Isamu Okamoto

Dr. Isamu Okamoto


Research Focus & Metrics

Academic Career Length

22Years (2005-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
9 July 2014 in Annals of Oncology
Verified
Journal Article
Open access
PDF file
KAK. Azuma
K. Azuma
KOK. Ota
K. Ota
AKA. Kawahara
A. Kawahara
SHS. Hattori
S. Hattori
EIE. Iwama
E. Iwama
IOIsamu Okamoto
Isamu Okamoto
Recent clinical trials have shown that immune-checkpoint blockade yields a clinical response in a subset of individuals with advanced nonsmall-cell lung cancer (NSCLC). We examined whether the expression of programmed death–ligand 1 (PD-L1) is related to clinicopathologic or prognostic factors in patients with surgically resected NSCLC. The expression of PD-L1 was evaluated by immunohistochemical analysis in 164 specimens of surgically resected NSCLC. Cell surface expression of PD-L1 in NSCLC cell lines was quantified by flow cytometry. Expression of PD-L1 in tumor specimens was significantly higher for women than for men, for never smokers than for smokers, and for patients with adenocarcinoma than for those with squamous cell carcinoma. Multivariate analysis revealed that the presence of epidermal growth factor receptor gene (EGFR) mutations and adenocarcinoma histology were significantly associated with increased PD-L1 expression in a manner independent of other factors. Cell surface expression of PD-L1 was also significantly higher in NSCLC cell lines positive for activating EGFR mutations than in those with wild-type EGFR. The EGFR inhibitor erlotinib downregulated PD-L1 expression in the former cell lines but not in the latter, suggesting that PD-L1 expression is increased by EGFR signaling conferred by activating EGFR mutations. A high level of PD-L1 expression in resected tumor tissue was associated with a significantly shorter overall survival for NSCLC patients. High expression of PD-L1 was associated with the presence of EGFR mutations in surgically resected NSCLC and was an independent negative prognostic factor for this disease.

31 August 2015 in Clinical Cancer Research
Verified
Journal Article
Open access
PDF file
KOKeiichi Ota
Keiichi Ota
KAKoichi Azuma
Koichi Azuma
AKAkihiko Kawahara
Akihiko Kawahara
SHSatoshi Hattori
Satoshi Hattori
EIEiji Iwama
Eiji Iwama
IOIsamu Okamoto
Isamu Okamoto
Purpose: Therapies targeted to the immune checkpoint mediated by PD-1 and PD-L1 show antitumor activity in a subset of patients with non–small cell lung cancer (NSCLC). We have now examined PD-L1 expression and its regulation in NSCLC positive for the EML4–ALK fusion gene. Experimental Design: The expression of PD-L1 at the protein and mRNA levels in NSCLC cell lines was examined by flow cytometry and by reverse transcription and real-time PCR analysis, respectively. The expression of PD-L1 in 134 surgically resected NSCLC specimens was evaluated by immunohistochemical analysis. Results: The PD-L1 expression level was higher in NSCLC cell lines positive for EML4–ALK than in those negative for the fusion gene. Forced expression of EML4–ALK in Ba/F3 cells markedly increased PD-L1 expression, whereas endogenous PD-L1 expression in EML4–ALK–positive NSCLC cells was attenuated by treatment with the specific ALK inhibitor alectinib or by RNAi with ALK siRNAs. Furthermore, expression of PD-L1 was downregulated by inhibitors of the MEK–ERK and PI3K–AKT signaling pathways in NSCLC cells positive for either EML4–ALK or activating mutations of the EGFR. Finally, the expression level of PD-L1 was positively associated with the presence of EML4–ALK in NSCLC specimens. Conclusions: Our findings that both EML4–ALK and mutant EGFR upregulate PD-L1 by activating PI3K–AKT and MEK–ERK signaling pathways in NSCLC reveal a direct link between oncogenic drivers and PD-L1 expression. Clin Cancer Res; 21(17); 4014–21. ©2015 AACR.

1 April 2015 in Lung Cancer
Verified
Journal Article
Closed access
MTMasayuki Takeda
Masayuki Takeda
IOIsamu Okamoto
Isamu Okamoto
KNKazuhiko Nakagawa
Kazuhiko Nakagawa

20 January 2022 in Journal of Clinical Oncology
Verified
Journal Article
Closed access
HTHirohito Tada
Hirohito Tada
TMTetsuya Mitsudomi
Tetsuya Mitsudomi
TMToshihiro Misumi
Toshihiro Misumi
KSKenji Sugio
Kenji Sugio
MTMasahiro Tsuboi
Masahiro Tsuboi
FGfor the West Japan Oncology Group
for the West Japan Oncology Group
PURPOSE: To investigate the efficacy of gefitinib as an adjuvant therapy for non–small-cell lung cancer patients with EGFR mutation. PATIENTS AND METHODS: IMPACT (WJOG6410L; University Hospital Medical Information Network Clinical Trials Registry: UMIN000006252 ), a randomized, open-label, phase III study, included patients with completely resected pathologic stage II-III non–small-cell lung cancer harboring EGFR mutations (exon 19 deletion or L858R) during September 2011 to December 2015. Patients were randomly assigned to receive gefitinib (250 mg once daily) for 24 months or cisplatin (80 mg/m2 on day 1) plus vinorelbine (25 mg/m2 on days 1 and 8; cis/vin) once every 3 weeks for four cycles. The primary end point was disease-free survival (DFS). RESULTS: Overall, 234 patients were randomly assigned. Among 232 eligible patients (116 each; excluding two who withdrew consent), the median DFS was 35.9 and 25.1 months in the gefitinib and cis/vin groups, respectively. However, Kaplan-Meier curves crossed around 4 years after surgery with no statistically significant difference (stratified log-rank P = .63; hazard ratio by stratified Cox proportional hazards model = 0.92; 95% CI, 0.67 to 1.28). Overall survival (OS) was also not different (stratified log-rank P = .89; hazard ratio = 1.03; 95% CI, 0.65 to 1.65), with the 5-year OS rates being 78.0% and 74.6% in the gefitinib and cis/vin groups, respectively. Treatment-related deaths occurred in 0 and three patients in the gefitinib and cis/vin groups, respectively. CONCLUSION: Although adjuvant gefitinib appeared to prevent early relapse, it did not prolong DFS or OS. However, similar DFS and OS may justify adjuvant gefitinib in the selected patient subsets, especially those deemed ineligible for platinum-doublet adjuvant therapy; however, this was not a noninferiority trial.

26 April 2021 in Journal of Thoracic Oncology
Verified
Journal Article
Open access
PDF file
YYYasuto Yoneshima
Yasuto Yoneshima
SMSatoshi Morita
Satoshi Morita
MAMasahiko Ando
Masahiko Ando
ANAtsushi Nakamura
Atsushi Nakamura
SIShunichiro Iwasawa
Shunichiro Iwasawa
IOIsamu Okamoto
Isamu Okamoto
Introduction We aimed to evaluate the efficacy and safety of nanoparticle albumin-bound (nab-) paclitaxel for previously treated patients with advanced NSCLC. Methods In this randomized, open-label, noninferiority phase 3 trial, we enrolled patients with advanced NSCLC previously treated with cytotoxic chemotherapy. Patients were randomly allocated (1:1) to receive docetaxel (60 mg/m2) on day 1 or nab-paclitaxel (100 mg/m2) on days 1, 8, and 15 of a 21-day cycle. The primary end point was overall survival (OS) analyzed on an intention-to-treat basis. Results Between May 22, 2015, and March 12, 2018, a total of 503 patients were randomly allocated to the treatment. Median OS was 16.2 months (95% confidence interval [CI]: 14.4–19.0) for the 252 patients allocated to nab-paclitaxel and 13.6 months (95% CI: 10.9–16.5) for the 251 patients allocated to docetaxel (hazard ratio = 0.85, 95.2% CI: 0.68–1.07). Median progression-free survival was 4.2 months (95% CI: 3.9–5.0) for the nab-paclitaxel group versus 3.4 months (95% CI: 2.9–4.1) for the docetaxel group (hazard ratio = 0.76, 95% CI: 0.63–0.92, p = 0.0042). The objective response rate was 29.9% (95% CI: 24.0–36.2) for the nab-paclitaxel group and 15.4% (95% CI: 10.9–20.7) for the docetaxel group (p = 0.0002). Adverse events of grade greater than or equal to 3 included febrile neutropenia (5 of 245 patients [2%] in the nab-paclitaxel group versus 55 of 249 patients [22%] in the docetaxel group) and peripheral sensory neuropathy (24 [10%] versus 2 [1%], respectively). Conclusions Nab-paclitaxel was noninferior to docetaxel in terms of OS. It should, thus, be considered a standard treatment option for previously treated patients with advanced NSCLC.

1 January 2018 in Lung Cancer
Verified
Journal Article
Closed access
KTKentaro Tanaka
Kentaro Tanaka
KIKumiko Isse
Kumiko Isse
TFTomomichi Fujihira
Tomomichi Fujihira
MTMitsuhiro Takenoyama
Mitsuhiro Takenoyama
LSLaura Saunders
Laura Saunders
IOIsamu Okamoto
Isamu Okamoto