Kenichi Suda

Kinki University, Ōsaka, Ōsaka, Japan

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Publications (29)111.97 Total impact

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    ABSTRACT: Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) often provide dramatic responses in lung cancer patients with somatic EGFR mutation. However, acquired resistance to the drugs usually emerges within a few years. EGFR T790M secondary mutation, MET gene amplification, and transformation to small cell lung cancer are well-validated mechanisms that underlie acquisition of resistance to EGFR-TKIs. In addition, many molecular aberrations have been reported as candidates for mechanisms of acquired resistance to EGFR-TKIs. Amplification of the CRKL gene was reportedly observed in 1 of 11 lung cancer patients with EGFR mutations who acquired resistance to EGFR-TKI. This study is the first report, to our knowledge, that validated the role of CRKL gene amplification as a mechanism for acquisition of resistance to EGFR-TKIs.
    Lung cancer (Amsterdam, Netherlands) 06/2014; · 3.14 Impact Factor
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    ABSTRACT: Lung adenocarcinomas among never-smokers are more common in females than in males; this implies that gender-dependent hormones promote smoking-unrelated lung adenocarcinoma. We therefore investigated mRNA expression of aromatase, an intrinsic estrogen synthetase, in lung adenocarcinoma and assessed its correlation to clinicopathological factors, including EGFR mutations and post-surgical prognosis. Aromatase mRNA expression in primary tumor samples from 110 lung adenocarcinoma patients was evaluated with qRT-PCR. Inhibitory effects of the aromatase inhibitor exemestane were assessed in lung adenocarcinoma cell lines (11-18 and HCC4006) that have EGFR mutations, separately and combined with EGFR tyrosine kinase inhibitor erlotinib. Aromatase gene expression was not correlated with patients' clinicopathologic factors, including EGFR mutation status. High aromatase expression was associated with poor prognosis, for both recurrence-free survival (P = 0.004) and overall survival (P = 0.003). Additionally, the prognostic significance of aromatase expression was limited to females, never-smokers, and patients with EGFR mutations, but not in their counterparts. HCC4006, which has a low aromatase mRNA expression level, was not sensitive to exemestane, either alone or combined with erlotinib. In contrast, growth of 11-18 cells, which have high aromatase expression, was significantly inhibited by exemestane, both alone and combined with erlotinib. Aromatase is a candidate prognostic factor in patients with lung adenocarcinoma, especially in those with EGFR mutations, and may also be a beneficial therapeutic target in those patients.
    Clinical Cancer Research 05/2014; · 7.84 Impact Factor
  • Kenichi Suda, Tetsuya Mitsudomi
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    ABSTRACT: Human cancers usually possess cumulative genetic aberrations. However, recent studies have revealed that the proliferation and survival of specific subsets of lung cancer depend on a few somatic mutation(s), so-called driver mutations. Representative driver mutations include the EGFR mutation and ALK translocation identified in about 40% and 3% of lung adenocarcinomas in Japan, respectively. These tumors are extremely sensitive to the respective tyrosine kinase inhibitors. This sensitivity has encouraged researchers and clinicians to explore novel driver mutations in lung cancers as future molecular targets. Driver mutations reported so far include the HER2 mutation, BRAF mutation, ROS1 translocation, RET translocation, and NTRK translocation in lung adenocarcinomas, and FGFR1 amplification, DDR2 mutation, and FGFR3 translocation in lung squamous cell carcinomas. However, despite initial dramatic responses, the acquisition of resistance to molecular targeted drugs is almost inevitable. Overcoming resistance to molecular targeted drugs, the key drugs at this time, is an urgent issue to improve the outcomes of lung cancer patients.
    Nihon Geka Gakkai zasshi. 05/2014; 115(3):130-6.
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    ABSTRACT: We here report a case of solitary pulmonary metastasis from malignant melanoma that presented as a pulmonary ground glass nodule. A 57-year-old man who had undergone resection of a malignant melanoma of the right bulbar conjunctiva at the age of 51 was referred to our hospital for management of a ground glass opacity in his left lung. Because radiological examination suggested the nodule was an adenocarcinoma in situ, computed tomography (CT) follow-up was planned. CT examination performed 9 months later showed the nodule had grown from 6 mm to 8 mm. Moreover, CT, which was performed 1.5 years after first detection revealed the nodule had grown upto 10 mm. He therefore underwent partial resection of the lung for diagnosis and treatment. Pathological examination of the resected specimen revealed atypical cells with melanin granules proliferating in a lepidic-like fashion. The cells were positive on S-100 staining, indicating a pulmonary metastasis from malignant melanoma. Thus, metastatic tumors from malignant melanoma can present as ground glass opacities.
    Thoracic Cancer. 04/2014;
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    ABSTRACT: Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy often provides a dramatic response in lung cancer patients with EGFR mutations. In addition, moderate clinical efficacy of the EGFR-TKI, erlotinib, has been shown in lung cancer patients with the wild-type EGFR. Numerous molecular mechanisms that cause acquired resistance to EGFR-TKIs have been identified in lung cancers with the EGFR mutations; however, few have been reported in lung cancers with the wild-type EGFR. We used H358 lung adenocarcinoma cells lacking EGFR mutations that showed modest sensitivity to erlotinib. The H358 cells acquired resistance to erlotinib via chronic exposure to the drug. The H358 erlotinib-resistant (ER) cells do not have a secondary EGFR mutation, either MET gene amplification nor PTEN downregulation; these have been identified in lung cancers with the EGFR mutations. From comprehensive screening of receptor tyrosine kinase phosphorylation, we observed increased phosphorylation of Insulin-like growth factor 1 receptor (IGF1R) in H358ER cells compared with parental H358 cells. H358ER cells responded to combined therapy with erlotinib and NVP-AEW541, an IGF1R-TKI. Our results indicate that IGF1R activation is a molecular mechanism that confers acquired resistance to erlotinib in lung cancers with the wild-type EGFR. © 2014 Wiley Periodicals, Inc.
    International Journal of Cancer 01/2014; · 6.20 Impact Factor
  • Kenichi Suda, Tetsuya Mitsudomi
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    ABSTRACT: Human cancers usually evolve through multistep processes. These processes are driven by the accumulation of abundant genetic and epigenetic abnormalities. However, some lung cancers depend on a single activated oncogene by somatic mutation, termed 'driver oncogenic mutations', for their proliferation and survival. EGFR(epidermal growth factor receptor) mutations and ALK(anaplastic lymphoma kinase) rearrangement are typical examples of such driver oncogenic mutations found in lung adenocarcinomas. EGFR-tyrosine kinase inhibitors (TKIs) or ALK-TKIs significantly improved treatment outcomes compared with conventional cytotoxic chemotherapy in patients with lung cancers harboring EGFR mutations or ALK rearrangement, respectively. Therefore, treatment strategies for lung cancers have dramatically changed from a 'general and empiric' to a 'personalized and evidence-based' approach according to the driver oncogenic mutation. Several novel driver oncogenic mutations, which are candidates as novel targets, such as ERBB2, BRAF, ROS1, and RET, have been discovered. Despite these successes, several limitations have arisen. One example is that some lung cancers do not respond to treatments targeting driver oncogenic mutations, as exemplified in KRAS-mutated lung cancers. Another is resistance to molecular-targeted drugs. Such resistance includes de novo resistance and acquired resistance. A number of molecular mechanisms underlying such resistance have been reported. These mechanisms can be roughly divided into three categories: alteration of the targeted oncogenes themselves by secondary mutations or amplification, activation of an alternative oncogenic signaling track, and conversion of cellular characteristics. Overcoming resistance is a current area of urgent clinical research. © 2014 S. Karger AG, Basel.
    Progress in tumor research. 01/2014; 41:62-77.
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    ABSTRACT: Objectives Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) often provide dramatic responses in lung cancer patients with somatic EGFR mutation. However, acquired resistance to the drugs usually emerges within a few years. EGFR T790 M secondary mutation, MET gene amplification, and transformation to small cell lung cancer are well-validated mechanisms that underlie acquisition of resistance to EGFR-TKIs. In addition, many molecular aberrations have been reported as candidates for mechanisms of acquired resistance to EGFR-TKIs. Amplification of the CRKL gene was reportedly observed in 1 of 11 lung cancer patients with EGFR mutations who acquired resistance to EGFR-TKI. This study is the first report, to our knowledge, that validated the role of CRKL gene amplification as a mechanism for acquisition of resistance to EGFR-TKIs. Materials and Methods We analyzed CRKL gene copy numbers, using a quantitative real-time PCR method, in 2 in vitro acquired-resistance cell-line models: 11 clinical samples from patients who developed acquired resistance to EGFR-TKIs, and 39 tumor specimens obtained from 7 autopsy patients whose cancers acquired resistance to EGFR-TKIs. Mutational status of EGFR codon 790 and copy numbers for the MET gene were also determined. Results and Conclusion In analysis for in vitro models, CRKL gene copy numbers were identical between EGFR-TKI-sensitive parental cells and their acquired resistant descendant cells. In addition, we found no clinical tumor specimens with acquired EGFR-TKI resistance to harbor amplified CRKL genes. These results indicate that CRKL gene amplification is rare in acquisition of resistance to EGFR-TKIs in lung cancer patients with EGFR mutations.
    Lung Cancer. 01/2014;
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    ABSTRACT: In the last 10−15 years, strategies and modalities of lung cancer treatment have changed dramatically. Meanwhile, the treatment objectives, the lung cancers themselves, have also changed, probably owing to early detection by computed tomography and aging of the population. In particular, the proportions of smaller lung cancers, lung adenocarcinomas with ground-glass opacity, and lung cancers in older patients are increasing. Along with these changes, surgeons have innovated and evaluated novel procedures for pulmonary resection. These include the application of minimally invasive surgical techniques, such as video-assisted thoracoscopic surgery (VATS) and robotic surgery, and sub-lobar resection, such as wedge resection and segmentectomy, for small peripheral lung cancers. Currently, VATS has gained wide acceptance and several institutions in Japan have started using robotic surgery for lung cancers. Two important clinical trials of sub-lobar resection for small peripheral lung cancers are now underway in Japan. In addition, surgery itself is of growing importance in lung cancer treatment. In particular, recent evidence supports the use of surgery in strictly selected patients with locally advanced disease, lung cancers with N2 lymph node metastases, small cell lung cancers, recurrent oligo-metastasis after pulmonary resection, or relapsed tumors after drug treatment. Surgical treatment also provides abundant tumor samples for molecular analysis, which can be used for drug selection in the adjuvant setting or after disease relapse. In the era of personalized treatment, surgery is still one of the most important treatment modalities to combat lung cancer.
    Respiratory Investigation. 01/2014;
  • Kenichi Suda, Tetsuya Mitsudomi
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    ABSTRACT: Recent advances in molecular target therapy have greatly improved treatment outcomes for cancers driven by oncogenic mutations. However despite initial dramatic responses, cancer cells eventually acquire resistance to these drugs, showing flexible and diverse responses. Interestingly, cancer cells may sometimes over-adapt to the environment with the drug, leading to a state in which cancer cells cannot survive without the drug. This interesting phenomenon, which can be termed as "drug dependency" or "drug addiction," is exemplified in preclinical acquired resistance models of BRAF-mutated melanoma treated with vemurafenib and EGFR-mutated lung cancer treated with EGFR tyrosine kinase inhibitors. By comparing these two preclinical models, we noticed intriguing parallels of "drug addicted" cancers: (a) overexpression of driver oncogenes as causes of acquired resistance; (b) overexpression of driver oncogenes causing MEK-ERK hyperactivation under drug free conditions; (c) hyperactivation of the MEK-ERK pathway as critical to this "drug addiction" phenomenon; (d) ongoing dependence on the driver oncogene; and (e) morphological changes in resistant cells under drug-free conditions. In this perspective article, we focus on this interesting and weird phenomenon and discuss treatment strategies to utilize this unintentional weakness of cancers.
    Molecular Cancer Research 07/2013; · 4.35 Impact Factor
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    ABSTRACT: The discovery in 2004 of activating mutations in the EGFR gene opened the era of personalized medicine in thoracic oncology. Treatment with drugs that target EGFR typically results in dramatic tumour response compared with conventional chemotherapy in patients with non-small-cell lung cancer. Subsequently, newer driver oncogenes such as ALK, ROS1 and RET have been discovered. Nevertheless, surgery has become safer and less invasive in the past 10-15 years. In the era of personalized medicine, thoracic surgeons have to think about their evolving roles. In this article, we discuss four topics relevant to this issue. Firstly, the value of surgical specimens as opposed to biopsy specimens for further understanding tumour biology is discussed. Secondly, extended indication of surgery in the era of targeted therapy is considered. Thirdly, in clinical trials that examine neoadjuvant therapy in patients selected by appropriate biomarkers, the important role of surgeons is highlighted. Finally, the possibility of personalizing the surgical procedure itself according to lung cancer subtypes defined by biomarkers is reviewed.
    Nature Reviews Clinical Oncology 02/2013; · 15.03 Impact Factor
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    ABSTRACT: It is often difficult to differentiate metachronous primary lung cancers from local pulmonary recurrences when the histopathological findings are similar. A 43-year-old man underwent right upper lobectomy with lymph node dissection for primary lung adenocarcinoma (p-T2aN0M0, stage IB). Fifteen years later, he developed a lung nodule in his right middle lobe. The tumor was preoperatively thought to be a metachronous second primary lung adenocarcinoma, and was surgically resected. Histopathological findings for both tumors were of poorly differentiated adenocarcinoma with mucus production. Both tumors also harbored the EML4 (echinoderm microtubule-associated protein-like 4)-ALK (anaplastic lymphoma kinase) fusion gene (variant 3a+b). Based on this molecular finding, the pulmonary nodule was considered to be a recurrence after very long latent period.
    Lung cancer (Amsterdam, Netherlands) 12/2012; · 3.14 Impact Factor
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    ABSTRACT: Many elderly patients suffer from lung cancers, but it is not clear if their lung cancers differ from those of younger patients. In this study, we compared genetic and prognostic characteristics of lung cancers of patients aged ≥75 years with those of patients aged ≤ 64 years. In the genetic analysis, we explored 292 surgically treated non-squamous cell lung cancers with known mutational status of epidermal growth factor (EGFR) and anaplastic lymphoma kinase (ALK). In the prognostic analysis, we retrospectively analyzed 405 surgically treated non-small cell lung cancers (NSCLCs) before the era of routine clinical application of post-surgical adjuvant chemotherapy. Postsurgical recurrence-free survival (RFS) was compared between elderly patients and younger counterparts. The genetic analysis showed elderly non-squamous cell lung cancer patients to have higher prevalence of EGFR mutations (53.1 % vs 42.0%, P = 0.15) and lower prevalence of the ALK translocation (0 % vs 4.5%, P = 0.23) than their younger counterparts. The prognostic analysis showed postsurgical RFS was similar between the elderly NSCLC patients and the younger patients. However in multivariate analysis, adjusting for gender, smoking status, pathological stage, and histology, elderly patients had significantly worse prognoses (HR 1.57, 95% CI, 1.08-2.29; P = 0.02) compared with younger patients. These results suggest differences in genetic and prognostic aspects between elderly lung cancer patients and younger lung cancer patients.
    Aging and disease. 12/2012; 3(6):438-43.
  • Kenichi Suda, Tetsuya Mitsudomi
    Nippon rinsho. Japanese journal of clinical medicine 11/2012; 70 Suppl 8:341-5.
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    ABSTRACT: Aging is one of the best, but rarely referred, risk factors for various types of cancer including lung cancer, because age could be a surrogate for accumulation of genetic events in cancers. Smoking inversely associates with the presence of epidermal growth factor receptor (EGFR) mutation in lung cancer, but its strong confounding with age and sex makes it difficult to evaluate sole impact of age. To clarify an impact of age on EGFR mutation, we conducted a cross-sectional study based on data of 1262 lung cancer patients. The associations between EGFR mutation and age, considering sex, smoking and histology, were evaluated using logistic regression models. In multivariate analysis, we found a significant increase of EGFR mutation prevalence by increase of age (p-trend=0.0004). Consistent trend was observed among never-smoking females (p-trend=0.011) and never-smoking males also showed similar trend although not significant. These were consistently observed when we limit the subject to those with adenocarcinoma. In conclusion, age independently associates with EGFR mutation among lung cancer. Positive association between EGFR mutation and age among never-smokers regardless of sex might indicate that EGFR mutation occurs cumulatively by unidentified internal/external factors other than smoking.
    Lung cancer (Amsterdam, Netherlands) 10/2012; · 3.14 Impact Factor
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    ABSTRACT: : Approximately 50% of lung cancer patients with epidermal growth factor receptor (EGFR)-mutations (deletion in exon 19 or L858R) who develop acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) reportedly carry a secondary EGFR T790M mutation. This mutation has been suggested to be present in tumor cells before EGFR-TKI treatment in a small population of individuals. Here, we use a highly sensitive colony hybridization technique in an attempt to evaluate the actual incidence of T790M in pretreatment tumor specimens. : DNA was extracted from surgically resected tumor tissues of 38 patients with the EGFR mutation and examined for the presence of T790M, using a standard polymerase chain reaction based method followed by a modified colony hybridization (CH) technique with an analytical sensitivity of approximately 0.01%. Associations between the T790M status and clinical characteristics including time to treatment failure (TTF) for EGFR-TKI were evaluated. : The T790M mutation analysis of the specimens from the 38 patients detected 30 mutants (79%). The median TTF was 9 months for the patients with pretreatment T790M and 7 months for the patients without the T790M mutation (p = 0.44). When the patients with T790M were divided into strongly positive and modestly positive subgroups in terms of the frequency of positive signals observed using CH technique, the 7 patients with strong positivity had a TTF that was significantly longer than that of the 8 patients without T790M (p = 0.0097) and of the 23 patients with modest positivity (p = 0.0019). : Our highly sensitive CH method showed that a subgroup of non-small-cell lung cancer patients with the EGFR mutation harbored the rare T790M allele before EGFR-TKI treatment. A high proportion of T790M allele may define a clinical subset with a relatively favorable prognosis.
    Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer 08/2012; 7(11):1640-4. · 4.55 Impact Factor
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    ABSTRACT: Although the EGF receptor tyrosine kinase inhibitors (EGFR-TKI) erlotinib and gefitinib have shown dramatic effects against EGFR mutant lung cancer, patients become resistant by various mechanisms, including gatekeeper EGFR-T790M mutation, Met amplification, and HGF overexpression, thereafter relapsing. Thus, it is urgent to develop novel agents to overcome EGFR-TKI resistance. We have tested the effects of the mutant-selective EGFR-TKI WZ4002 and the mutant-selective Met-TKI E7050 on 3 EGFR mutant lung cancer cell lines resistant to erlotinib by different mechanisms: PC-9/HGF cells with an exon 19 deletion, H1975 with an L858R mutation, and HCC827ER with an exon 19 deletion, with acquired resistance to erlotinib because of HGF gene transfection, gatekeeper T790M mutation, and Met amplification, respectively. WZ4002 inhibited the growth of H1975 cells with a gatekeeper T790M mutation, but did not inhibit the growth of HCC827ER and PC-9/HGF cells. HGF triggered the resistance of H1975 cells to WZ4002, whereas E7050 sensitized HCC827ER, PC-9/HGF, and HGF-treated H1975 cells to WZ4002, inhibiting EGFR and Met phosphorylation and their downstream molecules. Combined treatment potently inhibited the growth of tumors induced in severe-combined immunodeficient mice by H1975, HCC827ER, and PC-9/HGF cells, without any marked adverse events. These therapeutic effects were associated with the inhibition of EGFR and Met phosphorylation in vivo. The combination of a mutant-selective EGFR-TKI and a Met-TKI was effective in suppressing the growth of erlotinib-resistant tumors caused by gatekeeper T790M mutation, Met amplification, and HGF overexpression. Further evaluations in clinical trials are warranted. Mol Cancer Ther; 11(10); 2149-57. ©2012 AACR.
    Molecular Cancer Therapeutics 07/2012; 11(10):2149-57. · 5.60 Impact Factor
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    ABSTRACT: Lung cancers that harbor somatic activating mutations in the gene for the epidermal growth factor receptor (EGFR) depend on mutant EGFR for their proliferation and survival; therefore, lung cancer patients with EGFR mutations often dramatically respond to orally available EGFR tyrosine kinase inhibitors (TKIs). However, emergence of acquired resistance is virtually inevitable, thus limiting improvement in patient outcomes. To elucidate and overcome this acquired resistance, multidisciplinary basic and clinical investigational approaches have been applied, using in vitro cell line models or samples obtained from lung cancer patients treated with EGFR-TKIs. These efforts have revealed several acquired resistance mechanisms and candidates, including EGFR secondary mutations (T790M and other rare mutations), MET amplification, PTEN downregulation, CRKL amplification, high-level HGF expression, FAS-NFκB pathway activation, epithelial-mesenchymal transition, and conversion to small cell lung cancer. Interestingly, cancer cells harbor potential destiny and ductility together in acquiring resistance to EGFR-TKIs, as shown in in vitro acquired resistance models. Molecular mechanisms of "reversible EGFR-TKI tolerance" that occur in early phase EGFR-TKI exposure have been identified in cell line models. Furthermore, others have reported molecular markers that can predict response to EGFR-TKIs in clinical settings. Deeper understanding of acquired resistance mechanisms to EGFR-TKIs, followed by the development of molecular target drugs that can overcome the resistance, might turn this fatal disease into a chronic disorder.
    CANCER AND METASTASIS REVIEW 06/2012; 31(3-4):807-14. · 9.35 Impact Factor
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    ABSTRACT: The three major clinically relevant mechanisms of acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in EGFR mutant lung cancer are a second mutation in the EGFR gene (T790M), Met amplification, and increased expression of hepatocyte growth factor (HGF). Heat shock protein90 (Hsp90) is a 90 kDa molecular chaperone for proteins that include EGFR, Met, and echinoderm microtubule-associated proetin-like-4-the anaplastic lymphoma kinase. Here, we determined whether inhibition of Hsp90 could overcome HGF-triggered EGFR-TKI resistance in EGFR mutant lung cancer cells. The effects of the Hsp90 inhibitor 17-demethoxygeldanamycin (17-DMAG) on the growth of lung cancer cells resistant to the EGFR-TKI were examined in the presence and absence of HGF, and in cells transfected with the HGF gene in vitro and in vivo. EGFR-TKI erlotinib did not inhibit the growth of HGF-gene transfected Ma-1 (Ma-1/HGF) cells and H1975 cells, containing the EGFR L858R and T790M mutations, respectively. Erlotinib also did not inhibit the growth of PC-9 and Ma-1 cells, with deletions in EGFR exon19, in the presence of HGF. However, 17-DMAG induced apoptosis and markedly inhibited the growth of these cell lines, even in the presence of HGF. This inhibition by 17-DMAG was associated with decreased expression of EGFR and Met in tumor cells. An in vivo model of HGF-triggered erlotinib-resistance, which used Ma-1/HGF cells, showed that 17-DMAG markedly suppressed tumor growth by decreasing angiogenesis and increasing apoptosis. Hsp90 inhibitors may overcome HGF-triggered resistance to EGFR-TKIs and may result in more successful treatment of patients with EGFR-mutant lung cancers.
    Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer 05/2012; 7(7):1078-85. · 4.55 Impact Factor
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    ABSTRACT: Epidermal growth factor receptor (EGFR) is often overexpressed in non-small-cell lung cancer (NSCLC). Anti-EGFR agents, including EGFR-tyrosine kinase inhibitors are considered to be effective when a drug-sensitive EGFR mutation is present. However, inherent and acquired resistances are major problems of EGFR-targeting therapies. In this study, we performed EGFR knockdown by using small interfering RNAs in NSCLC cell lines to examine the significance of targeting EGFR for NSCLC therapy. We treated 13 NSCLC cell lines, including 8 EGFR mutant and 5 EGFR wild type by using gefitinib or small interfering RNAs against EGFR (siEGFR). Three cell lines (PC-9-GR1, RPC-9, and HCC827-ER) were experimentally established with acquired resistance to EGFR-tyrosine kinase inhibitors. The antitumor effect was determined by using an 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt (MTS) or colony formation assay. The protein expression was evaluated by using Western blotting. All 13 cell lines expressed EGFR protein, and siEGFR downregulated EGFR protein expression in all. The cell viability was suppressed by siEGFR in 6 of 8 EGFR-mutant cell lines (suppressed 57%-92% of control cells), including PC-9-GR1 and RPC-9. The NCI-H1650 and HCC827-ER harbored EGFR mutations but were not suppressed. Of note, PTEN (phosphatase and tensin homolog) was deleted in NCI-H1650, and c-MET was amplified in HCC827-ER. It was not suppressed in any of the EGFR wild-type cells except in the NCI-H411, in which EGFR is phosphorylated, which indicates its activation. Conclusions: Analysis of the results indicated that EGFR can be a therapeutic target in NSCLCs with EGFR activation. In contrast, targeting EGFR is not appropriate for tumors in which EGFR is not activated, even if EGFR is expressed.
    Clinical Lung Cancer 04/2012; 13(6):488-93. · 2.04 Impact Factor
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    ABSTRACT: Emergence of acquired resistance is virtually inevitable in patients with a mutation in the epidermal growth factor receptor gene (EGFR) treated with EGFR tyrosine kinase inhibitors (TKIs). Several novel TKIs that may prevent or overcome the resistance mechanisms are now under clinical development. However, it is unknown how tumor cells will respond to intensive treatment using these novel TKIs. We previously established HCC827EPR cells, which are T790M positive, through combined treatment with erlotinib and a MET-TKI from erlotinib-hypersensitive HCC827 cells. In this study, we treated HCC827EPR cells sequentially with an irreversible EGFR-TKI, CL-387,785, to establish resistant cells (HCC827CLR), and we analyzed the mechanisms responsible for resistance. In HCC827CLR cells, PTEN expression was downregulated and Akt phosphorylation persisted in the presence of CL-387,785. Akt inhibition restored CL-387,785 sensitivity. In addition, withdrawal of CL-387,785 reduced cell viability in HCC827CLR cells, indicating that these cells were "addicted" to CL-387,785. HCC827CLR cells overexpressed the EGFR, and inhibition of the EGFR or MEK-ERK was needed to maintain cell proliferation. Increased senescence was observed in HCC827CLR cells in the drug-free condition. Through long-term culture of HCC827CLR cells without CL-387,785, we established HCC827-CL-387,785-independent cells, which exhibited decreased EGFR expression and a mesenchymal phenotype. In conclusion, PTEN downregulation is a newly identified mechanism underlying the acquired resistance to irreversible EGFR-TKIs after acquisition of T790M against erlotinib. This series of experiments highlights the flexibility of cancer cells that have adapted to environmental stresses induced by intensive treatment with TKIs.
    Lung cancer (Amsterdam, Netherlands) 11/2011; 76(3):292-9. · 3.14 Impact Factor

Publication Stats

296 Citations
111.97 Total Impact Points

Institutions

  • 2014
    • Kinki University
      • Department of Surgery
      Ōsaka, Ōsaka, Japan
  • 2012
    • Okayama University
      • Department of Cancer and Thoracic Surgery
      Okayama, Okayama, Japan
    • Gunma University
      Maebashi, Gunma Prefecture, Japan
    • Kyushu University
      • Department of Surgery and Science
      Fukuoka-shi, Fukuoka-ken, Japan
  • 2009–2011
    • Aichi Cancer Center
      Ōsaka, Ōsaka, Japan