SPP1 and neoplasm: In addition to the inhibition of tumor growth in vivo, the SVVYGLR motif-recognizing anti-OPN mAb also suppressed the metastasis of inoculated ATL cells into peripheral blood (Fig. 3d) and metastasis to the liver (Fig. 3e) in vivo, suggesting that the SVVYGLR sequence in OPN is critical for regulating tumor growth and metastasis.