Cautions should be taken when using cell models for gastric cancer research

Gastric cancer (GC)-derived cell lines were generally used in basic cancer research and drug screening. However, it is always concerned about the difference between cultured cells and primary tumor by oncologists. To address this question, we compared differentially expressed genes (DEGs) in primary cancers, healthy tissues, and cell lines both in vitro and in silico. Seven reported genes with decreased expression in GCs by DNA methylation were analyzed in our cohort studies and experimentally validation. Selected datasets from TCGA (The Cancer Genome Atlas), CCLE (The Broad Institute Cancer Cell Line Encyclopedia), and GTEx (The Genotype-Tissue Expression project) were used to represent GCs, GC-derived cell lines, and healthy tissues respectively in the in silico analysis. Thirty gastric tissues together with six cell lines were used for validations. Unexpectedly, we experimentally found that reported cancer-related downregulated genes were only found in cancer cell lines but not in biopsies. The unchanged gene expressions in primary GCs were generally consistent with our cohort study, using information from cancerous (TCGA) and healthy tissues (GETx). Substantial differences were also found between DEGs of cancer tissues (TGCA)/ healthy tissues (GTEx) pair and cell lines (CCLE)/ healthy tissues (GTEx) pair, which confirmed the significant differences between primary cancer and cancer cell lines. Moreover, elevated expression of YWHAQ (14-3-3 δ) and THBS1 were observed in the GC biopsies, which might be potential biomarkers for GC diagnosis, considering the increased YWHAQ and THBS1 associated with poor survival rates in gastric cancer patients. In sum, it is suggested that cautions should be taken when using GC cell lines to study genes that show great differences between cell lines and tissues.