Targeting HER2 heterogeneity in breast cancer

Efficacy and safety of pyrotinib-based regimens in HER2 positive metastatic breast cancer: A retrospective real-world data study

OBJECTIVE

Pyrotinib is a novel irreversible tyrosine kinase inhibitor that has shown efficacy for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). This study explored the efficacy and safety of pyrotinib in the treatment of HER2-positive MBC patients in the real world.

METHODS

From September 2018 to February 2022, 137 female patients with HER2-positive MBC treated in this center were enrolled in this study. The follow-up period ended on January 12, 2023. The primary endpoint of this study was progression-free survival (PFS). Overall survival (OS), objective response rate (ORR), disease control rate (DCR), clinical benefit rate (CBR), central nervous system (CNS)-PFS, CNS-ORR, CNS-CBR, CNS-DCR, and adverse event (AE) were the secondary endpoints.

RESULTS

The ORR, DCR and CBR were 41.98 % (55/131), 87.79 % (115/131) and 44.27 % (58/131) in this cohort, respectively. The median PFS for this cohort was 10.37 months [95 % confidence interval (CI): 9.205-11.535] and the median OS was 37.53 months (not reached). Univariate and multivariate analyses showed that trastuzumab sensitivity was an independent predictor of improved PFS [hazard ratio (HR): 0.579 (0.371-0.904, p=0.016)] and improved OS [0.410 (0.213-0.790, p=0.008)]. Patients treated with a pyrotinib-based regimen as second-line and third-or-post-line therapy had poorer PFS [second-line: 3.315 (1.832-6.000, p<0.001); third-or-post-line: 3.304 (1.749-6.243, p<0.001)] and OS [second-line: 4.631 (1.033-20.771, p=0.045); third-or-post-line: 5.738 (1.212-27.174, p=0.028)]. There were 38 brain metastases (BM) patients in this study, the CNS-mPFS [14.37 months (7.815-20.925) vs. 7.83 months (7.047-8.613), p=0.375] and mOS [not reached vs. 36.40 months (18.551-54.249), p=0.034] were better in brain radiotherapy (BRT) group than NBRT group. 18.98 % (26/137) of patients experienced grade 3 or higher diarrhea. No AE-related death was reported.

CONCLUSION

This study confirms the promising antitumor activity and acceptable safety of real-world pyrotinib-based regimens for the treatment of HER2-positive MBC patients, particularly those who are trastuzumab-sensitive and who are receiving pyrotinib-based regimens as advanced first-line therapy. It has also been demonstrated that these regimens combined with BRT, provide better intracranial responses and long-term survival benefits for these patients with BM.

What Proportion of BRCA-Associated Breast Cancer Is Human Epidermal Growth Factor 2-Low and Eligible for Additional Targeted Therapy?

INTRODUCTION

DESTINY B04 provided clinical meaning to a new classification of human epidermal growth factor 2 (HER2) expression in breast cancer: HER2-low. Patients with germline breast cancer type 1 gene pathogenic variants (gBRCA1) often develop triple negative breast cancer (TNBC), but the proportion who could be classified as HER2-low and qualify for an additional targeted therapy option is unknown. This study aims to characterize the proportion of gBRCA1 or germline breast cancer type 2 gene pathogenic variants patients for whom these novel targeted therapies may be an option.

METHODS

We performed a retrospective chart review of patients with gBRCA1/2 treated at our institution for invasive breast cancer from 2000 to 2021. Synchronous or metachronous contralateral breast cancers were recorded separately. HER2 status was determined by immunohistochemistry and fluorescence in situ hybridization. We excluded patients without complete HER2 data.

RESULTS

Among the 95 breast cancers identified in our cohort of 85 gBRCA1/2 patients, 41 (43%) were TNBC, 38 (40%) were hormone receptor positive (HR+)/HER2-negative, and 16 (17%) were HER2-positive based on standard conventions. We found that 82% of the HR+/HER2-cancers and 66% of TNBCs would be reclassified as HER2-low. After stratifying by BRCA gene status, 64% of cancers in patients with gBRCA1 and 58% of cancers in patients with germline breast cancer type 2 gene pathogenic variants were HER2-low.

CONCLUSIONS

A significant portion of gBRCA1/2 patients who were previously diagnosed with TNBC or HR+/HER2- breast cancer would now be classified as HER2-low and could be considered for the use of trastuzumab deruxtecan in the metastatic setting. Outcome differences from therapy changes in this cohort should now be assessed.

Dynamic changes in tumor profiling reveal intra- and inter-tumoral heterogeneity focused on an uncharacterized HER2 mutation: a case report of a young breast cancer patient

Despite multiple recent advances in systemic therapy for metastatic breast cancer, cases which display suboptimal response to guideline-driven treatment are frequently seen in the clinic. Effective options for such patients are limited, particularly in later line of therapy, and selection of optimal treatment options is essentially empirical and based largely on considerations of previous regimens received. Comprehensive cancer profiling includes detection of genetic alterations in tissue and circulating tumor DNA (ctDNA), immunohistochemistry (IHC) from re-biopsied metastatic disease, circulating tumor cells (CTCs), gene expression analysis and pharmacogenomics. The advent of this methodology and application to metastatic breast cancer, facilitates a more scientifically informed approach to identification of optimal systemic therapy approaches independent of the restrictions implied by clinical guidelines. Here we describe a case of metastatic breast cancer where consecutive comprehensive tumor profiling reveals ongoing tumor evolution, guiding the identification of novel effective therapeutic strategies.

Biomarkers for Antibody-Drug Conjugates in Solid Tumors

The clinical development and then the progressive entry in clinical practice of antibody-drug conjugates (ADC) have marked a transformative advancement in the overall cancer treatment. ADCs have been extensively tested for a large number of tumors, reporting heterogeneous clinical efficacy and safety results. In some diseases, the advent of ADCs has yielded significant changes in the prognostic trajectory, portending an improvement of the survival and/or quality of life. ADCs are targeted agents, capable of delivering highly cytotoxic payloads selectively to antigen-expressing cancer cells. As such, they have been intended as perfect "bullets" to enable the promise of precision medicine, toward high-efficacy and limited-toxicity treatment options. However, only some approved ADCs are intended for the use in biomarker-selected patient populations, restricting potentially the opportunity to be more precise. Yet, key characteristics of modern ADCs might allow the activity of ADCs in tumors with heterogeneous or low expression of cancer antigens, resulting in a clinical activity that could sublimate the classic paradigm of a drug-to-target perfect match. In our review, we portrayed the current landscape of approved ADCs, reporting data of activity as related to the expression of the cancer antigens, and elucidating possible determinants of the safety and efficacy, including when used in a therapeutic sequence.

HER2-low breast cancer and response to neoadjuvant chemotherapy: a population-based cohort study

About half of breast cancers (BC) without amplification of the human epidermal growth factor receptor 2 (HER2) have a low HER2 protein expression level (HER2-low). The clinical impact of HER2-low and the response to neoadjuvant chemotherapy (NAC) is unclear. This study aimed to assess the association between HER2-low BC and pathological response to NAC. Data from the Dutch Pathology Registry were collected for 11,988 BC patients treated with NAC between 2014 and 2022. HER2-low BC was defined as an immunohistochemical score of 1+ or 2+ and a negative molecular reflex test. We compared clinicopathological features of HER2-0 versus HER2-low BC and assessed the correlation between HER2 status and the pathological complete response (pCR) rate after NAC, including overall survival. Among hormone receptor (HR)-positive tumours, 67% (n=4,619) were HER2-low, compared to 47% (n=1,167) in the HR-negative group. Around 32% (n=207) of patients had a discordant HER2 status between the pre-NAC biopsy and the corresponding post-NAC resection, within which 87% (n=165) changed from HER2-0 to HER2-low or vice versa. The pCR rate was significantly lower in HER2-low BC compared to HER2-0 BC within the HR-positive group (4% versus 5%; p=0.022). However, the absolute difference was limited, so the clinical relevance is questionable. In HR-negative cases, the difference in pCR was not significant (32% versus 34%; p=0.266). No significant difference in overall survival was observed between HER2-low and HER2-0 tumours, regardless of hormone receptor status. The antibody-drug conjugate trastuzumab deruxtecan (T-DXd) has improved survival outcomes of patients with HER2-low metastatic BC. The finding that one-third of the patients in this study had a discordant HER2 status between the pre-NAC biopsy and the post-NAC resection specimen could impact clinical decision-making should T-DXd be used in early BC treatment.

LncRNAs in necroptosis: Deciphering their role in cancer pathogenesis and therapy

Necroptosis, a controlled type of cell death that is different from apoptosis, has become a key figure in the aetiology of cancer and offers a possible target for treatment. A growing number of biological activities, including necroptosis, have been linked to long noncoding RNAs (lncRNAs), a varied family of RNA molecules with limited capacity to code for proteins. The complex interactions between LncRNAs and important molecular effectors of necroptosis, including mixed lineage kinase domain-like pseudokinase (MLKL) and receptor-interacting protein kinase 3 (RIPK3), will be investigated. We will explore the many methods that LncRNAs use to affect necroptosis, including protein-protein interactions, transcriptional control, and post-transcriptional modification. Additionally, the deregulation of certain LncRNAs in different forms of cancer will be discussed, highlighting their dual function in influencing necroptotic processes as tumour suppressors and oncogenes. The goal of this study is to thoroughly examine the complex role that LncRNAs play in controlling necroptotic pathways and how that regulation affects the onset and spread of cancer. In the necroptosis for cancer treatment, this review will also provide insight into the possible therapeutic uses of targeting LncRNAs. Techniques utilising LncRNA-based medicines show promise in controlling necroptotic pathways to prevent cancer from spreading and improve the effectiveness of treatment.

Open questions, current challenges, and future perspectives in targeting human epidermal growth factor receptor 2-low breast cancer

Approximately 60% of traditionally defined human epidermal growth factor receptor 2 (HER2)-negative breast cancers express low levels of HER2 [HER2-low; defined as immunohistochemistry (IHC) 1+ or IHC 2+/in situ hybridization (ISH)-]. HER2-low breast cancers encompass a large percentage of both hormone receptor-positive (up to 85%) and triple-negative (up to 63%) breast cancers. The DESTINY-Breast04 trial established that HER2-low tumors are targetable, leading to the approval of trastuzumab deruxtecan (T-DXd) as the first HER2-directed therapy for the treatment of HER2-low breast cancer in the United States and Europe. This change in the clinical landscape results in a number of questions and challenges-including those related to HER2 assessment and patient identification-and highlights the need for careful assessment of HER2 expression to identify patients eligible for T-DXd. This review provides context for understanding how to identify patients with HER2-low breast cancer with respect to sample types, scoring and reporting HER2 status, and testing methods and assays. It also discusses management of important T-DXd-related adverse events. Available evidence supports the efficacy of T-DXd in patients with any history of IHC 1+ or IHC 2+/ISH- scores; however, future research may further refine the population who could benefit from T-DXd or other HER2-directed therapies and identify novel methods for patient identification. Because HER2 expression can change with disease progression or treatment, and variability exists in scoring and interpretation of HER2 status, careful re-evaluation in certain scenarios may help to identify more patients who may benefit from T-DXd.

HER2 Low Expression in Primary Male Breast Cancer

Purpose

The introduction of HER2-targeting antibody drug conjugates (ADCs) offers new treatment options for female breast cancer patients (FBC) expressing low levels of HER2 (HER2 low). No evidence was found that HER2 low describes a new FBC subtype. There is a lack of studies determining the impact of HER2 low in male breast cancer (MBC). In this study, we evaluate the prevalence of HER2 low in primary MBC and correlate the results with patient characteristics.

Patients and Methods

In this study, histological specimens were obtained from 120 male patients diagnosed and treated for primary invasive breast cancer from 1995 to 2022 at Breast Cancer Units in Bergisch Gladbach, Chemnitz, and Zwickau, Germany. HER2 immunostaining and in situ hybridization were performed by central pathology and evaluated based on the ASCO/CAP guidelines. The correlation of expression of HER2 low with tumor biological characteristics and patient outcomes was investigated.

Results

Out of all cases, four patients (3.3%) showed HER2 positivity (3+), 39 (32.5%) patients were classified as HER2 low, 7 (5.8%) were HER2 2+ (no amplification), 32 (26.7%) were HER2 1+, and 77 (64.2%) were classified as HER2 zero. Out of 77 HER2 zero cases, 47 tumors (61.0%) showed incomplete staining, with <10% of tumor cells classified as HER2 ultralow. No statistical correlation between HER2 low and tumor biological characteristics and patients' survival was found.

Conclusion

Our findings show a notable, albeit lower, prevalence of HER2 low expression in primary MBC. However, tumors expressing HER2 low do not show specific tumor biological features to define a new breast cancer subtype in MBC. Our results suggest that a significant number of MBC patients could benefit from ADCs, as shown in FBC. Further studies are required to better understand HER2 low breast cancer, both generally and in MBC.

HER2-low and tumor infiltrating lymphocytes in triple-negative breast cancer: Are they connected?

Most patients with triple-negative breast cancer (TNBC) are not candidates for targeted therapy, leaving chemotherapy as the primary treatment option. Recently, immunotherapy has demonstrated promising results in TNBC, due to its immunogenicity. In addition, a novel antibody-drug conjugate, namely, trastuzumab-deruxtecan, has shown effectiveness in TNBC patients with low-HER2 expression (HER2-low). These novel treatment options raise the question about the potential association between the density of stromal tumor-infiltrating lymphocytes (sTILs) and the level of HER2 expression. We aimed to evaluate the association between the level of HER2 expression (HER2-low versus HER2-0) and density of sTILs in TNBC patients, and how they impact the response to neoadjuvant chemotherapy (NAC). This was a retrospective multicenter study including all TNBC patients diagnosed between 2018 and 2022. Central pathology review included sTILs percentages and level of HER2 expression. Tumors were reclassified as either HER2-0 (HER2 IHC 0) or HER2-low (IHC 1 + or 2 + with negative reflex test). Various clinicopathologic characteristics, including sTILs density, and response to NAC were compared between HER2-0 and HER2-low cases. In total, 753 TNBC patients were included in this study, of which 292 patients received NAC. Interobserver agreement between the original pathology report and central review was moderate (77% had the same IHC status after reclassification in either HER2-0 or HER2-low; k = 0.45). HER2-low TNBC represented about one third (36%) of the tumors. No significant difference in sTILs density or complete pathologic response rate was found between HER2-0 and HER2-low cases (p = 0.476 and p = 0.339, respectively). The density of sTILs (≥ 10% sTILs vs. < 10%) was independently associated with achieving a pCR (p = 0.011). In conclusion, no significant association was found between HER2-low status and density of sTILs nor response to NAC. Nonetheless, sTILs could be an independent biomarker for predicting NAC response in TNBC patients.

Detection of HER2 expression using 99mTc-NM-02 nanobody in patients with breast cancer: a non-randomized, non-blinded clinical trial

BACKGROUND

99mTc radiolabeled nanobody NM-02 (99mTc-NM-02) is a novel single photon emission computed tomography (SPECT) probe with a high affinity and specificity for human epidermal growth factor receptor 2 (HER2). In this study, a clinical imaging trial was conducted to investigate the relationship between 99mTc-NM-02 uptake and HER2 expression in patients with breast cancer.

METHODS

Thirty patients with pathologically confirmed breast cancer were recruited and imaged with both 99mTc-NM-02 SPECT/computed tomography (CT) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT. According to the treatment conditions before recruitment, patients were divided into two groups, the newly diagnosed group (n = 24) and the treated group (n = 6). The maximal standard uptake value (SUVmax) of 18F-FDG and SUVmax and mean SUV (SUVmean) of 99mTc-NM-02 in the lesions were determined to analyze the relationship with HER2 expression.

RESULTS

No meaningful relationship was observed between 18F-FDG uptake and HER2 expression in 30 patients with breast cancer. 99mTc-NM-02 uptake was positively correlated with HER2 expression in the newly diagnosed group, but no correlation was observed in the treated group. 99mTc-NM-02 uptake in HER2-positive lesions was lower in those with effective HER2-targeted therapy compared with the newly diagnosed group. 99mTc-NM-02 SPECT/CT detected brain and bone metastases of breast cancer with a different imaging pattern from 18F-FDG PET/CT. 99mTc-NM-02 showed no non-specific uptake in inflamed tissues and revealed intra- and intertumoral HER2 heterogeneity by SPECT/CT imaging in 9 of the 30 patients with breast cancer.

CONCLUSIONS

99mTc-NM-02 SPECT/CT has the potential for visualizing whole-body HER2 overexpression in untreated patients, making it a promising method for HER2 assessment in patients with breast cancer.

TRIAL REGISTRATION

NCT04674722, Date of registration: December 19, 2020.

High HER2 Intratumoral Heterogeneity Is a Predictive Factor for Poor Prognosis in Early-Stage and Locally Advanced HER2-Positive Breast Cancer

PURPOSE

Breast cancer tumors frequently have intratumoral heterogeneity (ITH). Tumors with high ITH cause therapeutic resistance and have human epidermal growth factor receptor 2 (HER2) heterogeneity in response to HER2-targeted therapies. This study aimed to investigate whether high HER2 heterogeneity levels were clinically related to a poor prognosis for HER2-targeted adjuvant therapy resistance in primary breast cancers.

METHODS

This study included patients with primary breast cancer (n = 251) treated with adjuvant HER2-targeted therapies. HER2 heterogeneity was manifested by the shape of HER2 fluorescence in situ hybridization amplification (FISH) distributed histograms with the HER2 gene copy number within a tumor sample. Each tumor was classified into a biphasic grade graph (high heterogeneity [HH]) group or a monophasic grade graph (low heterogeneity [LH]) group based on heterogeneity. Both groups were evaluated for disease-free survival (DFS) and overall survival (OS) for a median of ten years of annual follow-up.

RESULTS

Of 251 patients with HER2-positive breast cancer, 46 (18.3%) and 205 (81.7%) were classified into the HH and LH groups, respectively. The HH group had more distant metastases and a poorer prognosis than the LH group (DFS: p < 0.001 (HH:63% vs. LH:91% at 10 years) and for the OS: p = 0.012 (HH:78% vs. LH:95% at 10 years).

CONCLUSIONS

High HER2 heterogeneity is a poor prognostic factor in patients with HER2-positive breast cancer. A novel approach to heterogeneity, which is manifested by the shape of HER2 FISH distributions, might be clinically useful in the prognosis prediction of patients after HER2 adjuvant therapy.

Targeting HER2 heterogeneity in breast and gastrointestinal cancers

About 20% of breast and gastric cancers and 3% of colorectal carcinomas overexpress the human epidermal growth factor receptor 2 (HER2) and are sensitive to HER2-directed agents. The expression of HER2 may differ within the same tumoral lesion (spatial intralesional heterogeneity), from different tumor locations (spatial interlesional heterogeneity), and throughout treatments (temporal heterogeneity). Spatial and temporal heterogeneity may impact on response and resistance to HER2-targeting agents and its prevalence and predictive role changes across HER2-overexpressing solid tumors. Therefore, the definition and the characterization of HER2 heterogeneity pose many challenges and its implementation as a reproducible predictive biomarker would help in guiding treatment modulation.

Phase II Trial Assessing the Repeatability and Tumor Uptake of [68Ga]Ga-HER2 Single-Domain Antibody PET/CT in Patients with Breast Carcinoma

Human epidermal growth factor receptor 2 (HER2) status is used for decision-making in breast carcinoma treatment. The status is obtained through immunohistochemistry or in situ hybridization. These two methods have the disadvantage of necessitating tissue sampling, which is prone to error due to tumor heterogeneity or interobserver variability. Whole-body imaging might be a solution to map HER2 expression throughout the body. Methods: Twenty patients with locally advanced or metastatic breast carcinoma (5 HER2-positive and 15 HER2-negative patients) were included in this phase II trial to assess the repeatability of uptake quantification and the extended safety of the [68Ga]Ga-NOTA-anti-HER2 single-domain antibody (sdAb). The tracer was injected, followed by a PET/CT scan at 90 min. Within 8 d, the procedure was repeated. Blood samples were taken for antidrug antibody (ADA) assessment and liquid biopsies. On available tissues, immunohistochemistry, in situ hybridization, and mass spectrometry were performed to determine the correlation of HER2 status with uptake values measured on PET. If relevant preexisting [18F]FDG PET/CT images were available (performed as standard of care), a comparison was made. Results: With a repeatability coefficient of 21.8%, this imaging technique was repeatable. No clear correlation between PET/CT uptake values and pathology could be established, as even patients with low levels of HER2 expression showed moderate to high uptake. Comparison with [18F]FDG PET/CT in 16 patients demonstrated that in 7 patients, [68Ga]Ga-NOTA-anti-HER2 shows interlesional heterogeneity within the same patient, and [18F]FDG uptake did not show the same heterogeneous uptake in all patients. In some patients, the extent of disease was clearer with the [68Ga]Ga-NOTA-anti-HER2-sdAb. Sixteen adverse events were reported but all without a clear relationship to the tracer. Three patients with preexisting ADAs did not show adverse reactions. No new ADAs developed. Conclusion: [68Ga]Ga-NOTA-anti-HER2-sdAb PET/CT imaging shows similar repeatability to [18F]FDG. It is safe for clinical use. There is tracer uptake in cancer lesions, even in patients previously determined to be HER2-low or -negative. The tracer shows potential in the assessment of interlesional heterogeneity of HER2 expression. In a subset of patients, [68Ga]Ga-NOTA-anti-HER2-sdAb uptake was seen in lesions with no or low [18F]FDG uptake. These findings support further clinical development of [68Ga]Ga-NOTA-anti-HER2-sdAb as a PET/CT tracer in breast cancer patients.

Edge-generated N-doped carbon-supported dual-metal active sites for enhancing electrochemical immunoassay

Development of high-precision human epidermal growth factor receptor 2 (HER2) assay is essential for the early diagnostic and prevention of breast cancer. In this work, an innovative Fe/Mn bimetallic nanozyme at the edge of N-doped carbon defects (FeMn-NCedge) with abundant active sites was prepared through the hydrothermal synthetic method. FeMn-NCedge nanozyme displayed excellent peroxidase-like activity relative to the H2O2-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) system for generation of the oxidized TMB (oxTMB). As a proof-of-concept application, we constructed an electrochemical immunoassay for the detection of HER2 based on the unique merits of FeMn-NCedge. Initially, a sandwiched immunoreaction was carried out in the microtiter plate coated with monoclonal anti-HER2 capture antibodies using glucose oxidase (GOx)-labeled anti-HER2 as detection antibody. The carried GOx could catalyze glucose to produce H2O2, thus resulting in the formation of oxTMB with the assistance of TMB and FeMn-NCedge nanozyme. The produced oxTMB could be determined on the electrode by the chronoamperometry at an applied potential of +10 mV. Experimental results revealed that the steady-state current increased with the increasing HER2 concentration in the sample, and gave a good linear relationship within the dynamic range of 0.01-10 ng/mL at a limit of detection of 5.4 pg/mL HER2. In addition, good reproducibility, high specificity and acceptable accuracy were acquired for the measurement of human serum samples. Importantly, this method can be extended for quantitative monitoring other disease-related proteins by changing the corresponding antibodies.

Clinicopathologic Features and Prognosis of Female Early Breast Cancer With HER2 Low Expression: A Propensity Score Matched Analysis

Background

Metastatic breast cancer (MBC) patients with low expression of human epidermal growth factor 2 (HER2) have been proven to benefit from HER2 targeted therapy. We aimed to determine how HER2-low status affected survival and metastatic risk as well as how it affected pathological complete response (pCR) in neoadjuvant chemotherapy (NAC) patients.

Methods

According to the results of immunohistochemistry (IHC) and in situ hybridization (ISH) testing, 321 female patients were sorted into HER2-low (IHC 1+/2+ with ISH negative) and HER2-zero (IHC 0) groups using propensity score matching (PSM). Overall survival (OS), disease-free survival (DFS), and distant disease-free survival (DDFS) were compared for both groups, while pCR was only analyzed for NAC patients.

Results

In total, 97 patients in each group after PSM were included. We discovered that pCR was not associated with HER2 expression status in 45 patients who underwent NAC. Five-year OS in the HER2-low group was significantly higher (98.99%) than in the HER2-zero group (95.87%, P = .044); however, this difference was not reflected in the 5-year DFS (90.61 vs 90.52%, P = .868) and 5-year DDFS (93.67 vs 91.53%, P = .757). Meanwhile, multivariate analysis revealed that HER2-low expression could indicate better OS (P = .047, hazard ratios [HRs] = 16.121, 95% confidence interval [CI] = 1.035-251.046), but it had no prognostic value for DFS or DDFS.

Conclusion

When compared with HER2-zero expression, HER2-low expression was not connected to pCR and could not modify metastasis risk in female patients with early-stage breast cancer (BC), but it may prolong patient survival.

Cbl induced ubiquitination of HER2 mediate immune escape from HER2-targeted CAR-T

Breast cancer (BC) with high HER2 expression has higher recurrence rate and worse prognosis, and its immunotherapy is promising. Based on the high expression of HER2, develop Chimeric Antigen Receptor T-cell (CAR-T) and PDL-1 immunotherapy, and study the molecular pathways of related immune cells and recurrence. HER2-CAR-T cells were constructed using retroviruses, and their specific recognition and immune effects on HER2+ BC cells were verified by in vivo and in vitro experiments. PDL-1 was used as adjuvant immunotherapy, knocking down PDL-1 in tumor cells or dendritic cells, or depleted macrophages to study immune pathways. The negative regulation of HER2 by cbl was determined by IP, ubiquitination experiments, and segmented plasmids, elucidating the molecular mechanism of HER2+ BC recurrence after immunotherapy. HER2-CAR-T specifically recognizes HER2-positive tumor cells and inhibits tumor growth in vivo and in vitro, and anti-PDL1 treatment enhances the therapeutic effect of HER2-CAR-T on tumors. HER2-CART therapy eradicated solid tumors after PDL1 knockdown in dendritic cells. Immunotherapy of relapsed tumors lost HER2 expression by upregulating cbl. HER2-CAR-T shows specific recognition of HER2+ cells and can mediate immune response therapy with the cooperation of PDL-1.

Survivin expression as a prognostic marker for breast cancer

OBJECTIVE

Due to the speed of development observed in breast cancer, several studies aimed at discovering new biomarkers have been carried out in order to arrive at an early diagnosis. As survivin plays a fundamental role in the evasion of apoptosis in tumor cells, the aim of this study was to verify the expression profile of the survivin gene in paraffin-embedded breast tumor samples and associate it with the clinical characteristics of the patients.

METHODS

This is a cross-sectional study, for which 100 tumor samples were obtained from cancer patients treated throughout the year 2019 at Instituto de Mama do Cariri (Juazeiro do Norte, in the state of Ceará). This study included women over 30 years old who had confirmed breast cancer through anatomopathological examination but excluded those with non-neoplastic breast comorbidities, other neoplasms, or chronic diseases. Survivin gene expression was assessed by quantitative polymerase chain reaction.

RESULTS

The expression of survivin is associated with the lack of expression of estrogen (p=0.027) and progesterone (p>0.0005) receptors. It means that survivin expression is higher in patients in which labeling was absent for estrogen receptor and progesterone receptor.

CONCLUSION

Our data reinforce that survivin expression is higher in estrogen receptor-patients, thus representing an additional prognostic tool.

Investigation of Tumor Heterogeneity Using Integrated Single-Cell RNA Sequence Analysis to Focus on Genes Related to Breast Cancer-, EMT-, CSC-, and Metastasis-Related Markers in Patients with HER2-Positive Breast Cancer

Human epidermal growth factor receptor 2 (HER2) protein, which is characterized by the amplification of ERBB2, is a molecular target for HER2-overexpressing breast cancer. Many targeted HER2 strategies have been well developed thus far. Furthermore, intratumoral heterogeneity in HER2 cases has been observed with immunohistochemical staining and has been considered one of the reasons for drug resistance. Therefore, we conducted an integrated analysis of the breast cancer single-cell gene expression data for HER2-positive breast cancer cases from both scRNA-seq data from public datasets and data from our cohort and compared them with those for luminal breast cancer datasets. In our results, heterogeneous distribution of the expression of breast cancer-related genes (ESR1, PGR, ERBB2, and MKI67) was observed. Various gene expression levels differed at the single-cell level between the ERBB2-high group and ERBB2-low group. Moreover, molecular functions and ERBB2 expression levels differed between estrogen receptor (ER)-positive and ER-negative HER2 cases. Additionally, the gene expression levels of typical breast cancer-, CSC-, EMT-, and metastasis-related markers were also different across each patient. These results suggest that diversity in gene expression could occur not only in the presence of ERBB2 expression and ER status but also in the molecular characteristics of each patient.

Increased Expression of miR-223-3p and miR-375-3p and Anti-Inflammatory Activity in HDL of Newly Diagnosed Women in Advanced Stages of Breast Cancer

The expression of inflammation-related miRs bound to high-density lipoproteins (HDLs), the anti-inflammatory activity of HDLs isolated from individuals with breast cancer, and controls were determined. Forty newly diagnosed women with breast cancer naïve of treatment and 10 control participants were included. Cholesterol-loaded bone-marrow-derived macrophages were incubated with HDL from both groups and challenged with lipopolysaccharide (LPS). Interleukin 6 (IL6) and tumor necrosis factor (TNF) in the medium were quantified. The miRs in HDLs were determined by RT-qPCR. Age, body mass index, menopausal status, plasma lipids, and HDL composition were similar between groups. The ability of HDL to inhibit IL6 and TNF production was higher in breast cancer compared to controls, especially in advanced stages of the disease. The miR-223-3p and 375-3p were higher in the HDLs of breast cancer independent of the histological type of the tumor and had a high discriminatory power between breast cancer and controls. The miR-375-3p was greater in the advanced stages of the disease and was inversely correlated with the secretion of inflammatory cytokines. Inflammation-related miRs and the anti-inflammatory role of HDLs may have a significant impact on breast cancer pathophysiology.

Low and Ultra-Low HER2 in Human Breast Cancer: An Effort to Define New Neoplastic Subtypes

HER2-low and ultra-low breast cancer (BC) have been recently proposed as new subcategories of HER2 BC, supporting a re-consideration of immunohistochemical negative scores of 0, 1+ and the 2+/in situ hybridization (ISH) negative phenotype. In the present review, we outline the criteria needed to exactly distinguish HER2-low and ultra-low BC. Recent clinical trials have demonstrated significant clinical benefits of novel HER2 directing antibody-drug conjugates (ADCs) in treating these groups of tumors. In particular, trastuzumab-deruxtecan (T-Dxd), a HER2-directing ADC, has been recently approved by the US Food and Drug Administration as the first targeted therapy to treat HER2-low BC. Furthermore, ongoing trials, such as the DESTINY-Breast06 trial, are currently evaluating ADCs in patients with HER2-ultra low BC. Finally, we hope that new guidelines may help to codify HER2-low and ultra-low BC, increasing our knowledge of tumor biology and improving a targetable new therapeutical treatment.

Omics Technologies Improving Breast Cancer Research and Diagnostics

Breast cancer (BC) has yielded approximately 2.26 million new cases and has caused nearly 685,000 deaths worldwide in the last two years, making it the most common diagnosed cancer type in the world. BC is an intricate ecosystem formed by both the tumor microenvironment and malignant cells, and its heterogeneity impacts the response to treatment. Biomedical research has entered the era of massive omics data thanks to the high-throughput sequencing revolution, quick progress and widespread adoption. These technologies-liquid biopsy, transcriptomics, epigenomics, proteomics, metabolomics, pharmaco-omics and artificial intelligence imaging-could help researchers and clinicians to better understand the formation and evolution of BC. This review focuses on the findings of recent multi-omics-based research that has been applied to BC research, with an introduction to every omics technique and their applications for the different BC phenotypes, biomarkers, target therapies, diagnosis, treatment and prognosis, to provide a comprehensive overview of the possibilities of BC research.

The emergence of targeted therapy for HER2-low triple-negative breast cancer: a review of fam-trastuzumab deruxtecan

INTRODUCTION

Metastatic triple-negative breast cancer (TNBC) is an aggressive sub-type of breast cancer. Despite recent advances, metastatic TNBC remains difficult to treat with limited targeted treatment options. Fam-trastuzumab deruxtecan (T-DXd), is a novel antibody-drug conjugate (ADC) targeting human epidermal growth factor receptor 2 (HER2) and is composed of a unique linker bound to the topoisomerase I inhibitor DXd. T-DXd has significant anti-tumor activity in patients with HER2-low TNBC.

AREAS COVERED

This review reports on the mechanism, pre-clinical/clinical studies, efficacy, and tolerability of T-DXd. A literature search was conducted via PubMed using keywords such as 'fam-trastuzumab deruxtecan,' 'Enhertu,' and 'HER2-low cancers.'

EXPERT OPINION

The Phase III Destiny-Breast04 Trial showed benefit in progression-free and overall survival in patients with HER2-low metastatic breast cancers treated with T-DXd compared to treatment of physician's choice chemotherapy. T-DXd is the first pharmaceutical to effectively target a HER2-low population with clinically meaningful efficacy in patients with HER2-low TNBC. Compared to chemotherapy, T-DXd has a similar safety profile, with the additional need for close monitoring for interstitial lung disease. Given the clinical activity of T-DXd in TNBC, it is likely there will be continued efforts to refine HER2-low diagnostics and to develop additional ADCs with other protein targets.

Increased plasma lipids in triple-negative breast cancer and impairment in HDL functionality in advanced stages of tumors

The association between plasma lipids and breast cancer (BC) has been extensively explored although results are still conflicting especially regarding the relationship with high-density lipoprotein cholesterol (HDLc) levels. HDL mediates cholesterol and oxysterol removal from cells limiting sterols necessary for tumor growth, inflammation, and metastasis and this may not be reflected by measuring HDLc. We addressed recently diagnosed, treatment-naïve BC women (n = 163), classified according to molecular types of tumors and clinical stages of the disease, in comparison to control women (CTR; n = 150) regarding plasma lipids and lipoproteins, HDL functionality and composition in lipids, oxysterols, and apo A-I. HDL was isolated by plasma discontinuous density gradient ultracentrifugation. Lipids (total cholesterol, TC; triglycerides, TG; and phospholipids, PL) were determined by enzymatic assays, apo A-I by immunoturbidimetry, and oxysterols (27, 25, and 24-hydroxycholesterol), by gas chromatography coupled with mass spectrometry. HDL-mediated cell cholesterol removal was determined in macrophages previously overloaded with cholesterol and ¹⁴C-cholesterol. Lipid profile was similar between CTR and BC groups after adjustment per age. In the BC group, lower concentrations of TC (84%), TG (93%), PL (89%), and 27-hydroxicholesterol (61%) were observed in HDL, although the lipoprotein ability in removing cell cholesterol was similar to HDL from CRT. Triple-negative (TN) BC cases presented higher levels of TC, TG, apoB, and non-HDLc when compared to other molecular types. Impaired HDL functionality was observed in more advanced BC cases (stages III and IV), as cholesterol efflux was around 28% lower as compared to stages I and II. The altered lipid profile in TN cases may contribute to channeling lipids to tumor development in a hystotype with a more aggressive clinical history. Moreover, findings reinforce the dissociation between plasma levels of HDLc and HDL functionality in determining BC outcomes.

Development, efficacy and side effects of antibody‑drug conjugates for cancer therapy (Review)

Antibody-drug conjugates (ADCs) are anticancer drugs that combine cytotoxic small-molecule drugs (payloads) with monoclonal antibodies through a chemical linker and that transfer toxic payloads to tumor cells expressing target antigens. All ADCs are based on human IgG. In 2009, the Food and Drug Administration (FDA) approved gemtuzumab ozogamicin as the initial first-generation ADC. Since then, at least 100 ADC-related projects have been initiated, and 14 ADCs are currently being tested in clinical trials. The limited success of gemtuzumab ozogamicin has led to the development of optimization strategies for the next generation of drugs. Subsequently, experts have improved the first-generation ADCs and have developed second-generation ADCs such as ado-trastuzumab emtansine. Second-generation ADCs have higher specific antigen levels, more stable linkers and longer half-lives and show great potential to transform cancer treatment models. Since the first two generations of ADCs have served as a good foundation, the development of ADCs is accelerating, and third-generation ADCs, represented by trastuzumab deruxtecan, are ready for wide application. Third-generation ADCs are characterized by strong pharmacokinetics and high pharmaceutical activity, and their drug-to-antibody ratio mainly ranges from 2 to 4. In the past decade, the research prospects of ADCs have broadened, and an increasing number of specific antigen targets and mechanisms of cytotoxic drug release have been discovered and studied. To date, seven ADCs have been approved by the FDA for lymphoma, and three have been approved to treat breast cancer. The present review explores the function and development of ADCs and their clinical use in cancer treatment.

Detailed curriculum vitae of HER2-targeted therapy

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

Endocrine Disruptors in Food, Estrobolome and Breast Cancer

The microbiota is now recognized as one of the major players in human health and diseases, including cancer. Regarding breast cancer (BC), a clear link between microbiota and oncogenesis still needs to be confirmed. Yet, part of the bacterial gene mass inside the gut, constituting the so called "estrobolome", influences sexual hormonal balance and, since the increased exposure to estrogens is associated with an increased risk, may impact on the onset, progression, and treatment of hormonal dependent cancers (which account for more than 70% of all BCs). The hormonal dependent BCs are also affected by environmental and dietary endocrine disruptors and phytoestrogens which interact with microbiota in a bidirectional way: on the one side disruptors can alter the composition and functions of the estrobolome, ad on the other the gut microbiota influences the metabolism of endocrine active food components. This review highlights the current evidence about the complex interplay between endocrine disruptors, phytoestrogens, microbiome, and BC, within the frames of a new "oncobiotic" perspective.

Comparison of clinicopathological characteristics and response to neoadjuvant systemic therapy in patients with HER2-low-positive and HER2-zero breast cancer

Previous studies have observed that human epidermal growth factor receptor 2 (HER2)-low-positive patients and HER2-zero patients have different prognoses. This study was conducted to investigate whether there are differences in clinicopathological characteristics and the response to neoadjuvant systemic therapy (NST) defined as systemic treatment prior to surgery between HER2-low-positive patients and HER2-zero patients. We retrospectively analyzed the data of patients with HER2-negative breast cancer who received NST at the First Affiliated Hospital of Nanjing Medical University from 2014 to 2021. There were 238 patients with HER2-low-positive status and 198 patients with HER2-zero status. The proportion of hormone receptor (HR)-positive patients in the HER2-low-positive group was significantly higher than that in the HER2-zero group (82.8% vs 52.0%, p < 0.001). The HER2-low-positive group had more patients with low Ki67 expression (23.9% vs 16.2%, p = 0.045), higher mastectomy rate (94.5% vs 88.9%, p = 0.031), and larger pathological tumor size (21.6 vs 17.8 mm, p = 0.028) than the HER2-zero group. However, no significant differences were found in pathologic complete response (pCR) rates between the two groups. We draw a conclusion that patients with HER2-low status and HER2-zero status were not found to have different pCR rates after NST, irrespective of HR status. However, differences were observed in some clinicopathological characteristics between the two groups.

Resistance to antibody-drug conjugates in breast cancer: mechanisms and solutions

Antibody-drug conjugates (ADCs) are a rapidly developing therapeutic approach in cancer treatment that has shown remarkable activity in breast cancer. Currently, there are two ADCs approved for the treatment of human epidermal growth factor receptor 2-positive breast cancer, one for triple-negative breast cancer, and multiple investigational ADCs in clinical trials. However, drug resistance has been noticed in clinical use, especially in trastuzumab emtansine. Here, the mechanisms of ADC resistance are summarized into four categories: antibody-mediated resistance, impaired drug trafficking, disrupted lysosomal function, and payload-related resistance. To overcome or prevent resistance to ADCs, innovative development strategies and combination therapy options are being investigated. Analyzing predictive biomarkers for optimal therapy selection may also help to prevent drug resistance.

The HER2-low revolution in breast oncology: steps forward and emerging challenges

Approximately half of breast cancers (BCs), historically categorized as human epidermal growth factor receptor 2 (HER2)-negative, have low expression of HER2 defined as an immunohistochemical (IHC) score of 1+ or 2+ with negative in situ hybridization. Retrospective evidence suggest that HER2-low BC does not represent a distinct subtype from a biological and prognostic perspective. Nonetheless, it currently constitutes an essential biomarker to guide treatment selection and its introduction has led to reconsidering the binary classification of HER2 status according to which only patients with HER2-positive BC were thought to derive benefit from anti-HER2 therapies. Trastuzumab deruxtecan has recently been approved by the U.S. Food and Drug Administration for the treatment of patients with HER2-low metastatic BC based on the results of the DESTINY-Breast04 phase III trial, and other antibody-drug conjugates (ADCs) targeting HER2 are showing promising results. Treatment paradigms for both triple-negative and hormone receptor-positive BCs exhibiting HER2-low expression are thus rapidly evolving. Given its therapeutic implications, it is essential to accurately recognize the level of HER2 expression, and the development of more sensitive and reliable methods for HER2 testing and scoring is warranted, especially since the minimum threshold of HER2 expression required for T-DXd efficacy is currently under investigation. Given the signs of activity of T-DXd even in patients with HER2-0 (IHC 0) disease, an evolution in the way we define HER2-low is anticipated. Considering the expansion of the therapeutic armamentarium for BC patients, with several ADCs approaching the clinic, research efforts are needed to clarify whether the expression level of targets can enrich for responders to a given ADC as well as to understand mechanisms of resistance with the goal of optimizing the sequencing of ADCs.

Photoelectrochemical immunosensor for HER2 detection based on BiVO4-Bi2S3 heterojunction as photoactive material and CdS as signal probe

A sandwiched photoelectrochemical (PEC) sensor was developed for sensitive detection of human epidermal growth factor receptor 2 (HER2) based on BiVO₄-Bi₂S₃ heterojunction as the photoelectric material accompanied with magnetic nanoparticles for enrichment of HER2 and CdS for signal amplification. The in situ generation of Bi₂S₃ on the surface of BiVO₄ forming a BiVO₄-Bi₂S₃ heterojunction is more conducive to the transit of electron-hole pairs. Antibody-modified MNs are utilized to capture and separate HER2 from samples. After forming a sandwich immune structure, under illumination, the photocurrent shows an increasing trend with the increment of HER2 concentration. The PEC immunosensor displays a good linear concentration range between 1.00 and 1.00 × 10³ pg·mL^-1 and a low limit of detection down to 0.680 pg·mL^-1 (S/N = 3) for HER2 under a bias voltage of 0.1 V (vs. Ag/AgCl electrode). Furthermore, the sensor was successfully applied to detect HER2 in serum samples with recoveries that ranged between 96.1 and 114% with RSDs between 1.3 and 5.9%.

Antibody-Drug Conjugates: A New Therapeutic Approach for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subset associated with a worse prognosis and poor response to conventional chemotherapy. Despite recent advances in drug discovery, its management is still a challenge for clinicians, illuminating the unmet need to develop novel treatment approaches. Antibody-drug conjugates (ADC) are innovative oncology drugs that combine the specificity of monoclonal antibodies and the high efficacy of anticancer payloads, to deliver cytotoxic drugs selectively to cancer cells. Various ADCs were investigated for TNBC and have provided a promise for this aggressive women's cancer including the FDA-approved sacituzumab govitecan. In this chapter, we reviewed different ADCs studied for TNBC including their mechanisms of action, efficacy, and tolerability. Moreover, we have also discussed their therapeutic potential based on combinatorial approaches with other targeted therapies in early and metastatic TNBC.

The association between HER2-low expression and prognosis of breast cancer: a systematic review and meta-analysis

Background

The use of antibody-drug conjugates for the treatment of advanced-stage human epidermal growth factor receptor 2 (HER2)-low expression in breast cancer (BC) has shown prominent curative effects, which has led to increased academic interest. However, the role of HER2-low expression in the prognosis of BC remains controversial.

Methods

We conducted a systematic search of the PubMed, Embase, and Cochrane library databases and several oncology conferences until 20 September 2022. We used fixed- and random-effects models to calculate odds ratio (OR) or hazard ratio (HR) with 95% confidence interval (CI) for overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), and pathological complete response (pCR) rates.

Results

Overall, 26 studies encompassing 677,248 patients were included in the meta-analysis. Patients with HER2-low BC showed significantly better OS than those with HER2-zero BC in the overall population (HR = 0.90; 95% CI: 0.85-0.97) and hormone receptor-positive population (HR = 0.98; 95% CI: 0.96-0.99), whereas no significant difference was observed in the OS of the hormone receptor-negative population (p > 0.05). In addition, there was no significant difference in the DFS of the overall and hormone receptor-negative population (p > 0.05), but better DFS than those with HER2-zero BC in the hormone receptor-negative population (HR = 0.96; 95% CI: 0.94-0.99). There was also no significant difference in the PFS of the overall population, hormone receptor-positive, and hormone receptor-negative population (p > 0.05). Patients with HER2-low BC had a lower pCR rate after neoadjuvant treatment than those with HER2-zero BC.

Conclusions

Compared to patients with HER2-zero BC, those with HER2-low BC had better OS in the overall population and hormone receptor-positive population, DFS in hormone receptor-positive population and lower pCR in the overall population. The biological differences between HER2-low and HER2-zero BCs, particularly in hormone receptor-positive patients, and the relationship between HER2-low expression status and prognosis need to be explored further.

HER2-Low Status Is Not Accurate in Breast Cancer Core Needle Biopsy Samples: An Analysis of 5610 Consecutive Patients

Background: HER2-Low status is found in approximately half of breast cancer patients and shows potential benefits from novel antibody−drug conjugates (ADCs). Data on the accuracy of HER2-Low status between core needle biopsy (CNB) and surgical excision specimen (SES) samples are lacking. We aimed to investigate the accuracy of HER2-Low status diagnosis between CNB and SES samples. Methods: Consecutive early-stage breast cancer patients who underwent surgery from January 2009 to March 2022 with paired CNB and SES samples were retrospectively reviewed. HER2-Low was defined as IHC 1+ or IHC2+ and FISH-negative. Concordance rates were analyzed by the Kappa test. Further clinicopathological characteristics were compared among different HER2 status and their changes. Results: A total of 5610 patients were included, of whom 3209 (57.2%) and 3320 (59.2%) had HER2-Low status in CNB and SES samples, respectively. The concordance rate of HER2 status in the whole population was 82.37% (Kappa = 0.684, p < 0.001), and was 76.87% in the HER2-Negative patients (Kappa = 0.372, p < 0.001). Among 1066 HER2-0 cases by CNB, 530 patients were classified as HER2-Low tumors. On the contrary, in 3209 patients with HER2-Low tumor by CNB, 387 were scored as HER2-0 on the SES samples. ER-negative or Ki67 high expression tumor by CNB had a high concordance rate of HER2-Low status. Conclusions: A relatively low concordance rate was found when evaluating HER2-Low status between CNB and SES samples in HER2-Negative breast cancer patients, indicating the necessity of retesting HER2 low status at surgery, which may guide further therapy in the era of anti-HER2 ADCs.

Emerging Role of ERBB2 in Targeted Therapy for Metastatic Colorectal Cancer: Signaling Pathways to Therapeutic Strategies

Simple Summary

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second most common cause of cancer-related mortality worldwide. Currently available targeted therapies for metastatic CRC mainly target vascular endothelial growth factor and epidermal growth factor receptor in RAS wild-type tumors. Although Erb-B2 receptor tyrosine kinase 2 (ERBB2/human epidermal growth factor receptor 2) plays a significant therapeutic role in breast and gastric cancers, there are no licensed ERBB2-targeted therapies for metastatic CRC. This review aims to outline the molecular biology of ERBB2-positive metastatic CRC and potential targeted therapeutic strategies.

Abstract

Despite recent improvements in the comprehensive therapy of malignancy, metastatic colorectal cancer (mCRC) continues to have a poor prognosis. Notably, 5% of mCRC cases harbor Erb-B2 receptor tyrosine kinase 2 (ERBB2) alterations. ERBB2, commonly referred to as human epidermal growth factor receptor 2, is a member of the human epidermal growth factor receptor family of protein tyrosine kinases. In addition to being a recognized therapeutic target in the treatment of gastric and breast malignancies, it is considered crucial in the management of CRC. In this review, we describe the molecular biology of ERBB2 from the perspective of biomarkers for mCRC-targeted therapy, including receptor structures, signaling pathways, gene alterations, and their detection methods. We also discuss the relationship between ERBB2 aberrations and the underlying mechanisms of resistance to anti-EGFR therapy and immunotherapy tolerance in these patients with a focus on novel targeted therapeutics and ongoing clinical trials. This may aid the development of a new standard of care in patients with ERBB2-positive mCRC.

An Overview of Clinical Development of Agents for Metastatic or Advanced Breast Cancer Without ERBB2 Amplification (HER2-Low)

Importance

Erb-b2 receptor tyrosine kinase 2 (ERBB2; formerly HER2 [human epidermal growth factor receptor 2]) is an important prognostic and predictive factor in breast cancer. Anti-ERBB2 therapies have improved outcomes in ERBB2-positive breast cancer. However, based on current definitions, tumors with low ERBB2 expression are included in the ERBB2-negative subtype, and therefore, are ineligible for anti-ERBB2 therapies; patients with ERBB2-low (immunohistochemistry [IHC] 1 positive [+] or IHC 2+/in situ hybridization [ISH] negative [-]) tumors account for up to approximately 50% of breast cancer cases. Although the prognostic role of ERBB2-low needs to be defined, ERBB2 offers a potential therapeutic target in these patients.

Observations

Most breast cancer tumors have some ERBB2 expression, with ERBB2-low being more common in hormone receptor-positive than in hormone receptor-negative breast cancer. Although an early clinical study failed to demonstrate benefit of adjuvant trastuzumab for ERBB2-low disease, several novel anti-ERBB2 therapies have shown efficacy in ERBB2-low breast cancer, including the antibody-drug conjugate trastuzumab deruxtecan in a phase 3 trial, and trastuzumab duocarmazine and the bispecific antibody zenocutuzumab in early-phase studies. Although reports are conflicting, some differences in biology and patient outcomes have been found between ERBB2-low and ERBB2 IHC-0 breast cancer. Currently, no established guidelines exist for scoring ERBB2-low expression in breast cancer because the focus has been on binary classification as ERBB2-positive or ERBB2-negative. Additional interpretive cutoffs may be needed to select patients for treatment with effective agents in ERBB2-low breast cancer, along with standardized laboratory quality assurance programs to ensure consistent patient identification for eligibility for ERBB2-low targeting agents.

Conclusions and Relevance

This review suggests that ERBB2-low may be a distinct, clinically relevant breast cancer entity warranting reassessment of traditional diagnostic and therapeutic paradigms. Ongoing clinical trials and further investigations may provide optimized strategies for diagnosing and treating ERBB2-low breast cancer, including reproducible, consistent definitions to identify patients in this diagnostic category and demonstration of benefits of emerging therapies.

Improving HER2 testing reproducibility in HER2-low breast cancer

HER2 is a pillar biomarker in breast cancer, and it is assessed by immunohistochemistry (IHC) using a three-tier scoring system and reflex in situ hybridization (ISH) for IHC score 2+. Novel HER2-directed antibody-drug conjugates have demonstrated significant antitumor activity in breast cancers with low levels of HER2 expression, i.e. IHC score 1+ or ISH-negative IHC score 2+. Both primary and acquired resistance to anti-HER2 therapies remains a challenge in the treatment of breast cancers according to the HER2 positivity continuum. Thus, the ability to precisely discriminate among HER2-zero, HER2-low, and HER2-positive breast cancers is no longer a mere academic exercise. HER2 testing criteria, guidelines, and quality controls are re-gaining momentum for this new clinical need. Therefore, all preanalytical and analytical variables that might trouble the sensitivity and reproducibility of this test should be carefully considered to address all possible issues and open all possible therapeutic opportunities for breast cancer patients.

Lentiviral vector–based xenograft tumors as candidate reference materials for detection of HER2-low breast cancer

The human epidermal growth factor receptor 2 (HER2) is an important biomarker that plays a pivotal role in therapeutic decision-making for patients with breast cancer (BC). Patients with HER2-low BC can benefit from new HER2 targeted therapy. For ensuring the accurate and reproducible detection of HER2-low cancer, reliable reference materials are required for monitoring the sensitivity and specificity of detection assays. Herein, a lentiviral vector was used to transduce the HER2 gene into MDA-MB-231 cells that exhibited low HER2 density, and the cells were characterized by droplet digital PCR to accurately determine the copy number variation. Then, the formalin-fixed paraffin-embedded (FFPE) samples from xenografts were prepared and evaluated for suitability as candidate reference materials by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The FFPE reference materials were selected on the basis of IHC score of 2+ and negative FISH result to meet the requirement for HER2-low BC detection. Furthermore, the FFPE reference materials exhibited typical histological structures that resembled the clinical BC specimens. These novel FFPE reference materials displayed the high stability and homogeneity, and they were produced in high quantity. In summary, we generated high-quality reference materials for internal quality control and proficiency testing in HER2-low detection.

The development of peptide-drug conjugates (PDCs) strategies for paclitaxel

INTRODUCTION

Paclitaxel is a powerful and effective anti-tumor drug with wide clinical application. However, there are still some limitations, including poor water solubility, low specificity, and susceptibility to drug resistance. The peptide-drug conjugates (PDCs) represent a rising class of therapeutic drugs, which combines small-molecule chemotherapeutic drugs with highly flexible peptides through a cleavable or non-cleavable linker. When this strategy is applied, the therapeutic effects of paclitaxel can be improved.

AREAS COVERED

In this review, we discuss the application of the PDCs strategy in paclitaxel, including two parts: the tumor targeting peptide-paclitaxel conjugates and the cell penetrating peptide-paclitaxel conjugates.

EXPERT OPINION

Combining drugs with multifunctional peptides covalently is an effective strategy for delivering paclitaxel to tumors. Depending on different functional peptides, conjugates can increase the water solubility of paclitaxel, tumor permeability of paclitaxel, the accumulation of paclitaxel in tumor tissues, and enhance the antitumor effect of paclitaxel. In addition, due to the change of cell entry mechanism, partial conjugates can restore the therapeutic activity of paclitaxel against resistant tumors. Notably, in order to better translate into the clinical field in the future, more research should be conducted to ensure the safety and effectiveness of peptide-paclitaxel conjugates.

Non-conventional and Investigational PET Radiotracers for Breast Cancer: A Systematic Review

Breast cancer is one of the most common malignancies in women, with high morbidity and mortality rates. In breast cancer, the use of novel radiopharmaceuticals in nuclear medicine can improve the accuracy of diagnosis and staging, refine surveillance strategies and accuracy in choosing personalized treatment approaches, including radioligand therapy. Nuclear medicine thus shows great promise for improving the quality of life of breast cancer patients by allowing non-invasive assessment of the diverse and complex biological processes underlying the development of breast cancer and its evolution under therapy. This review aims to describe molecular probes currently in clinical use as well as those under investigation holding great promise for personalized medicine and precision oncology in breast cancer.

HER2 Low, Ultra-low, and Novel Complementary Biomarkers: Expanding the Spectrum of HER2 Positivity in Breast Cancer

HER2 status in breast cancer is assessed to select patients eligible for targeted therapy with anti-HER2 therapies. According to the American Society of Clinical Oncology (ASCO) and College of American Pathologists (CAP), the HER2 test positivity is defined by protein overexpression (score 3+) at immunohistochemistry (IHC) and/or gene amplification at in situ hybridization (ISH). The introduction of novel anti-HER2 compounds, however, is changing this paradigm because some breast cancers with lower levels of protein expression (i.e. score 1+/2+ with no gene amplification) benefited from HER2 antibody-drug conjugates (ADC). Recently, a potential for HER2 targeting in HER2 "ultra-low" (i.e. score 0 with incomplete and faint staining in ≤10% of tumor cells) and MutL-deficient estrogen receptor (estrogen receptor)-positive/HER2-negative breast cancers has been highlighted. All these novel findings are transforming the traditional dichotomy of HER2 status and have dramatically raised the expectations in this field. Still, a more aware HER2 status assessment coupled with the comprehensive characterization of the clinical and molecular features of these tumors is required. Here, we seek to provide an overview of the current state of HER2 targeting in breast cancers beyond the canonical HER2 positivity and to discuss the practical implications for pathologists and oncologists.

A designed cyclic peptide based on Trastuzumab used to construct peptide-drug conjugates for its HER2-targeting ability

Human epidermal growth factor receptor 2 (HER2) has been recognized as an important therapeutic target for its overexpression in many cancers. Trastuzumab is a monoclonal antibody targeting HER2, which has been approved by FDA to treat HER2-positive cancer. In this research, cyclic peptide Cyclo-GCGPep1 was designed based on the binding mode between antibody and HER2 protein in silico, which has been confirmed possessing good affinity with HER2. Cyclo-GCGPep1 was also used to construct peptide-drug conjugates with Camptothecin. Biological evaluations demonstrated that Conjugate 1 has a good antiproliferative activity on SK-BR-3 and NCI-N87 cells. Conjugate 1 retained the pro-apoptotic and Topo I inhibitory ability of Camptothecin. Meanwhile, it has good targeting ability towards HER2-positive cells with the help of Cyclo-GCGPep1. It also has better permeability in the tumor spheroid model than Camptothecin. In summary, the design of cyclic peptide derived from antibody is of significance for the discovery of targeting peptides and Conjugate 1 is expected as a good therapeutic agent for HER2-positive cancers.