Projects

Here is a list of funded research in the lab

CONVERTING AN ONCOGENE TO AN APOPTOTIC FACTOR BY MANIPULATING SIGNAL SEQUENCES

Changing the subcellular localization of a signal transducing protein involved in disease is a novel approach for therapeutic intervention. The subcellular location of some proteins plays a critical role in the etiology of disease. A precise example of this is Bcr- Abl protein, the causative agent of chronic myelogenous leukemia (CML). When Bcr-Abl is in the cytoplasm of cells, it behaves as an oncogene, but if forced to the nucleus, it becomes an apoptotic factor. CML is a myeloproliferative disorder characterized by increased proliferation of granulocytes and their immature precursors; with a median survival time of 4 to 6 years. The goal of this study is to use our ligand responsive protein switch constructs to control the subcellular location of Bcr-Abl, and convert Bcr- Abl from an oncogene to an apoptotic factor. It has been shown that depletion of Bcr- Abl from the cytoplasm by nuclear trapping of Bcr-Abl can result in apoptosis. If Bcr-Abl can be directed to the nucleus, it can be converted from an oncogene to an apoptotic factor. Since Bcr-Abl oligomerizes with itself to form tetramers, nuclear trapping could be achieved by introducing exogenously localization-controllable Bcr-Abl. Upon ligand induction, localization controllable Bcr-Abl will oligomerize with wt Bcr-Abl and will undergo transport to the nucleus, followed by cellular apoptosis. In Aim 1 we will subclone localization controllable versions of Bcr-Abl (Bcr-Abl protein switch, PS) with a fluorescent tag and show oligomerization with wild-type (wt) Bcr-Abl, translocate to the nucleus, and cause apoptosis of Bcr-Abl positive K562 cells. Localization of Bcr-Abl PS will be monitored by fluorescence microscopy, and apoptosis will be tested using standard cell death assays. Interaction of wt Bcr-Abl with Bcr-Abl PS will be determined using an in vivo oligomerization between wt Bcr-Abl and Bcr-Abl protein switch and mammalian two-hybrid assay. Aim 2 will test the Bcr-Abl PS in Gleevec.-resistant leukemic cells similarly. Aim 3 will test and use specific promoters that allow preferential expression of Bcr-Abl PS in leukemia cells only. Aim 4 will test if Bcr-Abl PS will eradicate/diminish leukemia in a human xenograft model using Balb/C nude mice injected with human leukemia cells. Our goal is to use ligand responsive protein switch constructs to control the subcellular location of Bcr-Abl, and convert Bcr-Abl from an oncogene to an apoptotic factor. Our long-term, ultimate goal is to use localization controllable versions of Bcr-Abl (as gene therapy) for treatment of CML.

SIMULTANEOUS TARGETING OF P53 TO THE NUCLEUS AND MITOCHONDRIA FOR CANCER THERAPY

The goal of this project is to target a tumor suppressor (p53) to 2 different cellular compartments as new dual gene therapy approach for breast and other types of cancers. In normal cells, p53 protein is located mostly in the nucleus of the cell where it can act as a tumor suppressor and cause apoptosis. Under certain conditions it is also apoptotically active when directed to the mitochondria. In many types of cancers, p53 is mislocalized to the cytoplasm or inactivated. Indeed, p53 has emerged as a master switch for cancer prevention and is actively pursued as the ultimate cancer therapeutic target. To target p53 to the nucleus, we will use our emerging protein switch technology to capture mislocalized p53 in the cell cytoplasm, which can be dragged to the nucleus with addition of an external drug. Once in the nucleus, p53 will cause death of the cancer cell. To target p53 to the mitochondria, an improved mitochondrially directed version of p53 will be created. This 2- gene therapy approach is likely to increase the potency of p53 cell-killing ability. The initial target to demonstrate this technology is breast cancer, with future use in inflammatory breast carcinoma (IBC), a very aggressive and deadly form of breast cancer. IBC has mislocalized or mutated p53 and therefore should readily respond to this type of therapy. This approach is applicable to all types of cancers involving p53 mislocalization, nuclear exclusion, mutation, or inactivation. The aims of this project are as follows: 1) Demonstrate that protein switch versions of p53 with nuclear localization signal (NLS) will translocate from the cytoplasm to the nucleus upon ligand addition and intrinsically cause apoptosis, or initiate enhanced apoptosis when binding endogenous mislocalized p53; 2) Prove that a nuclear-localization deficient version of p53 engineered with an improved mitochondrial targeting signal will trigger apoptosis via the intrinsic apoptotic pathway; 3) Assess the ability of the nuclear targeted protein switch-p53 from Aim 1, and the mitochondrially optimized p53 from Aim 2 in combination therapies to induce apoptosis in breast cancer cells, resulting in increased potency compared to the action of either construct alone. A cancer-specific promoter and delivery in cells using an adenoviral vector will also be tested; 4) Validate that the combination therapy from Aim 3 delivered via adenovirus vector will eradicate or reduce breast cancer in a human xenograft solid tumor murine model in vivo. Finally, the approach described here is more advantageous that current strategies (including administering wt p53 or small molecule inhibitors that can restore tumor suppressor function in some cases) because targeting of p53 directly to active compartments of the cell will allow triggering of both intrinsic and extrinsic pathways of apoptosis in a specific and simultaneous or synergistic manner. This dual gene therapy is also expected to be beneficial for other types of aggressive cancers that currently have no effective therapies. PUBLIC HEALTH RELEVANCE: The tumor suppressor p53 is inactive or malfunctioning in most types of cancer, and making restoration of p53 a prime candidate for cancer therapy. Our goal is to add p53 back into cancer cells, and simultaneously target p53 to its most active cellular compartments, the nucleus and mitochondria. Our long term goal is to use targeted delivery of p53 as a potent cancer therapeutic.