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Purpose: Patients with advanced non–small cell lung cancer (NSCLC) harboring activating EGFR mutations are initially responsive to tyrosine kinase inhibitors (TKI). However, therapeutic resistance eventually emerges, often via secondary EGFR mutations or EGFR-independent mechanisms such as epithelial-to-mesenchymal transition. Treatment options after EGFR-TKI resistance are limited as anti-PD-1/PD-L1 inhibitors typically display minimal benefit. Given that IL6 is associated with worse outcomes in patients with NSCLC, we investigate whether IL6 in part contributes to this immunosuppressed phenotype. Experimental Design: We utilized a syngeneic genetically engineered mouse model (GEMM) of EGFR-mutant NSCLC to investigate the effects of IL6 on the tumor microenvironment and the combined efficacy of IL6 inhibition and anti-PD-1 therapy. Corresponding in vitro studies used EGFR-mutant human cell lines and clinical specimens. Results: We identified that EGFR-mutant tumors which have oncogene-independent acquired resistance to EGFR-TKIs were more mesenchymal and had markedly enhanced IL6 secretion. In EGFR-mutant GEMMs, IL6 depletion enhanced activation of infiltrating natural killer (NK)- and T-cell subpopulations and decreased immunosuppressive regulatory T and Th17 cell populations. Inhibition of IL6 increased NK- and T cell–mediated killing of human osimertinib-resistant EGFR-mutant NSCLC tumor cells in cell culture. IL6 blockade sensitized EGFR-mutant GEMM tumors to PD-1 inhibitors through an increase in tumor-infiltrating IFNγ+ CD8+ T cells. Conclusions: These data indicate that IL6 is upregulated in EGFR-mutant NSCLC tumors with acquired EGFR-TKI resistance and suppressed T- and NK-cell function. IL6 blockade enhanced antitumor immunity and efficacy of anti-PD-1 therapy warranting future clinical combinatorial investigations.

Angiogenesis, the sprouting of new blood vessels from existing vessels, is one of six known mechanisms employed by solid tumors to recruit blood vessels necessary for their initiation, growth, and metastatic spread. The vascular network within the tumor facilitates the transport of nutrients, oxygen, and immune cells and is regulated by pro- and anti-angiogenic factors. Nearly four decades ago, VEGF was identified as a critical factor promoting vascular permeability and angiogenesis, followed by identification of VEGF family ligands and their receptors (VEGFR). Since then, over a dozen drugs targeting the VEGF/VEGFR pathway have been approved for approximately 20 solid tumor types, usually in combination with other therapies. Initially designed to starve tumors, these agents transiently “normalize” tumor vessels in preclinical and clinical studies, and in the clinic, increased tumor blood perfusion or oxygenation in response to these agents is associated with improved outcomes. Nevertheless, the survival benefit has been modest in most tumor types, and there are currently no biomarkers in routine clinical use for identifying which patients are most likely to benefit from treatment. However, the ability of these agents to reprogram the immunosuppressive tumor microenvironment into an immunostimulatory milieu has rekindled interest and has led to the FDA approval of seven different combinations of VEGF/VEGFR pathway inhibitors with immune checkpoint blockers for many solid tumors in the past 3 years. In this review, we discuss our understanding of the mechanisms of response and resistance to blocking VEGF/VEGFR, and potential strategies to develop more effective therapeutic approaches.

IL-6 modulates expression of NK receptor and their ligands in EGFR mutant tumors.

IL-6 modulates activation state of infiltrating T cells in EGFR mutant tumors.

Small cell lung cancer (SCLC) is an aggressive malignancy distinct from non–small cell lung cancer (NSCLC) in its metastatic potential and treatment response. Using an integrative proteomic and transcriptomic analysis, we investigated molecular differences contributing to the distinct clinical behavior of SCLCs and NSCLCs. SCLCs showed lower levels of several receptor tyrosine kinases and decreased activation of phosphoinositide 3-kinase (PI3K) and Ras/mitogen-activated protein (MAP)/extracellular signal–regulated kinase (ERK) kinase (MEK) pathways but significantly increased levels of E2F1-regulated factors including enhancer of zeste homolog 2 (EZH2), thymidylate synthase, apoptosis mediators, and DNA repair proteins. In addition, PARP1, a DNA repair protein and E2F1 co-activator, was highly expressed at the mRNA and protein levels in SCLCs. SCLC growth was inhibited by PARP1 and EZH2 knockdown. Furthermore, SCLC was significantly more sensitive to PARP inhibitors than were NSCLCs, and PARP inhibition downregulated key components of the DNA repair machinery and enhanced the efficacy of chemotherapy.Significance: SCLC is a highly lethal cancer with a 5-year survival rate of less than 10%. To date, no molecularly targeted agents have prolonged survival in patients with SCLCs. As a step toward identifying new targets, we systematically profiled SCLCs with a focus on therapeutically relevant signaling pathways. Our data reveal fundamental differences in the patterns of pathway activation in SCLCs and NSCLCs and identify several potential therapeutic targets for SCLCs, including PARP1 and EZH2. On the basis of these results, clinical studies evaluating PARP and EZH2 inhibition, together with chemotherapy or other agents, warrant further investigation. Cancer Discov; 2(9); 798–811. ©2012 AACR.Read the Commentary on this article by Rosell and Wannesson, p. 769.This article is highlighted in the In This Issue feature, p. 753.

EGFR-mutant NSCLC tumor cells with acquired resistance to an EGFR-TKI display augmented IL-6 gene expression.

PDF file, 35K, IC50 values for AZD2281 and AG01469 after 14d treatment.

PDF file, 54K, Small cell lung cancer cell lines.

PDF file, 61K, mRNA transcripts significantly different between SCLC and NSCLC tumors.

PDF file, 53K, mRNA transcripts significantly different between SCLC and NSCLC cell lines.

PDF file, 64K, Non-small cell lung cancer cell lines.

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PDF file, 95K, Antibodies used in reverse-phase protein microarrays

PDF file, 125K, Western blot of total PARP1.

PDF file, 83K, Proteins with ≥1.2-fold differential expression between small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).

Development of IL-6 knockout EGFR-mutant GEMM tumors.

EGFR-mutant NSCLC EGFR-independent tumor model is refractory to EGFR-TKI treatment.

PDF file - 167K, Different probes for the same gene vary within and across microarray platforms

Purpose: Epithelial–mesenchymal transition (EMT) has been associated with metastatic spread and EGF receptor (EGFR) inhibitor resistance. We developed and validated a robust 76-gene EMT signature using gene expression profiles from four platforms using non–small cell lung carcinoma (NSCLC) cell lines and patients treated in the Biomarker-Integrated Approaches of Targeted Therapy for Lung Cancer Elimination (BATTLE) study.Experimental Design: We conducted an integrated gene expression, proteomic, and drug response analysis using cell lines and tumors from patients with NSCLC. A 76-gene EMT signature was developed and validated using gene expression profiles from four microarray platforms of NSCLC cell lines and patients treated in the BATTLE study, and potential therapeutic targets associated with EMT were identified.Results: Compared with epithelial cells, mesenchymal cells showed significantly greater resistance to EGFR and PI3K/Akt pathway inhibitors, independent of EGFR mutation status, but more sensitivity to certain chemotherapies. Mesenchymal cells also expressed increased levels of the receptor tyrosine kinase Axl and showed a trend toward greater sensitivity to the Axl inhibitor SGI-7079, whereas the combination of SGI-7079 with erlotinib reversed erlotinib resistance in mesenchymal lines expressing Axl and in a xenograft model of mesenchymal NSCLC. In patients with NSCLC, the EMT signature predicted 8-week disease control in patients receiving erlotinib but not other therapies.Conclusion: We have developed a robust EMT signature that predicts resistance to EGFR and PI3K/Akt inhibitors, highlights different patterns of drug responsiveness for epithelial and mesenchymal cells, and identifies Axl as a potential therapeutic target for overcoming EGFR inhibitor resistance associated with the mesenchymal phenotype. Clin Cancer Res; 19(1); 279–90. ©2012 AACR.

Genetic profiling of 42 cases

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PDF file - 66K, CDH1 probes vary in their accuracy and dynamic range

Supplemental Figure 2. VEGFR TKIs inhibit the migration of NSCLC cells with KDR CNGs.

Purpose: VEGF pathway inhibitors have been investigated as therapeutic agents in the treatment of non–small cell lung cancer (NSCLC) because of its central role in angiogenesis. These agents have improved survival in patients with advanced NSCLC, but the effects have been modest. Although VEGFR2/KDR is typically localized to the vasculature, amplification of KDR has reported to occur in 9% to 30% of the DNA from different lung cancers. We investigated the signaling pathways activated downstream of KDR and whether KDR amplification is associated with benefit in patients with NSCLC treated with the VEGFR inhibitor vandetanib.Methods: NSCLC cell lines with or without KDR amplification were studied for the effects of VEGFR tyrosine kinase inhibitors (TKI) on cell viability and migration. Archival tumor samples collected from patients with platinum-refractory NSCLC in the phase III ZODIAC study of vandetanib plus docetaxel or placebo plus docetaxel (N = 294) were screened for KDR amplification by FISH.Results: KDR amplification was associated with VEGF-induced activation of mTOR, p38, and invasiveness in NSCLC cell lines. However, VEGFR TKIs did not inhibit proliferation of NSCLC cell lines with KDR amplification. VEGFR inhibition decreased cell motility as well as expression of HIF1α in KDR-amplified NSCLC cells. In the ZODIAC study, KDR amplification was observed in 15% of patients and was not associated with improved progression-free survival, overall survival, or objective response rate for the vandetanib arm.Conclusions: Preclinical studies suggest KDR activates invasion but not survival pathways in KDR-amplified NSCLC models. Patients with NSCLC whose tumor had KDR amplification were not associated with clinical benefit for vandetanib in combination with docetaxel. Clin Cancer Res; 22(8); 1940–50. ©2015 AACR.

PDF file - 136KB, Supplementary Table 1. Sumary of the clinicopathological characteristics of the patients with lung adecarcinomas examined for EZH2 and miR-101 expressions. Supplementary Table 2. Association between markers' expression and lung adenocarcinoma patient's clinical and pathological characteristics. Supplementary Table 3. Summary of Multivariate Analysis of Outcome in Lung Adenocarcinoma Patients by Adjuvant Chemoterapy and EZH2, miR-101 and Combination of EZH2/miR-101 Expression.

PDF file - 50K, Mesenchymal lines are sensitive to Axl inhibition by SGI-7079

Purpose: Resistance to VEGFR inhibitors is a major obstacle in the treatment of non–small cell lung cancer (NSCLC). We investigated the cellular mechanisms mediating resistance of NSCLCs to VEGFR tyrosine kinase inhibitors.Experimental Design: We generated murine models of human NSCLC and performed targeted inhibition studies with the VEGFR TKIs cediranib and vandetanib. We used species-specific hybridization of microarrays to compare cancer (human) and stromal (mouse) cell transcriptomes of TKI-sensitive and -resistant tumors. We measured tumor microvascular density and vessel tortuosity to characterize the effects of therapy on the tumor vascular bed. Circulating cytokine and angiogenic factor levels in patients enrolled in VEGFR TKI trials were correlated with clinical outcomes.Results: Murine xenograft models of human lung adenocarcinoma were initially sensitive to VEGFR TKIs, but developed resistance to treatment. Species-specific microarray analysis identified increased expression of stromal-derived hepatocyte growth factor (HGF) as a candidate mediator of TKI resistance and its receptor, c-MET, was activated in cancer cells and tumor-associated stroma. A transient increase in hypoxia-regulated molecules in the initial response phase was followed by adaptive changes resulting in a more tortuous vasculature. Forced HGF expression in cancer cells reduced tumor sensitivity to VEGFR TKIs and produced tumors with tortuous blood vessels. Dual VEGFR/c-MET signaling inhibition delayed the onset of the resistant phenotype and prevented the vascular morphology alterations. In patients with cancer receiving VEGFR TKIs, high pretreatment HGF plasma levels correlated with poorer survival.Conclusions: HGF/c-MET pathway mediates VEGFR inhibitor resistance and vascular remodeling in NSCLC. Clin Cancer Res; 23(18); 5489–501. ©2017 AACR.

Purpose: To investigate the mechanisms of regulation and role associated with enhancer of zeste homolog 2 (EZH2) expression in lung cancer cells.Experimental Design: We investigated the mechanisms of EZH2 expression associated with the VEGF/VEGFR-2 pathway. Furthermore, we sought to determine the role of EZH2 in response of lung adenocarcinoma to platinum-based chemotherapy, as well as the effect of EZH2 depletion on VEGFR-2–targeted therapy in lung adenocarcinoma cell lines. In addition, we characterized EZH2 expression in lung adenocarcinoma specimens and correlated it with patients' clinical characteristics.Results: In this study, we demonstrate that VEGF/VEGFR-2 activation induces expression of EZH2 through the upregulation of E2F3 and hypoxia-inducible factor-1α (HIF1α), and downregulated expression of miR-101. EZH2 depletion by treatment with 3-deazaneplanocin A and knockdown by siRNA decreased the expression of EZH2 and H3K27me3, increased PARP-C level, reduced cell proliferation and migration, and increased sensitivity of the cells to treatment with cisplatin and carboplatin. In addition, high EZH2 expression was associated with poor overall survival in patients who received platinum-based adjuvant therapy, but not in patients who did not receive this therapy. Furthermore, we demonstrated for the first time that the inhibition of EZH2 greatly increased the sensitivity of lung adenocarcinoma cells to the anti–VEGFR-2 drug AZD2171.Conclusion: Our results suggest that the VEGF/VEGFR-2 pathway plays a role in regulation of EZH2 expression via E2F3, HIF1α, and miR-101. EZH2 depletion decreases the malignant potential of lung adenocarcinoma and sensitivity of the cells to both platinum-based and VEGFR-2–targeted therapy. Clin Cancer Res; 20(14); 3849–61. ©2014 AACR.

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Purpose:Osimertinib was initially approved for T790M-positive non–small cell lung cancer (NSCLC) and, more recently, for first-line treatment of EGFR-mutant NSCLC. However, resistance mechanisms to osimertinib have been incompletely described.Experimental Design:Using cohorts from The University of Texas MD Anderson Lung Cancer Moonshot GEMINI and Moffitt Cancer Center lung cancer databases, we collected clinical data for patients treated with osimertinib. Molecular profiling analysis was performed at the time of progression in a subset of the patients.Results:In the 118 patients treated with osimertinib, 42 had molecular profiling at progression. T790M was preserved in 21 (50%) patients and lost in 21 (50%). EGFR C797 and L792 (26%) mutations were the most common resistance mechanism and were observed exclusively in T790M-preserved cases. MET amplification was the second most common alteration (14%). Recurrent alterations were observed in 22 genes/pathways, including PIK3CA, FGFR, and RET. Preclinical studies confirmed MET, PIK3CA, and epithelial-to-mesenchymal transition as potential resistance drivers. Alterations of cell-cycle genes were associated with shorter median progression-free survival (PFS, 4.4 vs. 8.8 months, P = 0.01). In 76 patients with progression, osimertinib was continued in 47 cases with a median second PFS (PFS2) of 12.6 months; 21 patients received local consolidation radiation with a median PFS of 15.5 months. Continuation of osimertinib beyond progression was associated with a longer overall survival compared with discontinuation (11.2 vs. 6.1 months, P = 0.02).Conclusions:Osimertinib resistance is associated with diverse, predominantly EGFR-independent genomic alterations. Continuation of osimertinib after progression, alone or in conjunction with radiotherapy, may provide prolonged clinical benefit in selected patients.See related commentary by Devarakonda and Govindan, p. 6112.

Supplemental Figure 1. (A) Calu-1 cells were treated with VEGF (50 ng/ml) for 15 minutes and phospho-p38 levels were evaluated by Western blotting. VEGF treatment resulted in activation of p38, and this was blocked with the addition of VEGFR TKIs axitinib or sorafenib. (B) A549, H23, and Calu-1 cells express minimal levels of VEGFR1 as determined by ELISA assay. SKNAS neuroblastoma cells serve as a positive control.

PDF file - 214K, The EMT signature genes

PDF file - 71K, Percentage tumor volume compared to control, survival and therapeutic efficacy at days 17 and 38 post-treatment

PDF file - 51K, EMT status of commonly mutated genes in NSCLC

In the TCGA NSCLC dataset there was a significantly greater prevalence of p53 mutations in patients with KDR CNG compared to KDR CNG negative patients (p = 0.001).

Supplementary figure legend

PDF file - 27K, SGI-7079 and erlotinib do not adversely affect animal body weight

Supplementary material methods figures and tables

PDF file - 96K, Structure of pyrrolopyrimidine AXL inhibitor SGI-7079

Supplemental Figures and Tables

Platform-match 18 cases

PDF file - 453KB, Figure 1. EZH2, VEGFR-2 and miR-101 expression in in additional cell lines. Figure 2. Effect of VEGF stimulation in the E2F expression. Figure 3. Effect of Hypoxia in the expression of EZH2,HIF-1alpha and miR-101. Figure 4. Effect of miR-101 overexpression in the expression of EZH2. Figure 5. Effect of treatment with DZNep on lung adenocarcinoma cell viability. Figure 6. Effect of VEGFR-2 overexpression in sensitivity to cisplatin.

Supplementary Tables 1-4 from Increased VEGFR-2 Gene Copy Is Associated with Chemoresistance and Shorter Survival in Patients with Non–Small-Cell Lung Carcinoma Who Receive Adjuvant Chemotherapy

Loss-of-function somatic mutations of STK11, a tumor suppressor gene encoding LKB1 that contributes to the altered metabolic phenotype of cancer cells, is the second most common event in lung adenocarcinomas and often co-occurs with activating KRAS mutations. Tumor cells lacking LKB1 display an aggressive phenotype, with uncontrolled cell growth and higher energetic and redox stress due to its failure to balance ATP and NADPH levels in response to cellular stimulus. The identification of effective therapeutic regimens for patients with LKB1-deficient non–small cell lung cancer (NSCLC) remains a major clinical need. Here, we report that LKB1-deficient NSCLC tumor cells displayed reduced basal levels of ATP and to a lesser extent other nucleotides, and markedly enhanced sensitivity to 8-Cl-adenosine (8-Cl-Ado), an energy-depleting nucleoside analog. Treatment with 8-Cl-Ado depleted intracellular ATP levels, raised redox stress, and induced cell death leading to a compensatory suppression of mTOR signaling in LKB1-intact, but not LKB1-deficient, cells. Proteomic analysis revealed that the MAPK/MEK/ERK and PI3K/AKT pathways were activated in response to 8-Cl-Ado treatment and targeting these pathways enhanced the antitumor efficacy of 8-Cl-Ado. Implications: Together, our findings demonstrate that LKB1-deficient tumor cells are selectively sensitive to 8-Cl-Ado and suggest that therapeutic approaches targeting vulnerable energy stores combined with signaling pathway inhibitors merit further investigation for this patient population.

Epidermal growth factor receptor (EGFR) mutations typically occur in exons 18–21 and are established driver mutations in non-small cell lung cancer (NSCLC)1–3. Targeted therapies are approved for patients with ‘classical’ mutations and a small number of other mutations4–6. However, effective therapies have not been identified for additional EGFR mutations. Furthermore, the frequency and effects of atypical EGFR mutations on drug sensitivity are unknown1,3,7–10. Here we characterize the mutational landscape in 16,715 patients with EGFR-mutant NSCLC, and establish the structure–function relationship of EGFR mutations on drug sensitivity. We found that EGFR mutations can be separated into four distinct subgroups on the basis of sensitivity and structural changes that retrospectively predict patient outcomes following treatment with EGFR inhibitors better than traditional exon-based groups. Together, these data delineate a structure-based approach for defining functional groups of EGFR mutations that can effectively guide treatment and clinical trial choices for patients with EGFR-mutant NSCLC and suggest that a structure–function-based approach may improve the prediction of drug sensitivity to targeted therapies in oncogenes with diverse mutations.

Introduction Lung adenocarcinomas harboring EGFR mutations do not respond to immune checkpoint blockade therapy and their EGFR wildtype counterpart. The mechanisms underlying this lack of clinical response have been investigated but remain incompletely understood. Methods We analyzed three cohorts of resected lung adenocarcinomas (Profiling of Resistance Patterns of Oncogenic Signaling Pathways in Evaluation of Cancer of Thorax, Immune Genomic Profiling of NSCLC, and The Cancer Genome Atlas) and compared tumor immune microenvironment of EGFR-mutant tumors to EGFR wildtype tumors, to identify actionable regulators to target and potentially enhance the treatment response. Results EGFR-mutant NSCLC exhibited low programmed death-ligand 1, low tumor mutational burden, decreased number of cytotoxic T cells, and low T cell receptor clonality, consistent with an immune-inert phenotype, though T cell expansion ex vivo was preserved. In an analysis of 75 immune checkpoint genes, the top up-regulated genes in the EGFR-mutant tumors (NT5E and ADORA1) belonged to the CD73/adenosine pathway. Single-cell analysis revealed that the tumor cell population expressed CD73, both in the treatment-naive and resistant tumors. Using coculture systems with EGFR-mutant NSCLC cells, T regulatory cell proportion was decreased with CD73 knockdown. In an immune-competent mouse model of EGFR-mutant lung cancer, the CD73/adenosine pathway was markedly up-regulated and CD73 blockade significantly inhibited tumor growth. Conclusions Our work revealed that EGFR-mutant NSCLC has an immune-inert phenotype. We identified the CD73/adenosine pathway as a potential therapeutic target for EGFR-mutant NSCLC.

We have previously demonstrated that PD-1 blockade decreased the incidence of high-grade dysplasia in a carcinogen-induced murine model of oral squamous cell carcinoma (OSCC). It remains unknown, however, whether there are additional factors involved in escape from immune surveillance that could serve as additional targets for immunoprevention. We performed this study to further characterize the immune landscape of oral premalignant lesions (OPL) and determine the impact of targeting of the PD-1, CTLA-4, CD40, or OX40 pathways on the development of OPLs and oral carcinomas in the 4-nitroquinoline 1-oxide model. The immune pathways were targeted using mAbs or, in the case of the PD-1/PD-L1 pathway, using PD-L1–knockout (PD-L1ko) mice. After intervention, tongues and cervical lymph nodes were harvested and analyzed for malignant progression and modulation of the immune milieu, respectively. Targeting of CD40 with an agonist mAb was the most effective treatment to reduce transition of OPLs to OSCC; PD-1 alone or in combination with CTLA-4 inhibition, or PD-L1ko, also reduced progression of OPLs to OSCC, albeit to a lesser extent. Distinct patterns of immune system modulation were observed for the CD40 agonists compared with blockade of the PD-1/PD-L1 axis with or without CTLA-4 blockade; CD40 agonist generated a lasting expansion of experienced/memory cytotoxic T lymphocytes and M1 macrophages, whereas PD-1/CTLA-4 blockade resulted in a pronounced depletion of regulatory T cells among other changes. These data suggest that distinct approaches may be used for targeting different steps in the development of OSCC, and that CD40 agonists merit investigation as potential immunoprevention agents in this setting.Prevention Relevance:PD-1/PD-L1 pathway blockade, as well as activation of the CD40 pathway, were able to prevent OPL progression into invasive OSCC in a murine model. A distinct pattern of immune modulation was observed when either the CD40 or the PD-1/PD-L1 pathways were targeted.

Background: ERBB2 (HER2) insertions and point mutations are oncogenic drivers in non-small cell lung cancer (NSCLC) and now has approved targeted therapy for this patient population. Here, we present the landscape of ERBB2 genetic alterations (alts) and co-mutations, and the comparison between ERBB2 and EGFR exon 20 insertions in NSCLC. Methods: Two large retrospective cohorts were analyzed. In the Geneplus (China) cohort, 1,281 newly diagnosed NSCLC patients (pts) harboring ERBB2 alt were analyzed based on tissue and/or ctDNA. In the Guardant360 (Guardant Health, Redwood City, USA) cohort, 1719 ctDNA profiles of newly diagnosed NSCLC samples harboring ERBB2 alts were evaluated, with clonal alterations defined as those with ≥50% ratio of the maximum somatic variant allele fraction. Results: In the Geneplus cohort of 1,281 pts with ERBB2 alts, 55% were female with a median age of 58 years. ERBB2 mutations or insertions were identified in 930 pts, ERBB2 amplification(amp)-only in 351 pts, with mutation and co-amp at 7.5%. Most common alterations were in the tyrosine kinase domain exon 20 (85%), with Y772_A775dupYVMA to be the most frequent (57.4%), followed by G776delinsVC/LC/VV/IC (10.6%), and S310X (10.4%). EBRR2-mutation NSCLC were frequently having PDL1 Conclusion: In two large independent cohorts, Chinese and Western, ERBB2 mutation and co-mutation patterns were similar. ERBB2 exon 20 insertions/mutations were dominant at over 80% with Y772_A775dupYVMA being the most common driver mutation; TP53 and EGFR were the most frequently co-occurred genes. ERBB2 mutation lung cancers had low TMB and PDL1, as expected in female dominant lung adenocarcinomas, similar to EGFR exon 20 NSCLC. Clonal VUSs may represent a novel subset of mutations to functionally characterize. Citation Format: Lingzhi Hong, Leylah Drusbosky, Yinyi Wang, Yuanyuan Xiong, Rongrong Chen, Simon Heeke, Monique B. Nilsson, Jianjun Zhang, John V. Heymach, Xiuning Le. Mutation and co-mutation landscape ofERBB2 alterations in advanced NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6087.

Activating ERBB2 (HER2) mutations occur across multiple malignancies, and although mutational hotpots vary by disease, HER2 mutations most frequently occur in the tyrosine kinase domain. Among lung cancer patients, the most common HER2 mutation is the exon 20 insertion mutations, Y772dupYVMA, which accounts for over 30% of all HER2 mutations in lung cancer. Recent clinical testing of trastuzumab deruxtecan (T-DXd), a HER2 antibody-drug conjugate (ADC), against HER2 mutant non-small cell lung cancer (NSCLC) demonstrated a confirmed objective response of 55%, a median duration of response of 9.3 months, and a median overall survival of 17.8 months, which ultimately led to the recent approval of T-DXd for HER2 mutant NSCLC. Acquired resistance to targeted agents remains a major clinical challenge, and HER2-mutant patients that initially respond to T-DXd will eventually develop progressive disease. Thus, understanding mechanism of T-DXd resistance and identifying targeted agents that remain effective in cells with acquired T-DXd resistance is of great clinical importance. We generated Ba/F3 cells expressing the HER2 YVMA mutation and assessed sensitivity to HER2 targeting agents by Cell Titer Glo assay. HER2 YVMA cells were sensitive to the EGFR/HER2 tyrosine kinase inhibitor (TKI) poziotinib and the HER2 ADC T-DXd. To generate HER2 ADC resistant cells, we cultured Ba/F3 HER2 YVMA cells in T-DXd continuously for 8 weeks at which point cells resumed rapid proliferation. Cell Titer Glo assay confirmed that Ba/F3 HER2 YVMA cells were sensitive to T-DXd with an IC50 of 195 μg/ml, whereas Ba/F3 HER2 YVMA T-DXd-resistant cells had an IC50 of greater than 1000 μg/ml. Notably, T-DXd resistant cells remained highly sensitive to the HER2 TKI poziotinib with an IC50 of 14 nM and 7.5 nM for T-DXd-resistant and parental cells, respectively. Moreover, T-DXd-resistant cells demonstrated reduced sensitivity to the topoisomerase inhibitor topotecan with an IC50 of 200 nM whereas parental cells had an IC50 of 66 nM, suggesting that acquired T-DXd resistance may be mediated by loss of sensitivity to the ADC payload. Collectively, these data demonstrate that HER2 TKIs such as poziotinib may retain anti-tumor cell activity in HER2 mutant tumor cells with acquired resistance to HER2 ADCs. Citation Format: Monique B. Nilsson, Alissa Poteete, Hibiki Udagawa, Xiaoxing Yu, Junqin He, Xiuning Le, John Heymach. Trastuzumab deruxtecan resistance is associated with reduced responsiveness to topoisomerase inhibitors (payload resistance) but no reduction in sensitivity to HER2 tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 383.

The VEGF pathway has been recognized as a key mediator of angiogenesis to support tumorigenesis. Multiple therapeutic agents targeting VEGF and VEGF receptors have been developed and approved for use in NSCLCs. Preclinical studies have found that the VEGF and EGFR pathways share common downstream signaling, and these pathways can function exclusively of one another during oncogenesis. In EGFR-mutant NSCLCs, up-regulated EGFR signaling increases VEGF through hypoxia-independent mechanisms, and elevated VEGF, in turn, contributes to the emergence of resistance to EGFR tyrosine kinase inhibitors (TKIs). In clinical trials, the addition of anti-VEGF therapy to EGFR TKIs considerably improved clinical outcomes. In recently reported large randomized studies, the addition of bevacizumab or ramucirumab to EGFR TKIs substantially improved progression-free survival in patients with TKI-naive EGFR-mutant NSCLC. This article reviews the preclinical and clinical data supporting dual inhibition of EGFR and VEGF in EGFR-mutant NSCLC as a way to improve patient outcomes.