VEGFR-2 expression was reported in 4T1cells [32], while VEGFR-1 is expressed on several types of tumor cells, both in vitro and in vivo [21], including at least 16 human breast carcinoma cell lines [33, 34], and it is particularly prominent in osteosarcoma bone lesions [35]. Here, FLT1 is linked to osteosarcoma.