Genetics; Molecular Biology
We constructed a fusion molecule (Icon) composed of factor VII, the natural ligand for Tissue Factor (TF), conjugated to the Fc domain of an IgG1 immunoglobulin. The factor VII domain binds with high affinity and specificity to TF, which is expressed selectively on the luminal surface of pathological angiogenic blood vessels, and the Fc domain activates an immune response that destroys the blood vessels. The Icon can be delivered as a protein, or by an adenoviral or nanoparticle vector carrying the Icon cDNA. The Icon showed efficacy and safety in mouse models of human cancer, and in mouse and pig models of macular degeneration, and is being prepared for a clinical trial. We described a novel mechanism of gene regulation, involving a tumor-suppressor protein (TSP) and a noncoding retroelement RNA (ncRNA). The TSP contains a DNA-binding domain that represses gene transcription, and RNA-binding domains (RBD) that bind a ncRNA, releasing the TSP and activating transcription. This mechanism is involved in embryogenesis, tumorigenesis, and steroidogenesis.
Specialized Terms: Development; Genetics; Medical Sciences; Molecular Biology
Extensive Research Description
The odd couple: A repressor protein and a retroelement RNA.
We described a novel mechanism for reversible regulation of gene transcription involving PSF, a conserved mammalian tumor-suppressor protein, and mVL30 RNA, a mouse noncoding retroelement RNA (1-4). PSF contains a DNA-binding domain (DBD) that binds to certain genes and represses transcription, and also contains RNA-binding domains (RBD) that bind mVL30 RNA, forming a complex that releases PSF from a gene and reverses repression. This regulatory mechanism has a role in oncogenesis and steroidogenesis, and probably in regulating cell proliferation during development. We isolated human retroelement RNAs that have a similar function as mVL30 RNA, which is not present in human cells. PSF belongs to a family of putative tumor-suppressor proteins containing RBD and DBD, and we are testing whether other members of this family have a similar function as PSF in regulating gene transcription. Other experiments include a molecular analysis of the protein-RNA regulatory mechanism and its normal and pathological roles.
Targeting pathological blood vessels for immunotherapy of cancer and macular degeneration.
We constructed a molecule called an Icon that activates a cytolytic immune response against cells expressing the transmembrane receptor tissue factor (TF). TF is expressed on endothelial cells lining the luminal surface of pathological blood vessels in tumors. The model for the Icon molecule is a Camelid IgG1 antibody composed of two heavy chains without associated light chains, each chain containing a VH targeting domain conjugated to the Fc effector domain. The Icon is similarly composed of two chains, each chain containing fVII, the natural ligand for TF as the targeting domain conjugated to an Fc domain. The Icon binds to TF with stronger affinity and specificity than can be achieved with an anti-TF antibody. Because the Icon is synthesized by recombinant DNA technology, the fVII and Fc domains can be derived from the species of choice. Pre-clinical immunotherapy tests were done by encoding the Icon in an adenoviral vector, which was injected into a tumor in a mouse model of human metastatic cancer (1-3). The infected tumor cells synthesized and secreted the icon into the systemic circulation, and the blood-borne Icon molecules bound to TF, activating an immune response that destroyed the pathological blood vessels without harming normal vessels. A clinical trial of the protocol is being arranged for cancer patients. Similar results were obtained with a mouse model of macular degeneration (4). We are testing a nanoparticle vector as an alternative to an adenoviral vector for delivering the Icon gene
Role of human noncoding RNAs in the control of tumorigenesis.
Li L, Feng T, Lian Y, Zhang G, Garen A, Song X. Role of human noncoding RNAs in the control of tumorigenesis. Proceedings Of The National Academy Of Sciences Of The United States Of America 2009, 106:12956-61. 2009
Factor VII-verteporfin for targeted photodynamic therapy in a rat model of choroidal neovascularization.
Lu F, Hu Z, Sinard J, Garen A, Adelman RA. Factor VII-verteporfin for targeted photodynamic therapy in a rat model of choroidal neovascularization. Investigative Ophthalmology & Visual Science 2009, 50:3890-6. 2009
Hepatitis RNA viruses and hepatocellular carcinoma.
Garen A. Hepatitis RNA viruses and hepatocellular carcinoma. Journal Of Viral Hepatitis 2008, 15:622. 2008
Regulatory roles of tumor-suppressor proteins and noncoding RNA in cancer and normal cell functions.
Garen A, Song X. Regulatory roles of tumor-suppressor proteins and noncoding RNA in cancer and normal cell functions. International Journal Of Cancer. Journal International Du Cancer 2008, 122:1687-9. 2008
Roles of PSF protein and VL30 RNA in reversible gene regulation.
Song X, Sun Y, Garen A. Roles of PSF protein and VL30 RNA in reversible gene regulation. Proceedings Of The National Academy Of Sciences Of The United States Of America 2005, 102:12189-93. 2005
Signal Transduction and Targeted Therapy
Garen, A. Nature. 2016
Full List of PubMed Publications
- Garen A: From a retrovirus infection of mice to a long noncoding RNA that induces proto-oncogene transcription and oncogenesis via an epigenetic transcription switch. Signal Transduct Target Ther. 2016; 2016 May 13. PMID: 29263895
- Krikun G, Hu Z, Osteen K, Bruner-Tran KL, Schatz F, Taylor HS, Toti P, Arcuri F, Konigsberg W, Garen A, Booth CJ, Lockwood CJ: The immunoconjugate "icon" targets aberrantly expressed endothelial tissue factor causing regression of endometriosis. Am J Pathol. 2010 Feb; 2009 Dec 30. PMID: 20042667
- Lu F, Hu Z, Sinard J, Garen A, Adelman RA: Factor VII-verteporfin for targeted photodynamic therapy in a rat model of choroidal neovascularization. Invest Ophthalmol Vis Sci. 2009 Aug; 2009 Apr 8. PMID: 19357351
- Garen A, Song X: Regulatory roles of tumor-suppressor proteins and noncoding RNA in cancer and normal cell functions. Int J Cancer. 2008 Apr 15. PMID: 18067128
- Song X, Sun Y, Garen A: Roles of PSF protein and VL30 RNA in reversible gene regulation. Proc Natl Acad Sci U S A. 2005 Aug 23; 2005 Aug 3. PMID: 16079199
- Song X, Sui A, Garen A: Binding of mouse VL30 retrotransposon RNA to PSF protein induces genes repressed by PSF: effects on steroidogenesis and oncogenesis. Proc Natl Acad Sci U S A. 2004 Jan 13; 2004 Jan 2. PMID: 14704271
- Li J, Sun Y, Garen A: Immunization and immunotherapy for cancers involving infection by a human papillomavirus in a mouse model. Proc Natl Acad Sci U S A. 2002 Dec 10; 2002 Nov 21. PMID: 12446839
- Song X, Wang B, Bromberg M, Hu Z, Konigsberg W, Garen A: Retroviral-mediated transmission of a mouse VL30 RNA to human melanoma cells promotes metastasis in an immunodeficient mouse model. Proc Natl Acad Sci U S A. 2002 Apr 30; 2002 Apr 16. PMID: 11959915