Comprehensive analyses using next-generation sequencing and immunohistochemistry enable precise treatment in advanced gastric cancer.
BACKGROUND
In advanced gastric cancer (AGC), most clinical trials are designed on the basis of protein expression or gene amplification of specific genes. Recently, next-generation sequencing (NGS) allowed us to comprehensively profile the tumor gene status. This study aimed to elucidate the profiling between gene alterations and protein expression in AGC to aid in future clinical trials on AGC.


METHODS
Formalin-fixed, paraffin-embedded tumor samples from 121 stage III/IV gastric cancer patients were examined for protein expression of tyrosine kinase receptors (RTKs; ERBB2, EGFR, c-MET, and FGFR2) using immunohistochemistry (IHC). Furthermore, 409 cancer-related genes were sequenced to detect mutations and copy number variations using NGS.


RESULTS
Most ERBB2 overexpression (IHC 3+) cases (80.0%) had ERBB2 amplification and did not have other RTK amplification or oncogene mutations. However, one-fourth of MET overexpression cases (25.0%) had ERBB2 alterations. EGFR and FGFR2 overexpression cases had ERBB2 alterations or other gene alterations such as KRAS or PIK3CA. On the other hand, most of the four RTK amplification cases (88.2%) were mutually exclusive with each amplification. However, RTK amplification did not simply correlate with protein overexpression, whereas cases with RTK high-level amplification had protein overexpression and rarely showed other co-existing gene alterations.


CONCLUSIONS
AGC involves a complicated arrangement of protein expression and gene alterations. Comprehensive analyses of NGS and IHC will be necessary to design the optimal therapy for treating the appropriate population of patients in future clinical trials.
Department of Experimental Therapeutics, National Cancer Center Hospital East, Chiba Division of Pathology, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Chiba Medical Science Program, Graduate School of Medicine, Keio University, Tokyo Department of Gastrointestinal Oncology, National Cancer Center Hospital East, Chiba.
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Kuboki
Division of Epigenomics, National Cancer Center Research Institute, Tokyo.
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Yamashita
Division of Epigenomics, National Cancer Center Research Institute, Tokyo.
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Niwa
Division of Epigenomics, National Cancer Center Research Institute, Tokyo.
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Ushijima
Division of Pathology, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Chiba.
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Nagatsuma
Division of Pathology, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Chiba.
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Kuwata
Department of Gastrointestinal Oncology, National Cancer Center Hospital East, Chiba.
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Yoshino
Department of Experimental Therapeutics, National Cancer Center Hospital East, Chiba Department of Gastrointestinal Oncology, National Cancer Center Hospital East, Chiba.
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Doi
Division of Pathology, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Chiba Medical Science Program, Graduate School of Medicine, Keio University, Tokyo.
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Ochiai
Exploratory Oncology Research and Clinical Trial Center, National Cancer Center, Chiba, Japan aohtsu@east.ncc.go.jp.
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Ohtsu
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D056915:DNA Copy Number Variations; D004252:DNA Mutational Analysis; D066246:ErbB Receptors / Q000378:metabolism; D005787:Gene Frequency; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007150:Immunohistochemistry; D025202:Molecular Diagnostic Techniques; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D013274:Stomach Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism
D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D018719:Erb-b2 Receptor Tyrosine Kinases; C512478:EGFR protein, human; C508053:ERBB2 protein, human; C491743:MET protein, human
amplification; gastric cancer; immunohistochemistry; mutation; next-generation sequencing