ABSTRACT
Chemically stabilized hammerhead ribozymes are nuclease-resistant, RNA-based oligonucleotides that selectively bind and cleave specific target RNAs. Due to their potential for specifically inhibiting gene expression, ribozymes are being investigated for therapeutic applications as well as for the elucidation of gene function. In particular, we have investigated ribozymes that target the mRNA of the vascular endothelial growth factor (VEGF) receptors because VEGF signaling is an important mediator of tumor angiogenesis and metastasis. Here we report pharmacodynamic studies testing anti-Flt-1 (VEGFR-1) and anti-KDR (VEGFR-2) ribozymes in animal models of solid tumor growth and metastasis. Ribozymes targeting either Flt-1 or KDR significantly inhibited primary tumor growth in a highly metastatic variant of Lewis lung carcinoma. However, only treatment with the anti-Flt-1 ribozyme resulted in a statistically significant and dose-dependent inhibition of lung metastasis in this model. The anti-Flt-1 ribozyme was then tested in a xenograft model of human metastatic colorectal cancer in which significant inhibition of liver metastasis was observed. Taken together, these data represent the first demonstration that synthetic ribozymes targeting VEGF receptor mRNA reduced the growth and metastasis of solid tumors in vivo.
Subject(s)
Antineoplastic Agents/therapeutic use , Neoplasm Metastasis/prevention & control , RNA, Catalytic/therapeutic use , RNA, Messenger/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Receptors, Growth Factor/antagonists & inhibitors , Animals , Carcinoma, Lewis Lung/drug therapy , Carcinoma, Lewis Lung/pathology , Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/pathology , Disease Models, Animal , Dose-Response Relationship, Drug , Female , Humans , Liver Neoplasms/prevention & control , Liver Neoplasms/secondary , Male , Mice , Mice, Inbred C57BL , Mice, Nude , Neoplasm Transplantation , RNA, Catalytic/genetics , RNA, Messenger/genetics , Receptor Protein-Tyrosine Kinases/genetics , Receptors, Growth Factor/genetics , Receptors, Vascular Endothelial Growth Factor , Transplantation, Heterologous , Tumor Cells, CulturedABSTRACT
Urokinase receptor antagonists based on the growth factor domains of both human and murine urokinase which show sub-nanomolar affinities for their homologous receptors have been expressed as recombinant proteins. Further modification of these molecules by preparing fusions with the constant region of human IgG has led to molecules with high affinities and long in vivo half-lives. Smaller peptidic inhibitors have been obtained by a combination of bacteriophage display and peptide analog synthesis. All of these molecules inhibit the binding of the growth factor domain of uPA to the uPA receptor and enhance binding of the uPA receptor to vitronectin. Protein uPA receptor antagonists were tested in an in vivo tumor model using the human breast carcinoma MDAmb231 in immunodeficient mice. Both human and murine receptor antagonists showed significant inhibition of primary tumor growth, demonstrating that in vivo, both tumor and stromal cell uPA receptor dependent plasminogen activation can modulate tumor growth.
