Mesenchymal Stem Cell: A Hard Nut to Crack in Cancer Development

Tumors are surrounded by various types of cells, including mesenchymal cells, immune cells, and vascular and lymphatic endothelial cells. In this context, it has been recognized that cell-to-cell communication in the tumor microenvironment is a dynamic mechanism that exerts significant effects on progression of carcinogenesis. Over the last decade, the discoveries that mesenchymal stem cells (MSCs) can migrate to sites of inflammation and neoplasia have been the subject of a growing interest due to their potential application in regenerative medicine and gene delivery. In particular, based on the report that MSCs are incorporated into tumor tissues, the impact of MSCs on tumor growth has been extensively investigated. Despite intense research, it is highly debatable whether MSCs are friends or foes of tumor. In this mini-review, I will introduce the contradicting observations on the role of MSCs in tumorigenesis and discuss why this discrepancy has been reported.