Four generations of EGFR TKIs associated with different pathogenic mutations in non-small cell lung carcinoma

EGFR degraders in non-small-cell lung cancer: Breakthrough and unresolved issue

The epidermal growth factor receptor (EGFR) has been well validated as a therapeutic target for anticancer drug discovery. Osimertinib has become the first globally accessible third-generation EGFR inhibitor, representing one of the most advanced developments in non-small-cell lung cancer (NSCLC) therapy. However, a tertiary Cys797 to Ser797 (C797S) point mutation has hampered osimertinib treatment in patients with advanced EGFR-mutated NSCLC. Several classes of fourth-generation EGFR inhibitors were consequently discovered with the aim of overcoming the EGFRC797S mutation-mediated resistance. However, no clinical efficacy data of the fourth-generation EGFR inhibitors were reported to date, and EGFRC797S mutation-mediated resistance remains an "unmet clinical need." Proteolysis-targeting chimeric molecules (PROTACs) obtained from EGFR-TKIs have been developed to target drug resistance EGFR in NSCLC. Some PROTACs are from nature products. These degraders compared with EGFR inhibitors showed better efficiency in their cellular potency, inhibition, and toxicity profiles. In this review, we first introduce the structural properties of EGFR, the resistance, and mutations of EGFR, and then mainly focus on the recent advances of EGFR-targeting degraders along with its advantages and outstanding challenges.

EGFR trafficking: effect of dimerization, dynamics, and mutation

Spontaneous dimerization of EGF receptors (EGFR) and dysregulation of EGFR signaling has been associated with the development of different cancers. Under normal physiological conditions and to maintain homeostatic cell growth, once EGFR signaling occurs, it needs to be attenuated. Activated EGFRs are rapidly internalized, sorted through early endosomes, and ultimately degraded in lysosomes by a process generally known as receptor down-regulation. Through alterations to EGFR trafficking, tumors develop resistance to current treatment strategies, thus highlighting the necessity for combination treatment strategies that target EGFR trafficking. This review covers EGFR structure, trafficking, and altered surface expression of EGFR receptors in cancer, with a focus on how therapy targeting EGFR trafficking may aid tyrosine kinase inhibitor treatment of cancer.

Recent Advances in Boosting EGFR Tyrosine Kinase Inhibitors-Based Cancer Therapy

Epidermal growth factor receptor (EGFR) plays a key role in signal transduction pathways associated with cell proliferation, growth, and survival. Its overexpression and aberrant activation in malignancy correlate with poor prognosis and short survival. Targeting inhibition of EGFR by small-molecular tyrosine kinase inhibitors (TKIs) is emerging as an important treatment model besides of chemotherapy, greatly reshaping the landscape of cancer therapy. However, they are still challenged by the off-targeted toxicity, relatively limited cancer types, and drug resistance after long-term therapy. In this review, we summarize the recent progress of oral, pulmonary, and injectable drug delivery systems for enhanced and targeting TKI delivery to tumors and reduced side effects. Importantly, EGFR-TKI-based combination therapies not only greatly broaden the applicable cancer types of EGFR-TKI but also significantly improve the anticancer effect. The mechanisms of TKI resistance are summarized, and current strategies to overcome TKI resistance as well as the application of TKI in reversing chemotherapy resistance are discussed. Finally, we provide a perspective on the future research of EGFR-TKI-based cancer therapy.

Applications of CRISPR/Cas technology against drug-resistant lung cancers: an update

Out of all the cancer types, the most prevalent one is lung cancer. Multiple genes and signaling pathways play role in the progression of lung cancer. Considering the wider prevalence and fatality of lung cancer it has become the focus of current cancer research. Though currently used approaches have shown positive results against lung cancer but success against non-small cell lung cancer (NSCLC) still looms as an enigma for the entire research fraternity. The development of resistance against inhibitors within a short span is one of the reasons responsible for the failure and relapse of lung cancer. Under these prevailing conditions genome/gene-editing technology using clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR associated proteins (Cas), popularly known as CRISPR/Cas technology offers a convenient and flexible method for inducing precise changes within the lung cancer cell. Additionally, CRISPR-barcoding and CRISPR knockout screens at the genome-wide level can help in the functional investigation of specific mutations and identification of novel cancer drivers respectively. Several variants of the CRISPR/Cas system are being developed to limit off-targeting with enhanced precision. The present review article updates the usefulness of CRISPR/Cas technology against various types of lung cancers.

B7-H3 is eligible for predicting clinical outcomes in lung adenocarcinoma patients treated with EGFR tyrosine kinase inhibitors

BACKGROUND

Not all lung adenocarcinoma (LUAD) patients with activating epidermal growth factor receptor (EGFR) mutations respond to tyrosine kinase inhibitors (TKIs) as intended. Thus, biomarkers are needed to identify patients who benefit most from EGFR-targeted therapy. Our previous in vitro data has shown that the co-signal molecule B7-H3 determines EGFR-TKI gefitinib susceptibility of EGFR-mutated LUAD cell lines, based on the potential crosslinking between B7-H3-induced signaling and EGFR signaling.

METHODS

We detected tumoral B7-H3 expression in the original biopsy from 56 treatment-naïve LUAD patients and analyzed the association between high/low B7-H3 expression with the clinical outcomes of first-line anti-EGFR therapy. The main criteria for the analysis of response were overall response rate (ORR), disease control rate (DCR), and progression-free survival (PFS), and the secondary criterion was overall survival (OS).

RESULTS

In the subgroups of B7-H3 high and low expression, the ORR were 16.0% (4/25) and 74.2% (23/31) (p<0.001), and the DCR were 36.0% (9/25) and 87.1% (27/31) (p<0.001), respectively. The PFS of B7-H3 high [median 8.7, 95% confidence interval (CI) 4.0-13.4] was significantly worse than that of B7-H3 low (median not reached) [HR 6.54 (95% CI 2.18-19.60), p=0.001]. The median OS was 15.9 (95% CI 10.0-21.8) months in the B7-H3 high cohort and 25.7 (95% CI 9.0-42.4) months in the B7-H3 low subjects [HR 2.08 (95% CI 1.07-4.02), p=0.03], respectively. Both the univariate and multivariate analyses identified B7-H3 as an independent factor associated with poor PFS (p=0.001, p=0.000) and OS (p=0.03, p=0.015).

CONCLUSION

B7-H3 may serve as a potential biomarker to predict clinical outcomes in EGFR-mutated LUAD patients treated with first-line EGFR-TKIs.

Role of Immune Checkpoint Inhibitor Therapy in Advanced EGFR-Mutant Non-Small Cell Lung Cancer

Over the last decade, the treatment of advanced non-small cell lung cancer (NSCLC) has undergone rapid changes with innovations in oncogene-directed therapy and immune checkpoint inhibitors. In patients with epidermal growth factor receptor (EGFR) gene mutant (EGFRm) NSCLC, newer-generation tyrosine kinase inhibitors (TKIs) are providing unparalleled survival benefit and tolerability. Unfortunately, most patients will experience disease progression and thus an urgent need exists for improved subsequent lines of therapies. The concurrent revolution in immune checkpoint inhibitor (ICI) therapy is providing novel treatment options with improved clinical outcomes in wild-type EGFR (EGFRwt) NSCLC; however, the application of ICI therapy to advanced EGFRm NSCLC patients is controversial. Early studies demonstrated the inferiority of ICI monotherapy to EGFR TKI therapy in the first line setting and inferiority to chemotherapy in the second line setting. Additionally, combination ICI and EGFR TKI therapies have demonstrated increased toxicities, and EGFR TKI therapy given after first-line ICI therapy has been correlated with severe adverse events. Nonetheless, combination therapies including dual-ICI blockade and ICI, chemotherapy, and angiogenesis inhibitor combinations are areas of active study with some intriguing signals in preliminary studies. Here, we review previous and ongoing clinical studies of ICI therapy in advanced EGFRm NSCLC. We discuss advances in understanding the differences in the tumor biology and tumor microenvironment (TME) of EGFRm NSCLC tumors that may lead to novel approaches to enhance ICI efficacy. It is our goal to equip the reader with a knowledge of current therapies, past and current clinical trials, and active avenues of research that provide the promise of novel approaches and improved outcomes for patients with advanced EGFRm NSCLC.

Hype or hope - Can combination therapies with third-generation EGFR-TKIs help overcome acquired resistance and improve outcomes in EGFR-mutant advanced/metastatic NSCLC?

Three generations of epidermal growth factor receptor - tyrosine kinase inhibitors (EGFR-TKIs) have been developed for treating advanced/metastatic non-small cell lung cancer (NSCLC) patients harboring EGFR-activating mutations, while a fourth generation is undergoing preclinical assessment. Although initially effective, acquired resistance to EGFR-TKIs usually arises within a year due to the emergence of clones harboring multiple resistance mechanisms. Therefore, the combination of EGFR-TKIs with other therapeutic agents has emerged as a potential strategy to overcome resistance and improve clinical outcomes. However, results obtained so far are ambiguous and ideal therapies for patients who experience disease progression during treatment with EGFR-TKIs remain elusive. This review provides an updated landscape of EGFR-TKIs, along with a description of the mechanisms causing resistance to these drugs. Moreover, it discusses the current knowledge, limitations, and future perspective regarding the use of EGFR-TKIs in combination with other anticancer agents, supporting the need for bench-to-bedside approaches in selected populations.

Emerging Approaches to Overcome Acquired Drug Resistance Obstacles to Osimertinib in Non-Small-Cell Lung Cancer

The pyrimidine core-containing compound Osimertinib is the only epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) from the third generation that has been approved by the U.S. Food and Drug Administration to target threonine 790 methionine (T790M) resistance while sparing the wild-type epidermal growth factor receptor (WT EGFR). It is nearly 200-fold more selective toward the mutant EGFR as compared to the WT EGFR. A tertiary cystein 797 to serine 797 (C797S) mutation in the EGFR kinase domain has hampered Osimertinib treatment in patients with advanced EGFR-mutated non-small-cell lung cancer (NSCLC). This C797S mutation is presumed to induce a tertiary-acquired resistance to all current reversible and irreversible EGFR TKIs. This review summarizes the molecular mechanisms of resistance to Osimertinib as well as different strategies for overcoming the EGFR-dependent and EGFR-independent mechanisms of resistance, new challenges, and a future direction.

Combined Treatment of Cinobufotalin and Gefitinib Exhibits Potent Efficacy against Lung Cancer

This study aimed to evaluate the efficacy of cinobufotalin combined with gefitinib in the treatment of lung cancer. A549 cells were treated with gefitinib, cinobufotalin, or cinobufotalin plus gefitinib. MTT assay, annexin-V/PI staining and flow cytometry, TUNEL staining, DCFH-DA staining, Western blot, and real-time RT-PCR were performed to investigate the synergistic inhibitory effect of cinobufotalin combined with gefitinib on the growth of A549 cells. Results showed that cinobufotalin synergized with gefitinib displayed inhibited cell viability and enhanced apoptosis in the combination group. Cinobufotalin combined with gefitinib induced a significant enhancement in reactive oxygen species (ROS) production accompanied by cell cycle arrest in the S phase arrest, characterized by upregulation of p21 and downregulation of cyclin A, cyclin E, and CDK2. Besides, cinobufotalin plus gefitinib downregulated the levels of HGF and c-Met. In summary, cinobufotalin combined with gefitinib impedes viability and facilitates apoptosis of A549 cells, indicating that the combined therapy might be a new promising treatment for lung cancer patients who are resistant to gefitinib.

Epidermal Growth Factor Receptor: Key to Selective Intracellular Delivery

Epidermal growth factor receptor (EGFR) is an integral surface protein mediating cellular response to a number of growth factors. Its overexpression and increased activation due to mutations is one of the most common traits of many types of cancer. Development and clinical use of the agents, which block EGFR activation, became a prime example of the personalized targeted medicine. However, despite the obvious success in this area, cancer cure remains unattainable in most cases. Because of that, as well as the result of the search for possible ways to overcome the difficulties of treatment, a huge number of new treatment methods relying on the use of EGFR overexpression and its changes to destroy cancer cells. Modern data on the structure, functioning, and intracellular transport of EGFR, its natural ligands, as well as signaling cascades triggered by the EGFR activation, peculiarities of the EGFR expression and activation in oncological disorders, as well as applied therapeutic approaches aimed at blocking EGFR signaling pathway are summarized and analyzed in this review. Approaches to the targeted delivery of various chemotherapeutic agents, radionuclides, immunotoxins, photosensitizers, as well as the prospects for gene therapy aimed at cancer cells with EGFR overexpression are reviewed in detail. It should be noted that increasing attention is being paid nowadays to the development of multifunctional systems, either carrying several different active agents, or possessing several environment-dependent transport functions. Potentials of the systems based on receptor-mediated endocytosis of EGFR and their possible advantages and limitations are discussed.