Intracellular levels of reactive oxygen species correlate with ABT-263 sensitivity in non-small-cell lung cancer cells.

ABT-263 (Navitoclax) is a BH3-mimetic drugs targeting anti-apoptotic B-cell lymphoma-2 (BCL-2) family proteins, including BCL-2, BCL-xL, and BCL-w, thereby inducing apoptosis. In small-cell lung cancer (SCLC) cells, the response to ABT-263 is associated with the expression of myeloid cell leukemia-1 (MCL-1) protein, however the efficacy of ABT-263 in non-small-cell lung cancer (NSCLC) has not been thoroughly evaluated. There are currently no established biomarkers for predicting the efficacy of ABT-263 treatment in NSCLC. We screened a panel of different NSCLC cell lines and found that ABT-263 inhibited cell proliferation and induced apoptosis in Calu-1, Calu-3, and BID007 cells. Inconsistent with previous reports on SCLC, low levels of MCL-1 did not predict the response to ABT-263 in NSCLC cells, however we found that intracellular levels of reactive oxygen species (ROS) in cancer cells were associated with sensitivity to ABT-263 in NSCLC cells. We also showed that increasing the level of intracellular ROS could enhance the sensitivity to ABT-263 in NSCLC cells. In summary, we propose that the intracellular levels of ROS could be used as a potential novel biomarker for predicting a response to ABT-263 in NSCLC. Furthermore, we show some evidence supporting the further assessment of ABT-263 as a new therapeutic strategy in patients with NSCLC combined with agents regulating ROS levels. We believe that our findings and follow-up studies on this matter would lead to novel diagnostic and treatment strategies in patients with NSCLC.

Factors associated with improvements in subjective symptoms of obstructive sleep apnea syndrome after continuous positive airway pressure therapy.

PURPOSE: Continuous positive airway pressure (CPAP) therapy improves subjective symptoms in obstructive sleep apnea syndrome (OSAS) patients; however, factors predicting symptom improvement post-CPAP therapy and the CPAP duration necessary for improving subjective symptoms are unclear. This study aimed to identify these factors and the appropriate nightly CPAP duration for improving subjective symptoms. METHODS: We recruited 359 subjects who completed both overnight polysomnography and subjective symptom assessments using the Epworth Sleepiness Scale (ESS), Zung Self-Depression Scale (SDS), and Pittsburgh Sleep Quality Index (PSQI). Firstly, we analyzed subject characteristics, and the associations between each assessment score and the Apnea-Hypopnea Index. These assessments were then repeated for 138 subjects who could continue for 3 months after starting CPAP. Secondly, associations between changes in self-reported outcome measures and nightly CPAP duration were analyzed. We identified subjects with abnormal initial ESS, PSQI, and SDS scores and divided them into "improvement" and "non-improvement" groups to examine factors associated with a positive outcome after CPAP therapy. RESULTS: Subjective symptom scores and proportions of subjects exceeding the cutoff values of each symptom score were not significantly related to OSAS severity. ESS, SDS, and PSQI scores improved 3 months after CPAP treatment, and factors involved in each improvement were found. Remarkably, longer CPAP nightly duration resulted in improvements in all subjective symptom scores. Furthermore, minimum durations between 4.75 and 5.40 h were necessary for improvements in subjective symptoms based on ROC curve analysis. CONCLUSIONS: Longer nightly CPAP use significantly improved OSAS subjective symptoms.

First case report of thyroid abscess caused by Helicobacter cinaedi presenting with thyroid storm.

BACKGROUND: Helicobacter cinaedi is a microaerobic Gram-negative spiral-shaped bacterium that causes enteritis, cellulitis, and bacteremia in both immunocompromised and immunocompetent patients. While there have been increasing numbers of reported H. cinaedi infections recently, there has been no thyroid abscess case caused by H. cinaedi presenting with thyroid storm. CASE PRESENTATION: A 50-year-old Japanese man presented with a 9-day history of high fever associated with palpitations, dry cough, and chronic diarrhea. The patient had a history of Basedow's disease that had been treated with thiamazole in the past. During the current episode, the patient was diagnosed with thyroid storm and treated accordingly. The blood culture taken on admission was positive for H. cinaedi. This finding was confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOFMS). A systemic computed tomography (CT) scan revealed a thyroid abscess as the site of infection and cause of the bacteremia. The 16S rRNA gene sequencing identified the pathogen of thyroid abscess as H. cinaedi. Clinical symptoms and laboratory data normalized on admission day 7 after treatment with both effective antibiotics and antithyroid drugs. CONCLUSIONS: The case study described a patient with a history of Basedow's disease that presented with a thyroid abscess caused by H. cinaedi with symptoms similar to those of thyroid storm. While this bacterium has been implicated in other infections, we believe this is the first time the bacteria has been documented to have caused a thyroid abscess.

A case of community-acquired pneumonia caused by Bacillus subtilis subsp. natto in an immunocompetent patient.

A 70-year-old immunocompetent male with a history of insomnia presented with pneumonia and bacteremia caused by Bacillus subtilis. The patient took benzodiazepines and regularly consumed alcohol and natto (fermented soybeans). Initial antibiotic treatment was not effective, and bronchoalveolar lavage was performed. Bronchoalveolar lavage fluid (BALF) analysis revealed an increased lymphocytes fraction, and B. subtilis was detected in the BALF. Whole-genome sequencing confirmed the congruence of the genetic sequences between the strain in the blood culture of the patient, BALF, and strain isolated from the consumed natto, confirming B. subtilis subsp. natto as the causative pathogen of pneumonia and bacteremia. Vancomycin followed by levofloxacin and systemic corticosteroid were used to treat the condition. This case highlights community-acquired pneumonia and bacteremia caused by B. subtilis subsp. natto, particularly in individuals who consume natto.

Social impact of brain fog and analysis of risk factors: Long COVID in Japanese population.

OBJECTIVE: To reveal the clinical features and assess risk factors linked to brain fog and its societal implications, including labor productivity, providing valuable insights for the future care of individuals who have experienced coronavirus disease 2019 (COVID-19). METHODS: We analyzed a comprehensive cohort dataset comprising 1,009 patients with COVID-19 admitted to Japanese hospitals. To assess brain fog, we analyzed patients who responded to a questionnaire indicating symptoms such as memory impairment and poor concentration. RESULTS: The prevalence of brain fog symptoms decreased 3 months posthospitalization but remained stable up to 12 months. Neurological symptoms such as taste and smell disorders and numbness at hospitalization correlated with a higher frequency of identifying brain fog as a long COVID manifestation. Our findings indicated that advanced age, female sex, a high body mass index, oxygen required during hospitalization, chronic obstructive pulmonary disease, asthma, and elevated C-reactive protein and elevated D-dimer levels were risk factors in patients exhibiting brain fog. Additionally, we demonstrated the negative impact of brain fog on labor productivity by presenteeism scores. INTERPRETATIONS: This study clarified the clinical characteristics of patients experiencing brain fog as a long COVID manifestation, specifically emphasizing neurological symptoms during hospitalization and their correlation with brain fog. Additionally, the study identified associated risk factors for its onset and revealed that the emergence of brain fog was linked to a decline in labor productivity.

TREX1 Inactivation Unleashes Cancer Cell STING-Interferon Signaling and Promotes Antitumor Immunity.

A substantial fraction of cancers evade immune detection by silencing Stimulator of Interferon Genes (STING)-Interferon (IFN) signaling. Therapeutic reactivation of this program via STING agonists, epigenetic, or DNA-damaging therapies can restore antitumor immunity in multiple preclinical models. Here we show that adaptive induction of three prime exonuclease 1 (TREX1) restrains STING-dependent nucleic acid sensing in cancer cells via its catalytic function in degrading cytosolic DNA. Cancer cell TREX1 expression is coordinately induced with STING by autocrine IFN and downstream STAT1, preventing signal amplification. TREX1 inactivation in cancer cells thus unleashes STING-IFN signaling, recruiting T and natural killer (NK) cells, sensitizing to NK cell-derived IFNγ, and cooperating with programmed cell death protein 1 blockade in multiple mouse tumor models to enhance immunogenicity. Targeting TREX1 may represent a complementary strategy to induce cytosolic DNA and amplify cancer cell STING-IFN signaling as a means to sensitize tumors to immune checkpoint blockade (ICB) and/or cell therapies. SIGNIFICANCE: STING-IFN signaling in cancer cells promotes tumor cell immunogenicity. Inactivation of the DNA exonuclease TREX1, which is adaptively upregulated to limit pathway activation in cancer cells, recruits immune effector cells and primes NK cell-mediated killing. Targeting TREX1 has substantial therapeutic potential to amplify cancer cell immunogenicity and overcome ICB resistance. This article is featured in Selected Articles from This Issue, p. 695.

A case of disseminated intravascular coagulation following tumour lysis syndrome due to small cell carcinoma of the lung.

A 64-year-old man was diagnosed with small cell lung cancer (SCLC) with multiple bone and liver metastases and bone marrow metastases. Spontaneous tumour lysis syndrome (TLS) was observed before starting chemotherapy with carboplatin, etoposide, and atezolizumab. The tumour further collapsed, and the patient developed disseminated intravascular coagulation (DIC) on day 4 of chemotherapy. The patient was successfully treated with intravenous hydration and rasburicase for TLS and subcutaneous unfractionated heparin for DIC. A large amount of tissue factor may be released in TLS, which could induce DIC. However, to the best of our knowledge, this is the first report of DIC following TLS in a case of SCLC. DIC following TLS in SCLC is a rare but life-threatening oncologic complication. Therefore, clinicians should be aware of this possibility when treating patients with advanced SCLC.

The germline factor DDX4 contributes to the chemoresistance of small cell lung cancer cells.

Human cancers often re-express germline factors, yet their mechanistic role in oncogenesis and cancer progression remains unknown. Here we demonstrate that DEAD-box helicase 4 (DDX4), a germline factor and RNA helicase conserved in all multicellular organisms, contributes to increased cell motility and cisplatin-mediated drug resistance in small cell lung cancer (SCLC) cells. Proteomic analysis suggests that DDX4 expression upregulates proteins related to DNA repair and immune/inflammatory response. Consistent with these trends in cell lines, DDX4 depletion compromised in vivo tumor development while its overexpression enhanced tumor growth even after cisplatin treatment in nude mice. Further, the relatively higher DDX4 expression in SCLC patients correlates with decreased survival and shows increased expression of immune/inflammatory response markers. Taken together, we propose that DDX4 increases SCLC cell survival, by increasing the DNA damage and immune response pathways, especially under challenging conditions such as cisplatin treatment.

Remarkable Differences in Calcification between the Primary Tumor and Metastatic Lymph Nodes in a Patient with ALK-Positive Non-Small-Cell Lung Cancer.

Calcified bilateral mediastinal lymph nodes are not common in malignant tumors. A 51-year-old woman presented to our hospital with a 20 mm nodule in the lower left lobe of the lung and extensive calcification in the bilateral mediastinal lymph nodes. Computed tomography indicated no calcification of the primary lesion. Immunohistochemical staining and fluorescent in situ hybridization detected an anaplastic lymphoma kinase (ALK) fusion. Treatment with alectinib, an ALK inhibitor, led to a significant reduction in tumor size and calcification in the lymph nodes. This case shows that different degrees of calcification can be associated with malignant tumors and may be reversible in some cases.

MET-Induced CD73 Restrains STING-Mediated Immunogenicity of EGFR-Mutant Lung Cancer.

Immunotherapy has shown limited efficacy in patients with EGFR-mutated lung cancer. Efforts to enhance the immunogenicity of EGFR-mutated lung cancer have been unsuccessful to date. Here, we discover that MET amplification, the most common mechanism of resistance to third-generation EGFR tyrosine kinase inhibitors (TKI), activates tumor cell STING, an emerging determinant of cancer immunogenicity (1). However, STING activation was restrained by ectonucleosidase CD73, which is induced in MET-amplified, EGFR-TKI-resistant cells. Systematic genomic analyses and cell line studies confirmed upregulation of CD73 in MET-amplified and MET-activated lung cancer contexts, which depends on coinduction of FOSL1. Pemetrexed (PEM), which is commonly used following EGFR-TKI treatment failure, was identified as an effective potentiator of STING-dependent TBK1-IRF3-STAT1 signaling in MET-amplified, EGFR-TKI-resistant cells. However, PEM treatment also induced adenosine production, which inhibited T-cell responsiveness. In an allogenic humanized mouse model, CD73 deletion enhanced immunogenicity of MET-amplified, EGFR-TKI-resistant cells, and PEM treatment promoted robust responses regardless of CD73 status. Using a physiologic antigen recognition model, inactivation of CD73 significantly increased antigen-specific CD8+ T-cell immunogenicity following PEM treatment. These data reveal that combined PEM and CD73 inhibition can co-opt tumor cell STING induction in TKI-resistant EGFR-mutated lung cancers and promote immunogenicity. SIGNIFICANCE: MET amplification upregulates CD73 to suppress tumor cell STING induction and T-cell responsiveness in TKI-resistant, EGFR-mutated lung cancer, identifying a strategy to enhance immunogenicity and improve treatment.

MPS1 inhibition primes immunogenicity of KRAS-LKB1 mutant lung cancer.

KRAS-LKB1 (KL) mutant lung cancers silence STING owing to intrinsic mitochondrial dysfunction, resulting in T cell exclusion and resistance to programmed cell death (ligand) 1 (PD-[L]1) blockade. Here we discover that KL cells also minimize intracellular accumulation of 2'3'-cyclic GMP-AMP (2'3'-cGAMP) to further avoid downstream STING and STAT1 activation. An unbiased screen to co-opt this vulnerability reveals that transient MPS1 inhibition (MPS1i) potently re-engages this pathway in KL cells via micronuclei generation. This effect is markedly amplified by epigenetic de-repression of STING and only requires pulse MPS1i treatment, creating a therapeutic window compared with non-dividing cells. A single course of decitabine treatment followed by pulse MPS1i therapy restores T cell infiltration in vivo, enhances anti-PD-1 efficacy, and results in a durable response without evidence of significant toxicity.

Activation of Tumor-Cell STING Primes NK-Cell Therapy.

Activation of the stimulator of interferon genes (STING) pathway promotes antitumor immunity but STING agonists have yet to achieve clinical success. Increased understanding of the mechanism of action of STING agonists in human tumors is key to developing therapeutic combinations that activate effective innate antitumor immunity. Here, we report that malignant pleural mesothelioma cells robustly express STING and are responsive to STING agonist treatment ex vivo. Using dynamic single-cell RNA sequencing of explants treated with a STING agonist, we observed CXCR3 chemokine activation primarily in tumor cells and cancer-associated fibroblasts, as well as T-cell cytotoxicity. In contrast, primary natural killer (NK) cells resisted STING agonist-induced cytotoxicity. STING agonists enhanced migration and killing of NK cells and mesothelin-targeted chimeric antigen receptor (CAR)-NK cells, improving therapeutic activity in patient-derived organotypic tumor spheroids. These studies reveal the fundamental importance of using human tumor samples to assess innate and cellular immune therapies. By functionally profiling mesothelioma tumor explants with elevated STING expression in tumor cells, we uncovered distinct consequences of STING agonist treatment in humans that support testing combining STING agonists with NK and CAR-NK cell therapies.

KRAS G12C inhibition and innate immune targeting.

INTRODUCTION: KRAS mutations drive tumorigenesis by altering cell signaling and the tumor immune microenvironment. Recent studies have shown promise for KRAS-G12C covalent inhibitors, which are advancing rapidly through clinical trials. The sequencing and combination of these agents with other therapies including immune checkpoint blockade (ICB) will benefit from strategies that also address the immune microenvironment to improve durability of response. AREAS COVERED: This paper reviews KRAS signaling and discusses downstream effects on cytokine production and the tumor immune microenvironment. RAS targeted therapy is introduced and perspectives on therapeutic targeting of KRAS-G12C and its immunosuppressive tumor microenvironment are offered. EXPERT OPINION: The availability of KRAS-G12C covalent inhibitors raises hopes for targeting this pervasive oncogene and designing better therapeutic combinations to promote anti-tumor immunity. A comprehensive mechanistic understanding of KRAS immunosuppression is required in order to prioritize agents for clinical trials.

Clinical Characteristics and Therapeutic Outcomes of Metastatic Peritoneal Carcinomatosis in Non-Small-Cell Lung Cancer.

BACKGROUND: Metastatic peritoneal carcinomatosis (MPC) is not common in patients with non-small cell lung cancer (NSCLC), and the clinical characteristics and treatment outcomes are still unclear. PATIENTS AND METHODS: We recruited 46 NSCLC patients with MPC at Keio University and affiliated hospitals (Keio Lung Oncology Group) between January 2011 and December 2017, then retrospectively investigated their clinical characteristics and the impact of treatment interventions on their survival. RESULTS: The profile of histological subtype was predominantly adenocarcinoma and 15 patients harbored driver oncogenes. Univariate and multivariate analysis demonstrated that performance status and the presence of a driver oncogene were significantly associated with the prolonged overall survival (OS). Regarding treatment, the median OS in the treatment group (9.3 months) was significantly longer than in the best supportive care group (1.3 months) (P < 0.0001). CONCLUSION: The prognosis of MPC in NSCLC patients who receive only the best supportive care is poor, but therapeutic intervention may improve prognosis.

Dynamic single-cell RNA sequencing identifies immunotherapy persister cells following PD-1 blockade.

Resistance to oncogene-targeted therapies involves discrete drug-tolerant persister cells, originally discovered through in vitro assays. Whether a similar phenomenon limits efficacy of programmed cell death 1 (PD-1) blockade is poorly understood. Here, we performed dynamic single-cell RNA-Seq of murine organotypic tumor spheroids undergoing PD-1 blockade, identifying a discrete subpopulation of immunotherapy persister cells (IPCs) that resisted CD8+ T cell-mediated killing. These cells expressed Snai1 and stem cell antigen 1 (Sca-1) and exhibited hybrid epithelial-mesenchymal features characteristic of a stem cell-like state. IPCs were expanded by IL-6 but were vulnerable to TNF-α-induced cytotoxicity, relying on baculoviral IAP repeat-containing protein 2 (Birc2) and Birc3 as survival factors. Combining PD-1 blockade with Birc2/3 antagonism in mice reduced IPCs and enhanced tumor cell killing in vivo, resulting in durable responsiveness that matched TNF cytotoxicity thresholds in vitro. Together, these data demonstrate the power of high-resolution functional ex vivo profiling to uncover fundamental mechanisms of immune escape from durable anti-PD-1 responses, while identifying IPCs as a cancer cell subpopulation targetable by specific therapeutic combinations.

Upregulation of FGF9 in Lung Adenocarcinoma Transdifferentiation to Small Cell Lung Cancer.

Transdifferentiation of lung adenocarcinoma to small cell lung cancer (SCLC) has been reported in a subset of lung cancer cases that bear EGFR mutations. Several studies have reported the prerequisite role of TP53 and RB1 alterations in transdifferentiation. However, the mechanism underlying transdifferentiation remains understudied, and definitive additional events, the third hit, for transdifferentiation have not yet been identified. In addition, no prospective experiments provide direct evidence for transdifferentiation. In this study, we show that FGF9 upregulation plays an essential role in transdifferentiation. An integrative omics analysis of paired tumor samples from a patient with transdifferentiated SCLC exhibited robust upregulation of FGF9. Furthermore, FGF9 upregulation was confirmed at the protein level in four of six (66.7%) paired samples. FGF9 induction transformed mouse lung adenocarcinoma-derived cells to SCLC-like tumors in vivo through cell autonomous activation of the FGFR pathway. In vivo treatment of transdifferentiated SCLC-like tumors with the pan-FGFR inhibitor AZD4547 inhibited growth. In addition, FGF9 induced neuroendocrine differentiation, a pathologic characteristic of SCLC, in established human lung adenocarcinoma cells. Thus, the findings provide direct evidence for FGF9-mediated SCLC transdifferentiation and propose the FGF9-FGFR axis as a therapeutic target for transdifferentiated SCLC. SIGNIFICANCE: This study demonstrates that FGF9 plays a role in the transdifferentiation of lung adenocarcinoma to small cell lung cancer.

Outcome of patients with lung cancer and severe psychiatric disorder admitted to a medical psychiatric unit.

The purpose of the present study was to evaluate the clinical profiles and treatment outcomes of patients with lung cancer admitted to the Medical Psychiatric Unit (MPU), which is built for patients with physical and severe psychiatric disorders. All medical records of patients with lung cancer admitted to the MPU of Tachikawa hospital were reviewed. The clinical outcomes of these patients were retrospectively evaluated between January 2010 and December 2016. A total of 24 patients in the MPU were histologically or cytologically diagnosed with primary lung cancer. Of these, 20 patients had schizophrenia, and 4 patients had a mood disorder. There were 15 patients who were diagnosed using bronchoscopy. The histology indicated adenocarcinoma, squamous cell carcinoma and non-small-cell lung cancer-not otherwise specified were in 11, 8, and 1 patient, respectively, while small-cell lung cancer was indicated in 4 patients. Surgery, chemoradiotherapy, radiotherapy, chemotherapy was performed in 13, 4, 2, 1 and 4 patients, respectively. The median survival time was 76.7 months for patients who underwent surgery, while it was 14.4 months for those who underwent chemoradiotherapy. In the MPU, patients with lung cancer and severe psychiatric disorders could be safely diagnosed, and patients with early-stage lung cancer exhibited long-term survival.

Tumor-Derived cGAMP Regulates Activation of the Vasculature.

Intratumoral recruitment of immune cells following innate immune activation is critical for anti-tumor immunity and involves cytosolic dsDNA sensing by the cGAS/STING pathway. We have previously shown that KRAS-LKB1 (KL) mutant lung cancer, which is resistant to PD-1 blockade, exhibits silencing of STING, impaired tumor cell production of immune chemoattractants, and T cell exclusion. Since the vasculature is also a critical gatekeeper of immune cell infiltration into tumors, we developed a novel microfluidic model to study KL tumor-vascular interactions. Notably, dsDNA priming of LKB1-reconstituted tumor cells activates the microvasculature, even when tumor cell STING is deleted. cGAS-driven extracellular export of 2'3' cGAMP by cancer cells activates STING signaling in endothelial cells and cooperates with type 1 interferon to increase vascular permeability and expression of E selectin, VCAM-1, and ICAM-1 and T cell adhesion to the endothelium. Thus, tumor cell cGAS-STING signaling not only produces T cell chemoattractants, but also primes tumor vasculature for immune cell escape.

A phase II trial of induction of erlotinib followed by cytotoxic chemotherapy for EGFR mutation-positive non-squamous non-small cell lung cancer patients.

BACKGROUND: No consensus has been reached regarding the treatment order and timing of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) and cytotoxic chemotherapy administration for EGFR mutation-positive non-small cell lung cancer (NSCLC) patients. METHODS: In this phase II trial, chemotherapy-naïve patients harboring activating EGFR mutations with stage IIIB/IV or post-surgical recurrent non-squamous NSCLC were enrolled. Patients were treated with erlotinib induction at 150 mg/day for 3 months. This was followed by cytotoxic chemotherapy with platinum plus pemetrexed, with or without bevacizumab, when the induction erlotinib achieved a CR or PR. The primary end point was the 1-year progression-free survival (PFS) rate, while the secondary end points were the response rate (RR), PFS, safety, and overall survival (OS). RESULTS: Twenty patients were enrolled in this study. The median age was 63 years. Eighteen patients had stage IV disease, and 2 patients had recurrent disease. Eleven patients achieved a PR after induction of erlotinib and 9 out of 11 patients were switched to chemotherapy. The 1-year PFS rate was 45.0% (90% CI 26.8-63.2), the overall RR was 55.0%, and the median PFS was 10.7 months in the intention-to-treat (ITT) population. Grade 3-4 adverse events were reported for 40% of the patients, including patients with leukopenia (10%), neutropenia (20%), and interstitial pneumonitis, bacterial pneumonia, rash, and nausea (all 5%). CONCLUSIONS: The primary end point of this study was not achieved. However, the therapy was well tolerated and may be a treatment option for a future study with patients responsive to short-term erlotinib treatment. CLINICAL TRIALS REGISTRATION NUMBER: UMIN ID: 000013125.

Efficacy of afatinib or osimertinib plus cetuximab combination therapy for non-small-cell lung cancer with EGFR exon 20 insertion mutations.

OBJECTIVES: Epidermal growth factor receptor (EGFR) mutation-positive lung cancer accounts for a significant subgroup of non-small cell lung cancers (NSCLC). Approximately 4-10% of EGFR mutations in NSCLC are EGFR exon 20 insertion mutations, which are reportedly associated with resistance to EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment. NSCLC patients carrying these mutations are rarely treated with EGFR-TKIs. The purpose of this study was to evaluate the efficacy of afatinib or osimertinib plus cetuximab combination therapy in experimental NSCLC models with EGFR exon 20 insertion mutations. MATERIALS AND METHODS: The EGFR mutations examined in this study were A763_Y764insFQEA, Y764_V765insHH, A767_V769dupASV, and D770_N771insNPG. Ba/F3 cells constitutively expressing wild type or mutated EGFR were used to determine the efficacy of afatinib or osimertinib plus cetuximab combination therapy in vitro. To determine the efficacy of the combination therapy in vivo, female BALB/c-nu mice were injected subcutaneously with 1 million Ba/F3 cells carrying EGFR A767_V769dupASV or Y764_V765insHH. RESULTS: We observed a mild but significant (P < 0.05) additive effect of the combination therapy against several EGFR exon 20 insertion mutations in vitro. Regarding EGFR A767_V769dupASV and EGFR Y764_V765insHH, cetuximab and afatinib single treatment did not induce significant inhibition of tumor formation; however, afatinib plus cetuximab combination treatment induced significant (P < 0.05) tumor growth inhibition without significant body weight loss or skin rash. CONCLUSION: The combination therapy induced a more potent inhibitory effect against several EGFR exon 20 insertion mutations than either therapy alone. Cetuximab can potentially increase the efficacy of afatinib or osimertinib in NSCLC with EGFR exon 20 insertion mutations.