Taking early preventive interventions to manage the challenging issue of acquired resistance to third-generation EGFR inhibitors

Multieffect Specific Nanovesicles for Homing Resistant Tumors and Overcoming Osimertinib-Acquired Resistance in NSCLC

Acquired resistance to osimertinib (Osi) remains a major obstacle in the treatment of patients with EGFR-mutant non-small cell lung cancer (NSCLC). AXL elevation is a known key mechanism of Osi-resistance, and therapeutic strategies remain scarce. Emerging evidence reveals that an increased intracellular glutathione (GSH) level induces Osi resistance. In this study, a new mechanism is identified by which GSH regulates AXL expression via glutathione peroxidase 4 (GPX4) in Osi-resistant cells. A multifunctional covalent organic framework (COF) nanoplatform for GSH consumption, AXL inhibition, and co-delivery of the AXL inhibitor (Brigatinib) and Osi is creatively constructed to confirm whether Osi sensitivity improves by simultaneously targeting GSH-AXL resistance mechanisms. Furthermore, it is coated, for the first time, the COF carrier system with specific vesicles to precisely home it into resistant tumors, where CDH2 adhesion molecules play a crucial role. The engineered multifunctional antiresistance-specific nanovesicles effectively inhibited the GSH-AXL axis, induced apoptosis in Osi-resistant cells both in vitro and in vivo, and delayed the progression of Osi-resistant tumors. Overall, these findings provide a novel strategy to overcome the Osi-acquired resistance caused by high AXL levels in NSCLC.

Anti-EGFR therapy can overcome acquired resistance to the third-generation ALK-tyrosine kinase inhibitor lorlatinib mediated by activation of EGFR

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related mortality. Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKIs) are standard treatments for EML4-ALK-positive NSCLC, but resistance to these agents remains a challenge. This study aimed to determine the mechanisms of acquired resistance to the third-generation ALK-TKI lorlatinib. Lorlatinib-resistant cell lines were established by prolonged exposure to a high concentration of lorlatinib. Activation of epidermal growth factor receptor (EGFR) caused by a decrease in endocytosis and degradation of protein was demonstrated to play an essential role in acquired resistance to lorlatinib. The interaction between the EGFR and ALK was investigated to identify binding sites and conformational changes in ALK. We performed high-throughput compound screening using a small-molecule drugs library comprising 510 antitumor agents in an effort to discover small-molecule compounds that target EGFR in lorlatinib-resistant cells. Combination treatment with ALK-TKI and anti-EGFR agents suppressed acquired resistance to ALK-TKIs caused by activation of EGFR in vitro and in vivo, suggesting that the combination of lorlatinib and an anti-EGFR agent could be effective in patients with lorlatinib-resistant NSCLC. This research provides insights into the mechanism of resistance to lorlatinib and suggests that it can be overcome by anti-EGFR treatment, offering a promising approach for treating resistance to lorlatinib mediated by EGFR activation in patients with ALK-positive NSCLC.

AXL: shapers of tumor progression and immunosuppressive microenvironments

As research progresses, our understanding of the tumor microenvironment (TME) has undergone profound changes. The TME evolves with the developmental stages of cancer and the implementation of therapeutic interventions, transitioning from an immune-promoting to an immunosuppressive microenvironment. Consequently, we focus intently on the significant role of the TME in tumor proliferation, metastasis, and the development of drug resistance. AXL is highly associated with tumor progression; however, previous studies on AXL have been limited to its impact on the biological behavior of cancer cells. An increasing body of research now demonstrates that AXL can influence the function and differentiation of immune cells, mediating immune suppression and thereby fostering tumor growth. A comprehensive analysis to identify and overcome the causes of immunosuppressive microenvironments represents a novel approach to conquering cancer. In this review, we focus on elucidating the role of AXL within the immunosuppressive microenvironments, discussing and analyzing the effects of AXL on tumor cells, T cells, macrophages, natural killer (NK) cells, fibroblasts, and other immune-stromal cells. We aim to clarify the contributions of AXL to the progression and drug resistance of cancer from its functional role in the immune microenvironment.

Inhibition of hTERT/telomerase/telomere mediates therapeutic efficacy of osimertinib in EGFR mutant lung cancer

The inevitable acquired resistance to osimertinib (AZD9291), an FDA-approved third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) for the treatment of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating or T790M resistant mutations, limits its long-term clinical benefit. Telomere maintenance via telomerase reactivation is linked to uncontrolled cell growth and is a cancer hallmark and an attractive cancer therapeutic target. Our effort toward understanding the action mechanisms, including resistance mechanisms, of osimertinib has led to the identification of a novel and critical role in maintaining c-Myc-dependent downregulation of hTERT, a catalytic subunit of telomerase, and subsequent inhibition of telomerase/telomere and induction of telomere dysfunction in mediating therapeutic efficacy of osimertinib. Consequently, osimertinib combined with the telomere inhibitor, 6-Thio-dG, which is currently tested in a phase II trial, effectively inhibited the growth of osimertinib-resistant tumors, regressed EGFRm NSCLC patient-derived xenografts, and delayed the emergence of acquired resistance to osimertinib, warranting clinical validation of this strategy to manage osimertinib acquired resistance.

Features and efficacy of triple-targeted therapy for patients with EGFR-mutant non-small-cell lung cancer with acquired BRAF alterations who are resistant to epidermal growth factor receptor tyrosine kinase inhibitors

BACKGROUND

The recommended first-line treatment for advanced epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) patients is EGFR-tyrosine kinase inhibitors (EGFR-TKIs). BRAF alterations have been identified as resistance mechanisms. We aimed to identify features of and subsequent treatment strategies for such patients.

PATIENTS AND METHODS

We conducted a systematic literature review of NSCLC patients harboring acquired BRAF alterations. Additionally, BRAF-altered NSCLC patients who progressed from EGFR-TKIs at West China Hospital of Sichuan University were screened. Patient characteristics, treatment options, and outcomes were analyzed.

RESULTS

A total of 104 patients were included, 2 of whom came from our center. Seventy-five patients (72.1%) harbored BRAF mutations (57 class I mutations, 7 class II mutations, 9 class III mutations, and 2 non-class I-III mutations), and 29 (27.9%) harbored BRAF fusions. Eighteen patients received triple-targeted therapy, including prior EGFR-TKIs plus dabrafenib and trametinib, and 23 patients received other treatments. The median progression-free survival was significantly longer in patients receiving triple-targeted therapy than in those receiving other treatments (8.0 versus 2.5 months, P < 0.001). Similar findings were observed in patients with BRAF mutations (9.0 versus 2.8 months, P = 0.004), particularly in those with BRAF class I mutations (9.0 versus 2.5 months, P < 0.001). A potential benefit was also observed among patients with BRAF fusions (5.0 versus 2.0 months, P = 0.230). Twenty patients (48.8%) experienced adverse events. Dose reduction of RAF or MEK inhibitor was required in five patients (12.2%). Five patients (12.2%) permanently discontinued treatment (three on triple-targeted therapy; one on prior EGFR-TKI plus vemurafenib; one on prior EGFR-TKI plus trametinib).

CONCLUSIONS

BRAF alterations, specifically BRAF mutations and BRAF fusions, facilitate resistance to EGFR-TKIs. Triple-targeted therapy is effective and safe for patients with EGFR-mutant NSCLC with acquired BRAF alterations, mainly among patients with BRAF class I mutations and potentially in patients with BRAF fusions.

Targeting Transient Receptor Potential Melastatin-2 (TRPM2) Enhances Therapeutic Efficacy of Third Generation EGFR Inhibitors against EGFR Mutant Lung Cancer

There is an urgent need to fully understand the biology of third generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs), particularly osimertinib, and to develop mechanism-driven strategies to manage their acquired resistance. Transient receptor potential melastatin-2 (TRPM2) functions as an important regulator of Ca2+ influx, but its role in mediating therapeutic efficacies of EGFR-TKIs and acquired resistance to EGFR-TKIs has been rarely studied. This study has demonstrated a previously undiscovered role of suppression of TRPM2 and subsequent inhibition of Ca2+ influx and induction of ROS and DNA damage in mediating apoptosis induction and the therapeutic efficacy of osimertinib against EGFR mutant NSCLC. The rebound elevation represents a key mechanism accounting for the emergence of acquired resistance to osimertinib and other third generation EGFR-TKIs. Accordingly, targeting TRPM2 is a potentially promising strategy for overcoming and preventing acquired resistance to osimertinib, warranting further study in this direction including the development of cancer therapy-optimized TRPM2 inhibitors.

Brigatinib, a newly discovered AXL inhibitor, suppresses AXL-mediated acquired resistance to osimertinib in EGFR-mutated non-small cell lung cancer

In addition to the classical resistance mechanisms, receptor tyrosine-protein kinase AXL is a main mechanism of resistance to third-generation epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) osimertinib in EGFR-mutated non-small cell lung cancer (NSCLC). Developing an effective AXL inhibitor is important to sensitize osimertinib in clinical application. In this study we assessed the efficacy of brigatinib, a second-generation of anaplastic lymphoma kinase (ALK)-TKI, as a novel AXL inhibitor, in overcoming acquired resistance to osimertinib induced by AXL activation. We established an AXL-overexpression NSCLC cell line and conducted high-throughput screening of a small molecule chemical library containing 510 anti-tumor drugs. We found that brigatinib potently inhibited AXL expression, and that brigatinib (0.5 μM) significantly enhanced the anti-tumor efficacy of osimertinib (1 μM) in AXL-mediated osimertinib-resistant NSCLC cell lines in vitro. We demonstrated that brigatinib had a potential ability to bind AXL kinase protein and further inhibit its downstream pathways in NSCLC cell lines. Furthermore, we revealed that brigatinib might decrease AXL expression through increasing K48-linked ubiquitination of AXL and promoting AXL degradation in HCC827OR cells and PC-9OR cells. In AXL-high expression osimertinib-resistant PC-9OR and HCC827OR cells derived xenograft mouse models, administration of osimertinib (10 mg·kg-1·d-1) alone for 3 weeks had no effect, and administration of brigatinib (25 mg·kg-1·d-1) alone caused a minor inhibition on the tumor growth; whereas combination of osimertinib and brigatinib caused marked tumor shrinkages. We concluded that brigatinib may be a promising clinical strategy for enhancing osimertinib efficacy in AXL-mediated osimertinib-resistant NSCLC patients.

Sialyltransferase ST3GAL4 confers osimertinib resistance and offers strategies to overcome resistance in non-small cell lung cancer

The third-generation EGFR-TKI osimertinib is widely used in EGFR-mutated positive non-small cell lung cancer (NSCLC) patients, but drug resistance is inevitable. The currently known mechanisms only explain resistance in a small proportion of patients. For most patients, the mechanism of osimertinib resistance is still unclear, especially for EGFR-independent resistance. Herein, we thoroughly investigated the novel mechanism of osimertinib resistance and treatment strategies. We identified that ST3GAL4, a sialyltransferase, catalyzes terminal glycan sialylation of receptor protein tyrosine kinases, which induces acquired resistance to osimertinib in vitro and in vivo. In addition, ST3GAL4 is generally overexpressed in osimertinib-resistant patients with unknown resistance mechanisms. ST3GAL4 modifies MET glycosylation on N785 with sialylation, which antagonizes K48-related ubiquitin-dependent MET degradation and subsequently activates MET and its downstream proliferation signaling pathways. Meanwhile, ST3GAL4 knockdown or inhibition by brigatinib resensitizes resistant non-small cell lung cancer cells to osimertinib in vitro and in vivo This study suggests that ST3GAL4 can induce acquired resistance to osimertinib, which may be an important EGFR-independent resistance mechanism Furthermore, targeting ST3GAL4 with brigatinib provides new strategies to overcome osimertinib resistance.

DNA topoisomerase II inhibition potentiates osimertinib's therapeutic efficacy in EGFR-mutant non-small cell lung cancer models

Development of effective strategies to manage the inevitable acquired resistance to osimertinib, a third-generation EGFR inhibitor for the treatment of EGFR-mutant (EGFRm) non-small cell lung cancer (NSCLC), is urgently needed. This study reports that DNA topoisomerase II (Topo II) inhibitors, doxorubicin and etoposide, synergistically decreased cell survival, with enhanced induction of DNA damage and apoptosis in osimertinib-resistant cells; suppressed the growth of osimertinib-resistant tumors; and delayed the emergence of osimertinib-acquired resistance. Mechanistically, osimertinib decreased Topo IIα levels in EGFRm NSCLC cells by facilitating FBXW7-mediated proteasomal degradation, resulting in induction of DNA damage; these effects were lost in osimertinib-resistant cell lines that possess elevated levels of Topo IIα. Increased Topo IIα levels were also detected in the majority of tissue samples from patients with NSCLC after relapse from EGFR tyrosine kinase inhibitor treatment. Enforced expression of an ectopic TOP2A gene in sensitive EGFRm NSCLC cells conferred resistance to osimertinib, whereas knockdown of TOP2A in osimertinib-resistant cell lines restored their susceptibility to osimertinib-induced DNA damage and apoptosis. Together, these results reveal an essential role of Topo IIα inhibition in mediating the therapeutic efficacy of osimertinib against EGFRm NSCLC, providing scientific rationale for targeting Topo II to manage acquired resistance to osimertinib.