ABSTRACT
Biomarker is defined as biological variables that correlate with biologic outcome. This review will discuss investigations into gastric cancer (GC) biomarkers by proteomic analysis. Proteomic analysis consists of 3 steps. The first step is the digestion and separation process using 2-dimensional electrophoresis gel or liquid chromatography. The second step is mass analysis using mass spectrometry. The third step is protein identification using databases. Clinical validation of proteins identified can help estimate expressions of cancer tissue and cancer cell line using Western blot and immunohistochemistry. Researchers can validate the association between protein expression and clinical data (tumor stage, cell type, survival, and recurrence), which helps identify the possibility of biomarkers for GC. After clinical validation, the next step is functional analysis in vitro and in vivo. This step is commonly performed by knock-in and knock-out studies on the proliferation, migration, and invasion using the cancer cell line. Animal studies also provide indirect evidence for the role of the proteins in tumor growth and metastasis in vivo. In conclusion, the proteomic analysis is one of the useful methods for detecting biomarkers for GC. Multidisciplinary approaches to protein, DNA, RNA, and epigenetics are crucial to the investigation for molecular biomarkers for GC.