Faculty Profiles - OHASHI Kadoaki

Discovery of a Mutant-Selective Covalent Inhibitor of EGFR that Overcomes T790M-Mediated Resistance in NSCLC Reviewed

Annette O. Walter, Robert Tjin Tham Sjin, Henry J. Haringsma, Kadoaki Ohashi, Jing Sun, Kwangho Lee, Aleksandr Dubrovskiy, Matthew Labenski, Zhendong Zhu, Zhigang Wang, Michael Sheets, Thia St Martin, Russell Karp, Dan van Kalken, Prasoon Chaturvedi, Deqiang Niu, Mariana Nacht, Russell C. Petter, William Westlin, Kevin Lin, Sarah Jaw-Tsai, Mitch Raponi, Terry Van Dyke, Jeff Etter, Zoe Weaver, William Pao, Juswinder Singh, Andrew D. Simmons, Thomas C. Harding, Andrew Allen

CANCER DISCOVERY 3 ( 12 ) 1404 - 1415 2013.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC CANCER RESEARCH

Patients with non-small cell lung cancer (NSCLC) with activating EGF receptor (EGFR) mutations initially respond to first-generation reversible EGFR tyrosine kinase inhibitors. However, clinical efficacy is limited by acquired resistance, frequently driven by the EGFR(T790M) mutation. CO-1686 is a novel, irreversible, and orally delivered kinase inhibitor that specifically targets the mutant forms of EGFR, including T790M, while exhibiting minimal activity toward the wild-type (WT) receptor. Oral administration of CO-1686 as single agent induces tumor regression in EGFR-mutated NSCLC tumor xenograft and transgenic models. Minimal activity of CO-1686 against the WT EGFR receptor was observed. In NSCLC cells with acquired resistance to CO-1686 in vitro, there was no evidence of additional mutations or amplification of the EGFR gene, but resistant cells exhibited signs of epithelial-mesenchymal transition and demonstrated increased sensitivity to AKT inhibitors. These results suggest that CO-1686 may offer a novel therapeutic option for patients with mutant EGFR NSCLC.
SIGNIFICANCE: We report the preclinical development of a novel covalent inhibitor, CO-1686, that irreversibly and selectively inhibits mutant EGFR, in particular the T790M drug-resistance mutation, in NSCLC models. CO-1686 is the first drug of its class in clinical development for the treatment of T790M-positive NSCLC, potentially offering potent inhibition of mutant EGFR while avoiding the on-target toxicity observed with inhibition of the WT EGFR. (C) 2013 AACR.

DOI： 10.1158/2159-8290.CD-13-0314

Lower gefitinib dose led to earlier resistance acquisition before emergence of T790M mutation in epidermal growth factor receptor-mutated lung cancer model. Reviewed International journal

Hiromi Hayakawa, Eiki Ichihara, Kadoaki Ohashi, Takashi Ninomiya, Masayuki Yasugi, Saburo Takata, Katsuya Sakai, Kunio Matsumoto, Nagio Takigawa, Mitsune Tanimoto, Katsuyuki Kiura

Cancer science 104 ( 11 ) 1440 - 6 2013.11

Language：English Publishing type：Research paper (scientific journal)

Non-small-cell lung cancers with epidermal growth factor receptor (EGFR) mutations are sensitive to EGFR tyrosine kinase inhibitors (TKIs); however, unlike cytotoxic agents, it is generally accepted that minimal doses of drugs inhibiting target molecules are sufficient when molecular-targeted agents, including EGFR-TKIs, are used. Thus, any utility of higher doses remains unclear. We compared low-dose (15 mg/kg) gefitinib therapy with high-dose (50 mg/kg) therapy using an EGFR-mutated lung cancer xenograft model. Both gefitinib doses induced tumor shrinkage, but tumors regrew in the low-dose group within 1 month, whereas tumors in the high-dose group did not. Neither the T790M mutation nor MET amplification was apparent in regrown tumors. We also compared outcomes after two doses of gefitinib (5 and 25 mg/kg) in a transgenic EGFR-mutated lung cancer mouse model. In line with the results obtained using the xenograft model, both gefitinib doses completely inhibited tumor growth, but tumors treated with the lower dose of gefitinib developed earlier drug resistance. In conclusion, a low gefitinib dose caused tumors to become drug-resistant prior to acquisition of the T790M mutation or MET amplification in EGFR-mutated models of lung cancer. This suggests that it is important to optimize the EGFR-TKI dose for treatment of EGFR mutation-associated lung cancer. Gefitinib may need to be given at a dose greater than the minimum required for inhibition of target molecules.

DOI： 10.1111/cas.12284

Next-generation sequencing of paired tyrosine kinase inhibitor-sensitive and -resistant EGFR mutant lung cancer cell lines identifies spectrum of DNA changes associated with drug resistance Reviewed

Peilin Jia, Hailing Jin, Catherine B. Meador, Junfeng Xia, Kadoaki Ohashi, Lin Liu, Valentina Pirazzoli, Kimberly B. Dahlman, Katerina Politi, Franziska Michor, Zhongming Zhao, William Pao

GENOME RESEARCH 23 ( 9 ) 1434 - 1445 2013.9

Language：English Publishing type：Research paper (scientific journal) Publisher：COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT

Somatic mutations in kinase genes are associated with sensitivity of solid tumors to kinase inhibitors, but patients with metastatic cancer eventually develop disease progression. In EGFR mutant lung cancer, modeling of acquired resistance (AR) with drug-sensitive cell lines has identified clinically relevant EGFR tyrosine kinase inhibitor (TKI) resistance mechanisms such as the second-site mutation, EGFR T790M, amplification of the gene encoding an alternative kinase, MET, and epithelial mesenchymal transition (EMT). The full spectrum of DNA changes associated with AR remains unknown. We used next-generation sequencing to characterize mutational changes associated with four populations of EGFR mutant drug-sensitive and five matched drug-resistant cell lines. Comparing resistant cells with parental counterparts, 18-91 coding SNVs/Indels were predicted to be acquired and 1-27 were lost; few SNVs/indels were shared across resistant lines. Comparison of two related parental lines revealed no unique coding SNVs/indels, suggesting that changes in the resistant lines were due to drug selection. Surprisingly, we observed more CNV changes across all resistant lines, and the line with EMT displayed significantly higher levels of CNV changes than the other lines with AR. These results demonstrate a framework for studying the evolution of AR and provide the first genome-wide spectrum of mutations associated with the development of cellular drug resistance in an oncogene-addicted cancer. Collectively, the data suggest that CNV changes may play a larger role than previously appreciated in the acquisition of drug resistance and highlight that resistance may be heterogeneous in the context of different tumor cell backgrounds.

DOI： 10.1101/gr.152322.112

Vandetanib is effective in EGFR-mutant lung cancer cells with PTEN deficiency Reviewed

Hiromasa Takeda, Nagio Takigawa, Kadoaki Ohashi, Daisuke Minami, Itaru Kataoka, Eiki Ichihara, Nobuaki Ochi, Mitsune Tanimoto, Katsuyuki Kiura

Experimental Cell Research 319 ( 4 ) 417 - 423 2013.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Academic Press Inc.

The effectiveness of vandetanib, an agent that targets RET, VEGFR and EGFR signaling, against EGFR-mutant lung cancer cells with PTEN loss was investigated. Two EGFR mutant non-small cell lung cancer (NSCLC) cell lines, PC-9 (PTEN wild type) and NCI-H1650 (PTEN null), were used. We transfected an intact PTEN gene into H1650 cells and knocked down PTEN expression in PC-9 cells using shRNA. The effectiveness of gefitinib and vandetanib was assessed using a xenograft model. While PC-9 cells were more resistant to vandetanib than gefitinib, H1650 cells were more sensitive to vandetanib than gefitinib. Both gefitinib and vandetanib suppressed the activation of EGFR and MAPK in H1650 cells, although phosphorylated AKT levels were not affected. In an H1650 cell xenograft model, vandetanib was also more effective than gefitinib. Although PTEN-transfected H1650 cells did not show restoration of sensitivity to gefitinib in vitro, the xenograft tumors responded to gefitinib and vandetanib. Knockdown of PTEN in PC-9 cells caused resistance to gefitinib. In conclusion, vandetanib might be effective in NSCLC with EGFR mutations that lack PTEN expression. The contribution of PTEN absence to vandetanib activity in NSCLC cells harboring EGFR mutations should be further examined. © 2012 Elsevier Inc.

DOI： 10.1016/j.yexcr.2012.12.018

Scopus

Daijiro Harada, Nagio Takigawa, Nobuaki Ochi, Takashi Ninomiya, Masayuki Yasugi, Toshio Kubo, Hiromasa Takeda, Eiki Ichihara, Kadoaki Ohashi, Saburo Takata, Mitsune Tanimoto, Katsuyuki Kiura

CANCER SCIENCE 103 ( 10 ) 1795 - 1802 2012.10

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as gefitinib and erlotinib, are effective for non-small cell lung cancer with activating EGFR mutations. However, even in patients with an initial dramatic response to such a drug, acquired resistance develops after 612 similar to months. A secondary mutation of T790M in EGFR and amplification of the MET gene account for this resistance; however, the mechanism(s) of approximately 30% of acquired resistance cases remain unknown. We established an erlotinib-resistant lung cancer cell line named PC-9/ER3 that harbors an EGFR mutation after continuously exposing PC-9 cells to erlotinib. PC-9/ER3 cells were 136-fold more resistant to erlotinib than the parental cells. Although the PC-9/ER3 cells did not carry the T790M mutation or MET amplification and had similar levels of phosphorylated (p) STAT3, pJAK2 increased in the resistant cells. It was found in the present study that 312 similar to h of exposure to erlotinib in both cell lines did not affect pJAK2 expression, but did result in increased pSTAT3 expression. pAkt in PC-9/ER3 cells was less suppressed than in PC-9 cells, although pEGFR and pMAPK were markedly suppressed in both cell lines. The combined treatment of erlotinib plus a JAK2 inhibitor (JSI-124) suppressed pAkt in PC-9/ER3 cells. Similarly, the combination of erlotinib plus JSI-124 or siRNA against JAK2 restored sensitivity to erlotinib in PC-9/ER3 cells. The combination of erlotinib plus JSI-124 was also effective for reducing PC-9/ER3 tumors in a murine xenograft model. Our results suggest that the activation of JAK2 partially accounts for acquired erlotinib resistance.(Cancer Sci, doi: 10.1111/j.1349-7006.2012.02363.x, 2012)

DOI： 10.1111/j.1349-7006.2012.02363.x

HER2 Amplification: A Potential Mechanism of Acquired Resistance to EGFR Inhibition in EGFR-Mutant Lung Cancers That Lack the Second-Site EGFR(T790M) Mutation Reviewed

Ken Takezawa, Valentina Pirazzoli, Maria E. Arcila, Caroline A. Nebhan, Xiaoling Song, Elisa de Stanchina, Kadoaki Ohashi, Yelena Y. Janjigian, Paula J. Spitzler, Mary Ann Melnick, Greg J. Riely, Mark G. Kris, Vincent A. Miller, Marc Ladanyi, Katerina Politi, William Pao

CANCER DISCOVERY 2 ( 10 ) 922 - 933 2012.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC CANCER RESEARCH

EGF receptor (EGFR)-mutant lung cancers eventually become resistant to treatment with EGFR tyrosine kinase inhibitors (TKI). The combination of EGFR-TKI afatinib and anti-EGFR antibody cetuximab can overcome acquired resistance in mouse models and human patients. Because afatinib is also a potent HER2 inhibitor, we investigated the role of HER2 in EGFR-mutant tumor cells. We show in vitro and in vivo that afatinib plus cetuximab significantly inhibits HER2 phosphorylation. HER2 overexpression or knockdown confers resistance or sensitivity, respectively, in all studied cell line models. FISH analysis revealed that HER2 was amplified in 12% of tumors with acquired resistance versus only 1% of untreated lung adenocarcinomas. Notably, HER2 amplification and EGFR(T790M) were mutually exclusive. Collectively, these results reveal a previously unrecognized mechanism of resistance to EGFR-TKIs and provide a rationale to assess the status and possibly target HER2 in EGFR-mutant tumors with acquired resistance to EGFR-TKIs.

DOI： 10.1158/2159-8290.CD-12-0108

STAT3 expression in activating EGFR-driven adenocarcinoma of the lung Reviewed

Saburo Takata, Nagio Takigawa, Yoshihiko Segawa, Toshio Kubo, Kadoaki Ohashi, Toshiyuki Kozuki, Norihiro Teramoto, Motohiro Yamashita, Shinichi Toyooka, Mitsune Tanimoto, Katsuyuki Kiura

LUNG CANCER 75 ( 1 ) 24 - 29 2012.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER IRELAND LTD

Bronchioloalveolar carcinoma (BAC) pattern is often seen at the margin of invasive adenocarcinomas. We investigated EGFR signaling abnormalities involved in the progression of adenocarcinoma. Fifty tumors were obtained from patients who underwent surgery for lung adenocarcinoma seen as dense areas in ground glass opacity on computed tomography. Six, 18, and 26 tumors <1 cm, 1-2 cm, and >= 2 cm in diameter, respectively, were analyzed. Of the 24 tumors <= 2 cm in diameter, nine were preinvasive and 15 were invasive. EGFR, pAKT, and pMAPK were overexpressed in the center of the adenocarcinoma compared to the BAC component (p < 0.01) by immunohistochemistry, while pSTAT3 expression was reversed (p = 0.017). In the tumors <= 2 cm in diameter, pSTAT3 expression in the central area was higher in preinvasive tumors than in invasive tumors (p = 0.005). pSTAT3 was identified in the BAC component of 88% of the EGFR mutant (n = 17) and 82% of the wild-type tumors (n = 33). Transgenic mice expressing delE748-A752 EGFR and two lung cancer cell lines (PC-9 mutant and A549 wild-type EGFR) were also investigated. In transgenic mice, pSTAT3 was overexpressed in the BAC component around the adenocarcinoma center. Two lung cancer cell lines that overexpressed pSTAT3 were equally sensitive to a JAK2/STAT3 inhibitor (JSI-124). The role of STAT3 in the progression of adenocarcinoma should be further pursued. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.lungcan.2011.05.015

Effect of gefitinib on N-nitrosamine-4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone induced lung tumorigenesis in A/J mice Reviewed

Ruptured Littoral Cell Angiosarcoma Causing Hemoperitoneum Reviewed

Hiromichi Yamane, Kadoaki Ohashi, Toshimitsu Suwaki, Nagio Takigawa

INTERNAL MEDICINE 51 ( 3 ) 337 - 338 2012

A new target for therapy in squamous cell carcinoma of the lung. Reviewed

Ohashi K, Pao W

Cancer Discovery 2011.1

Daizo Kishino, Katsuyuki Kiura, Nagio Takigawa, Hideki Katayama, Shoichi Kuyama, Ken Sato, Toshiaki Okada, Kadoaki Ohashi, Mitsune Tanimoto

LUNG CANCER 65 ( 3 ) 284 - 289 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER IRELAND LTD

Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). N-Nitrosamine-4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent carcinogen found in tobacco smoke, induces lung tumors in A/J mice. NNK induces cellular transformation resulting in the over-expression of EGFP. Accordingly, EGFR may be a target for cancer prevention. In this study, we investigated the effect of gefitinib on NNK-induced tumorigenesis and the carcinogenicity of gefitinib in A/J mice.
A total of 180 four-week-old female A/J mice were randomly divided into six groups: group 1 (controls), treated with deionized water; group 2, treated with 5 mg/kg p.o. gefitinib; group 3, treated with 50 mg/kg p.o. gefitinib (to test the carcinogenicity of gefitinib); group 4 (controls for NNK treatment), treated with deionized water; group 5, treated with 5 mg/kg p.o. gefitinib; and group 6, treated with 50 mg/kg p.o. gefitinib and injected with NNK once at 8 weeks of age to test the chemopreventive activity of gefitinib. Gefitinib was given once a day, 5 days a week by gavage, beginning at 4 weeks of age and continuing for 26 weeks. All mice were sacrificed at 30 weeks of age. The multiplicities of the NNK-induced lung tumors were significantly suppressed in a dose-dependent manner. Gefitinib had no effect on body weight at a low dose. The administration of gefitinib alone for 26 weeks did not induce tumorigenesis; instead, it significantly suppressed the incidence of spontaneous tumors in the mice, in contrast with other anticancer agents. Gefitinib did not induce lung fibrosis when compared with control mice by Azan-Mallory staining. Our results suggest that gefitinib has a weak but significant chemopreventive effect with no carcinogenicity or pulmonary toxicity in A/J mice. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.lungcan.2008.11.021

Effects of Vandetanib on Lung Adenocarcinoma Cells Harboring Epidermal Growth Factor Receptor T790M Mutation In vivo Reviewed

Eiki Ichihara, Kadoaki Ohashi, Nagio Takigawa, Masahiro Osawa, Atsuko Ogino, Mitsune Tanimoto, Katsuyuki Kiura

CANCER RESEARCH 69 ( 12 ) 5091 - 5098 2009.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC CANCER RESEARCH

Vandetanib is a novel multitarget tyrosine kinase inhibitor (TKI) that inhibits vascular endothelial growth factor receptor-2 (VEGFR-2), with additional inhibition of epidermal growth factor receptor (EGFR) and rearranged during transfection receptor signaling, which has shown promising results in clinical trials for advanced non-small cell lung cancer. However, the mechanisms of acquired resistance to vandetanib remain unclear. Therefore, we established in vitro vandetanib-resistant PC-9/VanR cells from PC-9, a vandetanib-sensitive lung adenocarcinoma cell line, by chronic exposure to this agent. PC-9/VanR cells were 50-fold more resistant to vandetanib than PC-9 cells in vitro. Compared with PC-9 cells, PC-9/VanR cells showed emergence of an EGFR T790M mutation, moderately elevated MET amplification, and similar VEGFR-2 inhibition by vandetanib. Note that phospho-MET in PC-9/VanR was suppressed following EGFR inhibition by an irreversible EGFR-TKI, indicating that MET signaling of PC-9/VanR was dependent on EGFR signaling and that MET amplification was not the primary mechanism of resistance to vandetanib. In contrast to the in vitro experiment, vandetanib effectively inhibited the growth of PC-9/VanR tumors in an in vivo xenograft model through the antiangiogenesis effects of VEGFR-2 inhibition. In conclusion, the multitarget TKI vandetanib induced or selected for the EGFR T790M mutation as observed previously with highly selective EGFR-TKIs. However, vandetanib retained significant efficacy in vivo against xenografts harboring the T790M mutation, providing a strong scientific rationale for investigating vandetanib in clinical settings where acquired resistance through emergence of EGFR T790M mutations limits the effectiveness of highly selective EGFR-TKIs. [Cancer Res 2009;69(12):5091-8]

DOI： 10.1158/0008-5472.CAN-08-4204

Combination of SN-38 with gefitinib or imatinib overcomes SN-38-resistant small-cell lung cancer cells Reviewed

Radiation necrosis mimicking progressive brain metastasis in a patient with non-small cell lung cancer Reviewed

Kadoaki Ohashi, Kastuyuki Kiura, Nagio Takigawa, Shigeki Umemura, Naruhito Kondo, Mistuhiro Takemoto, Kensuke Onoda, Motoi Aoe, Masahiro Tabata, Mistune Tanimoto

JOURNAL OF THORACIC ONCOLOGY 2 ( 8 ) 762 - 763 2007.8

Nagio Takigawa, Masami Takeyama, Toshiyuki Kozuki, Takuo Shibayama, Akiko Hisamoto, Katsuyuki Kiura, Atsuhiko Tada, Katsuyuki Hotta, Shigeki Umemura, Kadoaki Ohashi, Yoshiro Fujiwara, Saburo Takata, Eiki Ichihara, Masahiro Osawa, Masahiro Tabata, Mitsune Tanimoto, Kiyoshi Takahashi

ONCOLOGY REPORTS 17 ( 5 ) 983 - 987 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：PROFESSOR D A SPANDIDOS

Irinotecan is one of the effective anticancer agents for small-cell lung cancer (SCLC) and 7-ethyl-10-hydroxycampthothecin (SN-38) is an active metabolite of irinotecan. Gefitinib and imatinib are tyrosine kinase inhibitors which have clinical activities in several malignancies and they are also potent inhibitors of breast cancer resistance protein (BCRP) transporter, which confers the resistance of topoisomerase I inhibitors including SN-38 and topotecan. The cytotoxicity of SN-38, gefitinib and imatinib for the SN38-resistant cells (SBC-3/SN-38) from human SCLC cells, SBC-3, was evaluated using AlamarBlue assay. The drug concentration required to inhibit the growth of tumor cells by 50% (IC50) for 96-h exposure was used to evaluate the cytotoxicity. BCRP expression was determined by Western blotting and immunofluorescence staining. Intracellular topotecan accumulation was evaluated by flow cytometry. No differences were observed in the IC50 values (mean +/- SD) of the tyrosine kinase inhibitors between the SBC-3 cells and the SBC-3/SN-38 cells: 15 +/- 1.6 and 12 +/- 2.8 mu M of gefitinib, respectively; 15 +/- 0.51 and 14 +/- 3.9 mu M of imatinib, respectively. The SBC-3/SN-38 was 9.5-fold more resistant to SN-38 than the parental SBC-3. The SBC-3/SN-38 restored sensitivity to SN-38 when combined with 8 mu M gefitinib or 8 mu M imatinib, even though the IC50 values of SN-38 combined with gefitinib or imatinib in the SBC-3 cells did not change. BCRP was equally overexpressed in the SBC-3/SN-38 with and without gefitinib or imatinib. In addition, the BCRP expression on the SBC-3/SN-38 cell membrane with and without gefitinib seemed to be equal. Gefitinib increased intracellular accumulation of topotecan in the SBC-3/SN-38 cells. Gefitinib or imatinib reversed SN-38-resistance in these SCLC cells, possibly due to intracellular accumulation of SN-38 without any change in BCRP quantity. Irinotecan with gefitinib or imatinib might be effective for SCLC refractory to irinotecan.

Successful treatment of a patient with gastric and duodenal metastases from large cell carcinoma of the lung with carboplatin and gemcitabine Reviewed

Kadoaki Ohashi, Katsuyuki Kiura, Nagio Takigawa, Takaaki Mizushima, Hideo Ino, Masahiro Tabata, Hiroshi Ueoka, Mitsune Tanimoto

ANTICANCER RESEARCH 26 ( 6C ) 4695 - 4696 2006.11

Language：English Publishing type：Research paper (scientific journal) Publisher：INT INST ANTICANCER RESEARCH

A 62-year-old man with large cell carcinoma of the lung underwent a right upper lobectomy and four months later demonstrated a relapse in the stomach and duodenum. He received systemic chemotherapy consisting of carboplatin and gemcitabine. After the first cycle of chemotherapy, the duodenal lesion disappeared, however, the gastric lesion demonstrated no response. Considering the risk of bleeding or perforation, a partial gastroduodenal resection was therefore performed. Subsequently, he received adjuvant chemotherapy with the same regimen. He has since been doing well for 24 months after the recurrence. Although the prognosis for patients with gastrointestinal metastases from lung cancer tends to be extremely poor, treatment with chemotherapy and a metastasectomy have resulted in this patient, achieving a long survival.

Double mutation and gene copy number of EGFR in gefitinib refractory non-small-cell lung cancer Reviewed

Masaki Tokumo, Shinichi Toyookaa, Shuji Ichihara, Kadoaki Ohashi, Kazunori Tsukuda, Kouichi Ichimura, Masahiro Tabata, Katsuyuki Kiura, Motoi Aoe, Yoshifumi Sano, Hiroshi Date, Nobuyoshi Shimizu

LUNG CANCER 53 ( 1 ) 117 - 121 2006.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER IRELAND LTD

Mutations of the epidermal growth factor receptor (EGFR) gene have been reported in non-small-cell tung cancer (NSCLC), especially in patients with adenocarcinoma and never smokers. Some common somatic mutations in EGFR, including deletion mutations in exon 19 and leucine-to-arginine substitution at amino acid position 858 (L858R) in exon 21, have been examined for their ability to predict sensitivity to gefitinib or erlotinib, which are selective EGFR tyrosine kinase inhibitors (EGFR-TKIs). On the other hand, reports have shown that the threonine-to-methyonine substitution at amino acid position 790 (T790M) in exon 20 is related to gefitinib resistance. Some studies have indicated that high copy numbers of the EGFR gene may be a more effective molecular predictor to responsiveness and prolonged survival in patients treated with EGFR-TKIs. Here, we describe two NSCLC patients with the L858R mutation who did not respond to gefitinib. Case 1 harbored both the T790M and L858R mutations, and fluorescence in situ hybridization showed EGFR gene amplification. Case 2 harbored both the L858R and aspartic acid-to-thyrosine substitution at amino acid position 761 in exon 19 of EGFR mutations and had a high polysomy status for EGFR. In these two cases, tumors showed resistance to gefitinib treatment despite the presence of EGFR L858R mutation and increased copy number. Our findings encourage further molecular analysis to elucidate the relationship between the EGFR status, including mutations and amplifications, and the responsiveness of NSCLC to gefitinib. (c) 2006 Elsevier Ireland Ltd. All. rights reserved.

DOI： 10.1016/j.lungcan.2006.04.008