Mesenchymal Stem Cells Provide an Advantageous Tumor Microenvironment for the Restoration of Cancer Stem Cells

Objective: Accumulating evidences suggest that cancer-associated fibroblasts are provided from bone-marrow-derived mesenchymal stem cells (BM-MSCs); however, little is known about the mechanism(s) by which BM-MSCs accelerate cancer aggressiveness. Methods: Gastric carcinoma (GC)-derived MKN-7 cells were cocultured with UE6E7T-12 BM-MSCs. The gene expression profile in MKN-7 cells was investigated by microarray analysis. Between two major types of GCs (intestinal- and diffuse-type), the expression of genes was detected by immunohistochemistry. Results: We found that direct attachment to UE6E7T-12 induced proliferation and cluster formation of MKN-7 cells. Coculture with UE6E7T-12 increased the population of CD133+ MKN-7 cells in vitro and coimplantation of these in mice resulted in subcutaneous tumors in vivo. The wingless-type MMTV integration site (WNT) family member 5A (WNT5A) and transforming growth factor-β (TGF-β)-induced (TGFBI) genes were found to be upregulated in MKN-7 cells directly attached to UE6E7T-12. Recruitment of CD271+ BM-MSC was detected preferentially in the stroma of the diffuse-type GC and this type of GC cell also showed frequent expression of WNT5A, TGF-β type I receptor and CD133. Conclusion: BM-MSC-mediated activations of the WNT and TGF-β signaling pathways were thought to provide advantageous microenvironments for cancer progression by supporting the reacquisition and maintenance of cancer stem cells.