Abstract

Diffuse-type gastric carcinoma (DGC) is characterized by a highly malignant phenotype with prominent infiltration and stromal induction. We performed whole-exome sequencing on 30 DGC cases and found recurrent RHOA nonsynonymous mutations. With validation sequencing of an additional 57 cases, RHOA mutation was observed in 25.3% (22/87) of DGCs, with mutational hotspots affecting the Tyr42, Arg5 and Gly17 residues in RHOA protein. These positions are highly conserved among RHO family members, and Tyr42 and Arg5 are located outside the guanine nucleotide–binding pocket. Several lines of functional evidence indicated that mutant RHOA works in a gain-of-function manner. Comparison of mutational profiles for the major gastric cancer subtypes showed that RHOA mutations occur specifically in DGCs, the majority of which were histopathologically characterized by the presence of poorly differentiated adenocarcinomas together with more differentiated components in the gastric mucosa. Our findings identify a potential therapeutic target for this poor-prognosis subtype of gastric cancer with no available molecularly targeted drugs.

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Acknowledgements

We would like to thank K. Shiina, K. Sakuma, K. Nakano, A. Nishimoto and R. Sato for technical assistance. This study was supported by Grants-in-Aid for Scientific Research in Innovative Areas to the “Systems Cancer Project” (grant 22134003) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (S.I.), by JSPS (Japan Society for the Promotion of Science) KAKENHI grant 24221011 (H.A.), by a Health Labor Sciences Research Grant (H.A.) and by a grant for the Translational Systems Biology and Medicine Initiative (TSBMI) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (S.Y., K. Tatsuno and H.A.). The supercomputing resource was provided by the Human Genome Center (University of Tokyo).

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Affiliations

  1. Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.

    • Miwako Kakiuchi
    • , Hiroki Ueda
    • , Kengo Gotoh
    • , Shogo Yamamoto
    • , Kenji Tatsuno
    • , Hiroyuki Aburatani
    •  & Shumpei Ishikawa
  2. Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

    • Miwako Kakiuchi
    • , Keisuke Tateishi
    •  & Kazuhiko Koike
  3. Forerunner Pharma Research Co., Ltd., Tokyo, Japan.

    • Takashi Nishizawa
    •  & Shinichi Funahashi
  4. Department of Pathology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

    • Atsushi Tanaka
    • , Akimasa Hayashi
    • , Takashi Ichimura
    • , Tetsuo Ushiku
    • , Masashi Fukayama
    •  & Shumpei Ishikawa
  5. Translational Systems Biology and Medicine Initiative (TSBMI), The University of Tokyo, Tokyo, Japan.

    • Shogo Yamamoto
    • , Kenji Tatsuno
    •  & Hiroyuki Aburatani
  6. Department of Genomic Pathology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.

    • Hiroto Katoh
    •  & Shumpei Ishikawa
  7. Kamakura Research Laboratories, Chugai Pharmaceutical Co., Ltd., Kanagawa, Japan.

    • Yoshiaki Watanabe
  8. Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

    • Ikuo Wada
    • , Nobuyuki Shimizu
    • , Sachiyo Nomura
    •  & Yasuyuki Seto

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Contributions

S.I. and H.A. designed the study. M.K. processed samples and supervised exome sequencing. H.U., K.G., K. Tatsuno and S.Y. performed computational analyses. Y.S., M.F., I.W., N.S., A.H. and S.N. coordinated sample acquisition. H.K., T.I. and T.U. carried out pathological review and analysis. A.T. performed dissection analysis. T.N. and S.F. performed functional experiments. Y.W. carried out structural analysis. S.I. wrote the manuscript. H.A., M.F., K. Tateishi and K.K. were involved in critical review and discussion.

Competing interests

T.N. and S.F. are employees of Forerunner Pharma Research Co., Ltd. Y.W. is an employee of Chugai Pharmaceutical Co., Ltd.

Corresponding author

Correspondence to Shumpei Ishikawa.

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    Supplementary Text and Figures

    Supplementary Figures 1–5, Supplementary Tables 1–4 and 6, and Supplementary Note

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    Supplementary Table 5

    Summary statistics and data quality metrics for whole-exome sequencing and TruSeq Custom Amplicon sequencing for our discovery and validation cohort.

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    Supplementary Data Set 1

    Detailed somatic mutation data.

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DOI

https://doi.org/10.1038/ng.2984

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