Inhibition of tumor growth by plasminogen-related protein-B

Background: Various fragments of the fibrinolytic protein plasminogen can act as antiangiogenic factors and inhibit the growth of primary and metastatic tumors in mice. Plasminogen-related gene-B encodes a putative 9 kDa protein virtually identical to the plasminogen N-terminal activation peptide, a 77-amino acid motif that is liberated from the parent plasminogen molecule during conversion to the serine proteinase plasmin. Previous data have documented enhanced transcription of plasminogen-related gene-B in neoplastic tissues. Materials and Methods: We have tested the effects of recombinant versions of plasminogen-related protein-B and the plasminogen N-terminal activation peptide on the growth of tumors in mice, employing murine tumor cell lines implanted subcutaneously. Results: The recombinant plasminogen-related protein-B significantly inhibited the growth of primary tumors in mice, while recombinant plasminogen N-terminal activation peptide elicited only a slight inhibition of tumor growth. Conclusion: These data suggest that plasminogen-related protein-B may have utility as a novel cancer therapeutic.