Vascular endothelial growth factor fusion constructs used to inhibit osteoclastogenesis
The 121-amino acid isoform of vascular endothelial growth factor (VEGF 121 ) is linked by a flexible G4S tether to a cytotoxic molecule such as toxin gelonin or granzyme B and expressed as a soluble fusion protein. The VEGF 121 , fusion protein exhibits significant anti-tumor vascular-ablative effects that inhibit the growth of primary tumors and inhibit metastatic spread and vascularization of metastases. The VEGF 121 fusion protein also target osteoclast precursor cells in vivo and inhibits osteoclastogenesis.
1. A method of inhibiting the differentiation of an osteoclast precursor cell into a mature osteoclast, comprising contacting said osteoclast precursor cell with a biologically effective amount of a conjugate comprising a cytotoxic polypeptide and a VEGF polypeptide that binds to both vascular endothelial growth factor (VEGF) receptor type 1 (Flt-1) and VEGF receptor type 2 (kinase domain receptor/Flk-1), wherein differentiation of the osteoclast precursor cell is inhibited.
2. The method of claim 1 , wherein said conjugate is a fusion protein of said VEGF polypeptide and said cytotoxic polypeptide.
3. The method of claim 1 , wherein said VEGF polypeptide comprises an amino acid sequence selected from the group consisting of SEQ ID NOs:28-34.
4. The method of claim 1 , wherein said cytotoxic polypeptide is a toxin or a signal transduction protein capable of generating apoptotic signals.
5. The method of claim 4 , wherein said toxin is gelonin.
6. The method of claim 4 , wherein said signal transduction protein capable of generating apoptotic signals is selected from the group consisting of granzyme B, Bax, TNF-a, TNF-b, TNF-like molecule, TGF-b, IL-12, IL-3, IL-24, IL-18, TRAIL, IFN-a, IFN-b, IFN-g, Bcl-2, Fas ligand and caspases.
7. The method of claim 1 , wherein said conjugate is a fusion protein comprising the 121-amino acid isoform of vascular endothelial growth factor (VEGF 121 ) and gelonin or a fusion protein comprising VEGF 121 and granzyme B.
8. The method of claim 1 , wherein the osteoclast precursor cell is in a subject.
9. The method of claim 8 , wherein said subject suffers from osteoporosis or osteoarthritis.
10. The method of claim 8 , wherein said subject suffers from osteolytic lesions or bone lysis.
11. The method of claim 8 , wherein said subject suffers from skeletal metastases.
12. The method of claim 8 , wherein the biologically effective amount of the conjugate is administered to the subject.