Targeting SMURF2 as a novel therapy for EGFR driven tumors

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DESCRIPTION (provided by applicant): Over-expression of epidermal growth factor receptor (EGFR) drives several cancers including lung, head & neck (H&N) and colorectal, where targeting EGFR kinase activity has produced definite but limited successes. Based on previous reports and our preliminary studies, we hypothesize that the effectiveness of an anti-EGFR therapy can be greatly increased by facilitating EGFR protein degradation as opposed to simple inhibition of its kinase activity. Towards this goal, we have identified a novel interaction between EGFR and a HECT type ubiquitin ligase, Smad ubiquitination regulatory factor 2 (SMURF2), which is critical for EGFR protein stability and by targeting SMURF2 we can efficiently degrade EGFR to kill EGFR addicted cancer cells and stop the growth of human tumor xenografts. We have also discovered significant correlation of expression of the two proteins at the RNA and protein levels in a large group of lung and H&N cancer patients. The main goal of this proposal is to understand the molecular interaction between EGFR and SMURF2 in upper aerodigestive cancers and to develop a novel therapeutic strategy by inducing EGFR degradation via targeting SMURF2. We believe that by down-regulating SMURF2, EGFR will be more vulnerable to degradation, independent of its overexpression or mutation status in cancer and such a strategy will be therapeutically more potent as it can physically abolish EGFR. We propose to achieve these goals through 3 specific aims: In aim 1, we hypothesize that certain lysine residues are critical for SMURF2 mediated protein ubiquitination, responsible for EGFR protein stability. Specific aim 1 is to determine whether SMURF2-mediated ubiquitination can covalently modify certain lysine residues on EGFR to stabilize it from undergoing degradation. In specific aim 2, we hypothesize that by down-regulating SMURF2 via shRNA, we can reduce the tumor burden as individual therapy or can sensitize tumor cells that are resistant to currently available chemo-/radiotherapy. Specific aim 2 is to explore the therapeutic potential of SMURF2 targeting as a novel approach in upper aerodigestive cancer treatment. In aim 3, we hypothesize that EGFR and SMURF2 interacts in sequence specific manner in association with certain cofactors. Specific aim 3 we will identify the domain(s) of EGFR and cofactors that are assisting in its stable interaction and protein modification by SMURF2. Results obtained from this study will help us establish a novel approach targeting EGFR, independent of a drug resistant EGFR mutation by altering its ubiquitination status via SMURF2 targeting. We anticipate that successful completion of this project will not only provide a better mechanistic insight exploring the roles of ubiquitination in EGFR protein stability, it will also provide a strong foundation for the development of peptidomimetic scaffold or small molecule inhibitor, which can disrupt EGFR-SMURF2 interaction to kill cancer cells and will be beneficial for certain patients.