Project description:Although epidermal growth factor receptor (EGFR)-targeted therapy has improved clinical outcomes of patients with advanced non-small-cell lung cancer (NSCLC) carrying activating EGFR mutations, the development of acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs), including the promising third-generation ones, results in disease progression and has become an unavoidable problem that limits patient long-term benefit. The third-generation EGFR-TKIs, osimertinib and almonertinib, are now approved for the treatment of advanced NSCLC patients harboring activating EGFR mutations (first-line) and/or the resistant T790M mutation (second-line). Clinically, appropriate management of acquired resistance to third-generation EGFR-TKIs will substantially improve their long-term efficacy against EGFR-mutant NSCLC. Recent preclinical and clinical studies suggest that activation of the Ras/Raf/MEK/ERK signaling pathway may be an important resistance mechanism and accordingly co-targeting this pathway effectively overcomes and abrogates acquired resistance to third-generation EGFR-TKIs. This review focuses on discussing the scientific rationale for and potential of co-targeting MEK/ERK signaling in delaying and overcoming acquired resistance to third-generation EGFR-TKIs, particularly osimertinib.
Project description:Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) represent the standard of care for advanced non-small cell lung cancer (NSCLC) patients whose tumours harbor an activating EGFR mutation. Unfortunately, resistance to first- and second-generation EGFR-TKIs inevitably occurs in all patients with EGFR-mutant disease approximately within a year of treatment. At least half of these cases are attributed to the emergence of a secondary mutation in exon 20 of the EGFR gene, namely the T790M mutation. Third-generation EGFR-TKIs, including osimertinib and rociletinib, target this epigenic mutation, thus re-sensitizing cancer cells to EGFR-TKI inhibition. Osimertinib to date represents the standard of care in EGFR-mutant tumors after failure of first-line EGFR-TKIs by over-performing platinum-based chemotherapy in the recently reported AURA-3 randomized phase III clinical trial. The aim of this review is to describe the different treatment strategies that have been developed to reverse resistance to first- and second-line EGFR-TKIs, the corresponding mechanisms of resistance and the development of novel-generation EGFR-TKIs. We also discuss the challenge posed by the implementation of third-generation EGFR-TKIs earlier in the course of the disease in first-line treatment of EGFR-mutant NSCLC.
Project description:Angiogenesis in general and the vascular endothelial growth factor (VEGF) signaling axis in particular is a validated target in renal cell carcinoma (RCC). Clear-cell carcinoma of the kidney is now recognized as a malignancy that is sensitive to inhibitors of the VEGF pathway. Treatment options for patients with metastatic renal cell carcinoma have evolved in dramatic fashion over the past 6 years, and a new paradigm has developed. The cytokines interferon-α and interleukin-2 were previously utilized for therapy, but since December 2005, six new agents have been approved in the United States for the treatment of advanced RCC. Two are tyrosine kinase inhibitors (TKI's) including sunitinib and recently pazopanib, and the multikinase inhibitor sorafenib. The current review examines the evolving data with the next generation of TKI's, axitinib and tivozanib being developed for the treatment of advanced RCC. These agents were synthesized to provide increased target specificity and enhanced target inhibition. The preclinical and clinical data are examined, an overview of the development of these TKI's is provided, and discussion plus speculation concerning their potential roles as RCC therapy is provided.
Project description:Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are effective in patients with non-small-cell lung cancer (NSCLC) harboring EGFR mutations. However, due to acquired resistance to EGFR-TKIs, even patients on third-generation osimertinib have a poor prognosis. Resistance mechanisms are still not fully understood. Here, we demonstrate that the increased expression of MUSASHI-2 (MSI2), an RNA-binding protein, is a novel mechanism for resistance to EGFR-TKIs. We found that after a long-term exposure to gefitinib, the first-generation EGFR-TKI lung cancer cells harboring the EGFR-TKI-sensitive mutations became resistant to both gefitinib and osimertinib. Although other mutations in EGFR were not found, expression levels of Nanog, a stemness core protein, and activities of aldehyde dehydrogenase (ALDH) were increased, suggesting that cancer stem-like properties were increased. Transcriptome analysis revealed that MSI2 was among the stemness-related genes highly upregulated in EGFR-TKI-resistant cells. Knockdown of MSI2 reduced cancer stem-like properties, including the expression levels of Nanog, a core stemness factor. We demonstrated that knockdown of MSI2 restored sensitivity to osimertinib or gefitinib in EGFR-TKI-resistant cells to levels similar to those of parental cells in vitro. An RNA immunoprecipitation (RIP) assay revealed that antibodies against MSI2 were bound to Nanog mRNA, suggesting that MSI2 increases Nanog expression by binding to Nanog mRNA. Moreover, overexpression of MSI2 or Nanog conferred resistance to osimertinib or gefitinib in parental cells. Finally, MSI2 knockdown greatly increased the sensitivity to osimertinib in vivo. Collectively, our findings provide proof of principle that targeting the MSI2-Nanog axis in combination with EGFR-TKIs would effectively prevent the emergence of acquired resistance.
Project description:Patients with non-small-cell lung cancer (NSCLC) whose tumours harbour activating mutations within the epidermal growth factor receptor (EGFR) frequently derive significant clinical and radiographic benefits from treatment with EGFR tyrosine kinase inhibitors (TKIs). As such, prospective identification of EGFR mutations is now the standard of care worldwide. However, acquired therapeutic resistance to these agents invariably develops. Over the past 10 years, great strides have been made in defining the molecular mechanisms of EGFR TKI resistance in an effort to design rational strategies to overcome this acquired drug resistance. Approximately 60% of patients with acquired resistance to the EGFR TKIs (erlotinib, gefitinib, and afatinib) develop a new mutation within the drug target. This mutation-T790M-has been shown to alter drug binding and enzymatic activity of the mutant EGF receptor. Less common mechanisms of acquired resistance include MET amplification, ERBB2 amplification, transformation to small-cell lung cancer, and others. Here, we present a condensed overview of the literature on EGFR-mutant NSCLC, paying particular attention to mechanisms of drug resistance, recent clinical trial results, and novel strategies for identifying and confronting drug resistance, while also striving to identify gaps in current knowledge. These advances are rapidly altering the treatment landscape for EGFR-mutant NSCLC, expanding the armamentarium of available therapies to maximize patient benefit.
Project description:The discovery that mutations in the EGFR gene are detected in up to 50% of lung adenocarcinoma patients, along with the development of highly efficacious epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), has revolutionized the treatment of this frequently occurring lung malignancy. Indeed, the clinical success of these TKIs constitutes a critical milestone in targeted cancer therapy. Three generations of EGFR-TKIs are currently approved for the treatment of EGFR mutation-positive non-small cell lung cancer (NSCLC). The first-generation TKIs include erlotinib, gefitinib, lapatinib, and icotinib; the second-generation ErbB family blockers include afatinib, neratinib, and dacomitinib; whereas osimertinib, approved by the FDA on 2015, is a third-generation TKI targeting EGFR harboring specific mutations. Compared with the first- and second-generation TKIs, third-generation EGFR inhibitors display a significant advantage in terms of patient survival. For example, the median overall survival in NSCLC patients receiving osimertinib reached 38.6 months. Unfortunately, however, like other targeted therapies, new EGFR mutations, as well as additional drug-resistance mechanisms emerge rapidly after treatment, posing formidable obstacles to cancer therapeutics aimed at surmounting this chemoresistance. In this review, we summarize the molecular mechanisms underlying resistance to third-generation EGFR inhibitors and the ongoing efforts to address and overcome this chemoresistance. We also discuss the current status of fourth-generation EGFR inhibitors, which are of great value in overcoming resistance to EGFR inhibitors that appear to have greater therapeutic benefits in the clinic.
Project description:Although tyrosine kinase inhibitors (TKIs) targeting Epidermal Growth Factor Receptor (EGFR) activating mutations have significantly improved outcomes in EGFR-mutant non-small cell lung cancer, resistance inevitably develops. Despite the heterogeneity of resistance mechanisms, many induce activation of MAPK signaling in the presence of EGFR-TKIs. ARAF gene amplification is identified as one such mechanism that activates MAPK signaling by directly interacting with RAS, yet its clinicopathologic characteristics remain poorly understood. We characterized five cases with ARAF amplification resistant to first- or second-generation EGFR-TKIs and screened an additional 48 re-biopsied specimens following resistance to Osimertinib. Among Osimertinib-resistant tumors, we identified four cases with ARAF amplification. Overall, these nine ARAF-amplified resistant tumors retained their original founder EGFR mutation and lacked secondary alterations. Furthermore, we identified two cases showing histologic transformation from lung adenocarcinoma to small cell lung cancer (SCLC). SCLC can be classified into four subtypes defined by transcriptional signatures driven by specific transcription factors. To estimate the subtypes of these resistant tumors, RNA sequencing analysis was performed in paired samples before and after treatment with EGFR-TKIs.
Project description:Mutations in the EGFR kinase domain are implicated in non-small-cell lung cancer. Of particular interest is the drug-resistant double mutant (L858R/T790M, DM EGFR), which is not inhibited selectively by any approved kinase inhibitor. Here we apply bipartite tetracysteine display to demonstrate that DM and WT EGFR differ in structure outside the kinase domain. The structural difference is located within the cytoplasmic juxtamembrane segment (JM) that links the kinase domain with the extracellular and transmembrane regions and is essential for EGFR activation. We show further that third-generation DM EGFR-selective TKIs alter JM structure via allostery to restore the conformation found when WT EGFR is activated by the growth factors EGF and HB-EGF. This work suggests that the oncogenic activity of DM EGFR may extend beyond kinase activity per se to include kinase-independent activities. As JM structure may provide a biomarker for these kinase-independent functions, these insights could guide the development of allosteric, DM-selective inhibitors.
Project description:Osimertinib is a third-generation tyrosine kinase inhibitor (TKI) and currently the gold-standard for the treatment of patients suffering from non-small cell lung cancer (NSCLC) harboring T790M-mutated epidermal growth factor receptor (EGFR). The outcome of the treatment, however, is limited by the emergence of the C797S resistance mutation. Allosteric inhibitors have a different mode of action and were developed to overcome this limitation. However, most of these innovative molecules are not effective as a single agent. Recently, mutated EGFR was successfully addressed with osimertinib combined with the allosteric inhibitor JBJ-04-125-02, but surprisingly, structural insights into their binding mode were lacking. Here, we present the first complex crystal structures of mutant EGFR in complex with third-generation inhibitors such as osimertinib and mavelertinib in the presence of simultaneously bound allosteric inhibitors. These structures highlight the possibility of further combinations targeting EGFR and lay the foundation for hybrid inhibitors as next-generation TKIs.