The novel EGFR mutations (p.E746_S752delinsI, p.T751_I759delinsG, p.L747_S752delinsAA) in patients with non-small cell lung cancer and the clinical treatment strategy: three case reports

Epidermal growth factor receptor (EGFR) is an established driver gene in non-small cell lung cancer (NSCLC) and the common Exon 19 del mutation (p.E746_A750 del) has exhibited remarkable responses for EGFR tyrosine kinase inhibitors (TKIs). However, there is even less comprehension of the treatment strategy in NSCLC patients harboring uncommon Exon 19 delins mutation. Here, we identified three novel EGFR Exon 19 mutations (p.E746_S752delinsI, p.T751_I759delinsG, p.L747_S752delinsAA), and described the clinical treatment process. To our knowledge, the EGFR p.E746_S752delinsI mutation of the patient with advanced NSCLC could benefit from the treatment with Icotinib. Otherwise, for the NSCLC patients with early-stage, one harboring p.T751_I759delinsG mutation had an excellent recovery and the other harboring p.L747_S752delinsAA experienced a relapse after receiving horacoscopic radical resection, which means the patients with different Exon 19 delins mutation might have different prognosis. Our study also demonstrated that next-generation sequencing (NGS) is a crucial tool in guiding clinical treatment decisions in NSCLC. Furthermore, the real incidence of these mutation is not known, the routinely use of NGS surely will increase the detection of EGFR del-ins respect to the old tools used to screen for EGFR mutations.

Pulmonary complications of tyrosine kinase inhibitors and immune checkpoint inhibitors in patients with non-small cell lung cancer

The understanding of cancer biology and the identification of various molecular pathways and targeted oncogenic drivers have led to a paradigm shift in treatment of non-small cell lung cancer. In the last two decades, the therapeutic approach for non-small cell lung cancer (NSCLC) has gradually transitioned from empiric treatment with chemotherapeutic regimens to personalized medicine with precision targets. The major key players in these novel approaches involve targeted therapy, such as tyrosine kinase inhibitors (TKI) and immunotherapy, such as immune checkpoint inhibitors (ICI) blocking intrinsic down regulators of immunity, to achieve anti-cancer effects. These novel agents are generally better tolerated than chemotherapeutics and it is essential to be cognizant of the various drug related adverse effects. Regular follow up of patients with NSCLC by chest computed tomography (CT) surveillance to monitor for disease progression or recurrence is a prerequisite. It is becoming increasingly challenging to identify pulmonary complications related to the use of novel TKI and ICI. Our review focuses on various pulmonary complications of TKI and ICI in patients undergoing treatment for NSCLC, chest CT manifestations, management strategies, and treatment outcomes described in various case reports and case series.

Bispecific Targeting of EGFR and Urokinase Receptor (uPAR) Using Ligand-Targeted Toxins in Solid Tumors

Ligand-targeted toxins (LTTs) are bioengineered molecules which are composed of a targeting component linked to a toxin that induces cell death once the LTT binds its target. Bispecific targeting allows for the simultaneous targeting of two receptors. In this review, we mostly focus on the epidermal growth factor receptor (EGFR) as a target. We discuss the development and testing of a bispecific LTT targeting EGFR and urokinase-type plasminogen activator receptor (uPAR) as two attractive targets implicated in tumor growth and in the regulation of the tumor microvasculature in solid tumors. In vitro and mouse xenograft studies have shown that EGFR-targeted bispecific angiotoxin (eBAT) is effective against human solid tumors. Canine studies have shown that eBAT is both safe and effective against canine hemangiosarcoma, which is physiologically similar to human angiosarcoma. Finding the appropriate dosing strategy and sequencing of eBAT administration, in combination with other therapeutics, are among important factors for future directions. Together, the data indicate that eBAT targets cancer stem cells, it may have a role in inhibiting human tumor vasculature, and its bispecific conformation may have a role in reducing toxicity in comparative oncologic trials in dogs.

Modulating EGFR-MTORC1-autophagy as a potential therapy for persistent fetal vasculature (PFV) disease

Persistent fetal vasculature (PFV) is a human disease that results from failure of the fetal vasculature to regress normally. The regulatory mechanisms responsible for fetal vascular regression remain obscure, as does the underlying cause of regression failure. However, there are a few animal models that mimic the clinical manifestations of human PFV, which can be used to study different aspects of the disease. One such model is the Nuc1 rat model that arose from a spontaneous mutation in the Cryba1 (crystallin, beta 1) gene and exhibits complete failure of the hyaloid vasculature to regress. Our studies with the Nuc1 rat indicate that macroautophagy/autophagy, a process in eukaryotic cells for degrading dysfunctional components to ensure cellular homeostasis, is severely impaired in Nuc1 ocular astrocytes. Further, we show that CRYBA1 interacts with EGFR (epidermal growth factor receptor) and that loss of this interaction in Nuc1 astrocytes increases EGFR levels. Moreover, our data also show a reduction in EGFR degradation in Nuc1 astrocytes compared to control cells that leads to over-activation of the mechanistic target of rapamycin kinase complex 1 (MTORC1) pathway. The impaired EGFR-MTORC1-autophagy signaling in Nuc1 astrocytes triggers abnormal proliferation and migration. The abnormally migrating astrocytes ensheath the hyaloid artery, contributing to the pathogenesis of PFV in Nuc1, by adversely affecting the vascular remodeling processes essential to regression of the fetal vasculature. Herein, we demonstrate in vivo that gefitinib (EGFR inhibitor) can rescue the PFV phenotype in Nuc1 and may serve as a novel therapy for PFV disease by modulating the EGFR-MTORC1-autophagy pathway.

ABBREVIATIONS

ACTB: actin, beta; CCND3: cyclin 3; CDK6: cyclin-dependent kinase 6; CHQ: chloroquine; COL4A1: collagen, type IV, alpha 1; CRYBA1: crystallin, beta A1; DAPI: 4'6-diamino-2-phenylindole; EGFR: epidermal growth factor receptor; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFAP: glial fibrillary growth factor; KDR: kinase insert domain protein receptor; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MKI67: antigen identified by monoclonal antibody Ki 67; MTORC1: mechanistic target of rapamycin kinase complex 1; PARP: poly (ADP-ribose) polymerase family; PCNA: proliferating cell nuclear antigen; PFV: persistent fetal vasculature; PHPV: persistent hyperplastic primary vitreous; RPE: retinal pigmented epithelium; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase, polypeptide 1; SQSTM1/p62: sequestome 1; TUBB: tubulin, beta; VCL: vinculin; VEGFA: vascular endothelial growth factor A; WT: wild type.

Substrate-selective protein ectodomain shedding by ADAM17 and iRhom2 depends on their juxtamembrane and transmembrane domains

The metalloprotease ADAM17 (a disintegrin and metalloprotease 17) regulates EGF-receptor and TNFα signaling, thereby not only protecting the skin and intestinal barrier, but also contributing to autoimmunity. ADAM17 can be rapidly activated by many stimuli through its transmembrane domain (TMD), with the seven membrane-spanning inactive Rhomboids (iRhom) 1 and 2 implicated as candidate regulatory partners. However, several alternative models of ADAM17 regulation exist that do not involve the iRhoms, such as regulation through disulfide bond exchange or through interaction with charged phospholipids. Here, we report that a non-activatable mutant of ADAM17 with the TMD of betacellulin (BTC) can be rescued by restoring residues from the ADAM17 TMD, but only in Adam17^-/- cells, which contain iRhoms, not in iRhom1/2^-/- cells. We also provide the first evidence that the extracellular juxtamembrane domains (JMDs) of ADAM17 and iRhom2 regulate the stimulation and substrate selectivity of ADAM17. Interestingly, a point mutation in the ADAM17 JMD identified in a patient with Tetralogy of Fallot, a serious heart valve defect, affects the substrate selectivity of ADAM17 toward Heparin-binding epidermal growth factor like growth factor (HB-EGF), a crucial regulator of heart valve development in mice. These findings provide new insights into the regulation of ADAM17 through an essential interaction with the TMD1 and JMD1 of iRhom2.

The Dichotomous Nature of AZ5104 (an EGFR Inhibitor) Towards RORγ and RORγT

The RORC (RAR related orphan receptor C) gene produces two isoforms by alternative promoter usage: RORγ (nuclear receptor ROR-gamma isoform 1) and RORγT (nuclear receptor ROR-gamma isoform 1). Both proteins have distinct tissue distributions and are involved in several physiological processes, including glucose/lipid metabolism and the development of Th17 lymphocytes. Previously, we developed a stably transfected reporter cell line and used it to screen a library of kinase inhibitors. We found that AZ5104 acts as an RORγ agonist at low micromolar concentrations. Molecular docking analysis showed that this compound occupies the ligand binding domain of the receptor with a significant docking score. However, analysis of the biological activity of this compound in Th17 cells revealed that it downregulates RORγT expression and Th17-related cytokine production via inhibition of SRC-ERK-STAT3 (SRC proto-oncogene - extracellular regulated MAP kinase - signal transducer and activator of transcription 3). We thus identified a compound acting as an agonist of RORγ that, due to the inhibition of downstream elements of EGFR (epidermal growth factor receptor) signaling, exerts different biological activity towards a Th17-specific isoform. Additionally, our results may be relevant in the future for the design of treatments targeting signaling pathways that inhibit Th17-related inflammation in certain autoimmune disorders.

Early emergence of de novo EGFR T790M gatekeeper mutations during erlotinib treatment in PC9 non-small cell lung cancer cells

The emergence of the T790M gatekeeper mutation in the Epidermal Growth Factor Receptor (EGFR) gene is an important mechanism that can lead to the acquired resistance to EGFR-targeted tyrosine kinase inhibitors such as erlotinib or gefitinib. These drugs have been used in treating a subset of non-small cell lung cancer (NSCLC) patients harboring EGFR activating mutations. Here we investigated the paths leading to the acquisition of the T790M mutation by establishing an erlotinib resistant PC9 cell model harboring ectopically introduced EGFR cDNA. We detected the emergence of T790M mutation within the EGFR cDNA in a subset of erlotinib resistant PC9 cell models through Sanger sequencing and droplet digital PCR-based methods, demonstrating that T790M mutation can emerge via de novo events following treatment with erlotinib. In addition, we show that the de novo T790M bearing erlotinib resistant PC9 cells are sensitive to the 3rd generation EGFR-targeted drug, WZ4002. Furthermore, GFP-based competition cell proliferation assays reveal that PC9 cells ectopically expressing EGFR mutant become more rapidly resistant to erlotinib than parental PC9 cells through the acquisition of the T790M mutation. Taken together, we believe that our findings expand upon the previous notion of evolutionary paths of T790M development, providing an important clue to designing a therapeutic strategy to overcome drug resistance.

Concordant and Discordant EGFR Mutations in Patients With Multifocal Adenocarcinomas: Implications for EGFR-Targeted Therapy

PURPOSE

Adenocarcinoma remains the most common subtype of lung cancer in the United States. Most patients present with tumors that are invasive and often metastatic, but in some patients, multiple precursor in situ or minimally invasive adenocarcinoma tumors develop that can be synchronous and metachronous. These precursor lesions harbor the same spectrum of genetic mutations found in purely invasive adenocarcinomas, such as EGFR, KRAS, and p53 mutations. It is less clear, however, whether separate lesions in patients who present with multifocal disease share common underlying genetic driver mutations.

METHODS

Here we review the relevant literature on molecular driver alterations in adenocarcinoma precursor lesions. We then report 4 patients with multifocal EGFR mutant adenocarcinomas in whom we performed molecular testing on 2 separate lesions.

FINDINGS

In 2 of these patients, the mutations are concordant, and in 2 patients, the mutations are discordant. A review of the literature demonstrates increasing evidence that lesions with discordant mutations may confer a more favorable prognosis because they are unlikely to represent metastases.

IMPLICATIONS

Our findings suggest that the emergence of the dominant EGFR driver alteration is often independent between lesions in patients with multifocal adenocarcinomas, and thus the same targeted therapy may not be effective for all lesions. However, genetic testing of multiple lesions can help to distinguish separate primary tumors from metastatic disease.

Irreversible EGFR-TKIs: dreaming perfection

In the last few years, the treatment of Non-Small-Cell Lung Cancer (NSCLC) has dramatically changed. Presence of activating mutations in the Epidermal Growth Factor Receptor (EGFR) identified a particular group of NSCLC patients with different clinical characteristics and outcome. For EGFR mutant patients first-generation EGFR tyrosine-kinase inhibitors (TKIs), such as gefitinib and erlotinib, represent the best therapeutic option in first, second and maintenance setting. Unfortunately, all patients develop acquired resistance and despite an initial benefit, virtually all patients progress due to the development of resistance. Several molecular mechanisms are responsible for acquired resistance and the two prominent are the up-regulation of the downstream signal by mesenchymal-epidermal transition (MET) amplification and the emergence of T790M EGFR gatekeeper mutation. Preclinical and early clinical trials suggested a potential efficacy of a new class of panHER inhibitor, also called irreversible or covalent inhibitor, in overcome acquired resistance related to T790M. Afatinib, dacomitinib and neratinib, are currently in development in different setting and results from these trials are awaited in order to establish the role of these new compounds in the treatment of NSCLC.