SFRP2 and breast neoplasm: Moreover, a few genes involved in modulation of the extracellular matrix (ADAMTS4 [33], MMP1 [34], MMP3 [35], and angiogenesis (MFAP5 [36], SFRP2 [37], SRPK1 [38], VEGF [39], and CHI3L1 [40]) were found to be expressed at higher levels in the primary breast tumors compared with the bone metastases.