Purpose: To identify druggable oncogenic fusions in invasive mucinous adenocarcinoma (IMA) of the lung, a malignant type of lung adenocarcinoma in which KRAS mutations frequently occur.Experimental Design: From an IMA cohort of 90 cases, consisting of 56 cases (62%) with KRAS mutations and 34 cases without (38%), we conducted whole-transcriptome sequencing of 32 IMAs, including 27 cases without KRAS mutations. We used the sequencing data to identify gene fusions, and then performed functional analyses of the fusion gene products.Results: We identified oncogenic fusions that occurred mutually exclusively with KRAS mutations: CD74-NRG1, SLC3A2-NRG1, EZR-ERBB4, TRIM24-BRAF, and KIAA1468-RET. NRG1 fusions were present in 17.6% (6/34) of KRAS-negative IMAs. The CD74-NRG1 fusion activated HER2:HER3 signaling, whereas the EZR-ERBB4 and TRIM24-BRAF fusions constitutively activated the ERBB4 and BRAF kinases, respectively. Signaling pathway activation and fusion-induced anchorage-independent growth/tumorigenicity of NIH3T3 cells expressing these fusions were suppressed by tyrosine kinase inhibitors approved for clinical use.Conclusions: Oncogenic fusions act as driver mutations in IMAs without KRAS mutations, and thus represent promising therapeutic targets for the treatment of such IMAs.

Resistance to vandetanib, a type I RET kinase inhibitor, developed in a patient with metastatic lung adenocarcinoma harboring a CCDC6-RET fusion that initially exhibited a response to treatment. The resistant tumor acquired a secondary mutation resulting in a serine-to-phenylalanine substitution at codon 904 in the activation loop of the RET kinase domain. The S904F mutation confers resistance to vandetanib by increasing the ATP affinity and autophosphorylation activity of RET kinase. A reduced interaction with the drug is also observed in vitro for the S904F mutant by thermal shift assay. A crystal structure of the S904F mutant reveals a small hydrophobic core around F904 likely to enhance basal kinase activity by stabilizing an active conformer. Our findings indicate that missense mutations in the activation loop of the kinase domain are able to increase kinase activity and confer drug resistance through allosteric effects.

The CD74-Neuregulin1 (NRG1) fusion gene was recently identified in invasive mucinous adenocarcinoma, a malignant type of lung adenocarcinoma, and is considered to be a novel driver gene aberration. However, pathogenic functions of the CD74-NRG1 fusion gene are unknown, and the mechanism underlying the initiation of cancer stem cells (CSCs) and their maintenance in tumors with oncogenic fusion genes is still unclear. In this study, we observed that expression of the CD74-NRG1 fusion gene has an activity to increase the population of cells with CSC properties. CD74-NRG1 expression facilitated sphere formation of not only cancer cells but also non-cancerous lung epithelial cells. Using a limiting dilution assay in a xenograft model, we showed that expression of the CD74-NRG1 fusion gene enhanced tumor initiation. We observed that CD74-NRG1 expression stimulates phosphorylation of ErbB2/3 and activates the phosphatidylinositol 3-kinase (PI3K)/Akt/NF-κB signaling pathway. Furthermore, we found that levels of the secreted insulin-like growth factor 2 (IGF2) were increased, and phosphorylation levels of the receptor for IGF2, IGF1 receptor (IGF1R), were enhanced in cells expressing CD74-NRG1 in an NF-κB activity-dependent manner. These findings suggest that the NF-κB activity stimulated by CD74-NRG1 induces the IGF2 autocrine/paracrine circuit. In addition, tumor sphere formation induced by the CD74-NRG1 fusion gene was suppressed by inhibitors of ErbB2, PI3K, or NF-κB, or an anti-IGF2 antibody. Our study thus provides a rationale for developing important treatment options to block the signals that contribute to the CSC properties, ErbB/PI3K/Akt/NF-κB pathway, and IGF2 circuit, and to eradicate tumors and prevent their recurrence.

Development of lung adenocarcinoma (LADC), the most frequent histological type of lung cancer, depends in many cases on the activation of "driver" oncogenes such as KRAS, epidermal growth factor receptor (EGFR), and anaplastic lymphoma kinase (ALK). Inhibitors that target the EGFR and ALK tyrosine kinases show therapeutic effects against LADCs containing EGFR gene mutations and ALK gene fusions, respectively. Recently, we and others identified the RET fusion gene as a new targetable driver gene in LADC. The RET fusions occur in 1-2% of LADCs. Existing US Food and Drug Administration-approved inhibitors of RET tyrosine kinase show promising therapeutic effects both in vitro and in vivo, as well as in a few patients. Clinical trials are underway to investigate the therapeutic effects of RET tyrosine kinase inhibitors, such as vandetanib (ZD6474) and cabozantinib (XL184), in patients with RET fusion-positive non-small-cell lung cancer. (Cancer Sci 2013; 104: 1396-1400 Personalized Therapy of LADC L ung cancer is the leading cause of cancer-related mortality worldwide. Lung adenocarcinoma (LADC) is the most frequent type of lung cancer. LADC occurs both in smokers and non-smokers, and its incidence is increasing.(1) Genome analyses of LADC show that these tumors contain distinct genetic alterations that activate oncogenes.(2,3) Genetic alterations that result in the activation of several oncogenes are detected in a mutually exclusive manner (Fig. 1); of the hundreds of genes mutated in each case of LADC, these oncogenes are considered to be "driver genes".(4) Remarkably, molecular targeted therapy using inhibitory drugs against activated oncogene products has begun to replace conventional chemotherapy using cytotoxic drugs, even for first-line use.(2)The epidermal growth factor receptor (EGFR) gene is activated by single amino acid substitution mutations or in-frame amino acid deletion mutations in 10-20% of LADC cases in the USA and in 30-40% of cases in East Asia. (2) Tumors harboring these EGFR mutations respond to EGFR tyrosine kinase inhibitors (TKIs) such as erlotinib and gefitinib, thereby improving progression-free survival and quality of life. (5,6) In addition, 3-5% of LADC harbor fusions that result in the activation of the anaplastic lymphoma kinase (ALK) gene; such mutations are mutually exclusive with EGFR mutations. Inhibitors, such as crizotinib, that target ALK tyrosine kinase show marked therapeutic effects against ALK fusion-positive LADCs. (7)(8)(9) These results indicate that personalized therapy for LADC using TKIs selected on the basis of somatic genetic alterations has been realized already; indeed, 20% of USA ⁄ European and 40% of Asian LADC patients benefit from such therapies. Discovery of the RET Fusion Gene as a New Targetable Driver GeneIn 2012, four studies, including one by our group, identified fusions of the RET (rearranged during transfection) oncogene (10)(11)(12)(13) (Fig. 2). RET is a well-known driver oncogene kinase for thyroid cancer, and both activating mutations and fusions...

RET (REarranged during Transfection), which encodes a receptor tyrosine kinase for members of the glial cell line-derived neurotrophic factor, plays a role as driver oncogene in a variety of human cancers. Fusion of RET with several partner genes has been detected in papillary thyroid, lung, colorectal, pancreatic and breast cancers, and tyrosine kinase inhibitors (TKIs) for RET (particularly RET-specific inhibitors) show promising therapeutic effects against such cancers. Oncogenic mutations within the extracellular cysteine-rich and intracellular kinase domains of RET drive medullary thyroid carcinogenesis; the same mutations are also observed in a small subset of diverse cancers such as lung, colorectal and breast cancers. Considering the oncogenic nature of RET mutants, lung, colorectal and breast cancers are predicted to respond to RET TKIs in a manner similar to medullary thyroid cancer. In summary, cancers carrying oncogenic RET alterations as a driver mutation could be collectively termed ‘REToma’ and treated with RET TKIs in a tissue-agnostic manner.

ObjectivesAlthough positron emission tomography (PET) using [18F]-fluoro-2-deoxy-d-glucose (18F-FDG) is established as one of the first-choice imaging modalities in the diagnosis of chest malignancies, there are several problems to solve in clinical practice, such as false positive uptake in inflammatory diseases. The aim of this study was to evaluate the clinical usefulness of an amino acid tracer, α-[N-methyl-11C]-methylaminoisobutyric acid (11C-MeAIB), in the diagnosis of chest malignancies, in combination with 18F-FDG.SettingFifty-nine cases (57 patients, 66 ± 12 years old) who consulted to our institution for the wish to receive differential diagnosis of chest diseases were included. Purpose of the studies were as follows: differential diagnosis of newly developed lung nodules, n = 22; newly developed mediastinal lesions, n = 20; and both, n = 17 (including lung cancer: n = 19, lymphoma: n = 1, other cancers: n = 2, sarcoidosis: n = 15, non-specific inflammation: n = 18, other inflammatory: n = 4, respectively). Whole-body static PET or PET/CT scan was performed 20 and 50 min after the IV injection of 11C-MeAIB and 18F-FDG, respectively.Results11C-MeAIB uptake of malignant and benign lesions was statistically different both in pulmonary nodules (p < 0.005) and in mediastinal lesions (p < 0.0005). In visual differential diagnosis, 11C-MeAIB showed higher results (specificity: 73 %, accuracy: 81 %), compared to those in 18F-FDG (60, 73 %, respectively). In cases of sarcoidosis, 11C-MeAIB showed higher specificity (80 %) with lower uptake (1.8 ± 0.7) in contrast to the lower specificity (60 %) with higher uptake of 18F-FDG (7.3 ± 4.5).Conclusions11C-MeAIB PET/CT was useful in the differential diagnosis of pulmonary and mediastinal mass lesions found on CT. 11C-MeAIB PET or PET/CT showed higher specificity than that of 18F-FDG PET/CT in differentiating between benign and malignant disease. Our data suggest that the combination of 18F-FDG and 11C-MeAIB may improve the evaluation of chest lesions, when CT and 18F-FDG PET/CT are equivocal.

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Abstract. Since nanoparticle albumin-bound (nab)-paclitaxel exerts clinically meaningful antitumor effects on various malignancies, including breast, gastric and non-small-cell lung cancer, we hypothesized that treatment with nab-paclitaxel may also be beneficial for patients with small-cell lung cancer (SCLC). We herein evaluated the safety and efficacy of weekly, single-agent nab-paclitaxel in patients with refractory or relapsed SCLC. Between May, 2013 and February, 2015, 9 patients with refractory or relapsed SCLC were treated with single-agent nab-paclitaxel at the Kyoto University Hospital. The medical records of the patients were retrospectively reviewed. All the patients had been previously treated with ≥2 lines of chemotherapy prior to receiving nab-paclitaxel. The median number of cycles of nab-paclitaxel was 2 (range, 1-4) and 3 partial responses were observed (response rate: 33%). The toxicity was generally mild and manageable: Grade 3/4 adverse events were only observed in 1 patient (grade 3 leukopenia). Thus, weekly administration of nab-paclitaxel may be a viable treatment option in patients with refractory or relapsed SCLC. Considering that treatment options are quite limited in this patient population, further evaluation of this regimen may prove valuable in the clinical setting. IntroductionAlthough small-cell lung cancer (SCLC) is initially highly sensitive to chemotherapy and radiotherapy, the majority of the patients eventually experience disease relapse and their prognosis is generally poor. To date, topotecan is the only Food and Drug Administration-approved drug for relapsed or refractory SCLC. In Japan, amrubicin is also available; however, the overall treatment options for such patients is limited.Previous phase II studies have demonstrated that paclitaxel has antitumor activity in patients with pretreated SCLC (1). Recently, nanoparticle albumin-bound (nab)-paclitaxel (Abraxane ® ; Taiho, Tokyo, Japan) was developed to improve the therapeutic index of paclitaxel, and randomized studies have confirmed that nab-paclitaxel was more effective and exhibited a more favorable safety profile compared with conventional solvent-based paclitaxel (2).In this study, based on this background, we retrospectively reviewed 9 patients with refractory or relapsed SCLC who were treated with nab-paclitaxel at Kyoto University Hospital. . Between May, 2013 and February,2015, 64 patients with thoracic malignancies were treated with nab-paclitaxel. Of those patients, 8 had thymic tumors, 47 had non-small-cell lung cancer (NSCLC) and 9 had SCLC. Nab-paclitaxel (100 mg̸m 2 ) was administered on days 1, 8, and 15 of a 28-day cycle. Tumor response was evaluated by using the Response Evaluation Criteria in Solid Tumors, version 1.1 (3), and adverse events were graded by using the Common Terminology Criteria for Adverse Events, version 4.0 (http://ctep.cancer.gov/protocolDevelopment/electronic_applications/ctc.htm#ctc_40; http:// ctep.cancer.gov/protocolDevelopment/ electronic_applica-tions/ctc.htm#ctc_40%3E*). ...