Human circulating and tissue gastric cancer stem cells display distinct epithelial-mesenchymal features and behaviors.

INTRODUCTION: Metastasis is a leading cause of cancer-related-deaths worldwide. Recently, cancer stem cells (CSCs) have been believed to be responsible for tumor initiation and metastasis, but till now, difference of cellular features and behaviors between CSCs from tumor tissues (TCSCs) and circulation (CCSCs) remains largely unknown, which hinders the progression of targeted therapies for metastasis. METHODS AND RESULTS: Here, we provide the features of circulating gastric cancer stem cells (CGCSCs) isolated from human gastric adenocarcinoma. The CGCSCs and TGCSCs were culture in a same serum free stem cell culture medium, however the morphology are different with each other. EMT-associated markers were measured by Immunofluorescence, Western Blotting, and RT-PCR methods, and the results indicated that the CGCSCs and TGCSCs carry different epithelial-mesenchymal features. And then, proliferation and apoptosis assays revealed that the CGCSCs exhibited characteristics of higher proliferation and resistance to apoptosis in vitro. Soft agar assay and nude mice tumorigenicity assay displayed strong tumorigenicity of CGCSCs. Finally, Matrigel invasion assays and in vivo experimental metastasis assay were also performed, which demonstrated that CGCSCs carry high invasive and metastatic capabilities than TGCSCs. CONCLUSIONS: As expected, the CGCSCs indeed showed extremely invasive and metastatic properties. They also exhibited distinctive mesenchymal phenotypes, high self-renewal, proliferative capabilities, tumor induction and low apoptosis. Interestingly, CGCSCs show small cell-size than TGCSCs (tissue gastric cancer stem cells). The findings might help us to understand the biological characteristic of CGCSCs deeply, and give light to strategies for cancer therapies.