The Under-Appreciated Promiscuity of the Epidermal Growth Factor Receptor Family

Strategies Beyond 3rd EGFR-TKI Acquired Resistance: Opportunities and Challenges

The seminal identification of epidermal growth factor receptor (EGFR) mutations as pivotal oncogenic drivers in non-small cell lung cancer (NSCLC) has catalyzed the evolution of biomarker-guided therapeutic paradigms for advanced disease. Currently, third-generation EGFR tyrosine kinase inhibitors (EGFR-TKI) have revolutionized first-line treatment for advanced EGFR-mutated NSCLC, yet acquired resistance remains an inevitable and formidable clinical challenge. This review systematically summarizes molecular mechanisms underlying treatment resistance, with a focus on clinical challenges associated with central nervous system (CNS) metastases. Therapeutic resistance mechanisms are categorized into EGFR-dependent (on-target) pathways, typified by acquired kinase domain mutations (e.g., C797S), and EGFR-independent (off-target) pathways, involving compensatory activation of parallel signaling effectors (e.g., MET amplification, HER2 activation) or phenotypic transformation. We further evaluated contemporary diagnostic modalities for identifying resistance drivers and appraised emerging therapeutic strategies, including fourth-generation EGFR-TKI, various combination therapies, and antibody-drug conjugates (ADCs), and so forth, with emphasis on ongoing clinical trials that may transform the existing treatment paradigm. By synthesizing preclinical and clinical insights, this review aims to advance mechanistic understanding and propose therapeutic strategies to overcome acquired resistance to third-generation EGFR-TKI in first-line treatment.

Synthetic approaches for novel fused pyrimidine derivatives: Design, structural characterization, antiviral, antitumor, and molecular docking evaluation

The goal of this work was to synthesize new compounds for anticancer evaluation as a trial to obtain new antitumor agents with higher activity and fewer side effects. Therefore, the precursor 2,2'-(1,4-phenylenebis (thiazole-4,2-diyl))bis (3-(dimethylamino)acrylonitrile) (4) was used to synthesize various azolopyrimidine derivatives connected to the thiazole moiety. Compounds 5-11, including pyrazolopyrimidine, triazolopyrimidine, and others, were produced by reacting enaminonitrile 4 with different N-nucleophiles. Additionally, compounds 12-15, such as isoxazole and pyrimidinethione derivatives, were obtained by reacting compound 4 with guanidine, hydrazine hydrate, hydroxylamine hydrochloride, and thiourea. Enaminonitrile 4 was also treated with barbituric acid, isoxazolone, and pyrazolone to yield pyranopyrimidine derivatives 18-20. Moreover, enaminonitrile 4 reacts with C-nucleophiles namely ''acetylacetone, dimedone, 2-cyanomethylbenzothiazole, and 2-cyanomethylbenzimidazole'' to give pyrano derivatives 21, 22 and fused pyridone derivatives 23 and 24, respectively. The cytotoxic activity of 20 novel compounds against HSV-1, HIV-1, and various cancer cell lines was assessed, with compounds 5, 7, and 9 showing the strongest effects. Molecular docking studies further evaluated the binding affinity of these derivatives, with docking scores ranging from -7.8679 to -8.3013 kcal/mol. Several new azolopyrimidine derivatives linked to the thiazole moiety were effectively synthesized and assessed in the study, and they showed notable cytotoxic activity against HSV-1, HIV-1, and several cancer cell lines.

Immunoconjugates as an Efficient Platform for Drug Delivery: A Resurgence of Natural Products in Targeted Antitumor Therapy

The present review provides a detailed and comprehensive discussion on antibody-drug conjugates (ADCs) as an evolving new modality in the current therapeutic landscape of malignant diseases. The principle concepts of targeted delivery of highly toxic agents forsaken as stand-alone drugs are examined in detail, along with the biochemical and technological tools for their successful implementation. An extensive analysis of ADCs' major components is conducted in parallel with their function and impact on the stability, efficacy, safety, and resistance profiles of the immunoconjugates. The scope of the article covers the major classes of currently validated natural compounds used as payloads, with an emphasis on their structural and mechanistic features, natural origin, and distribution. Future perspectives in ADCs' design are thoroughly explored, addressing their inherent or emerging challenges and limitations. The survey also provides a comprehensive overview of the molecular rationale for active tumor targeting of ADC-based platforms, exploring the cellular biology and clinical relevance of validated tumor markers used as a "homing" mechanism in both hematological and solid tumor malignancies.

Extracellular proximal interaction profiling by cell surface-targeted TurboID reveals LDLR as a partner of liganded EGFR

Plasma membrane proteins play pivotal roles in receiving and transducing signals from other cells and from the environment and are vital for cellular functionality. Enzyme-based, proximity-dependent approaches, such as biotin identification (BioID), combined with mass spectrometry have begun to illuminate the landscape of proximal protein interactions within intracellular compartments. To extend the potential of these approaches to study the extracellular environment, we developed extracellular TurboID (ecTurboID), a method designed to profile the interactions between proteins on the surfaces of living cells over short timescales using the fast-acting biotin ligase TurboID. After optimizing our experimental and data analysis strategies to capture extracellular proximity interactions, we used ecTurboID to reveal the proximal interactomes of several plasma membrane proteins, including the epidermal growth factor receptor (EGFR). We found that EGF stimulation induced an association between EGFR and the low-density lipoprotein receptor (LDLR) and changed the interactome of LDLR by increasing its proximity with proteins that regulate EGFR signaling. The identification of this interaction between two well-studied and clinically relevant receptors illustrates the utility of our modified proximity labeling methodology for identifying dynamic extracellular associations between plasma membrane proteins.

Spatial and signaling overlap of growth factor receptor systems at clathrin-coated sites

Cellular communication is regulated at the plasma membrane by the interactions of receptor, adhesion, signaling, exocytic, and endocytic proteins. Yet, the composition and control of these complexes in response to external cues remain unclear. We use high-resolution and high-throughput fluorescence imaging to map the localization of growth factor receptors and related proteins at single clathrin-coated structures in human squamous HSC3 cells. We find distinct protein signatures between control cells and cells stimulated with growth factors. Clathrin sites at the plasma membrane are preloaded with some receptors but not others. Stimulation with epidermal growth factor induces capture and concentration of epidermal growth factor, fibroblast growth factor 1, and low-density lipoprotein receptor (EGFR, FGFR1, and LDLR). Regulatory proteins including ubiquitin ligase Cbl, the scaffold Grb2, and the mechanoenzyme dynamin2 are also recruited. Disrupting FGFR1 or EGFR activity with drugs prevents the recruitment of both EGFR and FGFR1. EGF was able to activate FGFR1 phosphorylation. Our data reveal novel coclustering and activation of receptors and regulatory factors at clathrin-coated sites in response to stimulation by a single growth factor, EGF or FGF. This behavior integrates growth factor signaling and allows for complex responses to extracellular cues and drugs at the plasma membrane of human cells.

Investigating underlying molecular mechanisms, signaling pathways, emerging therapeutic approaches in pancreatic cancer

Pancreatic adenocarcinoma, a clinically challenging malignancy constitutes a significant contributor to cancer-related mortality, characterized by an inherently poor prognosis. This review aims to provide a comprehensive understanding of pancreatic adenocarcinoma by examining its multifaceted etiologies, including genetic mutations and environmental factors. The review explains the complex molecular mechanisms underlying its pathogenesis and summarizes current therapeutic strategies, including surgery, chemotherapy, and emerging modalities such as immunotherapy. Critical molecular pathways driving pancreatic cancer development, including KRAS, Notch, and Hedgehog, are discussed. Current therapeutic strategies, including surgery, chemotherapy, and radiation, are discussed, with an emphasis on their limitations, particularly in terms of postoperative relapse. Promising research areas, including liquid biopsies, personalized medicine, and gene editing, are explored, demonstrating the significant potential for enhancing diagnosis and treatment. While immunotherapy presents promising prospects, it faces challenges related to immune evasion mechanisms. Emerging research directions, encompassing liquid biopsies, personalized medicine, CRISPR/Cas9 genome editing, and computational intelligence applications, hold promise for refining diagnostic approaches and therapeutic interventions. By integrating insights from genetic, molecular, and clinical research, innovative strategies that improve patient outcomes can be developed. Ongoing research in these emerging fields holds significant promise for advancing the diagnosis and treatment of this formidable malignancy.

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.

Nuclear Softness Promotes the Metastatic Potential of Large-Nucleated Colorectal Cancer Cells via the ErbB4-Akt1-Lamin A/C Signaling Pathway

Abnormal nuclear enlargement is a diagnostic and physical hallmark of malignant tumors. Large nuclei are positively associated with an increased risk of developing metastasis; however, a large nucleus is inevitably more resistant to cell migration due to its size. The present study demonstrated that the nuclear size of primary colorectal cancer (CRC) cells at an advanced stage was larger than cells at an early stage. In addition, the nuclei of CRC liver metastases were larger than those of the corresponding primary CRC tissues. CRC cells were sorted into large-nucleated cells (LNCs) and small-nucleated cells (SNCs). Purified LNCs exhibited greater constricted migratory and metastatic capacity than SNCs in vitro and in vivo. Mechanistically, ErbB4 was highly expressed in LNCs, which phosphorylated lamin A/C at serine 22 via the ErbB4-Akt1 signaling pathway. Furthermore, the level of phosphorylated lamin A/C was a negative determinant of nuclear stiffness. Taken together, CRC LNCs possessed greater constricted migratory and metastatic potential than SNCs due to ErbB4-Akt1-mediated lamin A/C phosphorylation and nuclear softening. These results may provide a potential treatment strategy for tumor metastasis by targeting nuclear stiffness in patients with cancer, particularly CRC.

The state of the art of EGFR exon 20 insertions in non-small cell lung cancer: Diagnosis and future perspectives

Insertions in the epidermal growth factor receptor (EGFR) exon 20 (Ex20Ins) are the third most incident mutations in non-small cell lung cancer (NSCLC). The hypervariable nature of these driver mutations hinders their identification by traditional polymerase chain reaction (PCR)-based methods, requiring a comprehensive sequencing approach to detect all possible insertions. The prognosis of patients with EGFR Ex20Ins is similar to those with wild-type NSCLC, since no targeted drugs are approved in the first-line setting, and platinum-based chemotherapy is currently the front-line treatment. However, the new generation of drugs currently being tested in first and post-platinum settings will likely change the management of this entity. Here, we summarize the latest data on EGFR Ex20Ins molecular characteristics, patient profile, identification challenges, and emerging therapies to help lung clinicians face a growing treatment landscape.

Host-derived growth factors drive ERK phosphorylation and MCL1 expression to promote osteosarcoma cell survival during metastatic lung colonization

PURPOSE

For patients with osteosarcoma, disease-related mortality most often results from lung metastasis-a phenomenon shared with many solid tumors. While established metastatic lesions behave aggressively, very few of the tumor cells that reach the lung will survive. By identifying mechanisms that facilitate survival of disseminated tumor cells, we can develop therapeutic strategies that prevent and treat metastasis.

METHODS

We analyzed single cell RNA-sequencing (scRNAseq) data from murine metastasis-bearing lungs to interrogate changes in both host and tumor cells during colonization. We used these data to elucidate pathways that become activated in cells that survive dissemination and identify candidate host-derived signals that drive activation. We validated these findings through live cell reporter systems, immunocytochemistry, and fluorescent immunohistochemistry. We then validated the functional relevance of key candidates using pharmacologic inhibition in models of metastatic osteosarcoma.

RESULTS

Expression patterns suggest that the MAPK pathway is significantly elevated in early and established metastases. MAPK activity correlates with expression of anti-apoptotic genes, especially MCL1. Niche cells produce growth factors that increase ERK phosphorylation and MCL1 expression in tumor cells. Both early and established metastases are vulnerable to MCL1 inhibition, but not MEK inhibition in vivo. Combining MCL1 inhibition with chemotherapy both prevented colonization and eliminated established metastases in murine models of osteosarcoma.

CONCLUSION

Niche-derived growth factors drive MAPK activity and MCL1 expression in osteosarcoma, promoting metastatic colonization. Although later metastases produce less MCL1, they remain dependent on it. MCL1 is a promising target for clinical trials in both human and canine patients.

Cost in the United States of FDA-approved small molecule protein kinase inhibitors used in the treatment of neoplastic and non-neoplastic diseases

Because genetic alterations including mutations, overexpression, translocations, and dysregulation of protein kinases are involved in the pathogenesis of many illnesses, this enzyme family is the target of many drug discovery programs worldwide. The FDA has approved 80 small molecule protein kinase inhibitors with 77 drugs orally bioavailable. The data indicate that 69 of these medicinals are approved for the management of neoplasms including solid tumors such as breast and lung cancer as well as non-solid tumors such as leukemia. Moreover, the remaining 11 drugs target non-neoplastic diseases including psoriasis, rheumatoid arthritis, and ulcerative colitis. The cost of drugs was obtained from www.pharmacychecker.com using the FDA label to determine the dosage and number of tablets required per day. This methodology excludes any private or governmental insurance coverage, which would cover the entire cost or more likely a fraction of the stated price. The average monthly cost for the treatment of neoplastic diseases was $17,900 with a price of $44,000 for futibatinib (used to treat cholangiocarcinomas with FGFR2 fusions) and minimum of $5100 for binimetinib (melanoma). The average monthly cost for the treatment of non-neoplastic diseases was $6800 with a maximum of $17,000 for belumosudil (graft vs. host disease) and a minimum of $200 for netarsudil eye drops (glaucoma). There is a negative correlation of the cost of the drugs and the incidence of the targeted disease. Many of these agents are or were designated as orphan drugs meaning that there are fewer than 200,000 potential patients in the United States.

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.

Oxidised IL-33 drives COPD epithelial pathogenesis via ST2-independent RAGE/EGFR signalling complex

BACKGROUND

Epithelial damage, repair and remodelling are critical features of chronic airway diseases including chronic obstructive pulmonary disease (COPD). Interleukin (IL)-33 released from damaged airway epithelia causes inflammation via its receptor, serum stimulation-2 (ST2). Oxidation of IL-33 to a non-ST2-binding form (IL-33ox) is thought to limit its activity. We investigated whether IL-33ox has functional activities that are independent of ST2 in the airway epithelium.

METHODS

In vitro epithelial damage assays and three-dimensional, air-liquid interface (ALI) cell culture models of healthy and COPD epithelia were used to elucidate the functional role of IL-33ox. Transcriptomic changes occurring in healthy ALI cultures treated with IL-33ox and COPD ALI cultures treated with an IL-33-neutralising antibody were assessed with bulk and single-cell RNA sequencing analysis.

RESULTS

We demonstrate that IL-33ox forms a complex with receptor for advanced glycation end products (RAGE) and epidermal growth factor receptor (EGFR) expressed on airway epithelium. Activation of this alternative, ST2-independent pathway impaired epithelial wound closure and induced airway epithelial remodelling in vitro. IL-33ox increased the proportion of mucus-producing cells and reduced epithelial defence functions, mimicking pathogenic traits of COPD. Neutralisation of the IL-33ox pathway reversed these deleterious traits in COPD epithelia. Gene signatures defining the pathogenic effects of IL-33ox were enriched in airway epithelia from patients with severe COPD.

CONCLUSIONS

Our study reveals for the first time that IL-33, RAGE and EGFR act together in an ST2-independent pathway in the airway epithelium and govern abnormal epithelial remodelling and muco-obstructive features in COPD.

Allosteric inhibition of the epidermal growth factor receptor through disruption of transmembrane interactions

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase (RTK) commonly targeted for inhibition by anticancer therapeutics. Current therapeutics target EGFR's kinase domain or extracellular region. However, these types of inhibitors are not specific for tumors over healthy tissue and therefore cause undesirable side effects. Our lab has recently developed a new strategy to regulate RTK activity by designing a peptide that specifically binds to the transmembrane (TM) region of the RTK to allosterically modify kinase activity. These peptides are acidity-responsive, allowing them to preferentially target acidic environments like tumors. We have applied this strategy to EGFR and created the PET1 peptide. We observed that PET1 behaves as a pH-responsive peptide that modulates the configuration of the EGFR TM through a direct interaction. Our data indicated that PET1 inhibits EGFR-mediated cell migration. Finally, we investigated the mechanism of inhibition through molecular dynamics simulations, which showed that PET1 sits between the two EGFR TM helices; this molecular mechanism was additionally supported by AlphaFold-Multimer predictions. We propose that the PET1-induced disruption of native TM interactions disturbs the conformation of the kinase domain in such a way that it inhibits EGFR's ability to send migratory cell signals. This study is a proof-of-concept that acidity-responsive membrane peptide ligands can be generally applied to RTKs. In addition, PET1 constitutes a viable approach to therapeutically target the TM of EGFR.

Pharmacokinetic/Pharmacodynamic Analysis of Savolitinib plus Osimertinib in an EGFR Mutation-Positive, MET-Amplified Non-Small Cell Lung Cancer Model

Osimertinib is a third-generation, irreversible, oral EGFR tyrosine kinase inhibitor (TKI) recommended as first-line treatment for patients with locally advanced/metastatic EGFR mutation-positive (EGFRm) non-small cell lung cancer (NSCLC). However, MET amplification/overexpression is a common acquired osimertinib resistance mechanism. Savolitinib is an oral, potent, and highly selective MET-TKI; preliminary data suggest that combining osimertinib with savolitinib may overcome MET-driven resistance. A patient-derived xenograft (PDX) mouse model with EGFRm, MET-amplified NSCLC was tested with a fixed osimertinib dose [10 mg/kg for exposures equivalent to (≈)80 mg], combined with doses of savolitinib (0-15 mg/kg, ≈0-600 mg once daily), both with 1-aminobenzotriazole (to better match clinical half-life). After 20 days of oral dosing, samples were taken at various time points to follow the time course of drug exposure in addition to phosphorylated MET and EGFR (pMET and pEGFR) change. Population pharmacokinetics, savolitinib concentration versus percentage inhibition from baseline in pMET, and the relationship between pMET and tumor growth inhibition (TGI) were also modeled. As single agents, savolitinib (15 mg/kg) showed significant antitumor activity, reaching ∼84% TGI, and osimertinib (10 mg/kg) showed no significant antitumor activity (34% TGI, P > 0.05 vs. vehicle). Upon combination, at a fixed dose of osimertinib, significant savolitinib dose-related antitumor activity was shown, ranging from 81% TGI (0.3 mg/kg) to 84% tumor regression (15 mg/kg). Pharmacokinetic-pharmacodynamic modeling showed that the maximum inhibition of both pEGFR and pMET increased with increasing savolitinib doses. Savolitinib demonstrated exposure-related combination antitumor activity when combined with osimertinib in the EGFRm MET-amplified NSCLC PDX model.

Recent findings on the impact of ErbB receptors status on prognosis and therapy of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer type, has often an aggressive course and is poorly responsive to current therapeutic approaches, so that 5-year survival rates for patients diagnosed with advanced disease is lower than 50%. The Epidermal Growth Factor Receptor (EGFR) has emerged as an established oncogene in HNSCC. Indeed, although HNSCCs are a heterogeneous group of cancers which differ for histological, molecular and clinical features, EGFR is overexpressed or mutated in a percentage of cases up to about 90%. Moreover, aberrant expression of the other members of the ErbB receptor family, ErbB2, ErbB3 and ErbB4, has also been reported in variable proportions of HNSCCs. Therefore, an increased expression/activity of one or multiple ErbB receptors is found in the vast majority of patients with HNSCC. While aberrant ErbB signaling has long been known to play a critical role in tumor growth, angiogenesis, invasion, metastatization and resistance to therapy, more recent evidence has revealed its impact on other features of cancer cells' biology, such as the ability to evade antitumor immunity. In this paper we will review recent findings on how ErbB receptors expression and activity, including that associated with non-canonical signaling mechanisms, impacts on prognosis and therapy of HNSCC.

Design, synthesis and Molecular modeling study of certain EGFRinhibitors with a quinazolinone scaffold as anti-hepatocellular carcinoma and Radio-sensitizers

A set of novel N-substituted-2-((4-oxo-3-phenyl-3,4-dihydroquinazolin-2-yl)thio)acetamide 3-16 were designed and synthesized from 2-mercapto-3-phenylquinazolinone 2. The targeted compounds were screened for their cytotoxic activity against the hepatocellular carcinoma cell line HepG-2. Compounds 8, 9, 10, and 11 with IC₅₀ values of 1.11, 4.28, 5.70, and 4.69 µM, respectively, showed 5.7- to 28-fold higher activities than the positive control doxorubicin (IC₅₀ 32.02 µM). Furthermore, compounds 8 and 9 were tested for EGFR inhibitory activity and demonstrated IC₅₀ values of 73.23 and 58.26  µM, respectively, when compared to erlotinib's IC₅₀ value of 9.79 µM. The most potent compounds, 8 and 9, were subjected to a single dose of 8 Gy of γ-radiation, and their cytotoxic efficacy was found to increase after irradiation, demonstrating the synergistic effect of γ-irradiation. Molecular docking was adopted for the most active compounds to confirm their mode of action.

HER3 Alterations in Cancer and Potential Clinical Implications

In recent years, the third member of the HER family, kinase impaired HER3, has become a target of interest in cancer as there is accumulating evidence that HER3 plays a role in tumor growth and progression. This review focuses on HER3 activation in bladder, breast, colorectal, and lung cancer disease progression. HER3 mutations occur at a rate up to ~10% of tumors dependent on the tumor type. With patient tumors routinely sequenced for gene alterations in recent years, we have focused on HER3 mutations in bladder, breast, colon, and lung cancers particularly in response to targeted therapies and the potential to become a resistance mechanism. There are currently several HER3 targeting drugs in the pipeline, possibly improving outcomes for cancer patients with tumors containing HER3 activation and/or alterations.

Control of cell metabolism by the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) triggers the activation of many intracellular signals that control cell proliferation, growth, survival, migration, and differentiation. Given its wide expression, EGFR has many functions in development and tissue homeostasis. Some of the cellular outcomes of EGFR signaling involve alterations of specific aspects of cellular metabolism, and alterations of cell metabolism are emerging as driving influences in many physiological and pathophysiological contexts. Here we review the mechanisms by which EGFR regulates cell metabolism, including by modulation of gene expression and protein function leading to control of glucose uptake, glycolysis, biosynthetic pathways branching from glucose metabolism, amino acid metabolism, lipogenesis, and mitochondrial function. We further examine how this regulation of cell metabolism by EGFR may contribute to cell proliferation and differentiation and how EGFR-driven control of metabolism can impact certain diseases and therapy outcomes.

Phytochemicals Derived from Goniothalamus elegans Ast Exhibit Anticancer Activity by Inhibiting Epidermal Growth Factor Receptor

Cancer is a major health burden and a leading cause of death worldwide, with numerous new molecules being studied and developed as therapeutic agents. In this study, the cytotoxicity of compounds derived from Goniothalamus elegans was evaluated for possible anticancer activity. It was observed that the crude methanol extract of G. elegans exerted the strongest cytotoxic activity against SW-480, AGS, and SK-LU-1 cell lines. In addition, two isolated alkaloids—namely, lysicamine and liriodenine—also showed strong inhibitory ability against similar cancer cell lines. To further investigate the compounds’ mechanism of action, a molecular docking approach was utilized to evaluate the potential of the two candidates to interact with the epidermal growth factor receptor. This assay estimated that lysicamine and liriodenine acquired protein binding affinities of −8.8 and −9.7 kcal/mol, respectively. Finally, the stabilities of the ligand–protein complexes were evaluated using molecular dynamics simulations of 100 ns each.

Thiosemicarbazones and selected tyrosine kinase inhibitors synergize in pediatric solid tumors: NDRG1 upregulation and impaired prosurvival signaling in neuroblastoma cells

Tyrosine kinase inhibitors (TKIs) are frequently used in combined therapy to enhance treatment efficacy and overcome drug resistance. The present study analyzed the effects of three inhibitors, sunitinib, gefitinib, and lapatinib, combined with iron-chelating agents, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) or di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC). Simultaneous administration of the drugs consistently resulted in synergistic and/or additive activities against the cell lines derived from the most frequent types of pediatric solid tumors. The results of a detailed analysis of cell signaling in the neuroblastoma cell lines revealed that TKIs inhibited the phosphorylation of the corresponding receptor tyrosine kinases, and thiosemicarbazones downregulated the expression of epidermal growth factor receptor, platelet-derived growth factor receptor, and insulin-like growth factor-1 receptor, leading to a strong induction of apoptosis. Marked upregulation of the metastasis suppressor N-myc downstream regulated gene-1 (NDRG1), which is known to be activated and upregulated by thiosemicarbazones in adult cancers, was also detected in thiosemicarbazone-treated neuroblastoma cells. Importantly, these effects were more pronounced in the cells treated with drug combinations, especially with the combinations of lapatinib with thiosemicarbazones. Therefore, these results provide a rationale for novel strategies combining iron-chelating agents with TKIs in therapy of pediatric solid tumors.

Depleting receptor tyrosine kinases EGFR and HER2 overcomes resistance to EGFR inhibitors in colorectal cancer

BACKGROUND

Epidermal growth factor receptor (EGFR) inhibitors, including cetuximab and panitumumab, are valuable therapeutics for colorectal cancer (CRC), but resistance to these inhibitors is common. The reason for such resistance is not well understood, which hampers development of better therapeutic strategies. Although activating mutations in KRAS, BRAF and PIK3CA are considered major drivers of CRC resistance to EGFR inhibitors, therapeutic targeting of these drug resistance drivers has not produced substantial clinical benefit.

METHODS

We exploited cell lines and mouse tumor models (cell line xenografts and patient derived xenografts) for experiments of genetic and pharmacologic depletion of EGFR and/or its family member HER2, including EGFR mutants, inhibition of EGFR ligand shedding, and biochemical analysis of signaling proteins, to delineate the mechanism of CRC resistance to EGFR inhibitors and to assess the therapeutic activity of PEPDG278D, which is a recombinant human protein that induces the degradation of both EGFR and HER2.

RESULTS

The sensitivity of CRC cells to cetuximab and panitumumab correlates with the ability of these drugs to induce EGFR downregulation. PEPDG278D strongly inhibits oncogenic signaling and growth of CRC cells by causing profound depletion of EGFR and HER2, regardless of activating mutations of KRAS, BRAF and PIK3CA. siRNA knockdown of EGFR or HER2 also inhibits CRC cells resistant to EGFR inhibitors. Tumors harboring mutated KRAS, BRAF and/or PIK3CA also overexpress EGFR ligands, further suggesting that EGFR signaling remains important to the tumors. While excessive tumor-generated high-affinity EGFR ligands block target engagement by PEPDG278D, aderbasib, an inhibitor of ADAM10 and ADAM17, enables PEPDG278D to exert strong antitumor activity by inhibiting ligand shedding. Moreover, adding fluorouracil, which is commonly used in CRC treatment, to the combination of PEPDG278D and aderbasib further enhances tumor inhibition.

CONCLUSIONS

Our study shows that CRC resistance to EGFR inhibitors results primarily from the inability of the inhibitors to downregulate their target and that a PEPDG278D-based combination treatment overcomes the resistance.

Bioluminescent RAPPID Sensors for the Single-Step Detection of Soluble Axl and Multiplex Analysis of Cell Surface Cancer Biomarkers

Early diagnosis of cancer is essential for the efficacy of treatment. Our group recently developed RAPPID, a bioluminescent immunoassay platform capable of measuring a wide panel of biomarkers directly in solution. Here, we developed and systematically screened different RAPPID sensors for sensitive detection of the soluble fraction of Axl (sAxl), a cell surface receptor that is overexpressed in several types of cancer. The best-performing RAPPID sensor, with a limit of detection of 8 pM and a >9-fold maximal change in emission ratio, was applied to measure Axl in three different contexts: clinically relevant sAxl levels (∼0.5 and ∼1 nM) in diluted blood plasma, proteolytically cleaved Axl in the cell culture medium of A431 and HeLa cancer cells, and Axl on the membrane of A431 cells. We further extended the sensor toolbox by developing dual-color RAPPID for simultaneous detection of Axl and EGFR on A431 and HeLa cells, as well as an AND-gate RAPPID that measures the concurrent presence of these two cell surface receptors on the same cell. These new RAPPID sensors provide attractive alternatives for more laborious protein detection and quantification methods such as FACS and immunostainings, due to their simple practical implantation and low intrinsic background signal.

EGFR signaling pathway as therapeutic target in human cancers

Epidermal Growth Factor Receptor (EGFR) enacts major roles in the maintenance of epithelial tissues. However, when EGFR signaling is altered, it becomes the grand orchestrator of epithelial transformation, and hence one of the most world-wide studied tyrosine kinase receptors involved in neoplasia, in several tissues. In the last decades, EGFR-targeted therapies shaped the new era of precision-oncology. Despite major advances, the dream of converting solid tumors into a chronic disease is still unfulfilled, and long-term remission eludes us. Studies investigating the function of this protein in solid malignancies have revealed numerous ways how tumor cells dysregulate EGFR function. Starting from preclinical models (cell lines, organoids, murine models) and validating in clinical specimens, EGFR-related oncogenic pathways, mechanisms of resistance, and novel avenues to inhibit tumor growth and metastatic spread enriching the therapeutic portfolios, were identified. Focusing on non-small cell lung cancer (NSCLC), where EGFR mutations are major players in the adenocarcinoma subtype, we will go over the most relevant discoveries that led us to understand EGFR and beyond, and highlight how they revolutionized cancer treatment by expanding the therapeutic arsenal at our disposal.

Imaging Endocytosis Dynamics in Health and Disease

Endocytosis is a critical process for cell growth and viability. It mediates nutrient uptake, guarantees plasma membrane homeostasis, and generates intracellular signaling cascades. Moreover, it plays an important role in dead cell clearance and defense against external microbes. Finally, endocytosis is an important cellular route for the delivery of nanomedicines for therapeutic treatments. Thus, it is not surprising that both environmental and genetic perturbation of endocytosis have been associated with several human conditions such as cancer, neurological disorders, and virus infections, among others. Over the last decades, a lot of research has been focused on developing advanced imaging methods to monitor endocytosis events with high resolution in living cells and tissues. These include fluorescence imaging, electron microscopy, and correlative and super-resolution microscopy. In this review, we outline the major endocytic pathways and briefly discuss how defects in the molecular machinery of these pathways lead to disease. We then discuss the current imaging methodologies used to study endocytosis in different contexts, highlighting strengths and weaknesses.

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.

Functional signaling test identifies HER2 negative breast cancer patients who may benefit from c-Met and pan-HER combination therapy

Background

Research is revealing the complex coordination between cell signaling systems as they adapt to genetic and epigenetic changes. Tools to uncover these highly complex functional linkages will play an important role in advancing more efficacious disease treatments. Current tumor cell signal transduction research is identifying coordination between receptor types, receptor families, and transduction pathways to maintain tumor cell viability despite challenging tumor microenvironment conditions.

Methods

In this report, coactivated abnormal levels of signaling activity for c-Met and HER family receptors in live tumor cells were measured by a new clinical test to identify a subpopulation of breast cancer patients that could be responsive to combined targeted therapies. The CELsignia Multi-Pathway Signaling Function (CELsignia) Test uses an impedance biosensor to quantify an individual patient’s ex vivo live tumor cell signaling response in real-time to specific HER family and c-Met co-stimulation and targeted therapies.

Results

The test identified breast tumors with hyperactive HER1, HER2, HER3/4, and c-Met coordinated signaling that express otherwise normal amounts of these receptors. The supporting data of the pre-clinical verification of this test included analyses of 79 breast cancer patients’ cell response to HER and c-Met agonists. The signaling results were confirmed using clinically approved matching targeted drugs, and combinations of targeted drugs in addition to correlative mouse xenograft tumor response to HER and c-Met targeted therapies.

Conclusions

The results of this study demonstrated the potential benefit of a functional test for identifying a subpopulation of breast cancer patients with coordinated abnormal HER and c-Met signaling for a clinical trial testing combination targeted 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.

Quantification of EGFR-HER2 Heterodimers in HER2-Overexpressing Breast Cancer Cells Using Liquid-Phase Electron Microscopy

Currently, breast cancer patients are classified uniquely according to the expression level of hormone receptors, and human epidermal growth factor receptor 2 (HER2). This coarse classification is insufficient to capture the phenotypic complexity and heterogeneity of the disease. A methodology was developed for absolute quantification of receptor surface density ρ_R, and molecular interaction (dimerization), as well as the associated heterogeneities, of HER2 and its family member, the epidermal growth factor receptor (EGFR) in the plasma membrane of HER2 overexpressing breast cancer cells. Quantitative, correlative light microscopy (LM) and liquid-phase electron microscopy (LPEM) were combined with quantum dot (QD) labeling. Single-molecule position data of receptors were obtained from scanning transmission electron microscopy (STEM) images of intact cancer cells. Over 280,000 receptor positions were detected and statistically analyzed. An important finding was the subcellular heterogeneity in heterodimer shares with respect to plasma membrane regions with different dynamic properties. Deriving quantitative information about EGFR and HER2 ρ_R, as well as their dimer percentages, and the heterogeneities thereof, in single cancer cells, is potentially relevant for early identification of patients with HER2 overexpressing tumors comprising an enhanced share of EGFR dimers, likely increasing the risk for drug resistance, and thus requiring additional targeted therapeutic strategies.

Plasma Metabolome Profiling by High-Performance Chemical Isotope-Labelling LC-MS after Acute and Medium-Term Intervention with Golden Berry Fruit (Physalis peruviana L.), Confirming Its Impact on Insulin-Associated Signaling Pathways

Purpose: Golden berry (Physalis peruviana L.) is an exotic fruit exported from Colombia to different countries around the world. A review of the literature tends to demonstrate a hypoglycaemic effect with an improvement in insulin sensitivity after oral ingestion of fruit extracts in animal models. However, little is known about their potential effects in humans, and very little is known about the mechanisms involved. This study aimed at identifying discriminant metabolites after acute and chronic intake of golden berry. Method: An untargeted metabolomics strategy using high-performance chemical isotope-labelling LC-MS was applied. The blood samples of eighteen healthy adults were analysed at baseline, at 6 h after the intake of 250 g of golden berry (acute intervention), and after 19 days of daily consumption of 150 g (medium-term intervention). Results: Forty-nine and 36 discriminant metabolites were identified with high confidence, respectively, after the acute and medium-term interventions. Taking into account up- and downregulated metabolites, three biological networks mainly involving insulin, epidermal growth factor receptor (EGFR), and the phosphatidylinositol 3-kinase pathway (PI3K/Akt/mTOR) were identified. Conclusions: The biological intracellular networks identified are highly interconnected with the insulin signalling pathway, showing that berry intake may be associated with insulin signalling, which could reduce some risk factors related to metabolic syndrome. Primary registry of WHO.

Prognostic features of the tumour microenvironment in oesophageal adenocarcinoma

Oesophageal adenocarcinoma (OAC) is a disease with an incredibly poor survival rate and a complex makeup. The growth and spread of OAC tumours are profoundly influenced by their surrounding microenvironment and the properties of the tumour itself. Constant crosstalk between the tumour and its microenvironment is key to the survival of the tumour and ultimately the death of the patient. The tumour microenvironment (TME) is composed of a complex milieu of cell types including cancer associated fibroblasts (CAFs) which make up the tumour stroma, endothelial cells which line blood and lymphatic vessels and infiltrating immune cell populations. These various cell types and the tumour constantly communicate through environmental cues including fluctuations in pH, hypoxia and the release of mitogens such as cytokines, chemokines and growth factors, many of which help promote malignant progression. Eventually clusters of tumour cells such as tumour buds break away and spread through the lymphatic system to nearby lymph nodes or enter the circulation forming secondary metastasis. Collectively, these factors need to be considered when assessing and treating patients clinically. This review aims to summarise the ways in which these various factors are currently assessed and how they relate to patient treatment and outcome at an individual level.

Design, Synthesis and Biological Evaluation of Novel Pyrazolo[1,2,4]triazolopyrimidine Derivatives as Potential Anticancer Agents

Three novel pyrazolo-[4,3-e][1,2,4]triazolopyrimidine derivatives (1, 2, and 3) were designed, synthesized, and evaluated for their in vitro biological activity. All three compounds exhibited different levels of cytotoxicity against cervical and breast cancer cell lines. However, compound 1 showed the best antiproliferative activity against all tested tumor cell lines, including HCC1937 and HeLa cells, which express high levels of wild-type epidermal growth factor receptor (EGFR). Western blot analyses demonstrated that compound 1 inhibited the activation of EGFR, protein kinase B (Akt), and extracellular signal-regulated kinase (Erk)1/2 in breast and cervical cancer cells at concentrations of 7 and 11 µM, respectively. The results from docking experiments with EGFR suggested the binding of compound 1 at the ATP binding site of EGFR. Furthermore, the crystal structure of compound 3 (7-(4-bromophenyl)-9-(pyridin-4-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine) was determined by single crystal X-ray analysis. Our work represents a promising starting point for the development of a new series of compounds targeting EGFR.

Fibroblast Growth Factor Receptors (FGFRs) and Noncanonical Partners in Cancer Signaling

Increasing evidence indicates that success of targeted therapies in the treatment of cancer is context-dependent and is influenced by a complex crosstalk between signaling pathways and between cell types in the tumor. The Fibroblast Growth Factor (FGF)/FGF receptor (FGFR) signaling axis highlights the importance of such context-dependent signaling in cancer. Aberrant FGFR signaling has been characterized in almost all cancer types, most commonly non-small cell lung cancer (NSCLC), breast cancer, glioblastoma, prostate cancer and gastrointestinal cancer. This occurs primarily through amplification and over-expression of FGFR1 and FGFR2 resulting in ligand-independent activation. Mutations and translocations of FGFR1-4 are also identified in cancer. Canonical FGF-FGFR signaling is tightly regulated by ligand-receptor combinations as well as direct interactions with the FGFR coreceptors heparan sulfate proteoglycans (HSPGs) and Klotho. Noncanonical FGFR signaling partners have been implicated in differential regulation of FGFR signaling. FGFR directly interacts with cell adhesion molecules (CAMs) and extracellular matrix (ECM) proteins, contributing to invasive and migratory properties of cancer cells, whereas interactions with other receptor tyrosine kinases (RTKs) regulate angiogenic, resistance to therapy, and metastatic potential of cancer cells. The diversity in FGFR signaling partners supports a role for FGFR signaling in cancer, independent of genetic aberration.

Elucidation of host-virus surfaceome interactions using spatial proteotyping

The cellular surfaceome and its residing extracellularly exposed proteins are involved in a multitude of molecular signaling processes across the viral infection cycle. Successful viral propagation, including viral entry, immune evasion, virion release and viral spread rely on dynamic molecular interactions with the surfaceome. Decoding of these viral-host surfaceome interactions using advanced technologies enabled the discovery of fundamental new functional insights into cellular and viral biology. In this review, we highlight recently developed experimental strategies, with a focus on spatial proteotyping technologies, aiding in the rational design of theranostic strategies to combat viral infections.

Thirty Years of HER3: From Basic Biology to Therapeutic Interventions

HER3 is a pseudokinase member of the EGFR family having a role in both tumor progression and drug resistance. Although HER3 was discovered more than 30 years ago, no therapeutic interventions have reached clinical approval to date. Because the evidence of the importance of HER3 is accumulating, increased amounts of preclinical and clinical trials with HER3-targeting agents are emerging. In this review article, we discuss the most recent HER3 biology in tumorigenic events and drug resistance and provide an overview of the current and emerging strategies to target HER3.

Orally effective FDA-approved protein kinase targeted covalent inhibitors (TCIs)

Because dysregulation of protein kinases owing to mutations or overexpression plays causal roles in human diseases, this family of enzymes has become one of the most important drug targets of the 21st century. Of the 62 protein kinases inhibitors that are approved by the FDA, seven of them form irreversible covalent adducts with their target enzymes. The clinical success of ibrutinib, an inhibitor of Bruton tyrosine kinase, in the treatment of mantle cell lymphomas following its approval in 2013 helped to overcome a general bias against the development of irreversible drug inhibitors. The other approved covalent drugs include acalabrutinib and zanubrutinib, which also inhibit Bruton tyrosine kinase. Furthermore afatinib, dacomitinib, and osimertinib, inhibitors of members of the epidermal growth factor receptor family (ErbB1/2/3/4), are used in the treatment of non-small cell lung cancers. Neratinib is an inhibitor of ErbB2 and is used in the treatment of ErbB2/HER2-positive breast cancer. The seven drugs considered in this review have a common mechanism of action; this process involves the addition of a protein cysteine thiolate anion (protein‒S:^-) to an acrylamide derivative (CH₂=CHC(=O)N(H)R) where R represents the pharmacophore. Such reactions are commonly referred to as Michael additions and each reaction results in the formation of a covalent bond between carbon and sulfur; the final product is a thioether. This process consists of two discrete steps; the first step involves the reversible association of the drug with its target enzyme so that a weakly electrophilic functionality, a warhead, is bound near an appropriately positioned nucleophilic cysteine. In the second step, a reaction occurs between the warhead and the target enzyme cysteine to form a covalently modified and inactive protein. For this process to work, the warhead must be appropriately juxtaposed in relationship to the cysteinyl thiolate so that the covalent addition can occur. Covalent inhibitors have emerged from the ranks of drugs to be avoided to become an emerging paradigm. Much of this recent success can be attributed to the clinical efficacy of ibrutinib as well as the other antagonists covered in this review. Moreover, the covalent inhibitor methodology is swiftly gaining acceptance as a valuable component of the medicinal chemist's toolbox and is primed to make a significant impact on the development of enzyme antagonists and receptor modulators.

Engineering AvidCARs for combinatorial antigen recognition and reversible control of CAR function

T cells engineered to express chimeric antigen receptors (CAR-T cells) have shown impressive clinical efficacy in the treatment of B cell malignancies. However, the development of CAR-T cell therapies for solid tumors is hampered by the lack of truly tumor-specific antigens and poor control over T cell activity. Here we present an avidity-controlled CAR (AvidCAR) platform with inducible and logic control functions. The key is the combination of (i) an improved CAR design which enables controlled CAR dimerization and (ii) a significant reduction of antigen-binding affinities to introduce dependence on bivalent interaction, i.e. avidity. The potential and versatility of the AvidCAR platform is exemplified by designing ON-switch CARs, which can be regulated with a clinically applied drug, and AND-gate CARs specifically recognizing combinations of two antigens. Thus, we expect that AvidCARs will be a highly valuable platform for the development of controllable CAR therapies with improved tumor specificity.

New analysis pipeline for high-throughput domain-peptide affinity experiments improves SH2 interaction data

Protein domain interactions with short linear peptides, such as those of the Src homology 2 (SH2) domain with phosphotyrosine-containing peptide motifs (pTyr), are ubiquitous and important to many biochemical processes of the cell. The desire to map and quantify these interactions has resulted in the development of high-throughput (HTP) quantitative measurement techniques, such as microarray or fluorescence polarization assays. For example, in the last 15 years, experiments have progressed from measuring single interactions to covering 500,000 of the 5.5 million possible SH2-pTyr interactions in the human proteome. However, high variability in affinity measurements and disagreements about positive interactions between published data sets led us here to reevaluate the analysis methods and raw data of published SH2-pTyr HTP experiments. We identified several opportunities for improving the identification of positive and negative interactions and the accuracy of affinity measurements. We implemented model-fitting techniques that are more statistically appropriate for the nonlinear SH2-pTyr interaction data. We also developed a method to account for protein concentration errors due to impurities and degradation or protein inactivity and aggregation. Our revised analysis increases the reported affinity accuracy, reduces the false-negative rate, and increases the amount of useful data by adding reliable true-negative results. We demonstrate improvement in classification of binding versus nonbinding when using machine-learning techniques, suggesting improved coherence in the reanalyzed data sets. We present revised SH2-pTyr affinity results and propose a new analysis pipeline for future HTP measurements of domain-peptide interactions.

Involvement of the epidermal growth factor receptor in IL-13-mediated corticosteroid-resistant airway inflammation

BACKGROUND

Effective treatment for severe asthma is a significant unmet need. While eosinophilic inflammation caused by type 2 cytokines is responsive to corticosteroid and biologic therapies, many severe asthmatics exhibit corticosteroid-unresponsive mixed granulocytic inflammation.

OBJECTIVE

Here, we tested the hypothesis that the pro-allergic cytokine, IL-13, can drive both corticosteroid-sensitive and corticosteroid-resistant responses.

RESULTS

By integration of in vivo and in vitro models of IL-13-driven inflammation, we identify a role for the epidermal growth factor receptor (EGFR/ERBB1) as a mediator of corticosteroid-unresponsive inflammation and bronchial hyperresponsiveness driven by IL-13. Topological data analysis using human epithelial transcriptomic data from the U-BIOPRED cohort identified severe asthma groups with features consistent with the presence of IL-13 and EGFR/ERBB activation, with involvement of distinct EGFR ligands. Our data suggest that IL-13 may play a dual role in severe asthma: on the one hand driving pathologic corticosteroid-refractory mixed granulocytic inflammation, but on the other hand underpinning beneficial epithelial repair responses, which may confound responses in clinical trials.

CONCLUSION AND CLINICAL RELEVANCE

Detailed dissection of those molecular pathways that are downstream of IL-13 and utilize the ERBB receptor and ligand family to drive corticosteroid-refractory inflammation should enhance the development of new treatments that target this sub-phenotype(s) of severe asthma, where there is an unmet need.

Multiple Growth Factor Targeting by Engineered Insulin-like Growth Factor Binding Protein-3 Augments EGF Receptor Tyrosine Kinase Inhibitor Efficacy

Resistance to cancer therapy is a challenge because of innate tumor heterogeneity and constant tumor evolution. Since the pathway of resistance cannot be predicted, combination therapies may address this progression. We discovered that in addition to IGF1 and IGF2, IGFBP-3 binds bFGF, HGF, neuregulin, and PDGF AB with nanomolar affinity. Because growth factors drive resistance, simultaneous inhibition of multiple growth factor pathways may improve the efficacy of precision therapy. Growth factor sequestration by IGFBP-3-Fc enhances the activity of EGFR inhibitors by decreasing cell survival and inhibiting bFGF, HGF, and IGF1 growth factor rescue and also potentiates the activity of other cancer drugs. Inhibition of tumor growth in vivo with adjuvant IGFBP-3-Fc with erlotinib versus erlotinib after treatment cessation supports that the combination reduces cell survival. Inhibition of multiple growth factor pathways may postpone resistance and extend progression-free survival in many cancer indications.

Receptor Tyrosine Kinases in Development: Insights from Drosophila

Cell-to-cell communication mediates a plethora of cellular decisions and behaviors that are crucial for the correct and robust development of multicellular organisms. Many of these signals are encoded in secreted hormones or growth factors that bind to and activate cell surface receptors, to transmit the cue intracellularly. One of the major superfamilies of cell surface receptors are the receptor tyrosine kinases (RTKs). For nearly half a century RTKs have been the focus of intensive study due to their ability to alter fundamental aspects of cell biology, such as cell proliferation, growth, and shape, and because of their central importance in diseases such as cancer. Studies in model organisms such a Drosophila melanogaster have proved invaluable for identifying new conserved RTK pathway components, delineating their contributions, and for the discovery of conserved mechanisms that control RTK-signaling events. Here we provide a brief overview of the RTK superfamily and the general mechanisms used in their regulation. We further highlight the functions of several RTKs that govern distinct cell-fate decisions in Drosophila and explore how their activities are developmentally controlled.

Deciphering HER2 Breast Cancer Disease: Biological and Clinical Implications

The main obstacle for designing effective treatment approaches in breast cancer is the extensive and the characteristic heterogeneity of this tumor. The vast majority of critical genomic changes occurs during breast cancer progression, creating a significant variability within primary tumors as well as between the primary breast cancer and their metastases, a hypothesis have already demonstrated in retrospective studies (1). A clear example of this is the HER2-positive breast cancer. In these tumors, we can find all of the transcriptional subtypes of breast cancer, even the basal like or luminal A subtypes. Although the HER2-enriched is the most representative transcriptional subtype in the HER2-positive breast cancer, we can find it too in breast cancers with HER2-negative status. This intrinsic subtype shows a high expression of the HER2 and is associated with proliferation-related genes clusters, among other features. Therefore, two hypotheses can be suggested. First, the HER2 amplification can be a well-defined driver event present in all of the intrinsic subtypes, and not a subtype marker isolated. Secondly, HER2-enriched subtype can have a distinctive transcriptional landscape independent of HER2 amplification. In this review, we present an extensive revision about the last highlights and advances in clinical and genomic settings of the HER2-positive breast cancer and the HER2-enriched subtype, in an attempt to improving the knowledge of the underlying biology of both entities and to explaining the intrinsic heterogeneity of HER2-positive breast cancers.

Targeting promiscuous heterodimerization overcomes innate resistance to ERBB2 dimerization inhibitors in breast cancer

Background

The oncogenic receptor tyrosine kinase (RTK) ERBB2 is known to dimerize with other EGFR family members, particularly ERBB3, through which it potently activates PI3K signalling. Antibody-mediated inhibition of this ERBB2/ERBB3/PI3K axis has been a cornerstone of treatment for ERBB2-amplified breast cancer patients for two decades. However, the lack of response and the rapid onset of relapse in many patients now question the assumption that the ERBB2/ERBB3 heterodimer is the sole relevant effector target of these therapies.

Methods

Through a systematic protein-protein interaction screen, we have identified and validated alternative RTKs that interact with ERBB2. Using quantitative readouts of signalling pathway activation and cell proliferation, we have examined their influence upon the mechanism of trastuzumab- and pertuzumab-mediated inhibition of cell growth in ERBB2-amplified breast cancer cell lines and a patient-derived xenograft model.

Results

We now demonstrate that inactivation of ERBB3/PI3K by these therapeutic antibodies is insufficient to inhibit the growth of ERBB2-amplified breast cancer cells. Instead, we show extensive promiscuity between ERBB2 and an array of RTKs from outside of the EGFR family. Paradoxically, pertuzumab also acts as an artificial ligand to promote ERBB2 activation and ERK signalling, through allosteric activation by a subset of these non-canonical RTKs. However, this unexpected activation mechanism also increases the sensitivity of the receptor network to the ERBB2 kinase inhibitor lapatinib, which in combination with pertuzumab, displays a synergistic effect in single-agent resistant cell lines and PDX models.

Conclusions

The interaction of ERBB2 with a number of non-canonical RTKs activates a compensatory signalling response following treatment with pertuzumab, although a counter-intuitive combination of ERBB2 antibody therapy and a kinase inhibitor can overcome this innate therapeutic resistance.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1127-y) contains supplementary material, which is available to authorized users.

Hnrnpab regulates neural cell motility through transcription of Eps8

Cell migration requires a complicated network of structural and regulatory proteins. Changes in cellular motility can impact migration as a result of cell-type or developmental stage regulated expression of critical motility genes. Hnrnpab is a conserved RNA-binding protein found as two isoforms produced by alternative splicing. Its expression is enriched in the subventricular zone (SVZ) and the rostral migratory stream within the brain, suggesting possible support of the migration of neural progenitor cells in this region. Here we show that the migration of cells from the SVZ of developing Hnrnpab^-/- mouse brains is impaired. An RNA-seq analysis to identify Hnrnpab-dependent cell motility genes led us to Eps8, and in agreement with the change in cell motility, we show that Eps8 is decreased in Hnrnpab^-/- SVZ tissue. We scrutinized the motility of Hnrnpab^-/- cells and confirmed that the decreases in both cell motility and Eps8 are restored by ectopically coexpressing both alternatively spliced Hnrnpab isoforms, therefore these variants are surprisingly nonredundant for cell motility. Our results support a model where both Hnrnpab isoforms work in concert to regulate Eps8 transcription in the mouse SVZ to promote the normal migration of neural cells during CNS development.

Small molecule inhibitors targeting the EGFR/ErbB family of protein-tyrosine kinases in human cancers

The EGFR family is among the most investigated receptor protein-tyrosine kinase groups owing to its general role in signal transduction and in oncogenesis. This family consists of four members that belong to the ErbB lineage of proteins (ErbB1-4). The ErbB proteins function as homo and heterodimers. These receptors contain an extracellular domain that consists of four parts: domains I and III are leucine-rich segments that participate in growth factor binding (except for ErbB2) and domains II and IV contain multiple disulfide bonds. Moreover, domain II participates in both homo and heterodimer formation within the ErbB/HER family of proteins. Seven ligands bind to EGFR including epidermal growth factor and transforming growth factor-α, none bind to ErbB2, two bind to ErbB3, and seven ligands bind to ErbB4. The extracellular domain is followed by a single transmembrane segment of about 25 amino acid residues and an intracellular portion of about 550 amino acid residues that contains (i) a short juxtamembrane segment, (ii) a protein kinase domain, and (iii) a carboxyterminal tail. ErbB2 lacks a known activating ligand and ErbB3 is kinase impaired. Surprisingly, the ErbB2-ErbB3 heterodimer complex is the most active dimer in the family. These receptors are implicated in the pathogenesis of a large proportion of lung and breast cancers, which rank first and second, respectively, in the incidence of all types of cancers (excluding skin) worldwide. On the order of 20% of non-small cell lung cancers bear activating mutations in EGFR. More than 90% of these patients have exon-19 deletions (⁷⁴⁶ELREA⁷⁵⁰) or the exon-21 L858R substitution. Gefitinib and erlotinib are orally effective type I reversible EGFR mutant inhibitors; type I inhibitors bind to an active enzyme conformation. Unfortunately, secondary resistance to these drugs occurs within about one year owing to a T790M gatekeeper mutation. Osimertinib is an irreversible type VI inhibitor that forms a covalent bond with C797 of EGFR and is FDA-approved for the treatment of patients with this mutation; type VI inhibitors generally form a covalent adduct with their target protein. Resistance also develops to this and related type VI inhibitory drugs owing to a C797S mutation; the serine residue is unable to react with the drugs to form a covalent bond. Approximately 20% of breast cancer patients exhibit ErbB2/HER2 gene amplification on chromosome 17q. One of the earliest targeted treatments in cancer involved the development of trastuzumab, a monoclonal antibody that interacts with the extracellular domain ErbB2/HER2 causing its down regulation. Surgery, radiation therapy, chemotherapy with cytotoxic drugs, and hormonal modulation are the mainstays in the treatment of breast cancer. Moreover, lapatinib and neratinib are FDA-approved small molecule ErbB2/HER2 antagonists used in the treatment of selected breast cancer patients. Of the approximate three dozen FDA-approved small molecule protein kinase inhibitors, five are type VI irreversible inhibitors and four of them including afatinib, osimertinib, dacomitinib, and neratinib are directed against the ErbB family of receptors (ibrutinib is the fifth and it targets Bruton tyrosine kinase). Avitinib, olmutinib, and pelitinib are additional type VI inhibitors in clinical trials for non-small cell lung cancer that target EGFR. Secondary resistance to both targeted and cytotoxic drugs is the norm, and devising and implementing strategies for minimizing or overcoming resistance is an important goal in cancer therapeutics.

Mechanism of Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors and a Potential Treatment Strategy

Treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) improves the overall survival of patients with EGFR-mutated non-small-cell lung cancer (NSCLC). First-generation EGFR-TKIs (e.g., gefitinib and erlotinib) or second-generation EGFR-TKIs (e.g., afatinib and dacomitinib) are effective for the treatment of EGFR-mutated NSCLC, especially in patients with EGFR exon 19 deletions or an exon 21 L858R mutation. However, almost all cases experience disease recurrence after 1 to 2 years due to acquired resistance. The EGFR T790M mutation in exon 20 is the most frequent alteration associated with the development of acquired resistance. Osimertinib-a third-generation EGFR-TKI-targets the T790M mutation and has demonstrated high efficacy against EGFR-mutated lung cancer. However, the development of acquired resistance to third-generation EGFR-TKI, involving the cysteine residue at codon 797 mutation, has been observed. Other mechanisms of acquired resistance include the activation of alternative pathways or downstream targets and histological transformation (i.e., epithelial⁻mesenchymal transition or conversion to small-cell lung cancer). Furthermore, the development of primary resistance through overexpression of the hepatocyte growth factor and suppression of Bcl-2-like protein 11 expression may lead to problems. In this report, we review these mechanisms and discuss therapeutic strategies to overcome resistance to EGFR-TKIs.

Cytotoxicity of Selenium Immunoconjugates against Triple Negative Breast Cancer Cells

Within the subtypes of breast cancer, those identified as triple negative for expression of estrogen receptor α (ESR1), progesterone receptor (PR) and human epidermal growth factor 2 (HER2), account for 10⁻20% of breast cancers, yet result in 30% of global breast cancer-associated deaths. Thus, it is critical to develop more targeted and efficacious therapies that also demonstrate less side effects. Selenium, an essential dietary supplement, is incorporated as selenocysteine (Sec) in vivo into human selenoproteins, some of which exist as anti-oxidant enzymes and are of importance to human health. Studies have also shown that selenium compounds hinder cancer cell growth and induce apoptosis in cancer cell culture models. The focus of this study was to investigate whether selenium-antibody conjugates could be effective against triple negative breast cancer cell lines using clinically relevant, antibody therapies targeted for high expressing breast cancers and whether selenium cytotoxicity was attenuated in normal breast epithelial cells. To that end, the humanized monoclonal IgG1 antibodies, Bevacizumab and Trastuzumab were conjugated with redox selenium to form Selenobevacizumab and Selenotrastuzumab and tested against the triple negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231 as well as a normal, immortalized, human mammary epithelial cell line, HME50-5E. VEGF and HER2 protein expression were assessed by Western. Although expression levels of HER2 were low or absent in all test cells, our results showed that Selenobevacizumab and Selenotrastuzumab produced superoxide (O2•-) anions in the presence of glutathione (GSH) and this was confirmed by a dihydroethidium (DHE) assay. Interestingly, superoxide was not elevated within HME50-5E cells assessed by DHE. The cytotoxicity of selenite and the selenium immunoconjugates towards triple negative cells compared to HME-50E cells was performed in a time and dose-dependent manner as measured by Trypan Blue exclusion, MTT assay and Annexin V assays. Selenobevacizumab and Selenotrastuzumab were shown to arrest the cancer cell growth but not the HME50-5E cells. These results suggest that selenium-induced toxicity may be effective in treating TNBC cells by exploiting different immunotherapeutic approaches potentially reducing the debilitating side effects associated with current TNBC anticancer drugs. Thus, clinically relevant, targeting antibody therapies may be repurposed for TNBC treatment by attachment of redox selenium.

Surfaceome nanoscale organization and extracellular interaction networks

The reductionist view of 'one target-one drug' has fueled the development of therapeutic agents to treat human disease. However, many compounds that have efficacy in vitro are inactive in complex in vivo systems. It has become clear that a molecular understanding of signaling networks is needed to address disease phenotypes in the human body. Protein signaling networks function at the molecular level through information transfer via protein-protein interactions. Cell surface exposed proteins, termed the surfaceome, are the gatekeepers between the intra- and extracellular signaling networks, translating extracellular cues into intracellular responses and vice versa. As 66% of drugs in the DrugBank target the surfaceome, these proteins are a key source for potential diagnostic and therapeutic agents. In this review article, we will discuss current knowledge about the spatial organization and molecular interactions of the surfaceome and provide a perspective on the technologies available for studying the extracellular surfaceome interaction network.