Introduction: Although the efficacy of molecular targeted therapies varies across actionable genomic alterations in NSCLC, comparisons within a single real-world cohort remain limited. Methods: We conducted a retrospective multi-institutional study of 810 consecutive Japanese patients with advanced or recurrent NSCLC harboring actionable genomic alterations who received molecular targeted therapy from 2017 to 2023. Patients were classified into the following three genomic groups: EGFR mutations (group A), ALK/ROS1/RET fusion oncogenes (group B), and others, including MET exon 14 skipping, BRAF V600E, and KRAS G12C mutations (group C). Treatment efficacy and safety were compared across the groups. Results: Treatment outcomes differed between the subgroups. Group B demonstrated the highest objective response rate (85.8%) and the longest median real-world progression-free survival (rwPFS; 42.5 mo); median overall survival (OS) was not reached. Group A had intermediate outcomes. Group C exhibited the shortest rwPFS (9.2 mo), poorer OS, and higher rates of treatment discontinuation due to adverse events. Such hierarchical differences were observed in patients with baseline central nervous system metastases and in those receiving first-line treatment. In multivariate analysis, genomic subgroup remained associated with rwPFS and OS, with fusion-driven tumors maintaining superior outcomes irrespective of other factors. Conclusions: This large real-world analysis yielded a hierarchy of therapeutic benefits across actionable genomic alterations in NSCLC. Patients with fusion-driven tumors benefited from targeted therapy, whereas those with EGFR-mutated tumors had intermediate outcomes. Treatment of patients with MET exon 14 skipping, BRAF V600E, and KRAS G12C mutations had limited efficacy and higher toxicity, underscoring the need for improved therapeutic strategies.

e20712 Background: Molecular targeted therapies have transformed the management of non–small cell lung cancer (NSCLC) with actionable genomic alterations. However, direct comparisons of treatment outcomes across different genomic subtypes within a single real-world cohort remain limited. We evaluated the relative efficacy and safety of targeted therapies across major actionable genomic alterations in a large Japanese real-world population. Methods: This multicenter retrospective study included 810 consecutive Japanese patients with advanced or recurrent NSCLC harboring actionable genomic alterations who received molecular targeted therapy between 2017 and 2023. Patients were classified into three genomic groups: EGFR mutations (Group A, n = 659), fusion oncogenes involving ALK/ROS1/RET (Group B, n = 106), and other actionable alterations including MET exon 14 skipping, BRAF V600E, and KRAS G12C (Group C, n = 45). Treatment outcomes, including objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and safety, were analyzed using Kaplan–Meier methods and multivariable Cox regression. Results: The median follow-up was 24.9 months overall (Group A 25.6, Group B 27.3, Group C 16.1). A total of 580 progression events and 398 deaths were observed. ORR differed significantly among groups (74.1% in Group A, 85.8% in Group B, and 68.9% in Group C; P = 0.014). Median PFS was 17.5 months in Group A, 42.5 months in Group B, and 9.2 months in Group C (P < 0.001). Median OS was not reached in Group B, compared with 39.3 months in Group A and 22.7 months in Group C (P < 0.001). In multivariable analyses adjusting for clinical covariates, genomic subgroup remained independently associated with both PFS and OS, with fusion-driven tumors demonstrating consistently superior outcomes. EGFR-mutated tumors showed intermediate outcomes, whereas Group C exhibited limited efficacy and higher treatment discontinuation due to adverse events. Conclusions: In this large Japanese real-world cohort, a clear hierarchy of therapeutic benefit across actionable genomic alterations was observed. Fusion oncogene–driven NSCLC derived exceptional and durable benefit from targeted therapy, EGFR-mutated tumors demonstrated intermediate outcomes, and MET exon 14 skipping, BRAF V600E, and KRAS G12C mutations remained associated with limited efficacy and higher toxicity. These findings underscore the clinical importance of genomic subtype–based treatment strategies and highlight unmet needs in selected molecular subsets.

We herein report an autopsy case of streptococcal toxic shock syndrome (STSS) with disseminated intravascular coagulation and multiple cerebral infarctions induced by Streptococcus dysgalactiae subsp. equisimilis in an 84-year-old male. Pathological examination revealed sepsis with hemophagocytosis in the reticular system and intravascular bacteria in multiple organs, originating from bacterial necrotizing fasciitis of the lower extremities. The brain MRI findings showed a diffusion weighted imaging-fluid-attenuated inversion-recovery mismatch, whereas the pathology was almost normal, thus supporting a hyperacute phase of cerebral infarction. The findings in this case help to elucidate the pathogenesis of STSS and develop appropriate treatment strategies.

A 74-year-old woman, who had been receiving olaparib for the treatment of ovarian cancer for more than a year, visited the emergency department complaining of a fever that had lasted for 1 month. She had been taking antipyretics and antibiotics for her fever, but without any effect. Although she had no symptoms other than fever, she had stopped taking olaparib for 1 week before her visit because she had developed anemia caused by myelosuppression from olaparib. After discontinuing olaparib, her maximum body temperature decreased. On admission, chest X-ray revealed no abnormalities, but chest CT showed diffuse ground-glass opacities. Chest CT taken 5 days later showed partial improvement; therefore, we diagnosed her with interstitial lung disease (ILD) associated with olaparib. After short-term steroid treatment, the ground-glass opacities disappeared, and the patient became afebrile. The CT scan taken for tumor evaluation 2 days before the onset of fever showed a few centrilobular nodular opacities and small patchy ground-glass opacities. These findings could indicate early lesions of ILD, but they seemed inconspicuous and nonspecific, and it might have been difficult to diagnose ILD then. To date, few cases of ILD associated with olaparib have been reported. However, based on previous reports, fever is often seen, and CT findings mainly comprise diffuse ground-glass opacities, and in some cases, centrilobular nodular shadows. Thus, in conjunction with the findings of the present case, these characteristics may be representative of olaparib-induced ILD.

Immune check point inhibitors (ICIs) have durable antitumor effects. However, autoimmune toxicities, termed immune-related adverse events, occur in some patients. We report a case of severe immune aplastic anemia (AA) in a patient with non -small cell lung cancer who was receiving atezolizumab with bevacizumab/carboplatin/paclitaxel. Although the cancer has not recurred, his bone marrow is depleted and he did not respond to immunosuppressive therapy. He has survived for 1.5 years with blood transfusions and infection control. Immune AA associated with ICIs is rare, and a treatment has not yet been established. This case report provides information on the management and treatment response of patients with AA caused by ICIs. Further studies should investigate the mechanism and pathogenesis of immune AA caused by ICIs.

Abstract Patients with non–small cell lung cancer (NSCLC) EGFR mutations have shown a dramatic response to EGFR inhibitors (EGFR-TKI). EGFR T790M mutation and MET amplification have been recognized as major mechanisms of acquired resistance to EGFR-TKI. Therefore, MET inhibitors have recently been used in NSCLC patients in clinical trials. In this study, we tried to identify the mechanism of acquired resistance to MET inhibitors. We analyzed the antitumor effects of two MET inhibitors, PHA-665752 and crizotinib, in 10 NSCLC cell lines. EBC-1 cells with MET amplification were the only cells that were sensitive to both MET inhibitors. We established PHA-665752–resistant EBC-1 cells, namely EBC-1R cells. Activation of KRAS, EGFR, and FGFR2 signaling was observed in EBC-1R cells by FISH and receptor tyrosine kinase phosphorylation antibody arrays. EBC-1R cells also showed overexpression of ATP-binding cassette subfamily B member 1 (ABCB1) as well as phosphorylation of MET. EBC-1R cells grew as cell spheres that exhibited cancer stem cell–like (CSC) properties and epithelial–mesenchymal transition (EMT). The level of miR-138 that targeted ABCB1 was decreased in EBC-1R cells. ABCB1 siRNA and the ABCB1 inhibitor elacridar could reduce sphere numbers and suppress EMT. Elacridar could also reverse resistance to PHA-665752 in EBC-1R cells. Our study demonstrated that ABCB1 overexpression, which was associated with CSC properties and EMT, was involved in the acquired resistance to MET inhibitors. Inhibition of ABCB1 might be a novel therapeutic strategy for NSCLC patients with acquired resistance to MET inhibitors. Mol Cancer Ther; 14(11); 2433–40. ©2015 AACR.

Supplemental Figure 1:Protein levels of p-MET, MET and ABCB1 were examined in 7 SQ cell lines by Western blot analysis Supplemental Figure 2: FGFR inhibition overcomes the resistance to PHA-665752 in EBC-1R cells Supplemental Figure 3: ABCB1 overexpression in cloned EBC-1R cells Supplemental Figure 4: Immunohistochemical staining for ABCB1 protein expression in tumor cells from SQ patients

Sarcoidosis is a multisystem disease with an unknown etiology and is characterized by the formation of noncaseating granulomas in the affected organs. We present the case of a 69-year-old male Japanese patient with bilateral hilar lymphadenopathy on chest radiographs for more than 10 years, left without further investigation. The patient reported no clinical symptoms. Chest computed tomography revealed ground-glass opacities and reticular shadows in both lungs, along with bilateral hilar and mediastinal lymphadenopathy. Lymphocytosis was observed in bronchoalveolar lavage fluid. Pathological examination of transbronchial lung biopsy revealed noncaseating, epithelioid granulomas congruous with sarcoidosis, together with other findings. There were no abnormalities on electrocardiogram, echocardiogram, and ophthalmic examination. For progressive dyspnea on exertion, systemic corticosteroid therapy with oral prednisolone (25 mg/day) was initiated in 2017 and gradually tapered. Despite this intervention, the decline in forced vital capacity (FVC) was accelerated. Three years later, the patient noticed swelling in his right wrist. Further investigation revealed elevated anti-cyclic citrullinated peptide antibodies and absence of noncaseating epithelioid granuloma on surgical biopsy, leading to the diagnosis of rheumatoid arthritis (RA). Thereafter, the anti-fibrotic agent nintedanib was initiated, because interstitial lung disease (ILD) was considered to have converted into a progressive fibrosing phenotype (PF-ILD) with overlapping RA-associated lung involvement. With treatment, the progression of decline in FVC was slowed, although home oxygen therapy was introduced.

Cell lines and drugs Clinical samples and Immunohistochemical staining

Background: Rechallenge with platinum-combination chemotherapy in patients with advanced non-small cell lung cancer (NSCLC) after disease progression on platinum-combination chemotherapy occasionally leads to a favorable response. The efficacy and safety of platinum-combination chemotherapy with or without immune-check-point inhibitor (ICI) for patients with recurrent NSCLC after surgery followed by adjuvant platinum-doublet chemotherapy remains uncertain.Methods: Patients who relapsed after surgery plus adjuvant platinum-doublet chemo-therapy and received platinum-combination chemotherapy with or without ICI between April 2011 and March 2021 at four Nippon Medical School hospitals were retrospectively analyzed.Results: Among 177 patients who received adjuvant platinum-doublet chemotherapy after surgery, a total of 30 patients who received platinum-combination rechemotherapy with or without ICI after relapse were included in this study. Seven patients received ICI-combined chemotherapy. The median disease-free survival (DFS) after surgery was 13.6 months. The objective response rate and disease-control rate were 46.7% and 80.0%, respectively. The median progression-free survival and overall survival were 10.2 and 37.5 months, respectively. Patients with longer DFS (=12 months) had a better prognosis than others. The most common grade =3 toxicity associated with this treatment was neutropenia (33%). Grade =3 immune-related adverse events were pneumonitis (14%) and colitis (14%). Treatment-related deaths did not occur in this study.Conclusion: Platinum-combination chemotherapy with or without ICI for patients with postoperative recurrent NSCLC who previously received adjuvant platinum-doublet chemotherapy was effective and safe. In particular, this therapy may be prom-ising for patients with longer DFS.

Supplemental Table 1. Gene copy numbers of MET, EGFR and KRAS in EBC-1R cells Supplemental Table 2. MiRNAs correlated with the sensitivity to PHA665752 Supplemental Table 3. ABCB1 protein expression in 50 lung squamous cell cancer patients　

Introduction The majority of pulmonary carcinoid (PC) tumors can be cured by surgical resection alone, but a significant proportion of patients experience recurrence. As PC is insensitive to conventional chemotherapy, further clarification of the molecular mechanisms of metastasis is needed in order to develop targeted therapeutics. Methods We performed comprehensive whole-exome sequencing (WES) of primary tumors and corresponding normal lung tissues from 14 PC patients (including 4 patients who developed postsurgical distant metastasis) and RNA sequencing of primary tumors from 6 PC patients (including 4 patients who developed postsurgical distant metastasis). Exon array-based gene expression analysis was performed in 25 cases of PC. Results We identified a total of 139 alterations in 136 genes. MUC6 and SPTA1 were recurrently mutated at a frequency of 21% (3/14) and 14% (2/14), respectively. Mucin protein family genes including MUC2, MUC4 and MUC6 were mutated in a mutually exclusive manner in 36% (5/14). Pathway analysis of the mutated genes revealed enrichment of genes involved in mitogen-activated protein kinase (MAPK) signaling, regulation of the actin cytoskeleton and focal adhesion, and transforming growth factor (TGF)-β signaling. RNA sequencing revealed a total of 8 novel fusion transcripts including one derived from a chromosomal translocation between the TRIB2 and PRKCE genes. All of the 8 fusion genes were detected in primary PCs that had developed metastasis after surgical resection. We identified 14 genes (DENND1B, GRID1, CLMN, DENND1B, NRP1, SEL1L3, C5orf13, TNFRSF21, TES, STK39, MTHFD2, OPN3, MET, and HIST1H3C) up-regulated in 5 PCs that had relapsed after surgical resection. Conclusions In this study we identified novel somatic mutations and chromosomal rearrangements in PC by examining clinically aggressive cases that had developed postsurgical metastasis. It will be essential to validate the clinical significance of these genetic changes in a larger independent patient cohort.

Background Idiopathic pulmonary fibrosis (IPF) is a progressive disease with high mortality, and the pathogenesis of the disease is still incompletely understood. Although lymphocytes, especially CD4 + CD25 + FoxP3 + regulatory T cells (Tregs), have been implicated in the development of IPF, contradictory results have been reported regarding the contribution of Tregs to fibrosis both in animals and humans. The aim of this study was to investigate whether a specific T cell subset has therapeutic potential in inhibiting bleomycin (BLM)-induced murine pulmonary fibrosis. Methods C57BL/6 mice received BLM (100 mg/kg body weight) with osmotic pumps (day 0), and pulmonary fibrosis was induced. Then, splenocytes or Tregs were adoptively transferred via the tail vein. The lungs were removed and subjected to histological and biochemical examinations to study the effects of these cells on pulmonary fibrosis, and blood samples were collected by cardiac punctures to measure relevant cytokines by enzyme-linked immunosorbent assay. Tregs isolated from an interleukin (IL)-10 knock-out mice were used to assess the effect of this mediator. To determine the roles of the spleen in this model, spleen vessels were carefully cauterized and the spleen was removed either on day 0 or 14 after BLM challenge. Results Splenocytes significantly ameliorated BLM-induced pulmonary fibrosis when they were administered on day 14. This effect was abrogated by depleting Tregs with an anti-CD25 monoclonal antibody. Adoptive transfer of Tregs on day 14 after a BLM challenge significantly attenuated pulmonary fibrosis, and this was accompanied by decreased production of fibroblast growth factor (FGF) 9-positive cells bearing the morphology of alveolar epithelial cells. In addition, BLM-induced plasma IL-10 expression reverted to basal levels after adoptive transfer of Tregs. Moreover, BLM-induced fibrocyte chemoattractant chemokine (CC motif) ligand-2 production was significantly ameliorated by Treg adoptive transfer in lung homogenates, accompanied by reduced accumulation of bone-marrow derived fibrocytes. Genetic ablation of IL-10 abrogated the ameliorating effect of Tregs on pulmonary fibrosis. Finally, splenectomy on day 0 after a BLM challenge significantly ameliorated lung fibrosis, whereas splenectomy on day 14 had no effect. Conclusions These findings warrant further investigations to develop a cell-based therapy using Tregs for treating IPF.

Pathogenesis of idiopathic pulmonary fibrosis (IPF) remains unclear. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that participates in the assembly and turnover of the extracellular matrix, whose expression is regulated by transforming growth factor (TGF)-β1 through activation of mammalian target of rapamycin complex 2 (mTORC2). Exchange factor found in platelets, leukemic, and neuronal tissues (XPLN) is an endogenous inhibitor of mTORC2. However, whether XPLN modulates SPARC expression remains unknown. Herein, we investigated the regulatory mechanisms of XPLN in human lung fibroblasts. Effect of XPLN on mTORC2 activity was evaluated by silencing XPLN in human foetal lung fibroblasts (HFL-1 cells), using small interfering RNA. SPARC expression was quantified by quantitative real-time RT-PCR and western blotting. Fibroblasts were treated with TGF-β1, histone deacetylase (HDAC) inhibitors, entinostat, or vorinostat, to assess their effects on XPLN expression. Moreover, the effect of mTORC1 inhibition on SPARC and XPLN was examined. XPLN depletion stimulated SPARC expression and Akt phosphorylation on Ser473. TGF-β1 treatment down-regulated XPLN via Smad 2/3. XPLN mRNA expression was up-regulated upon treatment with HDAC inhibitors in a concentration-dependent manner, and TGF-β1-induced SPARC expression was reversed by entinostat treatment. mTORC1 inhibition by rapamycin and Raptor depletion stimulated SPARC expression. In conclusion, this is the first study describing the involvement of XPLN in the regulation of SPARC. These findings may help uncover the regulatory mechanisms of the mTORC2-SPARC axis. The up-regulation of XPLN by HDAC inhibitors may be a novel therapeutic approach in patients with IPF.

Nintedanib (BIBF1120) is a multi-targeted angiokinase inhibitor and has been evaluated in idiopathic pulmonary fibrosis and advanced non-small cell lung cancer (NSCLC) patients in clinical studies. In the present study, we evaluated the antitumor effects of nintedanib in 16 NSCLC cell lines and tried to identify microRNA (miRNA) associated with sensitivity to nintedanib. No correlations between FGFR, PDGFR and VEGFR family activation and sensitivity to nintedanib were found. The difference in miRNA expression profiles between 5 nintedanib-sensitive and 5 nintedanib-resistant cell lines was evaluated by miRNA array and quantitative RT-PCR analysis (qRT-PCR). Expression of miR-200b, miR-200a and miR-141 belonging to the miR-200 family which contributes to epithelial-mesenchymal transition (EMT), was significantly lower in 5 nintedanib-resistant than in 5 nintedanib-sensitive cell lines. We examined the protein expression of EMT markers in these 10 NSCLC cell lines. E-cadherin expression was lower, and vimentin and ZEB1 expression were higher in 5 nintedanib-resistant cell lines. PC-1 was the most sensitive of the NSCLC cell lines to nintedanib. We established nintedanib-resistant PC-1 cells (PC-1R) by the stepwise method. PC-1R cells also showed decreased expression of miR-200b, miR-141 and miR-429 and increased expression of ZEB1 and ZEB2. We confirmed that induction of miR-200b or miR-141 enhanced sensitivity to nintedanib in nintedanib-resistant A549 and PC1-R cells. In addition, we evaluated the response to gefitinib in combination with nintedanib after TGF-β1 exposure of A549 cells. Nintedanib was able to reverse TGF-β1-induced EMT and resistance to gefitinib caused by miR-200b and miR-141 upregulation and ZEB1 downregulation. These results suggested that the miR-200/ZEB axis might be predictive biomarkers for sensitivity to nintedanib in NSCLC cells. Furthermore, nintedanib combined with gefitinib might be a novel therapeutic strategy for NSCLC cells with EMT phenotype and resistance to gefitinib.

Nintedanib (BIBF1120) is a multi-targeted angiokinase inhibitor and has been evaluated in idiopathic pulmonary fibrosis and advanced non-small cell lung cancer (NSCLC) patients in clinical studies. In the present study, we evaluated the antitumor effects of nintedanib in 16 NSCLC cell lines and tried to identify microRNA (miRNA) associated with sensitivity to nintedanib. No correlations between FGFR, PDGFR and VEGFR family activation and sensitivity to nintedanib were found. The difference in miRNA expression profiles between 5 nintedanib-sensitive and 5 nintedanib-resistant cell lines was evaluated by miRNA array and quantitative RT-PCR analysis (qRT-PCR). Expression of miR-200b, miR-200a and miR-141 belonging to the miR-200 family which contributes to epithelial-mesenchymal transition (EMT), was significantly lower in 5 nintedanib-resistant than in 5 nintedanib-sensitive cell lines. We examined the protein expression of EMT markers in these 10 NSCLC cell lines. E-cadherin expression was lower, and vimentin and ZEB1 expression were higher in 5 nintedanib-resistant cell lines. PC-1 was the most sensitive of the NSCLC cell lines to nintedanib. We established nintedanib-resistant PC-1 cells (PC-1R) by the stepwise method. PC-1R cells also showed decreased expression of miR-200b, miR-141 and miR-429 and increased expression of ZEB1 and ZEB2. We confirmed that induction of miR-200b or miR-141 enhanced sensitivity to nintedanib in nintedanib-resistant A549 and PC1-R cells. In addition, we evaluated the response to gefitinib in combination with nintedanib after TGF-β1 exposure of A549 cells. Nintedanib was able to reverse TGF-β1-induced EMT and resistance to gefitinib caused by miR-200b and miR-141 upregulation and ZEB1 downregulation. These results suggested that the miR-200/ZEB axis might be predictive biomarkers for sensitivity to nintedanib in NSCLC cells. Furthermore, nintedanib combined with gefitinib might be a novel therapeutic strategy for NSCLC cells with EMT phenotype and resistance to gefitinib.

Background Lung adenocarcinoma patients with EGFR gene mutations have shown a dramatic response to gefitinib. However, drug resistance eventually emerges which limits the mean duration of response. With that in view, we examined the correlations between MET gene status as assessed by fluorescence in situ hybridization (FISH) with overall survival (OS) and progression-free survival (PFS) in adenocarcinoma patients with EGFR gene mutations who had received gefitinib therapy. Methods We evaluated 35 lung cancer samples with EGFR mutation from adenocarcinoma patients who had received gefitinib. Gene copy numbers (GCNs) and amplification of MET gene before gefitinib therapy was examined by FISH. MET protein expression was also evaluated by immunohistochemistry (IHC). Results FISH assessment showed that of the 35 adenocarcinoma samples, 10 patients (29%) exhibited high polysomy (5 copies≦mean MET per cell) and 1 patient (3%) exhibited amplification (2≦ MET gene (red)/ CEP7q (green) per cell). IHC evaluation of MET protein expression could not confirm MET high polysomy status. The Eleven patients with MET FISH positivity had significantly shorter progression-free survival (PFS) and overall survival (OS) than the 24 patients who were MET FISH-negative (PFS: p = 0.001 and OS: p = 0.03). Median PFS and OS with MET FISH-positivity were 7.6 months and 16.8 months, respectively, whereas PFS and OS with MET FISH-negativity were 15.9 months and 33.0 months, respectively. Univariate analysis revealed that MET FISH-positivity was the most significant independent factor associated with a high risk of progression and death (hazard ratio, 3.83 (p = 0.0008) and 2.25 (p = 0.03), respectively). Conclusions Using FISH analysis to detect high polysomy and amplification of MET gene may be useful in predicting shortened PFS and OS after Gefitinib treatment in lung adenocarcinoma. The correlation between MET gene status and clinical outcomes for EGFR-TKI should be further evaluated using large scale samples.

Cancer‐initiating cell (CIC) hypothesis suggests that CICs may be responsible for the generation of tumors that recapitulate the histology of the primary tumor at distant sites. We investigated the distribution of CIC markers (podoplanin (PDPN), CD44, and p63) positive cells of lung squamous cell carcinoma (SqCC) within primary and matched lymph node (LN) metastatic tumors to confirm this hypothesis (n = 113). In 61 cases, the PDPN‐positive cells were localized in more peripheral areas of the tumor nests than the CD44‐ and p63‐positive cells. This distribution pattern corresponded to a ‘hierarchical distribution (HD)’ reported previously. Among the cases with HD‐(+) primary tumors (n = 61), the number showing HD‐(+) LN metastatic tumors was 31 (51%), while among the cases with HD‐(−) primary tumors (n = 52), the number showing HD‐(+) LN metastatic tumors was 7 (13%) (p < 0.01). Primary and matched pulmonary metastatic (PM) tumors were also analyzed (n = 31), and a significant relationship of the HD pattern between them was also detected (p = 0.01). These results indicate that PDPN‐positive cells might reflect the most immature cells in the differentiation process of metastatic SqCC and might generate metastatic tumors that recapitulate the histologic heterogeneity of the primary tumor.

Abstract Background Non-small cell lung cancer (NSCLC) patients with EGFR gene mutations have shown a dramatic responses to EGFR tyrosine kinase inhibitor (EGFR-TKI). However, it is recognized that, clinically, drug resistance eventually emerges and this limits the mean duration of response. Although mechanisms of acquired resistance to EGFR-TKI, such as T790M secondary mutation and MET amplification, have recently been described, other mechanisms of resistant to EGFR-TKI should be identified to broaden the therapeutic strategy for NSCLC in patients with EGFR gene mutations. Patients and Methods We evaluated 26 lung tumor samples from NSCLC patients who had received EGFR-TKI treatment from 2009 to 2011 at Nippon Medical School Hospital. Status of copy numbers and amplification of the MET gene were examined by fluorescence in situ hybridization (FISH) and estimated by high throughout automated image analysis. Results High copy number (>4 copies/cell) was observed in 6 patients (27%) and amplification (MET/CEP7 ≥2.0) was seen in 0 of 26 NSCLC patients. MET gene copy number status was not correlated with EGFR gene mutation, gender, histology, or smoking history. In 2 of the 6 cases with high copy number, high copy numbers were found at both the pre- and post-treatment stages. Among the 6 patients with high copy number, 5 patients achieved partial response (PR) and one patient showed stable disease (SD) with EGFR-TKI therapy. However, the 6 patients with high copy number had statistically significantly shorter progression-free survival (PFS) than the 20 patients with low copy numbers. (p=0.048, log-rank test). The median PFS of patients with High copy number and low copy numbers was 9.5 months and 24.4 months, respectively. Conclusion Detection of high copy number of the MET gene by FISH may be useful for predicting response to EGFR-TKI. The correlation between MET gene copy number and response to EGFR-TKI should be further evaluated using larger sample sizes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5548. doi:1538-7445.AM2012-5548