ROLE OF MIDKINE IN MOLECULAR TARGETED THERAPY TO TIP1 FOR LUNG CANCER TREATMENT

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PROJECT DESCRIPTION/ ABSTRACT Non-small cell lung cancer (NSCLC) ranks among the highest cancer-related mortalities world-wide. Molecular targeted therapy is a growing topic of investigation to improve therapeutic efficacy for NSCLC. A few targeted therapies that exploit aberrant protein expression profiles have been approved for NSCLC. However, the marginal percentage of cancers with improved efficacy observed with these therapeutic approaches highlights the need for discovery of additional molecular targets. The proposed research is significant as it will generate new molecular targets and treatment strategies for NSCLC therapy. We propose targeting of the scaffold protein TIP1 that is a novel target for lung cancer as identified by analysis of the cancer genome atlas datasets and NSCLC tumor tissue microarrays. The functional domain of TIP1 (PDZ domain) caps the C-terminus of many different cellular proteins that regulate important cellular functions. Knocking down TIP1 revealed that it plays an important role in cell signaling, cancer development, and progression making it an attractive target for anticancer therapeutics. Comparing antibodies targeting different epitopes of TIP1, it was found that antibodies against the PDZ domain of TIP1 were most effective in inducing direct cytotoxicity of lung cancer cells but not normal cells. Anti-PDZ/TIP1 antibodies injected into mice bearing lung cancer bind specifically to cancer cells and substantially enhance tumor control. Quantitative mass spectrometry identified Midkine (MDK) as a putative protein that modulates this cytotoxicity by anti-PDZ/TIP1 antibodies. Additional studies suggested that the β-catenin/Wnt signaling may be involved in this up-regulation of MDK after blocking of TIP1. Together, these studies led to the central hypothesis that MDK is upregulated by the anti-PDZ/TIP1 antibody via the β- catenin/Wnt signaling pathway, which subsequently modulates downstream cell death mechanisms. Aim 1 will elucidate the mechanisms of induction of MDK following blockade of the PDZ domain of TIP1. This aim will lead to identification of novel molecular targets for NSCLC treatment that have never been considered before. Aim 2 will evaluate the efficacy of blocking TIP1 function while simultaneously blocking MDK function in mouse models of NSCLC. This aim will guide the development of combination therapies to optimize efficacy of NSCLC treatment. This research is innovative because we are studying a novel molecular target, TIP1. Blocking the functional domain of TIP1 leads to NSCLC cell death. We also propose an innovative strategy of dual targeting TIP1 and MDK to enhance the therapeutic efficacy of NSCLC. Building on my cancer biology background, this K22 award will allow me to train in cutting edge proteomic and genomic approaches with special emphasis on identifying novel NSCLC molecular targets. I have proposed a research and training plan that will equip me with the highest skills to ensure my success as an independent investigator. Overall, the long-term goal of my future research, is to provide new opportunities for the development of novel therapies to treat lung cancer.