Shinnosuke Ikemura

Activation of the FGF2-FGFR1 Autocrine Pathway: A Novel Mechanism of Acquired Resistance to Gefitinib in NSCLC

Patients with non-small cell lung cancer (NSCLC) that harbors epidermal growth factor receptor (EGFR) mutations initially respond to EGFR-tyrosine kinase inhibitors (TKI) but eventually experience relapse. Acquired resistance to EGFR-TKIs is strongly associated with patient mortality. Thus, elucidation of the mechanism of acquired resistance to EGFR-TKIs is of great importance. In this study, gefitinib-resistant cell line models were established by long-term exposure to gefitinib using the gefitinib-sensitive lung cancer cell lines, PC9 and HCC827. Expression analyses indicated that both FGFR1 and FGF2 were increased in PC9 gefitinib-resistant (PC9 GR) cells as compared with PC9 naïve (PC9 na) cells. Importantly, proliferation of gefitinib-resistant cells was dependent on the FGF2 -FGFR1 pathway. Mechanistically, inhibition of either FGF2 or FGFR1 by siRNA or FGFR inhibitor (PD173074) restored gefitinib sensitivity in PC9 GR cells. These data suggest that FGF2 -FGFR1 activation through an autocrine loop is a novel mechanism of acquired resistance to EGFR-TKIs. Mol Cancer Res; 11(7); 759–67. ©2013 AACR.

Identification of microRNAs differentially expressed between lung squamous cell carcinoma and lung adenocarcinoma

Recent advances in the treatment of non-small cell lung cancer (NSCLC) with new agents require accurate histological subtyping at diagnosis to avoid the higher risk of an adverse response and to obtain the maximum therapeutic response. However, interobserver variability, tumor heterogeneity and the degree of differentiation may affect the decision concerning a pathological diagnosis of NSCLC. Therefore, the aim of this study was to identify specific microRNAs (miRNAs) as standardized biomarkers with high sensitivity and specificity in order to distinguish between squamous cell carcinoma (SCC) and adenocarcinoma (AC). Quantitative polymerase chain reaction (qPCR)‑based miRNA array analysis was performed to identify microRNAs differentially expressed between SCC and AC using 86 resected NSCLC samples in addition to adjacent normal tissues. The results were confirmed by independent qRT-PCR assays with the same test samples and 88 additional validation samples, and from this we evaluated the usefulness of the identified miRNAs as biomarkers to distinguish between SCC and AC. Three miRNAs (hsa-miR-196b, hsa-miR-205 and hsa-miR-375) were identified. Discriminant analysis combining the three miRNAs appeared to distinguish SCC from AC accurately in the test and validation samples, demonstrating a sensitivity and specificity of 76 and 80%, and 85 and 83%, respectively. hsa-miR-196b, hsa-miR-205 and hsa-miR-375 were identified as biomarkers capable of distinguishing between lung SCC and lung AC. These newly identified miRNAs may prove to be highly valuable molecular markers for the classification of NSCLC histological subtypes and may contribute to the pathogenesis of each subtype of NSCLC.

The Combination of Multiple Receptor Tyrosine Kinase Inhibitor and Mammalian Target of Rapamycin Inhibitor Overcomes Erlotinib Resistance in Lung Cancer Cell Lines through c-Met Inhibition

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) show antitumor activity in a subset of non–small cell lung cancer (NSCLC) patients. However, the initial tumor response is followed by recurrence. Several studies have suggested the importance of other receptor tyrosine kinases (RTK) and downstream kinases as potential targets in the treatment of NSCLC. We used the multiple-RTK inhibitor AEE788, which inhibits EGFR, vascular endothelial growth factor receptor, and human epidermal growth factor receptor 2, with and without the downstream kinase inhibitor RAD001 (an inhibitor of mammalian target of rapamycin). AEE788 inhibited cell growth more effectively than did erlotinib in three NSCLC cell lines examined (A549, H1650, and H1975). However, in the EGFR-TKI–resistant cell line H1975 harboring T790M resistance mutation, cell growth inhibition by AEE788 was only mild, and the phosphorylation of its leading targets such as EGFR and vascular endothelial growth factor receptor 2 was not inhibited. In H1975, AEE788 induced significantly greater cell growth inhibition when combined with RAD001 than when used alone. This cooperative effect was not seen with the combination of erlotinib and RAD001. We found that c-Met was highly phosphorylated in this cell line, and the phosphorylated c-Met was inhibited effectively by AEE788. Using a phospho-RTK array, the phosphorylation of c-Met and insulin-like growth factor-I receptor was inhibited by AEE788. These results suggest that upstream RTK inhibitor overcomes the acquired resistance to EGFR-TKI when combined with downstream kinase inhibitor. Thus, the combined inhibition of upstream and downstream RTKs is a promising strategy for the treatment of NSCLC. Mol Cancer Res; 8(8); 1142–51. ©2010 AACR.

Bronchoscopic Microsampling is a Useful Complementary Diagnostic Tool for Detecting Lung Cancer

PURPOSE Bronchoscopic microsampling (BMS) is a novel and direct method with which to obtain epithelial lining fluid (ELF) from the lungs. Analysis of DNA hypermethylation of tumor suppressor genes (TSGs) is expected to be a sensitive tool for the early detection of lung cancer. It has been reported that the existence of EGFR mutations and EML4-ALK gene rearrangements are related to the sensitivity of corresponding kinase inhibitors. We aimed to evaluate the suitability of ELF as a sample for analyzing molecular changes specific for lung cancer. PATIENTS AND METHODS We collected ELF from 61 lung cancer patients by BMS from the airway close to the peripheral lung nodule and purified the nucleic acids. We performed methylation specific PCR in each ELF as well as matched serum and tumor tissue for TSGs for DNA methylation analysis. We also examined EGFR mutations and EML4-ALK rearrangement. RESULTS The sensitivity for detecting DNA hypermethylation in ELF vs serum was 74.1% vs 18.5%. We found 60.1% of patients had at least one hypermethylation in ELF, while only 27.9% had it in serum. Of note, DNA hypermethylation was detected even in stage I patients (60.0%) and the detection rate was almost the same level in each stage. We also found the sensitivity for detecting EGFR mutation in ELF vs serum was 58.3% vs 8.3%. We detected an EML4-ALK fusion gene using ELF in one patient. CONCLUSIONS BMS is an alternative method to detect cancer specific genetic and epigenetic alterations and will be a useful complementary diagnostic tool for lung cancer. SUMMARY Investigation of genetic and epigenetic changes associated with lung cancer has clinical importance for its diagnosis and management. The clinical usefulness of bronchoscopic microsampling (BMS) in lung cancer has not yet been evaluated. This study demonstrates that BMS could be useful for detecting lung cancer specific molecular changes and valuable for early diagnosis and determination of treatment options for lung cancer.

Amplification of EGFR Wild-Type Alleles in Non–Small Cell Lung Cancer Cells Confers Acquired Resistance to Mutation-Selective EGFR Tyrosine Kinase Inhibitors

EGFR-mutated lung cancers account for a significant subgroup of non-small cell lung cancers overall. Third-generation EGFR tyrosine kinase inhibitors (TKI) are mutation-selective inhibitors with minimal effects on wild-type EGFR. Acquired resistance develops to these agents, however, the mechanisms are as yet uncharacterized. In this study, we report that the Src-AKT pathway contributes to acquired resistance to these TKI. In addition, amplification of EGFR wild-type alleles but not mutant alleles was sufficient to confer acquired resistance. These findings underscore the importance of signals from wild-type EGFR alleles in acquiring resistance to mutant-selective EGFR-TKI. Our data provide evidence of wild-type allele-mediated resistance, a novel concept of acquired resistance in response to mutation-selective inhibitor therapy in cancer treatment. Cancer Res; 77(8); 2078-89. ©2017 AACR.

Aggressive tumor microenvironment of solid predominant lung adenocarcinoma subtype harboring with epidermal growth factor receptor mutations

INTRODUCTION Tumor microenvironment critically affects cancer progression. This study aimed to identify differences in microenvironments of lung adenocarcinomas with epidermal growth factor receptor (EGFR) mutations by histological subtypes. METHODS The study cohort included 214 lung adenocarcinomas harboring EGFR mutations. We analyzed clinicopathological characteristics of lepidic (LPA), papillary (PPA), acinar (APA), and solid-predominant adenocarcinoma (SPA) subtypes, and examined expression levels of EGFR, E-cadherin, ezrin, laminin-5, ALDH1, and PD-L1 in cancer cells, and of CD34, CD204, podoplanin (PDPN), and FoxP3 in stromal cells in 4 subtypes (n=20 each). RESULTS SPA displayed significantly more frequent lymph node metastasis, lymphovascular invasion, and worse prognosis than the other subtypes. Ezrin expression levels in SPA were also significantly higher than in LPA, PPA, or APA (P<0.05, all). Laminin-5 and PD-L1 expression levels in SPA were significantly higher than in LPA (P<0.01 for both) and PPA (P<0.01 for both) and tended to be higher than in APA (laminin-5: P=0.096, PD-L1: P=0.081). Furthermore, SPA displayed higher levels of PDPN (+) cancer-associated fibroblasts (P<0.01) and CD204 (+) tumor-associated macrophages (P<0.05) than the other subtypes. CONCLUSION Compared with other predominant subtypes with EGFR mutations, the microenvironment of SPA with EGFR mutations is characterized by cancer cells with higher invasive and immune evasion potential and more abundant stromal cells with tumor-promoting functions, which would contribute to the more aggressive behavior of SPA.

Methylation‐induced downregulation of TFPI‐2 causes TMPRSS4 overexpression and contributes to oncogenesis in a subset of non‐small‐cell lung carcinoma

We identified transmembrane protease, serine 4 (TMPRSS4) as a putative, druggable target by screening surgically resected samples from 90 Japanese non‐small‐cell lung cancer (NSCLC) patients using cDNA microarray. TMPRSS4 has two druggable domains and was upregulated in 94.5% of the lung cancer specimens. Interestingly, we found that TMPRSS4 expression was associated with tissue factor pathway inhibitor 2 (TFPI‐2) expression in these clinical samples. In contrast to TMPRSS4, TFPI‐2 expression was downregulated in NSCLC samples. The in vitro induction of TFPI‐2 in lung cancer cell lines decreased the expression of TMPRSS4 mRNA levels. Reporter assay showed that TFPI‐2 inhibited transcription of TMPRSS4, although partially. Knockdown of TMPRSS4 reduced the proliferation rate in several lung cancer cell lines. When lung cancer cell lines were treated with 5‐aza‐2′‐deoxycytidine or trichostatin A, their proliferation rate and TMPRSS4 mRNA expression levels were also reduced through the upregulation of TFPI‐2 by decreasing its methylation in vitro. The TFPI‐2 methylation level in the low TMPRSS4 group appeared to be significantly low in NSCLC samples (P = 0.02). We found a novel molecular mechanism that TFPI‐2 negatively regulates cell growth by inhibiting transcription of TMPRSS4. We suggest that TMPRSS4 is upregulated by silencing of TFPI‐2 through aberrant DNA methylation and contributes to oncogenesis in NSCLC.

A Phase II study of S-1 and irinotecan combination therapy in previously treated patients with advanced non-small cell lung cancer

OBJECTIVE This Phase II study was conducted to evaluate the efficacy and safety of S-1 and irinotecan combination therapy as a second-line treatment in patients with advanced non-small cell lung cancer. METHODS Irinotecan was administered at 60 mg/m(2) on Days 1 and 8. Oral S-1 was administered on Days 1-14 every 3 weeks at 80 mg/day for patients with a body surface area of <1.25 m(2), 100 mg/day for patients with a body surface area of 1.25-1.5 m(2) and 120 mg/day for patients with a body surface area of >1.5 m(2). The primary endpoint was response rate, while the secondary endpoints were progression-free survival, overall survival and safety. RESULTS Thirty-one patients were enrolled in this study. The response and disease control rates were 6.5 and 58.1%, respectively. Progression-free survival and median survival time were 2.8 and 12.6 months, respectively. Grade 3-4 adverse events were reported for 29.0% of the patients. Hematological toxicities of Grade 3 or 4 included leukopenia (9.7%), neutropenia (9.7%), febrile neutropenia (3.2%), thrombopenia (3.2%) and anemia (6.5%). Non-hematological toxicities of Grade 3 or 4 included pneumonitis (6.5%), diarrhea, colitis, dyspnea, rash, oral mucositis, anorexia and pulmonary thromboembolism/deep vein thrombosis (3.2% each). CONCLUSIONS S-1 and irinotecan combination therapy at the present dose and schedule exhibited only modest efficacy with mild toxicities in previously treated patients with non-small cell lung cancer. No further clinical investigation with current dose and schedules is warranted for patients with non-small cell lung cancer who failed first-line platinum-based doublet chemotherapy.

Erlotinib as second‑ or third‑line treatment in elderly patients with advanced non‑small cell lung cancer: Keio Lung Oncology Group Study 001 (KLOG001)

The aim of this study was to assess the efficacy and safety of erlotinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), as second- or third-line treatment for elderly Japanese patients with non-small-cell lung cancer (NSCLC). The patients eligible for this phase II trial were aged ≥70 years, had stage III/IV or recurrent NSCLC, and had previously received 1 or 2 chemotherapy regimens that did not include EGFR-TKIs. The patients received erlotinib at a dose of 150 mg/day. The primary endpoint was overall response rate (ORR), and the secondary endpoints were progression-free survival (PFS), overall survival (OS) and toxicity. A total of 38 patients with a median age of 76 years were enrolled. The majority of the patients were men (66%), had an Eastern Cooperative Oncology Group performance status of 1 (58%), stage IV disease (66%) and adenocarcinoma (74%). Of the 35 patients, 13 (34%) had tumors with EGFR mutations. The ORR was 26.3% (95% confidence interval: 12.1-40.5%) and the disease control rate was 47.4%. The median PFS was 3.7 months and the median OS was 17.3 months. The grade 3 adverse events observed included rash (13%), diarrhea (5%), interstitial pneumonitis (5%), anorexia (3%) and gastrointestinal bleeding (3%). Grade 4 or 5 adverse events were not observed. The median OS did not differ significantly between patients aged <75 years (14.9 months) and those aged ≥75 years (19.0 months; P=0.226). Therefore, erlotinib was found to be effective and well-tolerated in elderly patients with previously treated NSCLC.

Changes in the tumor microenvironment during lymphatic metastasis of lung squamous cell carcinoma

Metastasis and growth in neoplastic lesions requires the multistep regulation of microenvironmental factors. We aimed to elucidate the microenvironmental changes in the process of lymphatic metastasis of lung squamous cell carcinoma. We examined the morphological characteristics of 102 cases of primary tumor (PT), 50 of intralymphatic tumor (ILT), 51 of lymph node (LN) micrometastasis (LN‐Mic; ≤2 mm in size), and 82 of LN macrometastasis (LN‐Mac; ≥10 mm in size). Afterwards we evaluated the expression of nine molecules (epidermal growth factor receptor, fibroblast growth factor receptor 2, CD44, aldehyde dehydrogenase 1, Podoplanin, E‐cadherin, S100A4, geminin, and ezrin) in matched PT, ILT, LN‐Mic, and LN‐Mac from 23 of these cases. The number of smooth muscle actin α‐positive fibroblasts, CD34‐positive microvessels and CD204‐positive macrophages were also examined. As a result, the mitotic index of tumor cells was significantly lower in ILT and LN‐Mic than PT and LN‐Mac (P < 0.001). Moreover, stromal reaction in ILT and LN‐Mic was less prominent than in PT and LN‐Mac (P < 0.001). Immunohistochemical study revealed that epidermal growth factor receptor expression level and frequency of geminin‐positive cells in ILT and LN‐Mic were significantly lower than in PT and LN‐Mac (P < 0.05). The number of stromal cells indicated by staining of CD34, CD204, and smooth muscle actin α in ILT and LN‐Mic was also significantly lower than in PT and LN‐Mac (P < 0.05). In lung squamous cell carcinoma, drastic microenvironmental changes (e.g., growth factor receptor expression and proliferative capacity of tumor cells and structural changes in stromal cells) occur during both the process of lymphatic permeation and the progression into macrometastases.