Yoko Shimada

KIF5B-RET fusions in lung adenocarcinoma

We identified in-frame fusion transcripts of KIF5B (the kinesin family 5B gene) and the RET oncogene, which are present in 1–2% of lung adenocarcinomas (LADCs) from people from Japan and the United States, using whole-transcriptome sequencing. The KIF5B-RET fusion leads to aberrant activation of RET kinase and is considered to be a new driver mutation of LADC because it segregates from mutations or fusions in EGFR, KRAS, HER2 and ALK, and a RET tyrosine kinase inhibitor, vandetanib, suppresses the fusion-induced anchorage-independent growth activity of NIH3T3 cells.

Identification of Genes Upregulated in ALK-Positive and EGFR/KRAS/ALK-Negative Lung Adenocarcinomas

Activation of the EGFR, KRAS, and ALK oncogenes defines 3 different pathways of molecular pathogenesis in lung adenocarcinoma. However, many tumors lack activation of any pathway (triple-negative lung adenocarcinomas) posing a challenge for prognosis and treatment. Here, we report an extensive genome-wide expression profiling of 226 primary human stage I-II lung adenocarcinomas that elucidates molecular characteristics of tumors that harbor ALK mutations or that lack EGFR, KRAS, and ALK mutations, that is, triple-negative adenocarcinomas. One hundred and seventy-four genes were selected as being upregulated specifically in 79 lung adenocarcinomas without EGFR and KRAS mutations. Unsupervised clustering using a 174-gene signature, including ALK itself, classified these 2 groups of tumors into ALK-positive cases and 2 distinct groups of triple-negative cases (groups A and B). Notably, group A triple-negative cases had a worse prognosis for relapse and death, compared with cases with EGFR, KRAS, or ALK mutations or group B triple-negative cases. In ALK-positive tumors, 30 genes, including ALK and GRIN2A, were commonly overexpressed, whereas in group A triple-negative cases, 9 genes were commonly overexpressed, including a candidate diagnostic/therapeutic target DEPDC1, that were determined to be critical for predicting a worse prognosis. Our findings are important because they provide a molecular basis of ALK-positive lung adenocarcinomas and triple-negative lung adenocarcinomas and further stratify more or less aggressive subgroups of triple-negative lung ADC, possibly helping identify patients who may gain the most benefit from adjuvant chemotherapy after surgical resection.

A genome-wide association study identifies two new susceptibility loci for lung adenocarcinoma in the Japanese population

Lung adenocarcinoma is the most common histological type of lung cancer, and its incidence is increasing worldwide. To identify genetic factors influencing risk of lung adenocarcinoma, we conducted a genome-wide association study and two validation studies in the Japanese population comprising a total of 6,029 individuals with lung adenocarcinoma (cases) and 13,535 controls. We confirmed two previously reported risk loci, 5p15.33 (rs2853677, Pcombined = 2.8 × 10−40, odds ratio (OR) = 1.41) and 3q28 (rs10937405, Pcombined = 6.9 × 10−17, OR = 1.25), and identified two new susceptibility loci, 17q24.3 (rs7216064, Pcombined = 7.4 × 10−11, OR = 1.20) and 6p21.3 (rs3817963, Pcombined = 2.7 × 10−10, OR = 1.18). These data provide further evidence supporting a role for genetic susceptibility in the development of lung adenocarcinoma.

ROS1-rearranged lung cancer: a clinicopathologic and molecular study of 15 surgical cases.

Recent discovery of ROS1 gene fusion in a subset of lung cancers has raised clinical interest, because ROS1 fusion–positive cancers are reportedly sensitive to kinase inhibitors. To better understand these tumors, we examined 799 surgically resected non–small cell lung cancers by reverse transcriptase polymerase chain reaction and identified 15 tumors harboring ROS1 fusion transcripts (2.5% of adenocarcinomas). The most frequent fusion partner was CD74 followed by EZR. The affected patients were often younger nonsmoking female individuals, and they had overall survival rates similar to those of the ROS1 fusion–negative cancer patients. All the ROS1 fusion–positive tumors were adenocarcinomas except 1, which was an adenosquamous carcinoma. Histologic examination identified an at least focal presence of either solid growth with signet-ring cells or cribriform architecture with abundant extracellular mucus in 53% of the cases. These 2 patterns are reportedly also characteristic of anaplastic lymphoma kinase (ALK)-rearranged lung cancers, and our data suggest a phenotypic resemblance between the ROS1-rearranged and ALK-rearranged tumors. All tumors except 1 were immunoreactive to thyroid transcription factor-1. Fluorescence in situ hybridization using ROS1 break-apart probes revealed positive rearrangement signals in 23% to 93% of the tumor cells in ROS1 fusion–positive cancers, which were readily distinguished using a 15% cutoff value from 50 ROS1 fusion–negative tumors tested, which showed 0% to 6% rearrangement signals. However, this perfect test performance was achieved only when isolated 3′ signals were included along with classic split signals in the definition of rearrangement positivity. Fluorescence in situ hybridization signal patterns were unrelated to 5′ fusion partner genes. All ROS1 fusion–positive tumors lacked alteration of EGFR, KRAS, HER2, ALK, and RET genes.

A Synthetic Lethality–Based Strategy to Treat Cancers Harboring a Genetic Deficiency in the Chromatin Remodeling Factor BRG1

The occurrence of inactivating mutations in SWI/SNF chromatin-remodeling genes in common cancers has attracted a great deal of interest. However, mechanistic strategies to target tumor cells carrying such mutations are yet to be developed. This study proposes a synthetic-lethality therapy for treating cancers deficient in the SWI/SNF catalytic (ATPase) subunit, BRG1/SMARCA4. The strategy relies upon inhibition of BRM/SMARCA2, another catalytic SWI/SNF subunit with a BRG1-related activity. Immunohistochemical analysis of a cohort of non-small-cell lung carcinomas (NSCLC) indicated that 15.5% (16 of 103) of the cohort, corresponding to preferentially undifferentiated tumors, was deficient in BRG1 expression. All BRG1-deficient cases were negative for alterations in known therapeutic target genes, for example, EGFR and DDR2 gene mutations, ALK gene fusions, or FGFR1 gene amplifications. RNA interference (RNAi)-mediated silencing of BRM suppressed the growth of BRG1-deficient cancer cells relative to BRG1-proficient cancer cells, inducing senescence via activation of p21/CDKN1A. This growth suppression was reversed by transduction of wild-type but not ATPase-deficient BRG1. In support of these in vitro results, a conditional RNAi study conducted in vivo revealed that BRM depletion suppressed the growth of BRG1-deficient tumor xenografts. Our results offer a rationale to develop BRM-ATPase inhibitors as a strategy to treat BRG1/SMARCA4-deficient cancers, including NSCLCs that lack mutations in presently known therapeutic target genes.

Contribution of nicotine acetylcholine receptor polymorphisms to lung cancer risk in a smoking-independent manner in the Japanese

Recent genome wide association (GWA) studies on European and American populations revealed association with lung cancer risk of single-nucleotide polymorphisms (SNPs) in the locus containing two nicotine acetylcholine receptor (CHRNA) genes, whose involvement in tobacco addiction had been indicated. Association with lung cancer risk in smokers was consistently, but that in non-smokers as well as that with smoking behavior was inconsistently, observed in these studies. To obtain further information on the significance of CHRNA SNPs in lung cancer risk, association of seven SNPs in this locus with lung cancer risk as well as smoking status was examined in a Japanese population by a case-control study of 1250 cases (562 adenocarcinoma, 391 squamous cell carcinoma and 297 small cell carcinoma) and 936 controls. The frequency of the haplotype consisting of minor alleles for three SNPs, rs8034190, rs16969968 and rs1051730, which had been defined as a susceptible haplotype in the GWA studies, was much lower in the Japanese population (0.013) than in European and American populations (0.3-0.4). However, this haplotype was significantly associated with lung cancer risk also in Japanese (odds ratio = 2.3, 95% confidence interval = 1.5-3.7, P = 0.00028, respectively). The association was observed both in smokers and non-smokers and in all histological types of lung cancers. Individuals with this haplotype showed higher smoking doses than those without; however, the difference was not statistically significant. These results strongly indicate that CHRNA SNPs confer lung cancer susceptibility in a small subset of Japanese in a smoking-independent manner.

Druggable Oncogene Fusions in Invasive Mucinous Lung Adenocarcinoma

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. Clin Cancer Res; 20(12); 3087–93. ©2014 AACR.

Genome-wide Identification of Genes with Amplification and/or Fusion in Small Cell Lung Cancer

To obtain a landscape of gross genetic alterations in small cell lung cancer (SCLC), genome‐wide copy number analysis and whole‐transcriptome sequencing were performed in 58 and 42 SCLCs, respectively. Focal amplification of known oncogene loci, MYCL1 (1p34.2), MYCN (2p24.3), and MYC (8q24.21), was frequently and mutually exclusively detected. MYCL1 and MYC were co‐amplified with other regions on either the same or the different chromosome in several cases. In addition, the 9p24.1 region was identified as being amplified in SCLCs without amplification of MYC family oncogenes. Notably, expression of the KIAA1432 gene in this region was significantly higher in KIAA1432 amplified cells than in non‐amplified cells, and its mRNA expression showed strong correlations with the copy numbers. Thus, KIAA1432 is a novel gene activated by amplification in SCLCs. By whole‐transcriptome sequencing, a total of 60 fusion transcripts, transcribed from 95 different genes, were identified as being expressed in SCLC cells. However, no in‐frame fusion transcripts were recurrently detected in ≥2 SCLCs, and genes in the amplified regions, such as PVT1 neighboring MYC and RLF in MYCL1 amplicons, were recurrently fused with genes in the same amplicons or with those in different amplicons on either the same or different chromosome. Thus, it was indicated that amplification and fusion of several genes on chromosomes 1 and 8 occur simultaneously but not sequentially through chromothripsis in the development of SCLC, and amplification rather than fusion of genes plays an important role in its development.

Frequent methylation-associated silencing of a candidate tumor-suppressor, CRABP1, in esophageal squamous-cell carcinoma.

Epigenetic alterations and the resulting inactivation of tumor suppressor genes often contribute to the development of various cancers. To identify novel candidates that may be silenced by aberrant methylation in esophageal squamous-cell carcinoma (ESCC), we analysed ESCC cell lines by a recently developed method known as bacterial artificial chromosome array-based methylated CpG island amplification (BAMCA), and selected candidates through BAMCA-assisted strategy. In the course of this program, we identified frequent CpG methylation-dependent silencing of the gene encoding cellular retinoic acid binding protein 1 (CRABP1) in our panel of ESCC cell lines. Expression of CRABP1 mRNA was restored in gene-silenced ESCC cells after treatment with 5-aza 2′-deoxycytidine. The DNA methylation status of the CRABP1 CpG island with clear promoter activity correlated inversely with expression of this gene. CpG methylation of CRABP1 was frequently observed in primary ESCC tissues as well. Restoration of CRABP1 expression in ESCC cells lacking the protein reduced cell growth by inducing arrest at G0–G1, whereas knockdown of the gene in cells expressing CRABP1 promoted cell growth. Among 113 primary ESCC tumors, the absence of immunoreactive CRABP1 was significantly associated with de-differentiation of cancer cells and with distant lymph-node metastases in the patients. These results indicate that CRABP1 appears to have a tumor-suppressor function in esophageal epithelium, and its epigenetic silencing may play a pivotal role during esophageal carcinogenesis. Its expression status in biopsies or resected tumors might serve as an index for identifying ESCC patients for whom combined therapeutic modalities would be recommended.

Individuals susceptible to lung adenocarcinoma defined by combined HLA-DQA1 and TERT genotypes.

Adenocarcinoma (ADC) is the commonest histological type of lung cancer, and its weak association with smoking indicates the necessity to identify high-risk individuals for targeted screening and/or prevention. By a genome-wide association study (GWAS), we identified an association of polymorphisms in the 6p21.31 locus containing four human leukocyte antigen (HLA) class II genes with lung ADC risk. DQA1*03 of the HLA-DQA1 gene was defined as a risk allele with odds ratio (OR) of 1.36 [95% confidence interval (CI) = 1.21-1.54, P = 5.3 x 10(-7)] by analysis of 1656 ADC cases and 1173 controls. DQA1*03 and the minor allele for a polymorphism, rs2736100, in TERT, another lung cancer susceptibility locus identified in recent GWASs on Europeans and Americans, were indicated to independently contribute to ADC risk with per allele OR of 1.43 (95% CI = 1.31-1.56, P = 7.8 x 10(-16)). Individuals homozygous both for the DQA1*03 and minor TERT alleles were defined as high-risk individuals with an OR of 4.76 (95% CI = 2.53-9.47, P = 4.2 x 10(-7)). The present results indicated that individuals susceptible to lung ADC can be defined by combined genotypes of HLA-DQA1 and TERT.