ANTI-PDZ DOMAIN ANTIBODIES ENHANCE THE EFFICACY OF RADIOTHERAPY

Poor prognosis cancers including cancers of the lung and glioblastoma show robust overexpresion of Tax Interacting Protein TIP The proposed research is a novel approach to cancer drug development in which we target this chaperone protein that binds to signal transduction proteins that enhance cell viability following cytotoxic therapy Stress responses in cancer cells are exaggerated over that of normal tissues Examples are signal transduction pathways that include GRP PKC PLC Rho and others Mechanisms by which these proteins dock on the plasma membrane in response to ionizing radiation include motor and scaffold proteins One scaffold protein that caps the carboxyl terminus of plasma membrane associated signaling proteins TIP is overexpressed in cancer and translocates to the surface of the cell membrane of cancer cells following exposure to ionizing radiation The functional domain of TIP is the PDZ binding domain which binds enzymes that regulate cell viability such as PLC PKC GPCR and Rho Our preliminary data show that gene silencing of TIP and blocking antibodies that bind to the PDZ domain of TIP enhance radiation induced cytotoxicity in cancer but not normal tissues Anti PDZ domain antibodies injected into mice bearing irradiated lung cancer bind specifically to cancer and substantially enhance tumor growth delay over that of controls We will study antibodies that enhance cytotoxity and improve tumor control One mechanism by which the anti PDZ domain antibodies enhance the efficacy of radiotherapy is through interruption of cell viability signal transduction pathways and subsequent programmed cell death specifically in cancer We will compare antibody fragment scFv to whole IgG antibodies that bind to the PDZ domain of TIP and determine which antibodies achieve cancer specific binding and enhancement of the efficacy of radiotherapy in cancer without normal tissue toxicity We will determine the lead human anti TIP antibody fragment that achieves cancer specific binding and cytotoxicity in cancer cells Our preliminary data show that assays which measure the interaction between anti TIP antibodies and radiation include the clonogenic and apoptosis assays We will compare our lead antibodies that are specific to the PDZ domain on TIP to determine which is the most cancer specific and cytotoxic We will determine the efficacy of anti TIP PDZ IgG compared to anti TIP PDZ scFv antibodies in mouse models of cancer We will determine the role of immune effector cells in the cancer response to anti TIP antibodies We Hypothesize that IgG could further enhance the efficacy of radiotherapy by activating immune effector cells We will study mouse models that lack Fc receptors and do not activate antibody mediated cancer cytotoxicity These mouse models will allow us to determine whether the efficacy of the anti TIP antibodies is a direct effect on cancer cells or whether immune effector cell activation contributes to the therapeutic effect