[EGFR Exon 20 Insertion Mutation: Research Status and New Treatment Strategies].

In non-small cell lung cancer (NSCLC), as an improtant oncogenic driver gene, epidermal growth factor receptor exon 20 insertion (EGFR ex20ins) has a unique protein structure and is primarily drug-resistant to traditional EGFR-tyrosine kinase inhibitors (EGFR-TKIs). In recent years, exploration of targeted therapy for EGFR ex20ins has never stopped. Firstly Mobocertinib and Amivantamab obtained approval from U.S. Food and Drug Administration (FDA) for EGFR ex20ins mutant NSCLC patients, then other drugs, such as Sunvozertinib, made breakthroughs and combination therapies also obtained gains. Multi-pronged measures are hopeful to overcome EGFR ex20ins drug resistance. As mentioned above, it's definitely important to gain deeper understanding of molecular mechanism of EGFR ex20ins and assess effect and difference between novel drugs. This review is devoted to make a summary about newest achievement so to provide valuable reference about precise therapy for patients with EGFR ex20ins.
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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.

Repeated rebiopsy for detection of EGFR T790M mutation in patients with advanced-stage lung adenocarcinoma: Associated factors and treatment outcomes of Osimertinib.

OBJECTIVES: This study was performed to investigate the detection rate of EGFR T790M mutation by repeated rebiopsy, to identify the clinical factors related to repeated rebiopsy, and to assess survival outcomes according to the methods and numbers of repeated rebiopsies in patients with lung adenocarcinoma who received sequential osimertinib after failure of previous 1st or 2nd generation EGFR-tyrosine kinase inhibitors. METHODS: This retrospective study included patients with advanced-stage lung adenocarcinoma who were confirmed to have EGFR T790M mutation and to have received osimertinib from January 2020 to February 2021 at Samsung Medical Center. The presence of T790M mutation was assessed based on either plasma circulating tumor DNA (ctDNA) or tissue specimens. Results A total of 443 patients underwent rebiopsy, with 186 (42.0%) testing positive for the T790M mutation by the sixth rebiopsy. The final analysis included 143 eligible patients. Progression-free survival was not significantly different in terms of the methods (tissue: 13.3 months, 95% confidence interval [CI]: [9.4, 23.5] vs plasma: 11.1 months, 95% CI: [8.1, 19.4], p = 0.33) and numbers (one: 13.4 months, 95% CI: [9.4, 23.5] vs two or more: 11.0 months, 95% CI: [8.1, 14.8], p = 0.51) of repeated rebiopsies. Longer overall survival (OS) was found in patients in whom T790M was detected by tissue specimens rather than by plasma ctDNA (2-year OS rate: 81.7% for tissue vs 63.9% for plasma, p = 0.0038). Factors related to the lower numbers of rebiopsies included age and bone metastasis. Factor associated with T790M detection in tissue rather than in plasma was pleural metastasis, while advanced tumor stage was related to T790M confirmation in plasma rather than in tissue. CONCLUSIONS: Repeated rebiopsy for T790M detection in patients with NSCLC can increase the detection rate of the mutation. Detection of T790M by plasma ctDNA might be related to poor survival outcomes.

CIB2 mediates acquired gefitinib resistance by inducing ZEB1 expression and epithelial-mesenchymal transition.

EGFR-TKIs have been used as frontline treatment in patients with advanced non-small cell lung cancer (NSCLC) suffering from the EGFR mutation. Gefitinib, the first-generation EGFR-TKI, has greatly improved survival rates in lung cancer patients, whereas acquired gefitinib resistance is still a critical issue that needs to be overcome. In our research, high expression levels of CIB2 were found in gefitinib-resistant lung cancer cells. CIB2 knockout rendered gefitinib-resistant cells more sensitive to gefitinib, and overexpression of CIB2 in parental cells was sufficient to induce more resistance to gefitinib. Inhibition of CIB2 in gefitinib-resistant lung cancer cells significantly induced cell apoptosis. To clarify the major molecular mechanism by which CIB2 increases gefitinib resistance, we demonstrated that raised CIB2 in lung cancer cells promoted epithelial-to-mesenchymal transition (EMT) through upregulation of ZEB1. Moreover, FOSL1 transcriptionally regulated CIB2 expression. Finally, CIB2 rendered tumors resistant to gefitinib treatment in vivo. Our results explored a new mechanism: upregulated CIB2 promoted EMT through ZEB1 to regulate gefitinib resistance, which could be a candidate therapeutic target for overcoming acquired resistance to EGFR-TKIs in NSCLC patients.

HER4 is a high-affinity dimerization partner for all EGFR/HER/ErbB family proteins.

Human epidermal growth factor receptors (HER)-also known as EGFR or ErbB receptors-are a subfamily of receptor tyrosine kinases (RTKs) that play crucial roles in cell growth, division, and differentiation. HER4 (ErbB4) is the least studied member of this family, partly because its expression is lower in later stages of development. Recent work has suggested that HER4 can play a role in metastasis by regulating cell migration and invasiveness; however, unlike EGFR and HER2, the precise role that HER4 plays in tumorigenesis is still unresolved. Early work on HER family proteins suggested that there are direct interactions between the four members, but to date, there has been no single study of all four receptors in the same cell line with the same biophysical method. Here, we quantitatively measure the degree of association between HER4 and the other HER family proteins in live cells with a time-resolved fluorescence technique called pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). PIE-FCCS is sensitive to the oligomerization state of membrane proteins in live cells, while simultaneously measuring single-cell protein expression levels and diffusion coefficients. Our PIE-FCCS results demonstrate that HER4 interacts directly with all HER family members in the cell plasma membrane. The interaction between HER4 and other HER family members intensified in the presence of a HER4-specific ligand. Our work suggests that HER4 is a preferred dimerization partner for all HER family proteins, even in the absence of ligands.

Assessing the Sensitivity of Nested PCR Followed by Direct Sequencing on Exosomal DNA for EGFR Mutation Detection in NSCL

Background: Early and minimally invasive detection of epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) patients is a promising tool to select patients for targeted therapy in order to improve their prognosis. This study aimed to identify a sensitive, cost-effective, and easily accessible noninvasive method for detecting the EGFR-targetable mutations in the plasma exosomal DNA (exoDNA)+ of patients with NSCLC. Methods: This retrospective observational study was conducted over 10 months, from December 2022 to October 2023, at Masih Daneshvari Hospital in Tehran, Iran. A total of 30 patients with stage II-IV NSCLC and targetable mutation in the EGFR gene were included in the study. Nested PCR and Sanger sequencing were used to evaluate EGFR mutations in the DNA extracted from circulating exosomes. Results: The study found a sensitivity of 76.6% for EGFR mutation detection on exoDNA compared to tissue results. No significant impact was observed based on tumor staging, histology, mutation type, smoking status, gender, or age. Conclusion: Therapeutically targetable driver mutations in the EGFR gene can be accurately detected using nested PCR followed by direct sequencing of plasma exoDNA from patients with NSCLC. This approach facilitates timely and more personalized treatment for NSCLC patients, ultimately improving patient prognosis. Additionally, this method reduces the reliance on invasive tissue biopsies and their associated complications.

[Advances in Diagnosis and Targeted Therapy of G719X/L861Q/S768I Mutant 
Non-small Cell Lung Cancer].

Lung cancer accounts for the highest proportion of cancer deaths in the world and poses a great threat to human health. About 30% to 40% of non-small cell lung cancer (NSCLC) is caused by point mutations, exon insertion and exon deletion of the epidermal growth factor receptor (EGFR). In addition to the common exon 19 deletion mutation and exon 21 L858R mutation, exon 18 G719X mutation, exon 21 L861Q mutation and exon 20 S768I mutation are the most important rare mutations. At present, the diagnostic methods for major rare mutations are mainly next-generation sequencing (NGS), digital polymerase chain reaction (dPCR), droplet digital PCR (ddPCR), etc. Regarding the targeted therapy of G719X/L861Q/S768I mutant NSCLC, the first generation EGFR-tyrosine kinase inhibitors (TKIs) have poor efficacy, while the second and third generation EGFR-TKIs have similar efficacy. The novel third generation EGFR-TKIs and combination therapy show a good therapeutic prospect. This article summarized the progress in the diagnosis and targeted therapy of G719X/L861Q/S768I mutant NSCLC, so as to provide reference for subsequent clinical drug use and research.
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Prognostic Impact of Postoperative Recurrence in Patients With Epidermal Growth Factor Receptor-Positive Non-Small Cell Lung Cancer.

BACKGROUND: Mutations in the epidermal growth factor receptor (EGFR) gene are the most common targetable gene alterations in non-small cell lung cancer (NSCLC). In Japan, approximately 40% of patients who undergo surgical resection for non-squamous NSCLC have EGFR mutations. However, no long-term studies have been conducted including a large number of EGFR-positive NSCLC patients with postoperative recurrence (PR). METHODS: We conducted a retrospective observational study of the data of EGFR-positive NSCLC patients with PR who had undergone surgery at the Shizuoka Cancer Center between October 2002 and November 2017. We evaluated post-recurrence overall survival (PRS) and postoperative overall survival (POS) using the Kaplan-Meier method and identify any associations between the clinical variables at recurrence and PRS using univariate and multivariate analysis. RESULTS: We enrolled 162 patients. The median observation time for PRS was 4.95 years (range, 0.82-13.25) and POS was 5.81 years (range, 2.84-16.71). The median PRS was 5.17 years (95% confidence interval [CI], 3.90-5.61) and POS was 7.07 years (95% CI, 5.88-8.01). Univariate analysis identified male sex (median PRS: 3.32 vs. 5.39 years; p < 0.05), bone metastasis (median PRS: 2.43 vs. 5.33 years; p < 0.05), and central nervous system (CNS) metastasis (median PRS: 3.05 vs. 5.39 years; p < 0.05) and multivariate analysis identified bone metastasis (hazard ratio [HR], 2.01; 95% CI, 1.23-3.28; p < 0.05) and CNS metastasis (HR, 1.84; 95% CI, 1.14-2.98; p < 0.05) as poor prognostic factors. The pattern of recurrence (oligo vs. non-oligo recurrence) was not a prognostic factor. Logistic regression analysis revealed the association between sex and the presence bone/CNS metastasis at recurrence. CONCLUSION: Our data may help visualize future prospects and determine the timing of osimertinib initiation. New treatment strategies need to be developed for patients with bone/CNS metastasis at the first recurrence.

Analysis of EGFR binding hotspots for design of new EGFR inhibitory biologics.

The epidermal growth factor (EGF) receptor (EGFR) is activated by the binding of one of seven EGF-like ligands to its ectodomain. Ligand binding results in EGFR dimerization and stabilization of the active receptor conformation subsequently leading to activation of downstream signaling. Aberrant activation of EGFR contributes to cancer progression through EGFR overexpression/amplification, modulation of its positive and negative regulators, and/or activating mutations within EGFR. EGFR targeted therapeutic antibodies prevent dimerization and interaction with endogenous ligands by binding the ectodomain of EGFR. However, these antibodies have had limited success in the clinic, partially due to EGFR ectodomain resistance mutations, and are only applicable to a subset of patients with EGFR-driven cancers. These limitations suggest that alternative EGFR targeted biologics need to be explored for EGFR-driven cancer therapy. To this end, we analyze the EGFR interfaces of known inhibitory biologics with determined structures in the context of endogenous ligands, using the Rosetta macromolecular modeling software to highlight the most important interactions on a per-residue basis. We use this analysis to identify the structural determinants of EGFR targeted biologics. We suggest that commonly observed binding motifs serve as the basis for rational design of new EGFR targeted biologics, such as peptides, antibodies, and nanobodies.

EGFR-mutated NSCLC: A roadmap to treatment sequences.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the standard of care for the management of EGFR-mutated non-small cell lung cancer. Recent results from the HARMONi-A trial lead to considering ivonescimab-a first-in-class, bispecific antibody targeting PD-1 and VEGF-plus chemotherapy as a new second-line option following third-generation TKIs.

Prognostic impact of nectin-like molecule-5 (CD155) expression in non-small cell lung cancer.

BACKGROUND: CD155 is a transmembrane protein that inhibits antitumor immune response and represents a predictor of worse prognosis in non-small-cell lung cancer (NSCLC). However, it remains unexplored its association with clinical characteristics and genomic status of Latin American patients. This study characterizes the CD155 expression and its clinical implications in this population. METHODS: Tissue biopsies from 86 patients with locally-advanced or metastatic NSCLC were assessed for CD155 protein expression, ALK rearrangements and EGFR mutations. Cutoff values for high CD155 expression (CD155high) were determined from receiver operating characteristic (ROC) curves according to 2-year survival. It was evaluated its association with clinicopathological features, median progression-free survival (mPFS) and overall survival (mOS). RESULTS: the cutoff score for CD155high was 155 in the entire cohort and in patients without oncogenic alterations, and it was 110 in patients with oncogenic alterations. Eighty-four patients (97.7%) were CD155 positive, of which fifty-six (65.0%) had CD155high. EGFR L858R mutation related to lower CD155 IHC score than exon 19 deletion. Individuals with CD155high showed a shorter mOS (13.0 vs. 30.8 months; HR: 1.96 [95% CI, 1.15-3.35]; p = 0.014). Patients without oncogenic alterations having a CD155high displayed shorter mPFS (1.6 vs. 6.4 months, HR: 2.09 [95% CI, 1.06-4.20]; p = 0.034) and mOS (2.9 vs. 23.1 months; HR: 1.27 [95% CI, 1.07- 4.42]; p = 0.032). Patients with oncogenic alterations having CD155high only showed a trend to shorter mOS (26.3 vs. 52.0 months; HR: 2.39 [95% CI, 0.98-5.83]; p = 0.058). CONCLUSION: CD155high is a predictor of worse outcomes in patients with advanced NSCLC, predominantly among those without oncogenic alterations. CD155 could be a potential biomarker and a molecular target in patients with poor responses to current therapies.

The impact of postoperative adjuvant therapy on EGFR-mutated stage IA lung adenocarcinoma with micropapillary pathological subtypes.

BACKGROUND: Micropapillary (MPP) adenocarcinoma is considered one of the most aggressive pathological types of lung adenocarcinoma (LADC). This retrospective study aimed to evaluate the prognostic significance and benefit of postoperative adjuvant therapy (PAT) in stage IA LADC patients with different proportions of MPP components. MATERIALS AND METHODS: We retrospectively examined clinical stage IA LADC patients who underwent surgical resection between August 2012 and December 2019. In terms of the proportion of MPP components (TPM), the tumors were reclassified into three categories: MPP patterns absent (TPMN); low proportions of MPP components (TPML); and high proportions of MPP components (TPMH). The dates of recurrence and metastasis were identified based on physical examinations and were confirmed by histopathological examination. RESULTS: Overall, 505 (TPMN, n = 375; TPML, n = 92; TPMH, n = 38) patients harboring EGFR mutations were enrolled in the study. Male sex (P = 0.044), high pathological stage (P < 0.001), and MPP pathological subtype (P < 0.001) were more frequent in the TPM-positive (TPMP) group than in the TPM-negative (TPMN) group. Five-year disease-free survival (DFS) rates were significantly lower in the TPMP group than in the TPMN group (84.5% vs. 93.4%, P = 0.006). In addition, patients with high proportions (greater than 10%) of MPP components had worse overall survival (OS) (91.0% vs. 98.9%, P = 0.025) than those with low proportions (5%≤ TPM ≤ 10%). However, postoperative EGFR tyrosine kinase inhibitors (TKIs) or adjuvant chemotherapy (ACT) cannot improve DFS and OS between EGFR-mutated patients with different proportions of MPP components. CONCLUSION: MPP was related to earlier recurrence and shortened survival time, even in stage IA. Further research needs a larger sample size to clarify that EGFR-mutated stage IA patients with MPP components obtain survival benefits from adjuvant therapy.

Potential therapeutic option for EGFR-mutant small cell lung cancer transformation: a case report and literature review.

Transformation from non-small cell lung cancer (NSCLC) to small cell lung cancer (SCLC) is rare and is associated with poor prognosis. However, the standard treatment protocols for patients with SCLC transformation remain unknown. Here, we report the case of a patient with advanced EGFR exon 19 deletion (19del) NSCLC who underwent SCLC transformation during targeted therapy. Biopsies and genetic testing were performed to adjust treatment regimens accordingly. The patient responded favorably to a combined treatment regimen comprising etoposide plus cisplatin chemotherapy and adebrelimab plus osimertinib. This case highlights the critical importance of acknowledging tumor heterogeneity in clinical decision-making and identifying potentially effective treatment options for patients with SCLC transformation. Additionally, we reviewed cases of the transformation of NSCLC to SCLC from 2017 to 2023.

Pediatric Fibromatosis Lacks the Internal Tandem Duplication of EGFR Seen in Congenital Mesoblastic Nephroma.

Classical and mixed congenital mesoblastic nephroma (CMN) are characterized by an internal tandem duplication (ITD) of the EGFR gene, in contrast to cellular CMN that usually harbors an ETV6::NTRK3 gene fusion. This same fusion occurs in infantile fibrosarcoma, and this tumor can be considered as the soft tissue equivalent of cellular CMN. A soft tissue equivalent of classic/mixed CMN remains undefined at the genetic level. Since classical CMN resembles fibromatosis of soft tissue histologically, we asked whether fibromatosis in children might show EGFR ITD. ITD was investigated using the polymerase chain reaction and primers for exons 18 and 25 of the EGFR gene. Seven of the eight cases of classical or mixed CMN were positive by this approach, but none of the five cellular CMNs. Of 11 cases of fibromatosis (six plantar, two digital, and three desmoid), none were positive for EGFR ITD. Within the limits of this small study, we conclude that pediatric fibromatosis is likely not characterized by EGFR ITD. There are isolated reports of pediatric soft tissue tumors that harbor EGFR ITD, but these have the appearance of infantile fibrosarcoma or mixed CMN rather than fibromatosis. We did not find any such cases, since all 14 cases of infantile fibrosarcoma in our study had an ETV6::NTRK3 fusion. The soft tissue tumors with EGFR ITD are not a morphologic match for the low-grade histology of classical CMN. Whether they have a similar favorable biology or behave more like fibrosarcoma with an ETV6::NTRK3 fusion or an alternative fusion involving other kinases remains to be determined.

Association of mean platelet volume (MPV), MPV/PLATELET (PLT) ratio, and lymphocyte/monocyte ratio (LMR) as poor prognostic factor in EGFR-mutant lung adenocarcinoma treated with EGFR tyrosine kinase inhibitor.

Introduction: Platelets (PLT) and host systemic inflammatory response (SIR) are known to be effective in the aggregation of cancer cells and the formation of metastasis. There are studies pointing out to the prognostic efficacy of lymphocyte-monocyte ratio (LMR) showing SIR activation and mean platelet volume (MPV) values indicating platelet activation in various cancer types. We predict that easy-to-access hemogram parameters such as MPV, MPV/PLT, and LMR can be guiding in the clinical follow-up period of patients with epidermal growth factor receptor (EGFR) positive mutation and who received EGFR, tyrosine kinase inhibitor (TKI) in the first-line treatment in predicting the progression of the disease, predicting the survival time of the patients, and evaluating the response to treatment. Materials and Methods: The study is retrospective and included patients with stage III and stage IV pulmonary adenocarcinoma with positive EGFR mutations and for whom TKI was used in the first-line treatment between January 2011 and January 2021. MPV, MPV/PLT, and LMR values of the patients were calculated before treatment. Age, sex, comorbidity, smoking history, TNM stage, metastasis localizations, EGFR mutation types, TKI treatments used in first-line treatment, and MPV, MPV/PLT, and LMR values at the 1st month of treatment were recorded. With Kaplan-Meier, six-month, one-year, three-year, and five-year survival rates, average life expectancy, and 95% confidence intervals for these periods were calculated. Variables that may affect progression and overall survival (OS) were determined by performing univariate and multivariate Cox regression analysis. Result: One hundred and two patients were included in the study. The mean age of the patients was 64.30 ± 12.6 years. Eighty-four patients were in stage IV at the time of diagnosis. The expected mean progression-free survival (PFS) period of the cases was found to be 13.3 months. The mean life expectancy of the cases was found to be 35.1 months. Web-based Cutoff Finder algorithm written in the R program (http://molpath.charite.de/cutoff) was used to determine the ideal cut points for MPV, MPV/PLT, and LMR. The cut-off values were found to be 7.55 fL for MPV, 0.251 for MPV/PLT, and 2.615 for LMR, respectively. In univariate Cox regression analysis, LMR level lower than 2.615 increased the rate of progression 1.747 times (95% confidence interval: 1.129-2.705) and the death rate 2.056 times (95% confidence interval: 1.217-3.475) (p= 0.012, p= 0.007). The mean PFS LMR cut-off value was 10.3 months, and 15.3 months, and mean OS durations were 25.1 months and 40.8 months for the groups with low and high cut-off values respectively (p= 0.011, p= 0.006 log-rank test). According to the results of multivariate Cox regression analysis, MPV/PLT < 0.251, smoking, presence of pleural and adrenal metastases, and gefitinib treatment were independent factors in determining PFS. The independent factors determining OS in multivariate Cox regression analysis were being male, platelet increase, MPV > 7.55, gefitinib treatment, and smoking. Conclusions: MPV, MPV/PLT, and LMR are potential biomarkers that can be used for the clinical follow-up of lung ADC patients receiving EGFR-TKI treatment.

PIM1 kinase promotes EMT-associated osimertinib resistance via regulating GSK3ß signaling pathway in EGFR-mutant non-small cell lung cancer.

Acquired resistance is inevitable in the treatment of non-small cell lung cancer (NSCLC) with osimertinib, and one of the primary mechanisms responsible for this resistance is the epithelial-mesenchymal transition (EMT). We identify upregulation of the proviral integration site for Moloney murine leukemia virus 1 (PIM1) and functional inactivation of glycogen synthase kinase 3ß (GSK3ß) as drivers of EMT-associated osimertinib resistance. Upregulation of PIM1 promotes the growth, invasion, and resistance of osimertinib-resistant cells and is significantly correlated with EMT molecules expression. Functionally, PIM1 suppresses the ubiquitin-proteasome degradation of snail family transcriptional repressor 1 (SNAIL) and snail family transcriptional repressor 2 (SLUG) by deactivating GSK3ß through phosphorylation. The stability and accumulation of SNAIL and SLUG facilitate EMT and encourage osimertinib resistance. Furthermore, treatment with PIM1 inhibitors prevents EMT progression and re-sensitizes osimertinib-resistant NSCLC cells to osimertinib. PIM1/GSK3ß signaling is activated in clinical samples of osimertinib-resistant NSCLC, and dual epidermal growth factor receptor (EGFR)/PIM1 blockade synergistically reverse osimertinib-resistant NSCLC in vivo. These data identify PIM1 as a driver of EMT-associated osimertinib-resistant NSCLC cells and predict that PIM1 inhibitors and osimertinib combination therapy will provide clinical benefit in patients with EGFR-mutant NSCLC.

L3MBTL1, a polycomb protein, promotes Osimertinib acquired resistance through epigenetic regulation of DNA damage response in lung adenocarcinoma.

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (EGFR-TKI) approved for patients with EGFR T790M resistance mutations as first- or second-line treatment of EGFR-positive patients. Resistance to Osimertinib will inevitably develop, and the underlying mechanisms are largely unknown. In this study, we discovered that acquired resistance to Osimertinib is associated with abnormal DNA damage response (DDR) in lung adenocarcinoma cells. We discovered that the polycomb protein Lethal(3) Malignant Brain Tumor-Like Protein 1 (L3MBTL1) regulates chromatin structure, thereby contributing to DDR and Osimertinib resistance. EGFR oncogene inhibition reduced L3MBTL1 ubiquitination while stabilizing its expression in Osimertinib-resistant cells. L3MBTL1 reduction and treatment with Osimertinib significantly inhibited DDR and proliferation of Osimertinib-resistant lung cancer cells in vitro and in vivo. L3MBTL1 binds throughout the genome and plays an important role in EGFR-TKI resistance. It also competes with 53BP1 for H4K20Me2 and inhibits the development of drug resistance in Osimertinib-resistant lung cancer cells in vitro and in vivo. Our findings suggest that L3MBTL1 inhibition is a novel approach to overcoming EGFR-TKI-acquired resistance.

A bispecific antibody targeting EGFR and AXL delays resistance to osimertinib.

Activating EGFR (epidermal growth factor receptor) mutations can be inhibited by specific tyrosine kinase inhibitors (TKIs), which have changed the landscape of lung cancer therapy. However, due to secondary mutations and bypass receptors, such as AXL (AXL receptor tyrosine kinase), drug resistance eventually emerges in most patients treated with the first-, second-, or third-generation TKIs (e.g., osimertinib). To inhibit AXL and resistance to osimertinib, we compare two anti-AXL drugs, an antibody (mAb654) and a TKI (bemcentinib). While no pair of osimertinib and an anti-AXL drug is able to prevent relapses, triplets combining osimertinib, cetuximab (an anti-EGFR antibody), and either anti-AXL drug are initially effective. However, longer monitoring uncovers superiority of the mAb654-containing triplet, possibly due to induction of receptor endocytosis, activation of immune mechanisms, or disabling intrinsic mutators. Hence, we constructed a bispecific antibody that engages both AXL and EGFR. When combined with osimertinib, the bispecific antibody consistently inhibits tumor relapses, which warrants clinical trials.