Recombinant Vgr-1/BMP-6-expressing tumors induce fibrosis and endochondral bone formation in vivo.
Members of the TGF-beta superfamily appear to modulate mesenchymal differentiation, including the processes of cartilage and bone formation. Nothing is yet known about the function of the TGF-beta-related factor vgr-1, also called bone morphogenetic protein-6 (BMP-6), and only limited studies have been conducted on the most closely related factors BMP-5, osteogenic protein-1 (OP-1) or BMP-7, and OP-2. Because vgr-1 mRNA has been localized in hypertrophic cartilage, this factor may play a vital role in endochondral bone formation. We developed antibodies to vgr-1, and documented that vgr-1 protein was expressed in hypertrophic cartilage of mice. To further characterize the role of this protein in bone differentiation, we generated CHO cells that overexpressed recombinant murine vgr-1 protein. Western blot analysis documented that recombinant vgr-1 protein was secreted into the media and was proteolytically processed to yield the mature vgr-1 molecule. To assess the biological activity of recombinant vgr-1 in vivo, we introduced the vgr-1-expressing CHO cells directly into the subcutaneous tissue of athymic nude mice. CHO-vgr-1 cells produced localized tumors, and the continuous secretion of vgr-1 resulted in tumors with a strikingly different gross and histological appearance as compared to the parental CHO cells. The tumors of control CHO cells were hemorrhagic, necrotic, and friable, whereas the CHO-vgr-1 tumors were dense, firm, and fibrotic. In contrast with control CHO tumors, the nests of CHO-vgr-1 tumor cells were surrounded by extensive connective tissue, which contained large regions of cartilage and bone. Further analysis indicated that secretion of vgr-1 from the transfected CHO tumor cells induced the surrounding host mesenchymal cells to develop along the endochondral bone pathway. These findings suggest that endochondral bone formation.
Gitelman
S E
SE
Department of Pediatrics, University of California at San Francisco 94143.
Kobrin
M S
MS
Ye
J Q
JQ
Lopez
A R
AR
Lee
A
A
Derynck
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001846:Bone Development / Q000502:physiology*; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D016466:CHO Cells / Q000637:transplantation; D002356:Cartilage / Q000254:growth & development / Q000378:metabolism / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000378:metabolism / Q000473:pathology; D006224:Cricetinae; D005355:Fibrosis / Q000378:metabolism; D006133:Growth Substances / Q000096:biosynthesis / Q000502:physiology*; D006984:Hypertrophy / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000502:physiology; D014176:Protein Biosynthesis; D011506:Proteins / Q000502:physiology*; D011994:Recombinant Proteins; D014162:Transfection
C525817:Bmp6 protein, mouse; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; D006133:Growth Substances; D009363:Neoplasm Proteins; D011506:Proteins; D011994:Recombinant Proteins