Understanding the biology of HER3 receptor as a therapeutic target in human cancer

Mechanisms of acquired resistance to HER2-Positive breast cancer therapies induced by HER3: A comprehensive review

Receptor tyrosine kinases (RTKs) are cell surface receptors with kinase activity that play a crucial role in diverse cellular processes. Among the RTK family members, Human epidermal growth factor receptor 2 (HER2) and HER3 are particularly relevant to breast cancer. The review delves into the complexities of receptor tyrosine kinase interactions, resistance mechanisms, and the potential of anti-HER3 drugs, offering valuable insights into the clinical implications and future directions in this field of study. It assesses the potential of anti-HER3 drugs, such as pertuzumab, in overcoming resistance observed in HER2-positive breast cancer therapies. The review also explores the resistance mechanisms associated with various drugs, including trastuzumab, lapatinib, and PI3K inhibitors, providing insights into the intricate molecular processes underlying resistance development. The review concludes by emphasizing the necessity for further clinical trials to assess the efficacy of HER3 inhibitors and the potential of developing safe and effective anti-HER3 treatments to improve treatment outcomes for patients with HER2-positive breast cancer.

A prospective study of HER3 expression pre and post neoadjuvant therapy of different breast cancer subtypes: implications for HER3 imaging therapy guidance

PURPOSE

HER3, a member of the EGFR receptor family, plays a central role in driving oncogenic cell proliferation in breast cancer. Novel HER3 therapeutics are showing promising results while recently developed HER3 PET imaging modalities aid in predicting and assessing early treatment response. However, baseline HER3 expression, as well as changes in expression while on neoadjuvant therapy, have not been well-characterized. We conducted a prospective clinical study, pre- and post-neoadjuvant/systemic therapy, in patients with newly diagnosed breast cancer to determine HER3 expression, and to identify possible resistance mechanisms maintained through the HER3 receptor.

EXPERIMENTAL DESIGN

The study was conducted between May 25, 2018 and October 12, 2019. Thirty-four patients with newly diagnosed breast cancer of any subtype (ER ± , PR ± , HER2 ±) were enrolled in the study. Two core biopsy specimens were obtained from each patient at the time of diagnosis. Four patients underwent a second research biopsy following initiation of neoadjuvant/systemic therapy or systemic therapy which we define as neoadjuvant therapy. Molecular characterization of HER3 and downstream signaling nodes of the PI3K/AKT and MAPK pathways pre- and post-initiation of therapy was performed. Transcriptional validation of finings was performed in an external dataset (GSE122630).

RESULTS

Variable baseline HER3 expression was found in newly diagnosed breast cancer and correlated positively with pAKT across subtypes (r = 0.45). In patients receiving neoadjuvant/systemic therapy, changes in HER3 expression were variable. In a hormone receptor-positive (ER +/PR +/HER2-) patient, there was a statistically significant increase in HER3 expression post neoadjuvant therapy, while there was no significant change in HER3 expression in a ER +/PR +/HER2+ patient. However, both of these patients showed increased downstream signaling in the PI3K/AKT pathway. One subject with ER +/PR -/HER2- breast cancer and another subject with ER +/PR +/HER2 + breast cancer showed decreased HER3 expression. Transcriptomic findings, revealed an immune suppressive environment in patients with decreased HER3 expression post therapy.

CONCLUSION

This study demonstrates variable HER3 expression across breast cancer subtypes. HER3 expression can be assessed early, post-neoadjuvant therapy, providing valuable insight into cancer biology and potentially serving as a prognostic biomarker. Clinical translation of neoadjuvant therapy assessment can be achieved using HER3 PET imaging, offering real-time information on tumor biology and guiding personalized treatment for breast cancer patients.

Resistance to Targeted Inhibitors of the PI3K/AKT/mTOR Pathway in Advanced Oestrogen-Receptor-Positive Breast Cancer

The PI3K/AKT/mTOR signalling pathway is one of the most frequently activated pathways in breast cancer and also plays a central role in the regulation of several physiologic functions. There are major efforts ongoing to exploit precision medicine by developing inhibitors that target the three kinases (PI3K, AKT, and mTOR). Although multiple compounds have been developed, at present, there are just three inhibitors approved to target this pathway in patients with advanced ER-positive, HER2-negative breast cancer: everolimus (mTOR inhibitor), alpelisib (PIK3CA inhibitor), and capivasertib (AKT inhibitor). Like most targeted cancer drugs, resistance poses a major problem in the clinical setting and is a factor that has frequently limited the overall efficacy of these agents. Drug resistance can be categorised into intrinsic or acquired resistance depending on the timeframe it has developed within. Whereas intrinsic resistance exists prior to a specific treatment, acquired resistance is induced by a therapy. The majority of patients with ER-positive, HER2-negative advanced breast cancer will likely be offered an inhibitor of the PI3K/AKT/mTOR pathway at some point in their cancer journey, with the options available depending on the approval criteria in place and the cancer's mutation status. Within this large cohort of patients, it is likely that most will develop resistance at some point, which makes this an area of interest and an unmet need at present. Herein, we review the common mechanisms of resistance to agents that target the PI3K/AKT/mTOR signalling pathway, elaborate on current management approaches, and discuss ongoing clinical trials attempting to mitigate this significant issue. We highlight the need for additional studies into AKT1 inhibitor resistance in particular.

Long road towards effective HER3 targeting in breast cancer

Breast cancer is a heterogeneous disease, encompassing multiple different subtypes. Thanks to the increasing knowledge of the diverse biological features of each subtype, most patients receive personalized treatment based on known biomarkers. However, the role of some biomarkers in breast cancer evolution is still unknown, and their potential use as a therapeutic target is still underexplored. HER3 is a member of the human epidermal growth factors receptor family, overexpressed in 50%-70% of breast cancers. HER3 plays a key role in cancer progression, metastasis development, and drug resistance across all the breast cancer subtypes. Owing to its critical role in cancer progression, many HER3-targeting therapies have been developed over the past decade with conflicting findings. Next-generation antibody-drug conjugates have recently shown promising results in solid tumors expressing HER3, including breast cancer. In this review, we discuss the HER3 role in the pathogenesis of breast cancer and its relevance across all subtypes. We also explore the new anti-HER3 treatment strategies, calling into question the significance of HER3 detection as crucial information in breast cancer treatment.

HER3 (ERBB3) amplification in liposarcoma - a putative new therapeutic target?

BACKGROUND

Liposarcomas are among the most common mesenchymal malignancies. However, the therapeutic options are still very limited and so far, targeted therapies had not yet been established. Immunotherapy, which has been a breakthrough in other oncological entities, seems to have no efficacy in liposarcoma. Complicating matters further, classification remains difficult due to the diversity of morphologies and nonspecific or absent markers in immunohistochemistry, leaving molecular pathology using FISH or sequencing as best options. Many liposarcomas harbor MDM2 gene amplifications. In close relation to the gene locus of MDM2, HER3 (ERBB3) gene is present and co-amplification could occur. Since the group of HER/EGFR receptor tyrosine kinases and its inhibitors/antibodies play a role in a broad spectrum of oncological diseases and treatments, and some HER3 inhibitors/antibodies are already under clinical investigation, we hypothesized that in case of HER3 co-amplifications a tumor might bear a further potential therapeutic target.

METHODS

We performed FISH analysis (MDM2, DDIT3, HER3) in 56 archived cases and subsequently performed reclassification to confirm the diagnosis of liposarcoma.

RESULTS

Next to 16 out of 56 cases needed to be re-classified, in 20 out of 54 cases, a cluster-amplification of HER3 could be detected, significantly correlating with MDM2 amplification. Our study shows that the entity of liposarcomas show specific molecular characteristics leading to reclassify archived cases by modern, established methodologies. Additionally, in 57.1% of these cases, HER3 was cluster-amplified profusely, presenting a putative therapeutic target for targeted therapy.

CONCLUSION

Our study serves as the initial basis for further investigation of the HER3 gene as a putative therapeutic target in liposarcoma.

Targeted dual degradation of HER2 and EGFR obliterates oncogenic signaling, overcomes therapy resistance, and inhibits metastatic lesions in HER2-positive breast cancer models

AIMS

Human epidermal growth factor receptor 2 (HER2) is an oncogenic receptor tyrosine kinase amplified in approximately 20% of breast cancer (BC). HER2-targeted therapies are the linchpin of treating HER2-positive BC. However, drug resistance is common, and the main resistance mechanism is unknown. We tested the hypothesis that drug resistance results mainly from inadequate or lack of inhibition of HER2 and its family member epidermal growth factor receptor (EGFR).

METHODS

We used clinically relevant cell and tumor models to assess the impact of targeted degradation of HER2 and EGFR on trastuzumab resistance. Trastuzumab is the most common clinically used HER2 inhibitor. Targeted degradation of HER2 and EGFR was achieved using recombinant human protein PEPDG278D, which binds to the extracellular domains of the receptors. siRNA knockdown was used to assess the relative importance of EGFR and HER2 in trastuzumab resistance.

RESULTS

Both HER2 and EGFR are overexpressed in all trastuzumab-resistant HER2-positive BC cell and tumor models and that all trastuzumab-resistant models are highly vulnerable to targeted degradation of HER2 and EGFR. Degradation of HER2 and EGFR induced by PEPDG278D causes extensive inhibition of oncogenic signaling in trastuzumab-resistant HER2-positive BC cells. This is accompanied by strong growth inhibition of cultured cells, orthotopic patient-derived xenografts, and metastatic lesions in the brain and lung of trastuzumab-resistant HER2-positive BC. siRNA knockdown indicates that eliminating both HER2 and EGFR is necessary to maximize therapeutic outcome.

CONCLUSIONS

This study unravels the therapeutic vulnerability of trastuzumab-resistant HER2-positive BC and shows that an agent that targets the degradation of both HER2 and EGFR is highly effective in overcoming drug resistance in this disease. The findings provide new insights and innovations for advancing treatment of drug-resistant HER2-positive breast cancer that remains an unmet problem.

Adipocyte Precursor-Derived NRG1 Promotes Resistance to FGFR Inhibition in Urothelial Carcinoma

Aberrations of the fibroblast growth factor receptor (FGFR) family members are frequently observed in metastatic urothelial cancer (mUC), and blocking the FGF/FGFR signaling axis is used as a targeted therapeutic strategy for treating patients. Erdafitinib is a pan-FGFR inhibitor, which has recently been approved by the FDA for mUC with FGFR2/3 alterations. Although mUC patients show initial response to erdafitinib, acquired resistance rapidly develops. Here, we found that adipocyte precursors promoted resistance to erdafitinib in FGFR-dependent bladder and lung cancer in a paracrine manner. Moreover, neuregulin 1 (NRG1) secreted from adipocyte precursors was a mediator of erdafitinib resistance by activating human epidermal growth factor receptor 3 (ERBB3; also known as HER3) signaling, and knockdown of NRG1 in adipocyte precursors abrogated the conferred paracrine resistance. NRG1 expression was significantly downregulated in terminally differentiated adipocytes compared with their progenitors. Pharmacologic inhibition of the NRG1/HER3 axis using pertuzumab reversed erdafitinib resistance in tumor cells in vitro and prolonged survival of mice bearing bladder cancer xenografts in vivo. Remarkably, data from single-cell RNA sequencing revealed that NRG1 was enriched in platelet-derived growth factor receptor-A (PDGFRA) expressing inflammatory cancer-associated fibroblasts, which is also expressed on adipocyte precursors. Together, this work reveals a paracrine mechanism of anti-FGFR resistance in bladder cancer, and potentially other cancers, that is amenable to inhibition using available targeted therapies.

SIGNIFICANCE

Acquired resistance to FGFR inhibition can be rapidly promoted by paracrine activation of the NRG1/HER3 axis mediated by adipocyte precursors and can be overcome by the combination of pertuzumab and erdafitinib treatment. See related commentary by Kolonin and Anastassiou, p. 648.

Targeting HER2/HER3 co-mutations in metastatic breast cancer: Case reports of exceptional responders to trastuzumab and pertuzumab therapy

BACKGROUND

Overexpression of HER2 plays an important role in cancer progression and is the target of multiple therapies in HER2-positive breast cancer. Recent studies have also highlighted the presence of activating mutations in HER2, and HER3 that are predicted to enhance HER2 downstream pathway activation in a HER2-dependent manner.

METHODS

In this report, we present two exceptional responses in hormone receptor-positive, HER2-nonamplified, HER2/HER3 co-mutated metastatic breast cancer patients who were treated with the anti-HER2-directed monoclonal antibodies, trastuzumab and pertuzumab.

RESULTS

Both patients acheived exceptional responses to treatment, suggesting that combined trastuzumab, pertuzumab, and endocrine therapy could be a highly effective therapy for these patients and our observations could help prioritize trastuzumab deruxtecan as an early therapeutic choice for patients whose cancers have activating mutations in HER2.

Targeting HER3 to overcome EGFR TKI resistance in NSCLC

Receptor tyrosine kinases (RTKs) play a crucial role in cellular signaling and oncogenic progression. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) have become the standard treatment for advanced non-small cell lung cancer (NSCLC) patients with EGFR-sensitizing mutations, but resistance frequently emerges between 10 to 14 months. A significant factor in this resistance is the role of human EGFR 3 (HER3), an EGFR family member. Despite its significance, effective targeting of HER3 is still developing. This review aims to bridge this gap by deeply examining HER3's pivotal contribution to EGFR TKI resistance and spotlighting emerging HER3-centered therapeutic avenues, including monoclonal antibodies (mAbs), TKIs, and antibody-drug conjugates (ADCs). Preliminary results indicate combining HER3-specific treatments with EGFR TKIs enhances antitumor effects, leading to an increased objective response rate (ORR) and prolonged overall survival (OS) in resistant cases. Embracing HER3-targeting therapies represents a transformative approach against EGFR TKI resistance and emphasizes the importance of further research to optimize patient stratification and understand resistance mechanisms.

ImmunoPET Targeting Receptor Tyrosine Kinase: Clinical Applications

Receptor tyrosine kinases, or RTKs, are one large family of cell surface receptors involved in signal transduction, which represent an integral part of the signaling pathways. They play a crucial role in most important cellular processes, starting with the cell cycle, proliferation and differentiation, as well as cell migration, metabolism and survival. The introduction of ImmunoPET evaluating the expression of RTKs by specific monoclonal antibodies (mAbs) or antibody fragments is regarded as a promising tool for imaging treatment efficacy and developing anticancer therapeutics. Our review focuses mainly on the current clinical research regarding ImmunoPET targeting RTKs, with particular interest in the epidermal growth factor family, or HER family, and vascular endothelial-derived growth factor/receptor.

Oncoinformatic screening of the gene clusters involved in the HER2-positive breast cancer formation along with the in silico pharmacodynamic profiling of selective long-chain omega-3 fatty acids as the metastatic antagonists

The HER2-positive patients occupy ~ 30% of the total breast cancer patients globally where no prevalent drugs are available to mitigate the frequent metastasis clinically except lapatinib and neratinib. This scarcity reinforced researchers' quest for new medications where natural substances are significantly considered. Valuing the aforementioned issues, this research aimed to study the ERBB2-mediated string networks that work behind the HER2-positive breast cancer formation regarding co-expression, gene regulation, GAMA-receptor-signaling pathway, cellular polarization, and signal inhibition. Following the overexpression, promotor methylation, and survivability profiles of ERBB2, the super docking position of HER2 was identified using the quantum tunneling algorithm. Supramolecular docking was conducted to study the target specificity of EPA and DHA fatty acids followed by a comprehensive molecular dynamic simulation (100 ns) to reveal the RMSD, RMSF, Rg, SASA, H-bonds, and MM/GBSA values. Finally, potential drug targets for EPA and DHA in breast cancer were constructed to determine the drug-protein interactions (DPI) at metabolic stages. Considering the values resulting from the combinational models of the oncoinformatic, pharmacodynamic, and metabolic parameters, long-chain omega-3 fatty acids like EPA and DHA can be considered as potential-targeted therapeutics for HER2-positive breast cancer treatment.

Targeting Epidermal Growth Factor Receptor for Cancer Treatment: Abolishing Both Kinase-Dependent and Kinase-Independent Functions of the Receptor

Epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, is activated by ligand binding, overexpression, or mutation. It is well known for its tyrosine kinase-dependent oncogenic activities in a variety of human cancers. A large number of EGFR inhibitors have been developed for cancer treatment, including monoclonal antibodies, tyrosine kinase inhibitors, and a vaccine. The EGFR inhibitors are aimed at inhibiting the activation or the activity of EGFR tyrosine kinase. However, these agents have shown efficacy in only a few types of cancers. Drug resistance, both intrinsic and acquired, is common even in cancers where the inhibitors have shown efficacy. The drug resistance mechanism is complex and not fully known. The key vulnerability of cancer cells that are resistant to EGFR inhibitors has not been identified. Nevertheless, it has been increasingly recognized in recent years that EGFR also possesses kinase-independent oncogenic functions and that these noncanonical functions may play a crucial role in cancer resistance to EGFR inhibitors. In this review, both kinase-dependent and -independent activities of EGFR are discussed. Also discussed are the mechanisms of actions and therapeutic activities of clinically used EGFR inhibitors and sustained EGFR overexpression and EGFR interaction with other receptor tyrosine kinases to counter the EGFR inhibitors. Moreover, this review discusses emerging experimental therapeutics that have shown potential for overcoming the limitation of the current EGFR inhibitors in preclinical studies. The findings underscore the importance and feasibility of targeting both kinase-dependent and -independent functions of EGFR to enhance therapeutic efficacy and minimize drug resistance. SIGNIFICANCE STATEMENT: EGFR is a major oncogenic driver and therapeutic target, but cancer resistance to current EGFR inhibitors remains a significant unmet clinical problem. This article reviews the cancer biology of EGFR as well as the mechanisms of actions and the therapeutic efficacies of current and emerging EGFR inhibitors. The findings could potentially lead to development of more effective treatments for EGFR-positive cancers.

HER-3 surface expression increases in advanced colorectal cancer representing a potential therapeutic target

HER-3 (also known as ErbB-3) is a human epidermal growth factor receptor tyrosine kinases family member, and its expression in CRC (colorectal cancer) tissues was previously associated with poor prognosis. In this study, HER-3 expression was analyzed by immunohistochemistry in two cohorts of early and advanced metastatic CRC patients. The first cohort included 180 patients diagnosed with CRC in absence of lymph nodes or distant metastases (Stage I and Stage II), while the second was obtained from 53 advanced metastatic CRC patients who developed synchronous (SM) and metachronous (MM) liver metastases. In the first early-stage CRC cohort, 86 out of 180 (47.8%) tumors showed membranous expression of HER-3, with a mean percentage of positive tumor cells of 25.7%; conversely, in advanced metastatic CRC primary tumors, HER-3 was detected in all specimens, with a mean percentage of positive tumor cells of 76.1%. Kaplan-Meier curves showed that in the advanced metastatic CRC group, patients with HER-3high tumors had a significantly lower Cancer-Specific Survival (CSS) rate compared to patients with HER-3low tumors (p = 0.021). Importantly, this worse CSS rate was observed only in the MM subgroup of patients with HER-3high tumors (p = 0.002). Multivariate analysis confirmed that high HER-3 expression represents a significant and strong risk factor for death in patients developing MM liver metastases (Hazard Ratio = 64.9; 95% Confidence Interval, 4.7-886.6; p = 0.002). In addition, using a specific anti-HER-3 antibody-drug conjugate, named EV20/MMAF, we showed that HER-3 + CRC cells can be efficiently targeted in vitro and in vivo. Overall, this study confirms that surface HER-3 is highly expressed in CRC and reveals that HER-3 expression increases in metastatic CRC patients compared to early stage. Importantly, the results suggest that HER-3 has a prognostic and therapeutic value in patients developing MM liver metastases.

Antibody drug conjugates: hitting the mark in pancreatic cancer?

Pancreatic cancer is one of the most common causes of cancer-related death, and the 5-year survival rate has only improved marginally over the last decade. Late detection of the disease means that in most cases the disease has advanced locally and/or metastasized, and curative surgery is not possible. Chemotherapy is still the first-line treatment however, this has only had a modest impact in improving survival, with associated toxicities. Therefore, there is an urgent need for targeted approaches to better treat pancreatic cancer, while minimizing treatment-induced side-effects. Antibody drug conjugates (ADCs) are one treatment option that could fill this gap. Here, a monoclonal antibody is used to deliver extremely potent drugs directly to the tumor site to improve on-target killing while reducing off-target toxicity. In this paper, we review the current literature for ADC targets that have been examined in vivo for treating pancreatic cancer, summarize current and on-going clinical trials using ADCs to treat pancreatic cancer and discuss potential strategies to improve their therapeutic window.

Human Epidermal Growth Factor Receptor 2/Human Epidermal Growth Factor Receptor 3 PET Imaging: Challenges and Opportunities

Human epidermal growth factor receptor 2 (HER2) and HER3 provide actionable targets for both therapy and imaging in breast cancer. Further, clinical trials have shown the prognostic impact of receptor status discordance in breast cancer. Intra- and intertumoral heterogeneity of both HER and hormone receptor expression contributes to inherent errors in tissue sampling, and single biopsies are incapable of identifying discordance in biomarker expression. Numerous PET radiopharmaceuticals have been developed to evaluate (or target for therapy) HER2 and HER3 expression. This review seeks to inform on challenges and opportunities in HER2 and HER3 PET imaging in both clinical and preclinical settings.

Next-generation antibody-drug conjugates for breast cancer: Moving beyond HER2 and TROP2

Antibody-drug conjugates (ADCs) have reshaped the treatment of several malignancies, including breast cancer. Two ADCs are currently approved for the treatment of each breast cancer subtype, including the HER2 targeted ADCs trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd), and the TROP2-targeted ADC sacituzumab govitecan. Each of the ADC components (antibody, linker, and payload) plays a key role in determining the efficacy and toxicity profile of an individual ADC, and their modification can lead to major changes in the clinical profile of these agents. Leveraging the knowledge from three decades of development in the field, several novel ADCs are currently being investigated. Some approaches include targeting different antigens beyond the established HER2/TROP2, or evaluating innovative constructs, such as bispecific ADCs, ADCs with dual payload, immune-modulating ADCs, radionuclide drug conjugates, and masked ADCs, among others. In this review article we discuss the evolving landscape of novel ADCs, highlighting opportunities and challenges emerging in the field.

HER3 functions as an effective therapeutic target in triple negative breast cancer to potentiate the antitumor activity of gefitinib and paclitaxel

BACKGROUND

Triple negative breast cancer (TNBC) represents a significant clinical challenge. Chemotherapy remains the mainstay for a large part of TNBC patients, whereas drug resistance and tumor recurrence frequently occur. It is in urgent need to identify novel molecular targets for TNBC and develop effective therapy against the aggressive disease.

METHODS

Immunohistochemistry was performed to examine the expression of HER3 in TNBC samples. Western blots were used to assess protein expression and activation. Cell proliferation and viability were determined by cell growth (MTS) assays. TCGA databases were analyzed to correlate HER3 mRNA expression with the clinical outcomes of TNBC patients. Specific shRNA was used to knockdown HER3 expression. IncuCyte system was utilized to monitor cell growth and migration. LIVE/DEAD Cell Imaging was to detect live and dead cells. HER3 recognition by our anti-HER3 monoclonal antibody (mAb) 4A7 was verified by ELISA, flow cytometry, and co-immunoprecipitation assays. Orthotopic tumor models were established in nude mice to determine the capability of TNBC cells forming tumors and to test if our mAb 4A7 could potentiate the antitumor activity of paclitaxel in vivo.

RESULTS

Elevated expression of HER3 was observed in approximately half of the TNBC specimens and cell lines tested. Analyses of TCGA databases found that the TNBC patients with high HER3 mRNA expression in the tumors showed significantly worse overall survival (OS) and relapse-free survival (RFS) than those with low HER3 expression. Specific knockdown of HER3 markedly inhibited TNBC cell proliferation and mammosphere formation in vitro and tumor growth in vivo. Our mAb 4A7 abrogated heregulin (a ligand for HER3), but not SDF-1 (a ligand for CXCR4)-induced enhancement of TNBC cell migration. Combinations of 4A7 and the EGFR-tyrosine kinase inhibitor (TKI) gefitinib dramatically decreased the levels of phosphorylated HER3, EGFR, Akt, and ERK1/2 in TNBC cells and potently induced growth inhibition and cell death. Moreover, 4A7 in combination with paclitaxel exerted significant antitumor activity against TNBC in vitro and in vivo.

CONCLUSIONS

Our data demonstrate that increased HER3 is an effective therapeutic target for TNBC and our anti-HER3 mAb (4A7) may enhance the efficacy of gefitinib or paclitaxel in TNBC.

HER3/Akt/mTOR pathway is a key therapeutic target for the reduction of triple‑negative breast cancer metastasis via the inhibition of CXCR4 expression

Triple‑negative breast cancer (TNBC), a highly metastatic subtype of breast cancer, and it has the worst prognosis among all subtypes of breast cancer. However, no effective systematic therapy is currently available for TNBC metastasis. Therefore, novel therapies targeting the key molecular mechanisms involved in TNBC metastasis are required. The present study examined whether the expression levels of human epidermal growth factor receptor 3 (HER3) were associated with the metastatic phenotype of TNBC, and evaluated the potential of HER3 as a therapeutic target in vitro and in vivo. A new highly metastatic 4T1 TNBC cell line, termed 4T1‑L8, was established. The protein expression levels in 4T1‑L8 cells were measured using luminex magnetic bead assays and western blot analysis. The HER3 expression levels and distant metastasis‑free survival (DMFS) in TNBC were analyzed using Kaplan‑Meier Plotter. Transwell migration and invasion assays were performed to detect migration and invasion. The anti‑metastatic effects were determined in an experimental mouse model of metastasis. The results revealed that the increased expression of the HER3/Akt/mTOR pathway was associated with a greater level of cell migration, invasion and metastasis of TNBC cells. In addition, it was found that high expression levels of HER3 were associated with a poor DMFS. The inhibition of the HER3/Akt/mammalian target of rapamycin (mTOR) pathway decreased the migration, invasion and metastasis of TNBC cells by decreasing the expression of C‑X‑C chemokine receptor type 4 (CXCR4). Furthermore, treatment of metastatic TNBC cells with everolimus inhibited their migration, invasion and metastasis by decreasing CXCR4 expression. Thus, targeting the HER3/Akt/mTOR pathway opens up a new avenue for the development of therapeutics against TNBC metastasis; in addition, everolimus may prove to be an effective therapeutic agent for the suppression of TNBC metastasis.

Desmocollin-1 is associated with pro-metastatic phenotype of luminal A breast cancer cells and is modulated by parthenolide

BACKGROUND

Desmocollin-1 (DSC1) is a desmosomal transmembrane glycoprotein that maintains cell-to-cell adhesion. DSC1 was previously associated with lymph node metastasis of luminal A breast tumors and was found to increase migration and invasion of MCF7 cells in vitro. Therefore, we focused on DSC1 role in cellular and molecular mechanisms in luminal A breast cancer and its possible therapeutic modulation.

METHODS

Western blotting was used to select potential inhibitor decreasing DSC1 protein level in MCF7 cell line. Using atomic force microscopy we evaluated effect of DSC1 overexpression and modulation on cell morphology. The LC-MS/MS analysis of total proteome on Orbitrap Lumos and RNA-Seq analysis of total transcriptome on Illumina NextSeq 500 were performed to study the molecular mechanisms associated with DSC1. Pull-down analysis with LC-MS/MS detection was carried out to uncover DSC1 protein interactome in MCF7 cells.

RESULTS

Analysis of DSC1 protein levels in response to selected inhibitors displays significant DSC1 downregulation (p-value ≤ 0.01) in MCF7 cells treated with NF-κB inhibitor parthenolide. Analysis of mechanic cell properties in response to DSC1 overexpression and parthenolide treatment using atomic force microscopy reveals that DSC1 overexpression reduces height of MCF7 cells and conversely, parthenolide decreases cell stiffness of MCF7 cells overexpressing DSC1. The LC-MS/MS total proteome analysis in data-independent acquisition mode shows a strong connection between DSC1 overexpression and increased levels of proteins LACRT and IGFBP5, increased expression of IGFBP5 is confirmed by RNA-Seq. Pathway analysis of proteomics data uncovers enrichment of proliferative MCM_BIOCARTA pathway including CDK2 and MCM2-7 after DSC1 overexpression. Parthenolide decreases expression of LACRT, IGFBP5 and MCM_BIOCARTA pathway specifically in DSC1 overexpressing cells. Pull-down assay identifies DSC1 interactions with cadherin family proteins including DSG2, CDH1, CDH3 and tyrosine kinase receptors HER2 and HER3; parthenolide modulates DSC1-HER3 interaction.

CONCLUSIONS

Our systems biology data indicate that DSC1 is connected to mechanisms of cell cycle regulation in luminal A breast cancer cells, and can be effectively modulated by parthenolide.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

HER3 targeting augments the efficacy of panobinostat in claudin-low triple-negative breast cancer cells

Patients with triple-negative breast cancer (TNBC) have a poor prognosis and high relapse rate due to limited therapeutic options. This study was conducted to determine the mechanisms of action of panobinostat, a pan-inhibitor of histone deacetylase (HDAC) and FDA-approved medication for multiple myeloma, in TNBC and to provide a rationale for effective drug combinations against this aggressive disease. RNA sequencing analyses of the claudin-low (CL) TNBC (MDA-MB-231) cells untreated or treated with panobinostat were performed to identify the differentially expressed genes. Adaptive alterations in gene expression were analyzed and validated in additional CL TNBC cells. Tumor xenograft models were used to test the in vivo antitumor activity of panobinostat alone or its combinations with gefitinib, an EGFR-tyrosine kinase inhibitor (TKI). Panobinostat potently inhibited proliferation and induced apoptosis in all TNBC cells tested. However, in CL TNBC cells, this HDAC inhibitor markedly enhanced expression of HER3, which interacted with EGFR to activate both receptors and Akt signaling pathways. Combinations of panobinostat and gefitinib synergistically suppressed CL TNBC cell proliferation and promoted apoptosis in vitro and in vivo. Upregulation of HER3 compromises the efficacy of panobinostat in CL TNBC. Inactivation of HER3 combined with panobinostat represents a practical approach to combat CL TNBC.

Antibody-drug conjugates: the evolving field of targeted chemotherapy for breast cancer treatment

Antibody-drug conjugates (ADCs) are a class of antineoplastic agents whose structure is composed of three main components: a monoclonal antibody (mAB) targeting a specific target antigen, a cytotoxic payload, and a linker binding the antibody to the payload. By combining the specificity of mABs with the high potency of the payloads, ADCs constitute a smart drug delivery system with improved therapeutic index. After recognition and binding of the mAB to its target surface antigen, ADCs are internalized by endocytosis by the tumor cell, releasing the payloads into the cytoplasm, where they exert their cytotoxic activity, eventually leading to cell death. The composition of some of the new ADCs confers additional functional properties that allow expanding their activity to neighboring cells not expressing the target antigen, constituting a valuable strategy to overcome tumor heterogeneity. Some of these 'off-target effects', such as the bystander effect, are possibly the mechanism underlying the antitumor activity demonstrated in patients with low expression of the target antigens, which represents an important paradigm shift in anticancer targeted therapy. Three ADCs are currently approved for the treatment of breast cancer (BC); two anti-HER2 (human epidermal growth factor receptor 2) ADCs (trastuzumab emtansine and trastuzumab deruxtecan); and one Trop-2-targeted ADC (sacituzumab govitecan). Based on the unprecedented efficacy data demonstrated by these agents, ADCs have been incorporated as part of standard regimens for all subtypes of advanced BC, as well as for high-risk early HER2-positive BC. Despite the remarkable advances, several hurdles still remain to overcome, including the development of reliable biomarkers for patient selection, prevention, and management of potentially severe toxicities, ADC resistance mechanisms, post-ADC resistance patterns, and optimal treatment sequencing and combinations. In this review, we will summarize the currently available evidence related to the use of these agents, as well as explore the current landscape of ADC development for BC treatment.

Targeted Therapies in Colorectal Cancer: Recent Advances in Biomarkers, Landmark Trials, and Future Perspectives

In 2022, approximately 600,000 cancer deaths were expected; more than 50,000 of those deaths would be from colorectal cancer (CRC). The CRC mortality rate in the US has decreased in recent decades, with a 51% drop between 1976 and 2014. This drop is attributed, in part, to the tremendous therapeutic improvements, especially after the 2000s, in addition to increased social awareness regarding risk factors and diagnostic improvement. Five-fluorouracil, irinotecan, capecitabine, and later oxaliplatin were the mainstays of mCRC treatment from the 1960s to 2002. Since then, more than a dozen drugs have been approved for the disease, betting on a new chapter in medicine, precision oncology, which uses patient and tumor characteristics to guide the therapeutic choice. Thus, this review will summarize the current literature on targeted therapies, highlighting the molecular biomarkers involved and their pathways.

Drug-induced oxidative stress in cancer treatments: Angel or devil?

Oxidative stress (OS), defined as redox imbalance in favor of oxidant burden, is one of the most significant biological events in cancer progression. Cancer cells generally represent a higher oxidant level, which suggests a dual therapeutic strategy by regulating redox status (i.e., pro-oxidant therapy and/or antioxidant therapy). Indeed, pro-oxidant therapy exhibits a great anti-cancer capability, attributing to a higher oxidant accumulation within cancer cells, whereas antioxidant therapy to restore redox homeostasis has been claimed to fail in several clinical practices. Targeting the redox vulnerability of cancer cells by pro-oxidants capable of generating excessive reactive oxygen species (ROS) has surfaced as an important anti-cancer strategy. However, multiple adverse effects caused by the indiscriminate attacks of uncontrolled drug-induced OS on normal tissues and the drug-tolerant capacity of some certain cancer cells greatly limit their further applications. Herein, we review several representative oxidative anti-cancer drugs and summarize their side effects on normal tissues and organs, emphasizing that seeking a balance between pro-oxidant therapy and oxidative damage is of great value in exploiting next-generation OS-based anti-cancer chemotherapeutics.

Molecular and clinical correlates of HER3 expression highlights its potential role as a therapeutic target in melanoma

Overexpression of the epidermal growth factor receptor family member HER3 (erbB3) has been implicated in several types of cancer and recently drugs targeting HER3 have shown promising clinical activity. In melanoma, HER3 overexpression has been linked to both metastasis formation and resistance to drug therapy in cell culture models. Here, we sought to characterise the expression of HER3 in 187 melanoma biopsies (149 cutaneous, 38 mucosal) using immunohistochemistry, as well as to analyse the association between HER3 expression and molecular, clinical and pathological variables. A subset of the cutaneous melanoma specimens was taken prior to treatment with immune checkpoint blockade therapy (pre-ICB) (n=79). HER3 expression (≥1+) was observed in 136 of 187 samples (∼73%). HER3 expression was found to be markedly lower in the mucosal melanomas, with 17 of the 38 tumours (∼45%) demonstrating no HER3 expression. In cutaneous melanomas, there was a negative association between HER3 expression and mutational load, a positive association with NRAS mutational status, and a trend of negative association with PD-L1 expression. In the pre-ICB cohort, an association was found between high HER3 expression (≥2+) and overall survival after anti-PD-1-based immunotherapy. Overall, our results indicate that HER3 is a promising therapeutic avenue in cutaneous melanoma worthy of further clinical evaluation.

Antibody-Drug Conjugates for Lung Cancer: Payloads and Progress

Antibody Drug Conjugates (ADCs) are a novel class of therapeutic that structurally comprise an antibody directed at a tumor epitope connected via a linker to a cytotoxic payload that have shown significant antitumor activity across a range of malignancies including lung cancer. In this article we review the pharmacology of ADCs, describe results of trials with ADCs directed at targets in lung cancer including Trophoblast cell-surface antigen 2(TROP2), HER3, MET, Carcinoembryonic antigen-related cell adhesion molecular 5(CECAM-5) and HER2. Trastuzumab Deruxtecan (also known as DS-8201a or T-DXd) an ADC directed at HER2 recently became the first ADC to receive FDA approval in lung cancer, on the basis of its activity in tumors with HER2 mutations, demonstrated in the Destiny-Lung01 and Lung02 trials.

Synergistic therapeutic potential of alpelisib in cancers (excluding breast cancer): Preclinical and clinical evidences

The phosphoinositide 3-kinase (PI3K) signaling pathway is well-known for its important role in cancer growth, proliferation and migration. The activation of PI3K pathway is always connected with endocrine resistance and poor prognosis in cancers. Alpelisib, a selective inhibitor of PI3K, has been demonstrated to be effective in combination with endocrine therapy in HR+ PIK3CA-mutated advanced breast cancer in preclinical and clinical trials. Recently, the synergistic effects of alpelisib combined with targeted agents have been widely reported in PIK3CA-mutated cancer cells, such as breast, head and neck squamous cell carcinoma (HNSCC), cervical, liver, pancreatic and lung cancer. However, previous reviews mainly focused on the pharmacological activities of alpelisib in breast cancer. The synergistic therapeutic potential of alpelisib in other cancers has not yet been well reviewed. In this review, an extensive study of related literatures (published until December 20, 2022) regarding the anti-cancer functions and synergistic effects of alpelisib was carried out through the databases. Useful information was extracted. We summarized the preclinical and clinical studies of alpelisib in combination with targeted anti-cancer agents in cancer treatment (excluding breast cancer). The combinations of alpelisib and other targeted agents significantly improved the therapeutic efficacy both in preclinical and clinical studies. Unfortunately, synergistic therapies still could not effectively avoid the possible toxicities and adverse events during treatment. Finally, some prospects for the combination studies in cancer treatment were provided in the paper. Taken together, this review provided valuable information for alpelisib in preclinical and clinical applications.

The role of the NDRG1 in the pathogenesis and treatment of breast cancer

Breast cancer (BC) is the leading cause of cancer death in women. This disease is heterogeneous, with clinical subtypes being estrogen receptor-α (ER-α) positive, having human epidermal growth factor receptor 2 (HER2) overexpression, or being triple-negative for ER-α, progesterone receptor, and HER2 (TNBC). The ER-α positive and HER2 overexpressing tumors can be treated with agents targeting these proteins, including tamoxifen and pertuzumab, respectively. Despite these treatments, resistance and metastasis are problematic, while TNBC is challenging to treat due to the lack of suitable targets. Many studies examining BC and other tumors indicate a role for N-myc downstream-regulated gene-1 (NDRG1) as a metastasis suppressor. The ability of NDRG1 to inhibit metastasis is due, in part, to the inhibition of the initial step in metastasis, namely the epithelial-to-mesenchymal transition. Paradoxically, there are also reports of NDRG1 playing a pro-oncogenic role in BC pathogenesis. The oncogenic effects of NDRG1 in BC have been reported to relate to lipid metabolism or the mTOR signaling pathway. The molecular mechanism(s) of how NDRG1 regulates the activity of multiple signaling pathways remains unclear. Therapeutic strategies that up-regulate NDRG1 have been developed and include agents of the di-2-pyridylketone thiosemicarbazone class. These compounds target oncogenic drivers in BC cells, suppressing the expression of multiple key hormone receptors including ER-α, progesterone receptor, androgen receptor, and prolactin receptor, and can also overcome tamoxifen resistance. Considering the varying role of NDRG1 in BC pathogenesis, further studies are required to examine what subset of BC patients would benefit from pharmacopeia that up-regulate NDRG1.

Antibody-drug conjugates in lung cancer: dawn of a new era?

Antibody-drug conjugates (ADCs) are one of fastest growing classes of oncology drugs in modern drug development. By harnessing the powers of both cytotoxic chemotherapy and targeted therapy, ADCs are unique in offering the potential to deliver highly potent cytotoxic agents to cancer cells which express a pre-defined cell surface target. In lung cancer, the treatment paradigm has shifted dramatically in recent years, and now ADCs are now joining the list as potential options for lung cancer patients. Since 2020, the first ADC for NSCLC patients has been FDA-approved (trastuzumab deruxtecan) and two ADCs have been granted FDA Breakthrough Therapy Designation, currently under evaluation (patritumab deruxtecan, telisotuzumab vedotin). Furthermore, several early-phase trials are assessing various novel ADCs, either as monotherapy or in combinations with advanced lung cancer, and more selective and potent ADCs are expected to become therapeutic options in clinic soon. In this review, we discuss the structure and mechanism of action of ADCs, including insights from pre-clinical work; we summarize the ADCs' recent progress in lung cancer, describe toxicity profiles of ADCs, and explore strategies designed to enhance ADC potency and overcome resistance. In addition, we discuss novel ADC strategies of interest in lung cancer, including non-cytotoxic payloads, such as immunomodulatory and anti-apoptotic agents.

A New View of Activating Mutations in Cancer

A vast effort has been invested in the identification of driver mutations of cancer. However, recent studies and observations call into question whether the activating mutations or the signal strength are the major determinant of tumor development. The data argue that signal strength determines cell fate, not the mutation that initiated it. In addition to activating mutations, factors that can impact signaling strength include (i) homeostatic mechanisms that can block or enhance the signal, (ii) the types and locations of additional mutations, and (iii) the expression levels of specific isoforms of genes and regulators of proteins in the pathway. Because signal levels are largely decided by chromatin structure, they vary across cell types, states, and time windows. A strong activating mutation can be restricted by low expression, whereas a weaker mutation can be strengthened by high expression. Strong signals can be associated with cell proliferation, but too strong a signal may result in oncogene-induced senescence. Beyond cancer, moderate signal strength in embryonic neural cells may be associated with neurodevelopmental disorders, and moderate signals in aging may be associated with neurodegenerative diseases, like Alzheimer's disease. The challenge for improving patient outcomes therefore lies in determining signaling thresholds and predicting signal strength.

Antibody-Drug Conjugates for the Treatment of HER2-Positive Breast Cancer

Human epidermal growth factor receptor 2 (HER2) receptor tyrosine kinase is overexpressed in 20-30% of breast cancers and is associated with poor prognosis and worse overall patient survival. Most women with HER2-positive breast cancer receive neoadjuvant chemotherapy plus HER2-targeted therapies. The development of HER2-directed therapeutics is an important advancement in targeting invasive breast cancer. Despite the efficacy of anti-HER2 monoclonal antibodies, they are still being combined with adjuvant chemotherapy to improve overall patient outcomes. Recently, significant progress has been made towards the development of a class of therapeutics known as antibody-drug conjugates (ADCs), which leverage the high specificity of HER2-targeted monoclonal antibodies with the potent cytotoxic effects of various small molecules, such as tubulin inhibitors and topoisomerase inhibitors. To date, two HER2-targeting ADCs have been approved by the FDA for the treatment of HER2-positive breast cancer: Ado-trastuzumab emtansine (T-DM1; Kadcyla^®) and fam-trastuzumab deruxtecan-nxki (T-Dxd; Enhertu^®). Kadcyla and Enhertu are approved for use as a second-line treatment after trastuzumab-taxane-based therapy in patients with HER2-positive breast cancer. The success of ADCs in the treatment of HER2-positive breast cancer provides novel therapeutic advancements in the management of the disease. In this review, we discuss the basic biology of HER2, its downstream signaling pathways, currently available anti-HER2 therapeutic modalities and their mechanisms of action, and the latest clinical and safety characteristics of ADCs used for the treatment of HER2-positive breast cancer.

Co-Targeting ErbB Receptors and the PI3K/AKT Axis in Androgen-Independent Taxane-Sensitive and Taxane-Resistant Human Prostate Cancer Cells

Simple Summary

Advanced prostate cancer that has progressed after standard therapies such as hormone therapy and taxane-based chemotherapies is an invariably lethal disease state with limited treatment options. There remains an important need to continue to identify new treatment approaches for such patients. We used two cell culture models of prostate cancer that are resistant to hormonal therapy and chemotherapy, and which also manifest some characteristics that are often associated with advanced prostate cancer, such as neuroendocrine differentiation, to evaluate the potential anti-cancer effects of targeting the key molecules, ErbB receptors and AKT. Using several complementary approaches, we found that the concurrent targeting of ErbB receptors and AKT with specific inhibitors was more effective than targeting each of them individually, independent of the underlying molecular characteristics or relative degrees of resistance to the taxanes that defined the prostate cancer models that were studied. Enhanced anti-tumor responses occurred both in vitro and in vivo with dual targeting, with the consistent inhibition particularly of AKT occurring in both settings. These studies provide a framework to evaluate the role of signal pathway modulation as a potential therapeutic strategy in treatment-refractory prostate cancer.

Abstract

Using two representative models of androgen-independent prostate cancer (PCa), PC3 and DU145, and their respective paclitaxel- and docetaxel-resistant derivatives, we explored the anti-tumor activity of targeting the ErbB receptors and AKT using small-molecule kinase inhibitors. These cells manifest varying degrees of neuroendocrine differentiation characteristics and differ in their expression of functional PTEN. Although the specific downstream signaling events post the ErbB receptor and AKT co-targeting varied between the PC3- and DU145-lineage cells, synergistic anti-proliferative and enhanced pro-apoptotic responses occurred across the wild-type and the taxane-resistant cells, independent of their basal AKT activation state, their degree of paclitaxel- or docetaxel-resistance, or whether this resistance was mediated by the ATP Binding Cassette transport proteins. Dual targeting also led to enhanced anti-tumor responses in vivo, although there was pharmacodynamic discordance between the PCa cells in culture versus the tumor xenografts in terms of the relative activation and inhibition states of AKT and ERK under basal conditions and upon AKT and/or ErbB targeting. The consistent inhibition, particularly of AKT, occurred both in vitro and in vivo, independent of the underlying PTEN status. Thus, co-targeting AKT with ErbB, and possibly other partners, may be a useful strategy to explore further for potential therapeutic effect in advanced PCa.

The Potential of Topoisomerase Inhibitor-Based Antibody–Drug Conjugates

DNA topoisomerases are essential enzymes that stabilize DNA supercoiling and resolve entanglements. Topoisomerase inhibitors have been widely used as anti-cancer drugs for the past 20 years. Due to their selectivity as topoisomerase I (TOP1) inhibitors that trap TOP1 cleavage complexes, camptothecin and its derivatives are promising anti-cancer drugs. To increase accumulation of TOP1 inhibitors in cancer cells through the targeting of tumors, TOP1 inhibitor antibody–drug conjugates (TOP1-ADC) have been developed and marketed. Some TOP1-ADCs have shown enhanced therapeutic efficacy compared to prototypical anti-cancer ADCs, such as T-DM1. Here, we review various types of camptothecin-based TOP1 inhibitors and recent developments in TOP1-ADCs. We then propose key points for the design and construction of TOP1-ADCs. Finally, we discuss promising combinatorial strategies, including newly developed approaches to maximizing the therapeutic potential of TOP1-ADCs.

Personalised Therapies for Metastatic Triple-Negative Breast Cancer: When Target Is Not Everything

Simple Summary

The purpose of the present review is to shed light on new molecular biomarkers in triple-negative breast cancer (TNBC), showing emerging therapeutic approaches related to specific molecular signatures and their mechanisms of action. A general overview of ongoing clinical trials, future perspectives and differences in approval by American and European regulatory authorities is provided.

Abstract

Triple-negative breast cancer—defined by the absence of oestrogen/progesterone receptors and human epidermal growth factor receptor 2 expression—is a complex and heterogeneous type of tumour characterised by poor prognosis, aggressive behaviour and lack of effective therapeutic strategies. The identification of new biomarkers and molecular signatures is leading to development of new therapeutic strategies including immunotherapy, targeted therapy and antibody-drug conjugates (ADCs). Against a background where chemotherapy has always been considered the standard of care, evolution towards a precision medicine approach could improve TNBC clinical practice in a complex scenario, with many therapeutic options and new drugs. The aim of this review was to focus on emerging therapeutic targets and their related specific therapy, discussing available and emerging drugs, underlining differences in approval by American and European regulatory authorities and showing the future perspective in the large number of ongoing clinical trials.

Patritumab deruxtecan (HER3-DXd), a novel HER3 directed antibody drug conjugate, exhibits in vitro activity against breast cancer cells expressing HER3 mutations with and without HER2 overexpression

ErbB3 (HER3), a member of the HER family, is overexpressed in various cancers and plays an important role in cell proliferation and survival. Certain HER3 mutations have also been identified as oncogenic drivers, making them potential therapeutic targets. In the current study, antitumor activity of patritumab deruxtecan (HER3-DXd), a HER3 directed antibody drug conjugate, was evaluated in tumor models with clinically reported HER3 mutations. MDA-MB-231, a HER3-negative human triple-negative breast cancer cell line, was transduced with lentiviral vectors encoding HER3 wild type (HER3^WT), one of 11 HER3 mutations, or HER3 empty vector (HER3^EV), in the presence/absence of HER2 overexpression. Targeted delivery of HER3-DXd was assessed using cell-surface binding, lysosomal trafficking, and cell-growth inhibition assays. HER3-DXd bound to the surface of HER3^WT and mutant cells in a similar, concentration-dependent manner but not to HER3^EV. HER3-DXd was translocated to the lysosome, where time- and concentration-dependent signals were observed in the HER3 mutant and HER3^WT cells. HER3-DXd inhibited the growth of HER3^WT and HER3 mutant cells. HER3-DXd activity was observed in the presence and absence of HER2 overexpression. These data suggest that HER3-DXd may have activity against tumors expressing wild type HER3 or clinically observed HER3 mutations, supporting further clinical evaluation.

Loss of Tpl2 activates compensatory signaling and resistance to EGFR/MET dual inhibition in v-RAS transduced keratinocytes

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of skin cancer in the United States, affecting one million people per year. Patients with aggressive disease have limited treatment options and high mortality, highlighting the need to identify new biomarkers linked to poor clinical outcome. HRAS mutations are found in skin papillomas and cSCCs and increase in frequency when MAP3K family members are inhibited, suggesting a link between blockade of mitogen-activated protein kinase (MAPK) signaling and initiation of RAS-primed cells. Tpl2, a MAP3K gene, can serve as a tumor suppressor gene in cSCC. We have previously shown that upon Tpl2 ablation, mice have heightened sensitivity to aberrant RAS signaling. Tpl2-/- mice display significantly higher numbers of papillomas and cSCCs in two-stage chemical carcinogenesis studies and increased tumorigenicity of keratinocytes expressing oncogenic v-rasHa in nude mouse skin grafts. In part, this is mediated through increased mesenchymal-epithelial transition factor (MET) receptor activity. Epidermal Growth Factor Receptor (EGFR) is reported to be an essential factor for MET-driven carcinogenesis and MET activation may confer resistance to EGFR therapies, suggesting that the concurrent use of both an EGFR inhibitor and a MET inhibitor may show promise in advanced cSCCs. In this study we assessed whether normal or Ras-transformed Tpl2-/- keratinocytes have aberrant EGFR signaling and whether concomitant treatment with EGFR/MET tyrosine kinase inhibitors was more effective than single agents in reducing growth and angiogenic potential of Ras-transformed keratinocytes. Tpl2-/- keratinocytes exhibited increased HER-2 and STAT-3 under basal conditions and elevated p-MET and p-EGFR when transduced with oncogenic RAS. Inhibition of MET by Capmatinib increased p-EGFR in Tpl2-/- keratinocytes and papillomas, and inhibition of EGFR by Gefitinib increased HER2 and HER3 signaling in both genotypes. Treatment of keratinocytes with EGFR and MET inhibitors, in combination, significantly enhanced endothelial tube formation, MMP-9 activity and activation of other RTKs, with more pronounced effects when Tpl2 was ablated. These data indicate that Tpl2 cross-talks with both EGFR and MET signaling pathways. Upon inhibition of EGFR/MET signaling, a myriad of escape mechanisms exists in keratinocytes to overcome targeted drug effects.

miR-101-5p Acts as a Tumor Suppressor in HER2-Positive Breast Cancer Cells and Improves Targeted Therapy

Purpose

Human epidermal growth factor receptor 2 positive (HER2+) breast cancers responding poorly to targeted therapy need improved treatment options. miR-101-5p has shown tumor-suppressive properties in multiple cancer forms, and we assessed the effect and mechanism of action of this miRNA in HER2+ breast cancer.

Methods

Expression levels of miR-101-5p in two clinical datasets, TCGA and METABRIC, were compared between tumor and normal adjacent samples, and across molecular subtypes and HER2 status. The ability of miR-101-5p to sensitize for treatment with lapatinib, tucatinib and trastuzumab was explored in HER2+ breast cancer cells responding poorly to such targeted drugs. Proliferation and apoptosis assays and downstream protein analysis were performed.

Results

Expression levels of miR-101-5p were significantly lower in tumor compared to normal adjacent tissue (p < 0.001), and particularly low in HER2+ tumors, both the HER2-enriched subtype (p ≤ 0.037) and clinical HER2-status (p < 0.001). In a HER2+ cell line (KPL4) responding poorly to targeted drugs, miR-101-5p overexpression inhibited proliferation (p < 0.001), and combinatorial treatment with lapatinib and trastuzumab significantly further decreased this inhibition (p = 0.004). Proteomic data and in silico analyses revealed PI3K/Akt- and HER2-pathways among the predicted regulated pathways. miR-101-5p alone (p = 0.018) and in combination with lapatinib and trastuzumab (p < 0.001) induced apoptosis, while the targeted drugs alone did not exert any significant effect neither on proliferation nor apoptosis.

Conclusion

miR-101-5p acts as a tumor suppressor by inducing apoptosis in HER2+ breast cancer and sensitizes cells with initially poor response to lapatinib and trastuzumab.

Recent advances and limitations in the application of kahalalides for the control of cancer

Since the discovery of the kahalalide family of marine depsipeptides in 1993, considerable work has been done to develop these compounds as new and biologically distinct anti-cancer agents. Clinical trials and laboratory research have yielded a wealth of data that indicates tolerance of kahalalides in healthy cells and selective activity against diseased cells. Currently, two molecules have attracted the greates level of attention, kahalalide F (KF) and isokahalalide F (isoKF, Irvalec, PM 02734, elisidepsin). Both compounds were originally isolated from the sarcoglossan mollusk Elysia rufescens but due to distinct structural characteristics it has been hypothesized and recently shown that the ultimate origin of the molecules is microbial. The search for their true source has been a subject of considerable research in the anticipation of finding new analogs and a culturable expression system that can produce sufficient material through fermentation to be industrially relevant.

Fusion-Associated Carcinomas of the Breast: Diagnostic, Prognostic, and Therapeutic Significance

Recurrent gene fusions comprise a class of viable genetic targets in solid tumors that have culminated several recent break-through cancer therapies. Their role in breast cancer, however, remains largely underappreciated due to the complexity of genomic rearrangements in breast malignancy. Just recently, we and others have identified several recurrent gene fusions in breast cancer with important clinical and biological implications. Examples of the most significant recurrent gene fusions to date include 1) ESR1-CCDC170 gene fusions in luminal B and endocrine resistant breast cancer that exert oncogenic function via modulating the HER2/HER3/SRC complex, 2) ESR1 exon 6 fusions in metastatic disease that drive estrogen-independent ER transcriptional activity, 3) BCL2L14-ETV6 fusions in a more aggressive form of the triple negative subtype that prime epithelial-mesenchymal transition and endow paclitaxel resistance, 4) the ETV6-NTRK3 fusion in secretory breast carcinoma that constitutively activates NTRK3 kinase, 5) the oncogenic MYB-NFIB fusion as a genetic driver underpinning adenoid cystic carcinomas of the breast that activates MYB pathway, and 6) the NOTCH/MAST kinase gene fusions that activate NOTCH and MAST signaling. Importantly, these fusions are enriched in more aggressive and lethal breast cancer presentations and appear to confer therapeutic resistance. Thus, these gene fusions could be utilized as genetic biomarkers to identify patients that require more intensive treatment and surveillance. In addition, kinase fusions are currently being evaluated in breast cancer clinical trials and on-going mechanistic investigation is exposing therapeutic vulnerabilities in patients with fusion positive disease. This article is protected by copyright. All rights reserved.

Differential tumor inhibitory effects induced by HER3 extracellular subdomain-specific mouse monoclonal antibodies

PURPOSE

The therapeutic potential of targeting the human epidermal growth factor receptor-3 (ErbB3/HER3) has long been ignored due to impaired tyrosine kinase function and low expression level in tumor cells compared with EGFR and HER2. Although recent investigations have explored the potential benefit of HER3 targeting and several anti-HER3 agents have been developed, there is still a critical need to design and produce more efficient therapeutics. This study was designed to develop tumor inhibitory monoclonal antibodies (MAbs) against different extracellular subdomains of HER3.

METHODS

Distinct extracellular subdomains of HER3 (D_I+II and D_III+IV) were utilized to produce MAbs by hybridoma technology. Biochemical and functional characteristics of these MAbs were then investigated by various methodologies, including immunoblotting, flow cytometry, cell proliferation, cell signaling, and enzyme-linked immunosorbent assays.

RESULTS

Four anti-D_I+II and six anti-D_III+IV MAbs were obtained, selected based on their ability to bind recombinant full HER3 extracellular domain (ECD). Our data showed that only one anti-D_I+II and four anti-D_III+IV MAbs recognized the native form of HER3 by immunoblotting. Four MAbs recognized the membranous HER3 by flow cytometry leading to induction of different levels of receptor internalization and subsequent degradation. Results of cell proliferation assays using these MAbs indicated that they differentially inhibited proliferation of HER3-expressing cancer cells and showed considerable synergistic effects in combination with trastuzumab. Selected MAb with the highest inhibitory effect significantly inhibited the phosphorylation of AKT and ERK1/2 molecules.

CONCLUSION

Some of the anti-HER3 MAbs produced in this study displayed tumor inhibitory function and may be considered promising candidates for future HER3-targeted cancer therapy.

The Yin and Yang of ERBB4: Tumor Suppressor and Oncoprotein

ERBB4 (HER4) is a member of the ERBB family of receptor tyrosine kinases, a family that includes the epidermal growth factor receptor (EGFR/ERBB1/HER1), ERBB2 (Neu/HER2), and ERBB3 (HER3). EGFR and ERBB2 are oncoproteins and validated targets for therapeutic intervention in a variety of solid tumors. In contrast, the role that ERBB4 plays in human malignancies is ambiguous. Thus, here we review the literature regarding ERBB4 function in human malignancies. We review the mechanisms of ERBB4 signaling with an emphasis on mechanisms of signaling specificity. In the context of this signaling specificity, we discuss the hypothesis that ERBB4 appears to function as a tumor suppressor protein and as an oncoprotein. Next, we review the literature that describes the role of ERBB4 in tumors of the bladder, liver, prostate, brain, colon, stomach, lung, bone, ovary, thyroid, hematopoietic tissues, pancreas, breast, skin, head, and neck. Whenever possible, we discuss the possibility that ERBB4 mutants function as biomarkers in these tumors. Finally, we discuss the potential roles of ERBB4 mutants in the staging of human tumors and how ERBB4 function may dictate the treatment of human tumors. SIGNIFICANCE STATEMENT: This articles reviews ERBB4 function in the context of the mechanistic model that ERBB4 homodimers function as tumor suppressors, whereas ERBB4-EGFR or ERBB4-ERBB2 heterodimers act as oncogenes. Thus, this review serves as a mechanistic framework for clinicians and scientists to consider the role of ERBB4 and ERBB4 mutants in staging and treating human tumors.

Pharmacological Potential and Chemical Composition of Crocus sativus Leaf Extracts

Crocus sativus L. (saffron) has been traditionally used as a food coloring or flavoring agent, but recent research has shown its potent pharmacological activity to tackle several health-related conditions. Crocus sp. leaves, and petals are the by-products of saffron production and are not usually used in the medicine or food industries. The present study was designed to determine the chemical composition of the water and ethanolic extracts of C. sativus leaves and test their cytotoxic activity against melanoma (IGR39) and triple-negative breast cancer (MDA-MB-231) cell lines by MTT assay. We also determined their anti-allergic, anti-inflammatory, and anti-viral activities. HPLC fingerprint analysis showed the presence of 16 compounds, including hydroxycinnamic acids, xanthones, flavonoids, and isoflavonoids, which could contribute to the extracts’ biological activities. For the first time, compounds such as tectoridin, iristectorigenin B, nigricin, and irigenin were identified in Crocus leaf extracts. The results showed that mangiferin (up to 2 mg/g dry weight) and isoorientin (8.5 mg/g dry weight) were the major active ingredients in the leaf extracts. The ethanolic extract reduced the viability of IGR39 and MDA-MB-231 cancer cells with EC₅₀ = 410 ± 100 and 330 ± 40 µg/mL, respectively. It was more active than the aqueous extract. Kaempferol and quercetin were identified as the most active compounds. Our results showed that Crocus leaves contain secondary metabolites with potent cytotoxic and antioxidant activities.

Antibody drug conjugates in non-small cell lung cancer: An emerging therapeutic approach

The current standard-of-care for the treatment of advanced non-small cell lung cancer (NSCLC) incorporates targeted therapies, immune-checkpoint inhibitors (ICI) and systemic chemotherapy. Antibody-drug conjugates (ADC) are a class of anti-cancer therapy capable of transporting cytotoxic drugs directly to tumour cells, thus harnessing the strengths of both cytotoxic chemotherapy and targeted therapy. In this review we provide a comprehensive review the design, mode of action, and mechanisms of resistance to ADCs in NSCLC. We also summarize the clinical development of several promising ADCs in early phase clinical trials for the treatment NSCLC. including ADCs against well-established targets (e.g.HER2 in breast cancer, Nectin4 in urothelial cancer), novel antigenic targets (e.g. HER3, TROP2, PTK7, CEACAM5), as well as promising combinations with agents known to be active in NSCLC such as tyrosine kinase inhibitors and ICI therapy, as a strategy to overcome mechanisms of resistance to ADC therapy.

Profiling novel pharmacology of receptor complexes using Receptor-HIT

Many receptors are able to undergo heteromerisation, leading to the formation of receptor complexes that may have pharmacological profiles distinct from those of the individual receptors. As a consequence of this, receptor heteromers can be classed as new drug targets, with the potential for achieving greater specificity and selectivity over targeting their constituent receptors. We have developed the Receptor-Heteromer Investigation Technology (Receptor-HIT), which enables the detection of receptor heteromers using a proximity-based reporter system such as bioluminescence resonance energy transfer (BRET). Receptor-HIT detects heteromers in live cells and in real time, by utilising ligand-induced signals that arise from altered interactions with specific biomolecules, such as ligands or proteins. Furthermore, monitoring the interaction between the receptors and the specific biomolecules generates functional information about the heteromer that can be pharmacologically quantified. This review will discuss various applications of Receptor-HIT, including its use with different classes of receptors (e.g. G protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs) and others), its use to monitor receptor interactions both intracellularly and extracellularly, and also its use with genome-edited endogenous proteins.

Phase 1 dose escalation study of seribantumab (MM-121), an anti-HER3 monoclonal antibody, in patients with advanced solid tumors

Background Overactivation of human epidermal growth factor receptor 3 (HER3) triggers multiple intracellular pathways resulting in tumor cell survival. This Phase 1 study assessed the safety, efficacy, and pharmacokinetics (PK) of seribantumab, a fully human anti-HER3 monoclonal antibody. Methods Adult patients with advanced or refractory solid tumors were treated in six dose cohorts of seribantumab: 3.2, 6, 10, 15, or 20 mg/kg weekly, or 40 mg/kg loading dose followed by 20 mg/kg weekly maintenance dose (40/20 mg/kg) using a modified 3 + 3 dose escalation strategy with cohort expansion. Primary objectives were identification of a recommended Phase 2 dose (RP2D) and determination of objective response rate. Secondary objectives were assessment of safety, dose-limiting toxicities, and PK. Results Forty-four patients (26 dose escalation; 18 dose expansion) were enrolled. Seribantumab monotherapy was well tolerated with most adverse events being transient and mild to moderate (grade 1 or 2) in severity; maximum tolerated dose was not reached. The highest dose, 40/20 mg/kg, was identified as RP2D. Best response was stable disease, reported in 24% and 39% of patients during the dose escalation and expansion portions of the study, respectively. Seribantumab terminal half-life was ≈100 h; steady state concentrations were reached after 3–4 weekly doses. Conclusions Seribantumab monotherapy was well tolerated across all dose levels. Safety and PK data from this study support further seribantumab investigations in genomically defined populations.

Clinical trial registration NCT00734305. August 12, 2008.

MiR-125a-5p inhibits cell proliferation, cell cycle progression, and migration while promoting apoptosis in head and neck cancers by targeting ERBB3

OBJECTIVE

Head and neck cancer is one of the most common cancer types worldwide. MicroRNAs play a vital regulatory role in the occurrence and development of cancer. The objective of this study is to explore the mechanism of miR-125a-5p in the proliferation, migration and apoptosis of head and neck cancer cells and define its target genes.

METHODS

The effects of miR-125a-5p on head and neck cancer cells proliferation, cell cycle distribution, apoptosis and migration were evaluated by colony formation, BrdU assay, flow cytometry and transwell assays. The potential target gene of miR-125a-5p was determined by luciferase activity assay and western blot analysis.

RESULTS

In this study, overexpression of miR-125a-5p significantly inhibited the proliferation of head and neck cancer cells, whereas inhibition of miR-125a-5p enhanced their proliferation. BrdU assay and flow cytometry revealed that miR-125a-5p might inhibit the proliferation of cancer cells by causing cell cycle arrest. Cell apoptosis assay and Transwell assay indicated that miR-125a-5p induced cell apoptosis and inhibited cell migration of cancer cells. Other experiments confirmed that miR-125a-5p could significantly downregulate its expression by binding to ERBB3 to inhibit proliferation and ERBB3 could at least partially mediate the inhibition of miR-125a-5p on the proliferation of head and neck cancer cells.

CONCLUSION

The findings of this study suggested that the miR-125a-5p/ERBB3 axis might play a role in the proliferation, regulation of cell cycle, migration and apoptosis of head and neck cancer cells, potentially offering a new target for treatments of head and neck cancers.

EV20/NMS-P945, a Novel Thienoindole Based Antibody-Drug Conjugate Targeting HER-3 for Solid Tumors

HER-3 is becoming an attractive target for antibody-drug conjugate (ADC)-based therapy. Indeed, this receptor and its ligands are found to be overexpressed in several malignancies, and re-activation of its downstream signaling axis is known to play a critical role in modulating the sensitivity of targeted therapeutics in different tumors. In this study, we generated a novel ADC named EV20/NMS-P945 by coupling the anti-HER-3 antibody EV20 with a duocarmycin-like derivative, the thienoindole (TEI) NMS-P528, a DNA minor groove alkylating agent through a peptidic cleavable linker. This ADC showed target-dependent cytotoxic activity in vitro on several tumor cell lines and therapeutic activity in mouse xenograft tumor models, including those originating from pancreatic, prostatic, head and neck, gastric and ovarian cancer cells and melanoma. Pharmacokinetics and toxicological studies in monkeys demonstrated that this ADC possesses a favorable terminal half-life and stability and it is well tolerated. These data support further EV20/NMS-P945 clinical development as a therapeutic agent against HER-3-expressing malignancies.

PET and SPECT Imaging of the EGFR Family (RTK Class I) in Oncology

The human epidermal growth factor receptor family (EGFR-family, other designations: HER family, RTK Class I) is strongly linked to oncogenic transformation. Its members are frequently overexpressed in cancer and have become attractive targets for cancer therapy. To ensure effective patient care, potential responders to HER-targeted therapy need to be identified. Radionuclide molecular imaging can be a key asset for the detection of overexpression of EGFR-family members. It meets the need for repeatable whole-body assessment of the molecular disease profile, solving problems of heterogeneity and expression alterations over time. Tracer development is a multifactorial process. The optimal tracer design depends on the application and the particular challenges of the molecular target (target expression in tumors, endogenous expression in healthy tissue, accessibility). We have herein summarized the recent preclinical and clinical data on agents for Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) imaging of EGFR-family receptors in oncology. Antibody-based tracers are still extensively investigated. However, their dominance starts to be challenged by a number of tracers based on different classes of targeting proteins. Among these, engineered scaffold proteins (ESP) and single domain antibodies (sdAb) show highly encouraging results in clinical studies marking a noticeable trend towards the use of smaller sized agents for HER imaging.

A human epidermal growth factor receptor 3/heregulin interaction inhibitor aptamer discovered using SELEX

The interaction of human epidermal growth factor receptor 3 (HER3) and heregulin (HRG) is involved in resistance to human epidermal growth factor receptor 2 (HER2)-targeted cancer treatment, such as therapies using anti-HER2 monoclonal antibody. Therefore, inhibition of the HER3/HRG interaction is potentially valuable therapeutic target for cancer treatment. In this study, we used in vitro selection, also known as systematic evolution of ligands by exponential enrichment (SELEX) against the extracellular domain of human HER3, and discovered a novel RNA aptamer. Pull-down and bio-layer interferometry assays showed that RNA aptamer discovered specifically bound to HER3 with a dissociation constant (K_D) of 700 nM. Pull-down assays using chemiluminescence detection also revealed that the HER3-binding RNA aptamer inhibited interactions between HER3 and human HRG. These results indicated that the novel HER3-binding RNA aptamer has potential to be used as basic tool in a range of applications involving HER3/HRG interactions, including research, therapeutic, and diagnostic applications.