Research Grants Awarded
Targeting the Neovasculature for Immunotherapy and Photodynamic Therapy of Breast Cancer
Background: Targeting tumor vasculature (neovasculature) for cancer therapy is a better strategy than targeting tumor cells. One of the problems for targeting neovasculature is difficult to find a specific target. Objective/Hypothesis: We chose to target a cell receptor Tissue Factor (TF) for development of immunotherapy and photodynamic therapy (PDT) of solid tumors. The reasons are as follows. (1) TF is a specific target that is abnormally expressed on tumor vascular endothelial cells but not on normal vascular endothelial cells, and also on many types of tumor cells including breast tumor cells, thus providing a specific, universal and accessible target molecule for immunotherapy of multiple solid tumors; (2) TF can be endocytosed into cells upon its natural ligand (coagulation factor VII, fVII) binding, thus the endocytosis process can internalize a photosensitizer into target cells. Selection is a critical step for success of targeted PDT for cancer; (3) our preliminary data showed that Icon-mediated immunotherapy caused regression of human breast cancer in SCID mice, suggesting targeting TF therapies could have potentials for treatment of breast cancer. Specific Aims: To target TF, we propose to use the natural ligand for TF, fVII, instead of making monoclonal antibodies. Because fVII binds to TF with remarkable affinity and specificity than can be achieved by an antibody. In addition, there is no need of humanization process because the TF-targeting fVII molecules, called Icons, are made by DNA recombinant technology. The Specific Aims are to (1) construct two forms of Icon molecules (Icon-1 and Icon-2) for immunotherapy and PDT, respectively; (2) test the safety and efficacy of Icon-1-mediated immunotherapy in mice; (3) test the safety and efficacy of Icon-2-targeted PDT in vitro and in vivo. Study Design: The Icon molecules are constructed by DNA recombinant technology and purified by affinity columns. The Icon-1-mediated immunotherapy will be tested as intravenous injections of Icon protein or intratumoral injections of an adenoviral vector encoding the Icon in mouse models of human and mouse breast cancers. For PDT, the Icon-2 will be covalently conjugated to verteporfin, a photosensitizer that has been tested as unconjugated dye for PDT of macular degeneration and cancer. The Icon-2-verteporfin conjugate will be activated by 689 nm laser light. The effect of Icon-targeted PDT on breast cancer cells in vitro will be determined using MTS assay and clonogenic assay, and the effect in vivo will be tested in mouse models of breast cancers. Potential Outcomes and Benefits of the Research: A Phase I trial involving intratumoral injections of the Icon vector is planned for several types of cancer including breast cancer early next year at three major cancer centers. After completion of the proposal, we will obtain the preclinical data on efficacy and safety of the Icon-mediated therapies on breast cancer. Thus, the outcomes of this proposal will help to enroll breast cancer patients and to design the dose escalation and schedule for the clinical trial. PDT procedure will be applied to FDA separately for another clinical trial.
Cancerous cells, like normal cells, need nutrition and oxygen that are provided in blood circulation through blood vessels. However, tumor blood vessels especially the vascular endothelial cells, the inner layer of blood vessels, are different from normal vascular endothelial cells, due to expression of some novel molecules that are not present on normal vascular endothelial cells. Thus finding these novel molecules in tumor blood vessels can help to develop novel therapies to specifically destroy tumor blood vessels, consequently to shut down the blood supplies, and eventually to kill tumor cells. The strategy of destroying tumor blood vessels is believed to be more effective than that of directly killing tumor cells. It has been reported that tissue Factor (TF) is one of these novel protein molecules that are only present on tumor vascular endothelial cells but not on normal vascular endothelial cells. More interestingly, it is also present on many types of solid cancer cells including breast cancer. Although TF is expressed on extravascular cells of several normal tissues and in the adventitial layer of the blood vessel wall, it is sequestered at these sites by the tight endothelial cell layer of the normal vasculature. Therefore TF can be used as a common specific target on both of tumor blood vessels and tumor cells for development of immunotherapy for multiple solid tumors including breast cancer. Moreover, it is known that TF is a cell receptor and a natural ligand for TF is coagulation factor VII. After binding of fVII to TF, the VII/TF complex will be internalized into cells. This process is called endocytosis. The ability of fVII to endocytose can be adapted to selectively bring a photosensitizer into tumor cells or tumor vascular endothelial cells for development of targeted photodynamic therapy, which is different therapeutic procedure and can be used independently or be combined with cancer immunotherapy. In this proposal, we propose to construct two forms of targeting molecules, called Icons, to target TF. Both Icon molecules contain fVII molecule(s) as targeting domain. For immunotherapy, we will add an effector domain, for killing target cells, to the end of fVII molecules because binding of fVII to TF itself does not kill target cells. For photodynamic therapy, we will construct another Icon molecule that will be conjugated with a laser light sensitive photosensitizer. Both therapeutic procedures will be tested for effect and safety in mice carrying human or mouse breast tumors. A Phase I trial involving intratumoral injections of the Icon vector is planned for several types of cancer including breast cancer early next year at three major cancer centers. After completion of the proposal, we will obtain the preclinical data on efficacy and safety of the Icon-mediated therapies on breast cancer. Thus, the outcomes of this proposal will help to better design the clinical trial for breast cancer patients. PDT procedure will be applied to FDA separately for another clinical trial.