Furthermore, Kaplan et al. (2005) investigating the role of MSCs to contribute to pre-metastatic sites, observed that bone marrow-derived hematopoietic progenitor cells that expressed vascular endothelial growth factor receptor 1 (VEGFR1; also known as Flt1) homed to tumor-specific pre-metastatic sites and formed cellular clusters before the arrival of tumor cells [113]. This evidence concerns the gene FLT1 and neoplasm.