A review of research progress on mechanisms and overcoming strategies of acquired osimertinib resistance

Targeting HER3 to overcome EGFR TKI resistance in NSCLC

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

Understanding the feasibility of chemotherapeutic and immunotherapeutic targets against non-small cell lung cancers: an update of resistant responses and recent combinatorial therapies

Despite consistent progress in prompt diagnosis and curative therapies in the last decade, lung cancer (LC) continues to threaten mankind, accounting for nearly twice the casualties compared to prostate, breast, and other cancers. Statistics associate ~25% of 2021 cancer-related deaths with LC, more than 80% of which are explicitly caused by tobacco smoking. Prevailing as small and non-small cell pathologies, with respective occurring frequency of nearly 15% and 80-85%, non-small cell LCs (NSCLCs) are prominently distinguished into lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), subtypes. Since the first use of epidermal growth factor receptor (EGFR) inhibitor gefitinib for NSCLC treatment in 2002, immense progress has been made for targeted therapies with the next generation of drugs spanning across the chronological generations of small molecule inhibitors. The last two years have overseen the clinical approval of more than 10 therapeutic agents as first-line NSCLC medications. However, uncertain mutational aberrations as well as systemic resistant responses, and abysmal overall survival curtail the combating efficacies. Of late, immune checkpoint inhibitors (ICIs) against various molecules including programmed cell death-1 (PD-1) and its ligand (PD-L1) have been demonstrated as reliable LC treatment targets. Keeping these aspects in mind, this review article discusses the success of NSCLC chemo and immunotherapies with their characteristic effectiveness and future perspectives.

Receptor tyrosine kinase inhibitors in cancer

Targeted therapy is a new cancer treatment approach, involving drugs that particularly target specific proteins in cancer cells, such as receptor tyrosine kinases (RTKs) which are involved in promoting growth and proliferation, Therefore inhibiting these proteins could impede cancer progression. An understanding of RTKs and the relevant signaling cascades, has enabled the development of many targeted drug therapies employing RTK inhibitors (RTKIs) some of which have entered clinical application. Here we discuss RTK structures, activation mechanisms and functions. Moreover, we cover the potential effects of combination drug therapy (including chemotherapy or immunotherapy agents with one RTKI or multiple RTKIs) especially for drug resistant cancers.

A Case of Epidermal Growth Factor Receptor-Mutated Non-Small-Cell Lung Cancer: Multi-Line Treatment and Resistance Mechanisms

In the non-small-cell lung cancer (NSCLC) subtype, adenocarcinoma is the most common histology. The choice of first-line treatment depends on the mutational status. We present a case of a 54-year-old non-smoker woman with lung adenocarcinoma and extensive metastatic disease at diagnosis. The genetic analysis demonstrated a sensitizing epidermal growth factor receptor (EGFR) exon 19 mutation and she began treatment with a first-generation EGFR tyrosine kinase inhibitor (TKI), erlotinib. Due to successively acquired resistances and disease progression, six treatment lines were pursued, including third-generation EGFR TKI and chemotherapy. The patient accomplished an overall survival of 47 months. This case emphasized the importance of monitoring tumor mutational alterations, allowing us to implement a multi-line treatment. Targeted therapy in advanced NSCLC largely improved the overall survival of these patients.

Survival benefit of combinatorial osimertinib rechallenge and entrectinib in an EGFR-mutant NSCLC patient with acquired LMNA-NTRK1 fusion following osimertinib resistance

Acquired resistance to osimertinib is inevitable and heterogeneous despite its documented efficacy against EGFR-mutated non-small cell lung cancer (NSCLC). Subsequent therapeutic options assume the dominant form of the resistance mechanism; however, the more rare oncogenic driver, NTRK1 fusion, has also reportedly conferred osimertinib resistance. Nevertheless, clear-cut options when NSCLCs are driven by EGFR mutation and the subsequent NTRK fusion are lacking. This is a case of NSCLC wherein exon 19 deletion in EGFR (19del) and acquired LMNA-NTRK1 fusion were accompanied by the persistence of EGFR T790M. The patient underwent peritoneal metastasis after multiple targeted therapies: gefitinib, osimertinib, chemotherapy, and anlotinib plus docetaxel (in clinical trials). Osimertinib was subsequently re-administered with the NTRK fusion inhibitor entrectinib, resulting in remission of peritoneal metastases even after slow progression of pancreatic metastasis over the following 5 months. An extensive literature review to identify the efficacies of therapies for NTRK fusion as the means to acquired resistance to EGFR TKIs revealed that blocking both the EGFR mutation and the subsequent NTRK fusion can provide clinical benefits following EGFR TKIs resistance; however, the efficacy and safety of combination therapies must be further investigated. To precisely manage EGFR-mutated NSCLCs, it is also essential to identify the resistance mechanisms by repeating biopsies.

Anti-EGF nanobodies enhance the antitumoral effect of osimertinib and overcome resistance in non-small cell lung cancer (NSCLC) cellular models

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that is effective against the EGFR T790M mutation in patients with advanced non-small-cell lung cancer (NSCLC). However, acquired resistance appears invariably due to several mechanisms. The strategy of using EGF-targeted nanobodies (Nbs) to block the initial step of the EGFR pathway constitutes a new research area. Nbs offer several advantages compared to traditional mAbs, such as their reduced size, increased stability, and tissue penetration, which provide key advantages for targeting soluble tumoral growth factors. In this study we investigated the efficacy of anti-EGF Nbs to reduce Osimertinib resistance. Two anti-EGF Nbs, generated in our laboratory, were shown to inhibit cell viability and colony formation in PC9 and PC9-derived osimertinib-resistant cell lines. The combination of these Nbs with osimertinib improved the antitumor efficacy of this EGFR-TKI in cell viability and colony formation experiments. In a mechanistic study of the EGFR pathway, the combination treatment dampened the activation of downstream proteins such as Akt and Erk1/2 MAP kinases. In addition, it increased cellular apoptosis and decreased the expression of Hes1, a cancer stem cell marker involved in metastasis and osimertinib resistance. We conclude that the addition of anti-EGF nanobodies enhances the antitumor properties of osimertinib, thus representing a potentially effective strategy for NSCLC patients.

TMEM16A, a Homoharringtonine Receptor, as a Potential Endogenic Target for Lung Cancer Treatment

Lung cancer has the highest rate of incidence and mortality among all cancers. Most chemotherapeutic drugs used to treat lung cancer cause serious side effects and are susceptible to drug resistance. Therefore, exploring novel therapeutic targets for lung cancer is important. In this study, we evaluated the potential of TMEM16A as a drug target for lung cancer. Homoharringtonine (HHT) was identified as a novel natural product inhibitor of TMEM16A. Patch-clamp experiments showed that HHT inhibited TMEM16A activity in a concentration-dependent manner. HHT significantly inhibited the proliferation and migration of lung cancer cells with high TMEM16A expression but did not affect the growth of normal lung cells in the absence of TMEM16A expression. In vivo experiments showed that HHT inhibited the growth of lung tumors in mice and did not reduce their body weight. Finally, the molecular mechanism through which HHT inhibits lung cancer was explored by western blotting. The findings showed that HHT has the potential to regulate TMEM16A activity both in vitro and in vivo and could be a new lead compound for the development of anti-lung-cancer drugs.