Noninvasive dynamic fluorescence imaging of human melanomas reveals that targeted inhibition of bFGF or FGFR-1 in melanoma cells blocks tumor growth by apoptosis.
BACKGROUND
Two prominent biological features of the advanced stages of human melanoma are their high degree of vascularity and high-level expression of basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor-1 (FGFR-1). Given these characteristics, human melanoma serves as an ideal model to address an important question regarding the efficacy of angiogenesis-based cancer therapy. To induce tumor growth arrest and regression, does it suffice to block expression of bFGF and/or FGFR-1 in only the melanoma cells, or is it essential to inhibit expression of bFGF and/or FGFR-1 in both the melanoma cells and the melanoma cell-interspersing vasculature?


METHODS
Primary and metastatic human melanomas, grown as subcutaneous tumors in nude mice, were injected twice a week with vector constructs containing the human tyrosinase promoter and antisense- oriented human bFGF or FGFR-1 cDNA. On alternating days, the bFGF and FGFR-1 antisense-targeted tumors received injections of cyanine fluorochrome-conjugated antibodies to a human melanoma and mouse blood vessel marker. Noninvasive, dynamic fluorescence imaging was used to document the cellular events that took place inside the tumors as the result of blocking expression of bFGF or FGFR-1 in the melanoma cells.


RESULTS
In vivo, ex vivo, and in vitro fluorescence imaging of the bFGF and FGFR-1 antisense-targeted tumors demonstrated that inhibiting bFGF and FGFR-1 signaling in only the melanoma cells suffices to inhibit tumor growth due to massive induction of melanoma cell apoptosis.


CONCLUSIONS
The investigations presented in this study document that inhibiting expression of bFGF or FGFR-1 in only the melanoma cells is as effective in blocking tumor growth as simultaneously inhibiting bFGF or FGFR-1 synthesis in the melanoma cells and the melanoma cell-interspersing vasculature. Furthermore, blocking expression of bFGF or FGFR-1 in the melanoma cells did not lead to activation or increased production of another angiogenic molecule, suggesting the absence of a "salvage pathway" that can circumvent or rescue the blockage of bFGF/FGFR-1 in the melanoma cells.
Valesky
Marianne
M
Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Spang
Aaron J
AJ
Fisher
Gregory W
GW
Farkas
Daniel L
DL
Becker
Dorothea
D
D000818:Animals; D017209:Apoptosis; D001358:Avian Sarcoma Viruses / Q000235:genetics; D002455:Cell Division; D016228:Endothelial Growth Factors / Q000032:analysis; D016222:Fibroblast Growth Factor 2 / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007267:Injections; D008222:Lymphokines / Q000032:analysis; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D014442:Monophenol Monooxygenase / Q000235:genetics; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D016376:Oligonucleotides, Antisense; D017468:Receptors, Fibroblast Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D016222:Fibroblast Growth Factor 2; D014442:Monophenol Monooxygenase; C496348:FGFR1 protein, human; C496349:Fgfr1 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1