Abstract 1016: Direct contact with bone marrow-derived mesenchymal stem cells provides an advantageous microenvironment for restoration of cancer stem cell-like features

Abstract

Abstract [Background] The cancer stem cell (CSC) model is the concept that only the CSCs can generate a tumor, based on its self-renewal properties and enormous proliferative potential. Understanding of CSCs is an urgent problem not only for cancer prevention and diagnosis but also development of novel therapeutic approaches against cancer. On the other hand, tumor-stromal interaction plays an important role in the process of cancer invasion and metastasis; however, little is known about biological significance of bone marrow-derived mesenchymal stem cells (BM-MSCs) on development and progression of cancer cells. [Methods] Human BM-MSC-derived UE6E7T-12 cells and human gastric carcinoma (GC)-derived MKN-7 cells were used in this study. MACS microbeads system (EpCAM and CD133) was used for cell separation. To identify gene that are upregulated in MKN-7 cells in the presence of coculture with UE6E7T-12 cells, cDNA microarray analysis was performed. Expressions of CSC-and epithelial-mesenchymal transition (EMT)-related molecules were examined using RT-PCR, Western blot and immunohistochemistry. The CSC-like features were investigated by the in vivo limiting dilution tumorigenicity test and the multipotency test. [Results] When cocultured, MKN-7 cells showed direct attachment with UE6E7T-12 cells and formed tumor spheres. The phenomenon was significant only when the cells were cocultured with UE6E7T-12 cells but not differentiated fibroblasts. Interestingly, co-incubation with UE6E7T-12 cells increased the number of CD133+ cells even in the CD133- MKN-7 cells with upregulation of CSC- and EMT-related gene transcripts. After confirming that CD133 can be a CSC maker in MKN-7 cells, MKN-7 cells, UE6E7T-12 cells and both were injected into SCID mice subcutaneously. Co-injection of MKN7 and UE6E7T-12 cells developed subcutaneous tumor mass, which was accompanied by proliferation of Vimentin+ stroma and increase of CD133+ MKN-7 cells. In the presence of coculture with UE6E7T-12 cells, MKN-7 cells (original, CD133+ and CD133-) commonly showed a total of 65 upregulated genes. Among these genes upregulated, we focused on the Wnt5a and TGFbeta-inducible (TGFb-I) genes. Therefore, we treated CD133- MKN-7 cells with recombinant Wnt5a and TGFb1 and investigated the altered population of CD133+ cells. Surprisingly, we found that these extracellular stimuli restored CD133+ MKN-7 cells with increased mRNA levels of CSC markers and EMT transcription factors. [Conclusion] This is the first report that BM-MSC-mediated induction of Wnt and TGFb signaling pathways is important for re-acquisition of CSC-like features in GC-derived MKN-7 cells. Also, these findings suggest that BM-MSCs may provide an advantageous microenvironment for cancer aggressiveness. Restoration of CSC-like features may overlap with EMT in the process of cancer progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1016.