are often classified as 'bystander' or 'non-bystander' depending on their ability to diffuse out of targeted cells into adjacent cells that may be antigen negative or more distant from tumor vessels, helping to overcome heterogeneous distribution. Seven of the eleven FDA-approved ADCs employ these bystander payloads, but the depth of penetration and cytotoxic effects as a function of physicochemical properties and mechanism of action have not been fully characterized. Here, we utilized tumor spheroids and pharmacodynamic marker staining to quantify tissue penetration of the three major classes of agents: microtubule inhibitors, DNA-damaging agents, and topoisomerase inhibitors. PAMPA data and co-culture assays were performed to compare to the 3D tissue culture data. The results demonstrate a spectrum in bystander potential and tissue penetration depending on the physicochemical properties and potency of the payload. Generally, directly targeted cells show a greater response even with bystander payloads, consistent with the benefit of deeper ADC penetration. These results are compared to computational simulations to help scale the data from in vitro and preclinical animal models to the clinic.

Identification of a Six-Gene Prognostic Signature Characterized by Tumor Microenvironment Immune Profiles in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is widely acknowledged to be extremely sensitive to immunotherapy, emphasizing the tremendous impacts on which the tumor microenvironment (TME) has shown. However, the molecular subgroups characterized by the TME features scarcely serve as the risk stratification guides in clinical practice for survival outcomes and immunotherapy response prediction. This study generated fresh insights into a novel TME-related prognostic signature derived from The Cancer Genome Atlas database using integrated bioinformatics analyses. Subsequently, Kaplan–Meier survival analysis, receiver operating characteristic analysis, and univariate and multivariate Cox regression analysis were performed to evaluate and validate the efficacy and the accuracy of the signature in ccRCC prognosis. Furthermore, we discovered that the risk score presented an increased likelihood of correlation with miscellaneous clinicopathological characteristics, natural killer cell-mediated cytotoxicity, immune cell infiltration levels, and immune checkpoint expression. These findings highlighted the notion that the six-gene signature characterized by the TME features may have implications on the risk stratification for personalized and precise immunotherapeutic management.

A bispecific antibody targeting HER2 and PD-L1 inhibits tumor growth with superior efficacy

Activation of the programmed cell death protein 1 and programmed cell death ligand 1 (PD-1/PD-L1) signaling axis plays important roles in intrinsic or acquired resistance to human epidermal growth factor receptor 2 (HER2)-directed therapies in the clinic. Therefore, therapies simultaneously targeting both HER2 and PD-1/PD-L1 signaling pathways are of great significance. Here, aiming to direct the anti-PD-L1 responses toward HER2-expressing tumor cells, we constructed a humanized bispecific IgG1 subclass antibody targeting both HER2 and PD-L1 (HER2/PD-L1; BsAb), which displayed satisfactory purity, thermostability, and serum stability. We found that BsAb showed enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity in vitro. In the late phase of peripheral blood mononuclear cell (PBMC)-humanized HER2⁺ tumor xenograft models, BsAb showed superior therapeutic efficacies as compared with monoclonal antibodies (mAbs) or combination treatment strategies. In cynomolgus monkeys, BsAb showed favorable pharmacokinetics and toxicity profiles when administered at a 10 mg/kg dosage. Thus, HER2/PD-L1 BsAb was demonstrated as a potentially effective option for managing HER2⁺ and trastuzumab-resistant tumors in the clinic. We propose that the enhanced antitumor activities of BsAb in vivo may be due to direct inhibition of HER2 signaling or activation of T cells.

Targeting TIGIT for Immunotherapy of Cancer: Update on Clinical Development

Immune checkpoint blockers have dramatically improved the chances of survival in patients with metastatic cancer, but only a subset of the patients respond to treatment. Search for novel targets that can improve the responder rates and overcome the limitations of adverse events commonly seen with combination therapies, like PD-1 plus CTLA-4 blockade and PD-1/PD-L1 plus chemotherapy, led to the development of monoclonal antibodies blocking T-cell immunoglobulin and ITIM domain (TIGIT), a inhibitory checkpoint receptor expressed on activated T cells and NK cells. The strategy showed potential in pre-clinical and early clinical studies, and 5 molecules are now in advanced stages of evaluation (phase II and above). This review aims to provide an overview of clinical development of anti-TIGIT antibodies and describes the factors considered and thought process during early clinical development. Critical aspects that can decide the fate of clinical programs, such as origin of the antibody, Ig isotype, FCγR binding, and the dose as well as dosing schedule, are discussed along with the summary of available efficacy and safety data from clinical studies and the challenges in the development of anti-TIGIT antibodies, such as identifying patients who can benefit from therapy and getting payer coverage.

Immunotherapy for Dogs: Still Running Behind Humans

Despite all good intentions, dogs are still running behind humans in effective cancer immunotherapies. The more effective treatments in humans, like infusions of CAR-T and NK-cells are not broadly pursued for canines due to significant costs, the rather complicated logistics and the lack of targetable surface antigens. Monoclonal antibodies are challenging to develop considering the limited knowledge about canine target antigens and about their mode of action. Although immunogenic vaccines could be less costly, this approach is hampered by the fact that cancer by itself is immuno-suppressive and any preceding chemotherapy may suppress any clinically meaningful immune response. This review - rather than providing a comprehensive listing of all available immunotherapies for dogs, aims at pointing out the issues that are holding back this field but which hopefully can be addressed so that dogs can "catch up" with what is available to humans.

Purification and In Vitro Evaluation of an Anti-HER2 Affibody-Monomethyl Auristatin E Conjugate in HER2-Positive Cancer Cells

Simple Summary

Antibody-drug conjugates (ADCs) represent an innovative class of anticancer agents specifically aimed at targeting cancer cells, reducing damage to healthy tissues but showing some weaknesses. A promising approach for the development of high-affinity tumor targeting ADCs is the use of engineered protein drugs, such as affibody molecules. Our aim was to develop a more efficient purification method for the cytotoxic conjugate Z_HER2:2891DCS-MMAE that targets human epidermal growth factor receptor 2 (HER2)-positive breast cancer cells. The conjugate is based on Z_HER2:2891 affibody and a drug conjugation sequence (DCS), which allowed for site-specific conjugation of the cytotoxic auristatin E molecule (MMAE) to the affibody. We tested the in vitro efficacy of Z_HER2:2891DCS-MMAE on several parameters, such as cell viability, proliferation, migration, and apoptosis. Our results confirmed that the cytotoxic conjugate efficiently interacts with high affinity with HER2 positive cancer cells, allowing the selective and specific delivery of the cytotoxic payload.

Abstract

A promising approach for the development of high-affinity tumor targeting ADCs is the use of engineered protein drugs, such as affibody molecules, which represent a valuable alternative to monoclonal antibodies (mAbs) in cancer-targeted therapy. We developed a method for a more efficient purification of the Z_HER2:2891DCS affibody conjugated with the cytotoxic antimitotic agent auristatin E (MMAE), and its efficacy was tested in vitro on cell viability, proliferation, migration, and apoptosis. The effects of Z_HER2:2891DCS-MMAE were compared with the clinically approved monoclonal antibody trastuzumab (Herceptin^®). To demonstrate that Z_HER2:2891DCS-MMAE can selectively target HER2 overexpressing tumor cells, we used three different cell lines: the human adenocarcinoma cell lines SK-BR-3 and ZR-75-1, both overexpressing HER2, and the triple-negative breast cancer cell line MDA-MB-231. MTT assay showed that Z_HER2:2891DCS-MMAE induces a significant time-dependent toxic effect in SK-BR-3 cells. A 30% reduction of cell viability was already found after 10 min exposure at a concentration of 7 nM (IC₅₀ of 80.2 nM). On the contrary, MDA-MB-231 cells, which express basal levels of HER2, were not affected by the conjugate. The cytotoxic effect of the Z_HER2:2891DCS-MMAE was confirmed by measuring apoptosis by flow cytometry. In SK-BR-3 cells, increasing concentrations of conjugated affibody induced cell death starting from 10 min of treatment, with the strongest effect observed after 48 h. Overall, these results demonstrate that the ADC, formed by the anti-HER2 affibody conjugated to monomethyl auristatin E, efficiently interacts with high affinity with HER2 positive cancer cells in vitro, allowing the selective and specific delivery of the cytotoxic payload.

Pharmacological Basis of Breast Cancer Resistance to Therapies - An Overview

Breast cancer (BC) is a molecular heterogeneous disease and often patients with similar clinico-pathological characteristics may display different response to treatment. Cellular processes, including uncontrolled cell-cycle, constitutive activation of signalling pathways parallel to or downstream of HER2 and alterations in DNA-repair mechanisms are the main features altered in the tumor. These cellular processes play significant roles in the emergence of therapy resistance. The introduction of target therapies as well as immunotherapies has improved the management of breast cancer. Furthermore, several therapeutic options are available to overcome resistance and physicians could overcome the challenge of resistant BC using combinatorial drug strategies and incorporating novel biomarkers. Molecular profiling promises to help in refine personalized treatment decisions and catalyse the development of further strategies when resistances inevitably occur. The search for biological explanations for treatment failure helps to clarify the phenomenon and allows to incorporate new biomarkers into clinical practice that can lead to adequate solutions to overcome it. This review provides a summary of genetic and molecular aspects of resistance mechanisms to available treatments for BC patients, and its clinical implications.

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.

Anti-HER2 antibody prolongs overall survival disproportionally more than progression-free survival in HER2-Positive metastatic breast cancer patients

Background

This meta-analysis aimed to test the hypothesis that the HER2-positive metastatic breast cancer (mBC) patients treated with anti-HER2 antibodies in trial intervention arms have a greater prolongation of overall survival (OS) than of progression-free survival (PFS) and this extra-prolongation of median survival time in OS relates specifically to the anti-HER2 antibody.

Methods

The NCBI/Pubmed and Cochrane databases were searched systematically for HER2-positive or mBC trials published in English during January 1999–November 2017. Treatment arms with shorter PFS were considered as the “control” arm, whereas those with longer PFS as the “test” arm. The between-treatment drug differences were grouped into nine categories. Groups with or without anti-HER2 antibodies were pooled respectively for comparisons. The interrelationships between PFS and OS hazard ratios (HRs) and median survival time differences were investigated by conducting fixed-effects and mixed-effects linear meta-regression analyses.

Results

Twenty-eight trials (10,928 patients) from 438 articles were collected, and four with missing data were excluded in meta-regression analysis. Overall median PFS (HR = 0.73, 95% CI: 0.68–0.78) and median OS (HR = 0.82, 95% CI: 0.77–0.87) weakly favored the longer PFS arm with a weak correlation between the PFS and OS HRs. However, the between-treatment drug difference was anti-HER2 antibody, the absolute increment in median OS time was double that of median PFS time (p < 0.001) and linearly correlated, which was not found with any non-anti-HER2 antibody drug differences.

Conclusions

Anti-HER2 antibody in patients with HER2-positive mBC prolonged OS more than PFS and mandates further investigation.

•

Our study dissected the overall survival benefit over progression-free survival in HER-2 positive metastatic breast cancer treated with anti-HER2 antibody by meta-analysis.

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Use of anti-HER2 antibodies, but not other anticancer drugs, to treat HER2-positive metastatic breast cancer independently predicted the OS compared with PFS.

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The design of future clinical trials should consider anti-HER2 antibodies carefully in the treatment armamentarium for HER2-positive metastatic breast cancer.

Defucosylation of Tumor-Specific Humanized Anti-MUC1 Monoclonal Antibody Enhances NK Cell-Mediated Anti-Tumor Cell Cytotoxicity

Simple Summary

Antibodies with their high specificity to antigens have been widely used in cancer immunotherapy. Natural killer (NK) cells are a group of innate immune cells which have strong cytotoxicity against cancerous cells, virus infected cells, or transformed cells. NK cells express abundant Fc receptors that can bind tumor-specific antibodies, thus allowing them to precisely redirect and eliminate cancer cells. In this study, we demonstrated that NK cells cytotoxicity toward MUC1-positive hematologic and solid tumor can be further enhanced by a humanized 5E5 anti-MUC1 antibody. Furthermore, Fc defucosylation of the antibodies further boosted the kill capacity of NK cells. We believe that our humanized anti-MUC1 antibody is a promising therapeutic candidate for clinical cancer treatment.

Abstract

Antibodies are commonly used in cancer immunotherapy because of their high specificity for tumor-associated antigens. The binding of antibodies can have direct effects on tumor cells but also engages natural killer (NK) cells via their Fc receptor. Mucin 1 (MUC1) is a highly glycosylated protein expressed in normal epithelial cells, while the under-glycosylated MUC1 epitope (MUC1-Tn/STn) is only expressed on malignant cells, making it an interesting diagnostic and therapeutic target. Several anti-MUC1 antibodies have been tested for therapeutic applications in solid tumors thus far without clinical success. Herein, we describe the generation of fully humanized antibodies based on the murine 5E5 antibody, targeting the tumor-specific MUC1-Tn/STn epitope. We confirmed that these antibodies specifically recognize tumor-associated MUC1 epitopes and can activate human NK cells in vitro. Defucosylation of these newly developed anti-MUC1 antibodies further enhanced antigen-dependent cellular cytotoxicity (ADCC) mediated by NK cells. We show that endocytosis inhibitors augment the availability of MUC1-Tn/STn epitopes on tumor cells but do not further enhance ADCC in NK cells. Collectively, this study describes novel fully humanized anti-MUC1 antibodies that, especially after defucosylation, are promising therapeutic candidates for cellular immunotherapy.

The role of infiltrating lymphocytes in the neo-adjuvant treatment of women with HER2-positive breast cancer

Background

Pre-treatment tumour-associated lymphocytes (TILs) and stromal lymphocytes (SLs) are independent predictive markers of future pathological complete response (pCR) in HER2-positive breast cancer. Whilst studies have correlated baseline lymphocyte levels with subsequent pCR, few have studied the impact of neoadjuvant therapy on the immune environment.

Methods

We performed TIL analysis and T-cell analysis by IHC on the pretreatment and ‘On-treatment’ samples from patients recruited on the Phase-II TCHL (NCT01485926) clinical trial. Data were analysed using the Wilcoxon signed-rank test and the Spearman rank correlation.

Results

In our sample cohort (n = 66), patients who achieved a pCR at surgery, post-chemotherapy, had significantly higher counts of TILs (p = 0.05) but not SLs (p = 0.08) in their pre-treatment tumour samples. Patients who achieved a subsequent pCR after completing neo-adjuvant chemotherapy had significantly higher SLs (p = 9.09 × 10^–3) but not TILs (p = 0.1) in their ‘On-treatment’ tumour biopsies. In a small cohort of samples (n = 16), infiltrating lymphocyte counts increased after 1 cycle of neo-adjuvant chemotherapy only in those tumours of patients who did not achieve a subsequent pCR. Finally, reduced CD3 + (p = 0.04, rho = 0.60) and CD4 + (p = 0.01, rho = 0.72) T-cell counts in 'On-treatment' biopsies were associated with decreased residual tumour content post-1 cycle of treatment; the latter being significantly associated with increased likelihood of subsequent pCR (p < 0.01).

Conclusions

The immune system may be ‘primed’ prior to neoadjuvant treatment in those patients who subsequently achieve a pCR. In those patients who achieve a pCR, their immune response may return to baseline after only 1 cycle of treatment. However, in those who did not achieve a pCR, neo-adjuvant treatment may stimulate lymphocyte influx into the tumour.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06244-1.

The Prognostic Impact of HER2 Genetic and Protein Expression in Pancreatic Carcinoma-HER2 Protein and Gene in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal and clinically heterogeneous disease with a limited benefit from human epidermal growth factor receptor 2 (HER2)-targeted therapy. Recently, some studies have addressed the antitumoral effect of novel anti-HER2 drugs in HER2 low-expressing tumors. However, there have been few studies on the significance of low HER2 expression and genetic heterogeneity in PDAC. Using immunohistochemistry and dual-color silver-enhanced in situ hybridization based on the Trastuzumab for a gastric cancer scoring scheme, we evaluated HER2 protein expression, gene amplification, and genetic heterogeneity in three groups (HER2-neg, HER2-low, HER2-pos) of 55 patients. Among the 55 cases, 41.8% (23/55) showed HER2 expression of any intensity. HER2 amplification independent of HER2 expression was 25.5% (14/55). Patients in both these groups had a shorter overall survival than did patients in the HER2-neg group. HER2 genetic heterogeneity was identified in 37 (70.9%) of the 55 cases, mainly in HER2-neg and HER2-low groups. HER2 genetic heterogeneity significantly correlated with worse survival in the HER2-low and HER2-neg groups of PDAC. These findings support the hypothesis that low-level HER2 expression and heterogeneity have significant clinical implications in PDAC. HER2 heterogeneity might indicate the best strategies of combination therapies to prevent the development of subdominant clones with resistance potential.

The anti-B7-H4 checkpoint synergizes trastuzumab treatment to promote phagocytosis and eradicate breast cancer

Trastuzumab is a humanized mAb used to treat HER2-overexpressing breast cancer; however its mechanisms remain to be fully elucidated. Previous studies suggest a role for immunity in mediating trastuzumab-specific antitumor effects. This study evaluated the role(s) of trastuzumab and other antibodies on macrophage activation and Ab-dependent cell-mediated phagocytosis (ADCP) of HER2+ breast cancer cells in vitro and in vivo. We employed orthotopic implantation of HER2+ murine breast cancer (BC) cells in immunocompetent mouse models, a human HER2+ BC xenograft in an immune humanized mouse model, and human PDXs involving adoptive transfer of autologous macrophages to simulate an endogenous mammary tumor-immune microenvironment. Our study demonstrated that trastuzumab greatly and consistently increased macrophage frequency and tumor-cell phagocytosis, and that concurrent knockdown of B7-H4 by a neutralizing antibody increased immune cell infiltration and promoted an antitumor phenotype. Furthermore, neoadjuvant trastuzumab therapy significantly upregulated B7-H4 in the cancer-infiltrating macrophages of HER2+ BC patients, which predicted poor trastuzumab response. We suggest that strategies to specifically enhance ADCP activity might be critical to overcoming resistance to HER2 mAb therapies by inhibiting tumor growth and potentially enhance antigen presentation. Furthermore, these results advance the understanding of macrophage plasticity by uncovering a dual role for ADCP in macrophages involving elimination of tumors by engulfing cancer cells while causing a concomitant undesired effect by upregulating immunosuppressive checkpoints.

Effects of HER Family-targeting Tyrosine Kinase Inhibitors on Antibody-dependent Cell-mediated Cytotoxicity in HER2-expressing Breast Cancer

PURPOSE

Antibody-dependent cell-mediated cytotoxicity (ADCC) is one mechanism of action of the monoclonal antibody (mAb) therapies trastuzumab and pertuzumab. Tyrosine kinase inhibitors (TKIs), like lapatinib, may have added therapeutic value in combination with mAbs through enhanced ADCC activity. Using clinical data, we examined the impact of lapatinib on HER2/EGFR expression levels and natural killer (NK) cell gene signatures. We investigated the ability of three TKIs (lapatinib, afatinib, and neratinib) to alter HER2/immune-related protein levels in preclinical models of HER2-positive (HER2⁺) and HER2-low breast cancer, and the subsequent effects on trastuzumab/pertuzumab-mediated ADCC.

EXPERIMENTAL DESIGN

Preclinical studies (proliferation assays, Western blotting, high content analysis, and flow cytometry) employed HER2⁺ (SKBR3 and HCC1954) and HER2-low (MCF-7, T47D, CAMA-1, and CAL-51) breast cancer cell lines. NCT00524303 provided reverse phase protein array-determined protein levels of HER2/pHER2/EGFR/pEGFR. RNA-based NK cell gene signatures (CIBERSORT/MCP-counter) post-neoadjuvant anti-HER2 therapy were assessed (NCT00769470/NCT01485926). ADCC assays utilized flow cytometry-based protocols.

RESULTS

Lapatinib significantly increased membrane HER2 levels, while afatinib and neratinib significantly decreased levels in all preclinical models. Single-agent lapatinib increased HER2 or EGFR levels in 10 of 11 (91%) tumor samples. NK cell signatures increased posttherapy (P = 0.03) and associated with trastuzumab response (P = 0.01). TKI treatment altered mAb-induced NK cell-mediated ADCC in vitro, but it did not consistently correlate with HER2 expression in HER2⁺ or HER2-low models. The ADCC response to trastuzumab and pertuzumab combined did not exceed either mAb alone.

CONCLUSIONS

TKIs differentially alter tumor cell phenotype which can impact NK cell-mediated response to coadministered antibody therapies. mAb-induced ADCC response is relevant when rationalizing combinations for clinical investigation.

A randomized phase II study to determine the efficacy and tolerability of two doses of eribulin plus lapatinib in trastuzumab-pretreated patients with HER-2-positive metastatic breast cancer (E-VITA)

The E-VITA study evaluated the efficacy and tolerability of two schedules of eribulin and lapatinib in patients with trastuzumab-pretreated HER-2-positive metastatic breast cancer. This multicenter, open-label phase II trial, randomly assigned patients with trastuzumab-pretreated HER-2-positive metastatic breast cancer to lapatinib 1000 mg daily with eribulin 1.23 mg/m (equivalent to 1.4 mg/m eribulin mesylate) days 1+8 every 21 days (split-dose arm) or eribulin 1.76 mg/m (equivalent to 2.0 mg/m eribulin mesylate) day 1 every 21 days (3-weekly arm). Time to progression and tolerability were defined as primary end points; no sample size calculation for formal comparison of efficacy data has been performed. Secondary end points included objective response rate, clinical benefit rate, and overall survival. Overall, 43 patients of a planned number of 80 patients were recruited. At a median follow-up of 28.7 months, the median time to progression was 8.1 months [95% confidence interval (CI): 4.8-9.4] in the split-dose arm and 6.5 months (95% CI: 4.6-13.4) in the 3-weekly arm. Objective response rate was 52.4% (95% CI: 31.0-73.7) in the split-dose arm and 45.0% (95% CI: 23.2-66.8) in the 3-weekly arm, and clinical benefit rate was 71.4% (95% CI: 52.1-90.8) and 75.0% (95% CI: 56.0-94.0), respectively. Overall survival was also similar in both arms. The most frequent grade 3-4 adverse events were neutropenia (58.5%) and leukopenia (39.0%). The combination of eribulin and lapatinib showed an acceptable safety profile with less toxicity observed in the eribulin 1.23 mg/m day 1+8 group. This might be an alternative regimen when other treatment options are exhausted. Therefore, further clinical studies are warranted.

Pharmacogenetics for severe adverse drug reactions induced by molecular-targeted therapy

Molecular-targeted drugs specifically interfere with molecules that are frequently overexpressed or mutated in cancer cells. As such, these drugs are generally considered to precisely attack cancer cells, thereby inducing fewer adverse drug reactions (ADRs). However, molecular-targeted drugs can still cause characteristic ADRs that, although rarely severe, can be life-threatening. Therefore, it is becoming increasingly important to be able to predict which patients are at risk of developing ADRs after treatment with molecular-targeted therapy. The emerging field of pharmacogenetics aims to better distinguish the genetic variants associated with drug toxicity and efficacy to improve the selection of therapeutic strategies for each genetic profile. Here, we provide an overview of the current reports on the relationship between genetic variants and molecular-targeted drug-induced severe ADRs in oncology.

Evaluation of the Anti-Tumor Activity of the Humanized Monoclonal Antibody NEO-201 in Preclinical Models of Ovarian Cancer

Purpose: Despite high initial response rates with cytoreductive surgery, conventional chemotherapy and the incorporation of biologic agents, ovarian cancer patients often relapse and die from their disease. New approaches are needed to improve patient outcomes. This study was designed to evaluate the antitumor activity of NEO-201 monoclonal antibody (mAb) in preclinical models of ovarian cancer where the NEO-201 target is highly expressed.

Experimental Design: Functional analysis of NEO-201 against tumor cell lines was performed by antibody-dependent cellular cytotoxicity (ADCC) assays. Binding of NEO-201 to tumor tissues and cell lines were determined by immunohistochemistry (IHC) and flow cytometry, respectively. Further characterization of the antigen recognized by NEO-201 was performed by mass spectrometry. Ovarian cancer models were used to evaluate the anti-tumor activity of NEO-201 in vivo. NEO-201 at a concentration of 250 g/mouse was injected intraperitoneally (IP) on days 1, 4, and 8. Human PBMCs were injected IP simultaneously as effector cells.

Results: Both IHC and flow cytometry revealed that NEO-201 binds prominently to the colon, pancreatic, and mucinous ovarian cancer tissues and cell lines. Immunoprecipitation of the antigen recognized by NEO-201 was performed in human ovarian, colon, and pancreatic cancer cell lines. From these screening, carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and CEACAM6 were identified as the most likely targets of NEO-201. Our results confirmed that NEO-201 binds different types of cancers; the binding is highly selective for the tumor cells without cross reactivity with the surrounding healthy tissue. Functional analysis revealed that NEO-201 mediates ADCC killing against human ovarian and colorectal carcinoma cell lines in vitro. In addition, NEO-201 inhibited tumor growth in the presence of activated human PBMCs in orthotopic mouse models of both primary and metastatic ovarian cancer. Importantly, NEO-201 prolonged survival of tumor-bearing mice.

Conclusions: These data suggested that NEO-201 has an antitumor activity against tumor cells expressing its antigen. Targeting an antigen expressed in tumors, but not in normal tissues, allows patient selection for optimal treatment. These findings strongly indicate that NEO-201 warrants clinical testing as both a novel therapeutic and diagnostic agent for treatment of ovarian carcinomas. A first in human clinical trial evaluating NEO-201 in adults with chemo-resistant solid tumors is ongoing at the NIH clinical Center.

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.

Cancer Stem Cells and Combination Therapies to Eradicate Them

Cancer stem cells (CSCs) show self-renewal ability and multipotential differentiation, like normal stem or progenitor cells, and which proliferate uncontrollably and can escape the effects of drugs and phagocytosis by immune cells. Traditional monotherapies, such as surgical resection, radiotherapy and chemotherapy, cannot eradicate CSCs, however, combination therapy may be more effective at eliminating CSCs. The present review summarizes the characteristics of CSCs and several promising combination therapies to eradicate them.

Roles of neutrophil/lymphocyte ratio in prognosis and in differentiation of potential beneficiaries in HER2-positive breast cancer with trastuzumab therapy

Background

The relationship of neutrophil/lymphocyte ratio (NLR) to prognosis of HER2-positive breast cancer (BC) is not well studied. We aimed to assess the prognostic role of NLR in HER2-positive BC patients treated with or without trastuzumab.

Methods

The clinical data of 843 HER2-positive BC patients from July 2013 to July 2018 were collected. The difference among variables was calculated by chi-square test. The associations between clinicopathological factors, NLR and disease-free survival (DFS) were analyzed by univariate and multivariate analyses.

Results

Patients were divided into three groups. In group 1 containing 255 patients without trastuzumab treatment, pretreatment NLR showed no predictive value. Patients with trastuzumab treatment were divided into two groups on equal, according to pretreatment NLR values, low NLR (group 2) and high NLR (group 3). Patients in group 2 showed significantly higher 3-year DFS rate than patients in group 1 and group 3 (95.3% vs. 91.6% vs. 90.5%, respectively, P = 0.011); patients in the group 1 and group 3 had a similar 3-year DFS outcome. Multivariate analysis showed high pretreatment NLR was significantly associated with shorter DFS (HR = 2.917, 95% CI = 1.055–8.062, P = 0.039) in HER2-positive BC patients treated with trastuzumab.

Conclusions

Among HER2-positive trastuzumab-treated BC patients, low pretreatment NLR value was associated with better DFS, and it might help to differentiate potential beneficiaries of trastuzumab treatment.

Engineering Targeting Materials for Therapeutic Cancer Vaccines

Therapeutic cancer vaccines constitute a valuable tool to educate the immune system to fight tumors and prevent cancer relapse. Nevertheless, the number of cancer vaccines in the clinic remains very limited to date, highlighting the need for further technology development. Recently, cancer vaccines have been improved by the use of materials, which can strongly enhance their intrinsic properties and biodistribution profile. Moreover, vaccine efficacy and safety can be substantially modulated through selection of the site at which they are delivered, which fosters the engineering of materials capable of targeting cancer vaccines to specific relevant sites, such as within the tumor or within lymphoid organs, to further optimize their immunotherapeutic effects. In this review, we aim to give the reader an overview of principles and current strategies to engineer therapeutic cancer vaccines, with a particular focus on the use of site-specific targeting materials. We will first recall the goal of therapeutic cancer vaccination and the type of immune responses sought upon vaccination, before detailing key components of cancer vaccines. We will then present how materials can be engineered to enhance the vaccine's pharmacokinetic and pharmacodynamic properties. Finally, we will discuss the rationale for site-specific targeting of cancer vaccines and provide examples of current targeting technologies.