Inhibiting Interaction of PNUTS with the MYC Family of Oncoproteins to Effectively Target Breast Cancer
Abstract
Overarching Challenges: 1) Identify what drives breast cancer, e.g., the MYC oncoprotein, and determine how to stop it. 2) Revolutionize treatment regimens by replacing them with ones that are more effective, less toxic, and impact survival. Thus, we aim to leverage our exciting data to breakthrough long-standing barriers and significantly improve the treatment and outcome of patients with BC. MYC is a protein that drives approximately half of all breast cancers. The normal function of MYC is as a master regulator that controls the function of many genes, thereby unleashing cells to grow in an uncontrolled manner. One analogy is that MYC is like the conductor of an orchestra, where the instruments are genes important for cell growth. To function as a master regulator MYC must interact with other molecules, called proteins, to turn on and off many cellular genes. MYC drives breast cancer when it becomes deregulated, either because the cell makes too much of the protein or no longer keeps protein levels carefully balanced. Because of its central role in driving breast cancer, MYC has been a drug target for many years. However, all attempts at developing a drug that would turn off MYC have failed. We now know that the reason for the failures is that MYC has no solid structure for a drug to bind to. Instead, the protein is flexible and adapts to fit the binding pockets of its partner proteins. This provides a new idea on how to turn off MYC. If we can block the site on a partner protein where MYC needs to bind, then MYC could not interact and would be turned off. The question then becomes which partner protein to target? This was not an easy question to answer because identifying MYC binding partners has also been difficult, as MYC is highly labile and falls apart very easily. We overcame this hurdle and identified several known and novel MYC interactors by using a new in-cell labelling technology that tags proteins physically close to MYC within the breast cancer cell. For the first time, we have a view of MYC’s protein partners. We honed in on one called PNUTS as it regulates a process that we had previously shown regulated MYC activity. Indeed, our further work showed that PNUTS is indeed essential for MYC activity as a cancer driver. Next, we identified the part of MYC that binds to PNUTS and the part of PNUTS that binds to MYC. Then we determined the shape of the piece of PNUTS that binds MYC; first on its own, then with the MYC piece bound to it. That led to a major discovery; MYC becomes structured when it binds to the pocket on PNUTS. We then made use of the extensive drug development knowledge in Dr. Al-Awar’s group to determine that the pocket on PNUTS to which MYC binds is druggable. This was the moment we knew we had an opportunity to actually develop a drug that would bind to PNUTS, preclude MYC interaction. To start the drug discovery process, we need to be able to rapidly screen thousands of compounds. Here we partnered with Dr. Andrews as he has expertise in high-throughput screening. His lab optimized and validated the assay using 2000 compounds in a pilot screen. That test resulted in three compounds that scored positive. Not surprisingly from this small inexpensive library Dr. Al-Awar determined that none of the three compounds is acceptable for building a drug. Now the team will work together to screen the 140,000 compound collection assembled by Dr. Al-Awar’s team that includes compounds with drug-like properties and has the type of compounds that could bind the PNUTS pocket and inhibit MYC interaction. This large compound library has recently been transferred to Dr. Andrews’ lab. After the screen, Dr. Andrews will test the positives (called Hits) by independent complimentary assays to distinguish which Hits work best. Dr. Al-Awar’s team will then analyze the Hits for potential drug development and they will generate or purchase related compounds so that we can begin to optimize and build a drug.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 05, 2021
- Source ID
- W81XWH2110367
Entities
People
- Linda Z Penn
Organizations
- United States Army
- University Health Network