Masayuki Shitara

RET expression and detection of KIF5B/RET gene rearrangements in Japanese lung cancer

RET encodes the tyrosine kinase receptor of growth factors belonging to the glial‐derived neurotrophic factor family. Recently, RET gene rearrangements with N‐terminal of KIF5B gene were identified in lung adenocarcinomas from large‐scale sequencing. We investigated RET mRNA expression by real‐time reverse‐transcriptase polymerase chain reaction (RT‐PCR) assay using LightCycler, and KIF5B/RET gene rearrangements using newly established fluorescence in situ hybridization (FISH) analysis in surgically treated nonsmall cell lung cancer (NSCLC) cases. RET protein expression was also investigated by immunohistochemistry (IHC). This study included 157 surgically removed NSCLC cases for mRNA level analyses. The RET/β actin mRNA levels were not significantly different between lung cancer (6.359 ± 15.268) and adjacent normal lung tissues (8.205 ± 28.931, P = 0.6332). Tumor/normal (T/N) ratio of RET/β actin mRNA levels was not different within gender, stage, smoking status, and pathological subtypes. T/N ratio of RET/β actin mRNA levels was significantly higher in KIF5B/RET rearrangement samples (161.763 ± 123.488) than in wild‐type samples (5.9013 ± 17.148, P = 0.044). Although RET IHC positivity was not perfectly correlated with KIF5B/RET arrangement, we have detected the KIF5B/RET rearrangements using FISH analysis. Thus, we have successfully introduced FISH for diagnosing KIF5B/RET positive lung adenocarcinoma. This method facilitates the molecular evaluation for RET fusions and could be applicable in clinical practice to detect lung cancer that may be responsive to RET inhibitors.

Overexpression of GLUT1 correlates with Kras mutations in lung carcinomas.

Glucose is the major source of energy for cells, and glucose transporter 1 (GLUT1) is the most common glucose transporter. GLUT1 has been found to be aberrantly expressed in several tumor types. From the results of the microarray and serial analysis of gene expression (SAGE), GLUT1 transcript expression was found to be higher in clones with mutant Kras alleles. We hypothesized that GLUT1 overexpression might be correlated with clinicopathological features of Japanese lung cancers. Immunohistochemistry for GLUT1 was performed in 283 surgically treated non-small cell lung cancer (NSCLC) cases from Nagoya City University Hospital. Thirty-six Kras mutant carcinoma cases were included. GLUT1 overexpression was found in 138 (48.8%) lung cancer patients. The GLUT1 overexpression status was significantly correlated with gender (women 31.9% vs. men 54.5%, P<0.0001), smoking status (never smoker 31.4% vs. smoker 59.4%, P<0.0001) and pathological subtypes (adenocarcinoma 36.4% vs. non‑adenocarcinoma 74.5%, P<0.0001). In addition, the GLUT1 overexpression status was significantly correlated with gene mutation status, including EGFR (mutation-positive 23.4% vs. -negative 58.3%, P<0.0001) and Kras (mutation-positive 66.7% vs. -negative 46.6%, P=0.038). The survival of patients with GLUT1 overexpression (n=137, 50 were deceased) was significantly worse when compared to the patients with normal expression of GLUT1 (n=142, 31 were deceased) (Log-rank test, P=0.0009). Thus, GLUT-1 overexpression correlates with an aggressive phenotype of lung carcinoma.

Usefulness of immunohistochemistry for the detection of the BRAF V600E mutation in Japanese lung adenocarcinoma

PURPOSE Mutations in components of the mitogen-activated protein kinase (MAPK) cascade may be a new candidate for target for lung cancer. The usefulness of immunohistochemistry (IHC) as a new approach for the detection of BRAF V600E in cancer patients has been recently reported. METHODS To increase the sensitivity, we modified BRAF V600E expression detection assay by IHC using mutation specific antibody. From the screening step, we found a novel 599 insertion T BRAF mutation in lung adenocarcinoma. In this study included 26 surgically removed cases with EGFR, Kras, erbB2, EML4-ALK and KIF5B-RET wild-type (wt) lung adenocarcinomas, including 7 BRAF mutants (5 V600E, 1 N581I, and 1 novel 599 insertion T mutation) analyzed by DNA sequencing. Detection of the BRAF V600E mutation was carried out by the Dako EnVision™ FLEX detection system using the VE1 clone antibody and compared with the results of direct sequencing. RESULTS The autostainer IHC VE1 assay was positive in 5 of 5 (100%) BRAF V600E-mutated tumors and negative in 20 of 21 (95.2%) BRAF non-V600E tumors, except for a novel 599 insertion T case. CONCLUSION IHC using the VE1 clone and FLEX linker is a specific method for the detection BRAF V600E and may be an alternative to molecular biology for the detection of mutations in lung adenocarcinomas. This method might be useful for screening to use molecular target therapy for lung adenocarcinomas.

Increased FGFR1 copy number in lung squamous cell carcinomas

The basic fibroblast growth factor (bFGF), via activation of its receptor, FGFR1, has been postulated to be an important inducer of host stromal response and angiogenesis. More recently, FGFR1 amplifications were investigated using large-scale single nucleotide polymorphism arrays in lung cancer. We hypothesized that FGFR1 overexpression may be correlated with the clinicopathological features of lung cancers. The increased copy number of the FGFR1 gene was analyzed by real-time polymerase chain reaction amplifications in 100 surgically treated non-small cell lung cancer cases from Nagoya City University Hospital. Sixty-five squamous cell carcinoma cases were included. An increased FGFR1 gene copy number was found in 32 (32%) lung cancer patients. The increased FGFR1 copy number status significantly correlated with gender (females 13.8% vs. males 39.4%, p=0.0173), smoking status (never smoker 4.2% vs. smoker 40.8%, p=0.0004) and pathological subtypes (squamous cell carcinoma 41.5% vs. non-squamous cell carcinoma 14.3%, p=0.0066). However, within the squamous cell carcinomas the FGFR1 copy number status did not significantly correlate with gender, smoking status, pathological stages and differentiation status of the lung cancers. Thus, the FGFR1 copy number is common within squamous cell carcinoma.

Genotype analysis of the NRF2 gene mutation in lung cancer

Nuclear factor (erythroid derived 2)-like 2 (NRF2, gene name NFE2L2) gene mutations have been previously identified in lung cancers. The constitutive activation of NRF2 resulting from gene mutations has been correlated with the poor prognosis of patients with squamous cell lung cancer. However, DNA sequencing using PCR methods described to date is time-consuming and requires significant quantities of DNA. Thus, this existing approach is not suitable for a routine pre-therapeutic screening program. We genotyped the NRF2 gene mutation status in 262 surgically treated lung cancer cases using LightCycler analysis. The presence of the NRF2 gene mutation was confirmed by direct sequencing. We detected 6 cases (2.3%) with NRF2 gene mutations in our cohort, particularly smokers (P=0.04) with squamous histology (P=0.0001). NRF2 gene mutations were present in 10% (6/60) of the lung squamous cell carcinoma (SqCC) cases. The NRF2 gene mutation was exclusive of epidermal growth factor receptor mutations. The NRF2 gene mutation occurred with a tendency towards a higher frequency in male patients. Patients with the NRF2 gene mutation (n=22, 11 succumbed to disease) had a significantly worse prognosis when compared with the patients with the wild-type NRF2 gene (n=521, 98 succumbed to disease) from a larger cohort study (log-rank test, P<0.0001) even upon multivariate analysis. In our study, NRF2 gene mutations played a role in the prognosis of patients with SqCC of the lung.

APOBEC3B gene overexpression in non‑small-cell lung cancer

Recent study results have demonstrated that a subclass of apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) cytidine deaminase may induce mutation clusters in various types of cancer. From the Cancer Genome Altas, an APOBEC mutation pattern was identified in bladder, cervical, breast, head and neck and lung cancers. In the present study, APOBEC3B mRNA expression was investigated using quantitative reverse transcription-polymerase chain reaction (RT-qPCR) assay using LightCycler in surgically treated non-small-cell lung cancer (NSCLC) cases. Additionally, 88 surgically removed Japanese NSCLC cases were analyzed for mRNA level. The results showed that APOBEC3B/β-actin mRNA levels were significantly higher in lung cancer (1,598.481±6,465.781) when compared to adjacent normal lung tissues (2,116.639±8,337.331, P=0.5453). The tumor/normal (T/N) ratio of APOBEC3B/β-actin mRNA levels was not different within the gender, age, smoking status and pathological stages. The T/N ratio of APOBEC3B/β-actin mRNA levels was not significantly different in epidermal growth factor receptor (EGFR) or Kras mutation-positive cases as compared to the wild-type cases.

Polymorphisms in intron 1 of the EGFR gene in non‑small cell lung cancer patients

The epidermal growth factor receptor (EGFR) gene is highly polymorphic and its expression and activity may be affected by various polymorphisms. There have been several studies examining associations between EGFR polymorphisms and clinical outcome of lung cancer therapy; however, the underlying mechanism is largely unknown. The present study investigated EGFR polymorphism status and its correlation with clinicopathological features in Japanese non-small cell lung cancer (NSCLC) patients. We investigated 5 polymorphisms in the EGFR gene (−216G/T, −191C/A, 8227G/A, D994D and R497K) in 274 surgically-treated NSCLC patients. TaqMan single nucleotide polymorphism (SNP) genotyping assays and a PCR-based assay were used to analyze these polymorphisms. In our cohort of patients we did not find any evidence of the −191C/A polymorphism. Our results showed that the patients with the 8227GA or AA type in intron 1 had a significantly better prognosis with the anti-EGFR therapy than the patients with the GG type (p=0.0448) in terms of recurrence of lung cancer. No significant association was observed between 3 other SNPs (−216G/T, D994D and R497K) and clinicopathological features. The EGFR 8227G/A polymorphism in intron 1 may be associated with clinical outcome in NSCLC patients treated with EGFR tyrosine kinase inhibitors.

Genetic profiling of thymic carcinoma using targeted next-generation sequencing

OBJECTIVES Thymic carcinoma is a rare mediastinal neoplasm and little is known about its tumorigenesis. There is no effective treatment except for complete resection, and the prognosis of advanced cases is poor. To identify the mutations associated with tumorigenesis, we analyzed genetic profile of thymic carcinoma using targeted next-generation sequencing. MATERIALS AND METHODS We sequenced about 409 cancer-related genes in 12 thymic squamous cell carcinoma tissues including 10 tumor/normal tissue pairs using Ion AmpliSeq Cancer Panel and Ion PGM Sequencer. We filtered the mutations with Ingenuity Variant Analysis, SIFT, PolyPhen-2, and PROVEAN. RESULTS AND CONCLUSION Twenty-five candidate mutations in 24 genes were identified, including five tyrosine kinase genes (KIT, DDR2, PDGFRA, ROS1, IGF1R). There was no recurrent mutation among the samples studied. The KIT exon 11 deletion mutation in 1 patient was an activating mutation and may be an oncogenic driver mutation. Genetic profiling of thymic carcinoma using targeted next-generation sequencing was performed. The mutation status of thymic squamous cell carcinoma is highly heterogeneous.

Keap1 mutations in lung cancer patients

Kelch-like ECH-associated protein 1 (Keap1) inhibits nuclear factor erythroid 2-related 2 (NEF2L2; also named NRF2)-induced cytoprotection and has been hypothesized to represent a candidate tumor suppressor. We have previously reported the somatic mutations of the NRF2 gene (NFE2L2), however, the correlation between the Keap1 mutation and the clinicopathological features of lung cancer has not been well investigated. Therefore, in the present study, the Keap1 mutational status in non-small cell lung cancer (NSCLC) patients was investigated by reverse transcription PCR and direct sequencing. The study included 76 surgically-removed lung cancer cases from patients of the Nagoya City University Hospital in which the EGFR and NFE2L2 mutation status was already established. Keap1 mutations were identified in 2 (2.6%) adenocarcinoma patients with a history of heavy smoking. These mutations were identified to exist exclusively. The Keap1 mutation was only detected in patients with advanced adenocarcinoma (4.3%) and the completely exclusive status of this mutation and others, including EGFR, Kas, erbB2 and NRF2L2, is likely to improve the selection of personalized therapy for lung cancer.

Prognosis of recurrent non-small cell lung cancer following complete resection

Prognosis following recurrence subsequent to complete resection of non-small-cell lung cancer (NSCLC) is considered a multifactorial process dependent on clinicopathological, biological and treatment characteristics. Gefitinib was approved for lung cancer treatment in Japan in 2002. The aim of the current study was to quantify the prognostic effects of these characteristics on post-recurrence prognosis. In total, 127 NSCLC patients were analyzed who underwent complete resection and subsequently had recurrent cancer. The correlation between characteristics of the initial and recurrent disease with post-recurrence prognosis was investigated. The factors clearly associated with post-recurrence prognosis using Cox proportional hazards models were age at recurrence (those <65 years of age typically had better prognoses) and interval between initial resection and recurrence (intervals of <1 year accompanied a worse prognosis). Epidermal growth factor receptor (EGFR) mutant patients treated with EGFR tyrosine kinase inhibitors (TKIs), exhibited the longest median survival following recurrence (37.4 months) in the sample. Treatment, particularly EGFR TKIs for recurrent NSCLC, was observed to significantly prolong survival. The results of the study highlight that various treatment modalities according to the clinical background of the patient should be considered in patients with postoperative recurrent NSCLC.