EWS::FLI1 drives tumorigenesis in part by creating aberrant, phase-separated, nuclear speckle-related biomolecular condensates that dysregulate mRNA splicing
Many types of cancers, particularly sarcomas, are caused and maintained by specific oncogenic fusion proteins. These fusion proteins are like the mythical chimera and contain parts of two proteins. The EWS::FLI1 chimera, is the major driver of Ewing Sarcoma (ES). EWS::FLI1 is part EWS, which a protein that normally performs many tasks in the nucleus, including participating in making mRNA from DNA. The FLI1 part of EWS::FLI1 causes this chimera protein to stick to DNA; the sticking to DNA helps the chimera decide which genes it might alter. In directing which mRNA is produced, EWS::FLI1 acts as a conductor of the symphony. However, EWS::FLI1 does much more including changing the mRNA in a process called splicing. Splicing eliminates parts of the mRNA so that it is another level of control by EWS::FLI1 as to what proteins are made when the mRNA goes to the cytoplasm. If EWS::FLI1 is the conductor, the mRNA is music, then splicing might be sending the harp player away for a section of the music that does not require a harp.
The proposal is based on a deeper understanding of EWS::FLI1 as it regulates mRNA splicing. There is strong agreement that EWS::FLI1 regulates splicing, but it requires protein partners to change the splicing. Think of the orchestra manager escorting the harp player away when they are not needed. Our challenge is to find those protein partners that are critical for EWS::FLI1 to control splicing, e.g. find out who the orchestra manager is. By finding out which proteins are required for the EWS::FLI1 altered splicing, we can use that information to eventually create new treatments to target those interactions. Our laboratory has significant experience in this area since we were the first to create a treatment, TK-216, that sticks to EWS::FLI1. TK-216 prevents EWS::FLI1 from interacting with some proteins. We showed in a recently published clinical trial of TK-216 that while it helped some patients, others did not respond for long periods of time. We are going to use this proposal to find some new protein partners and better understand how they work with EWS::FLI1. Future work would be directed to finding the next generation of inhibitory treatments.
We hypothesize that EWS::FLI1 drives tumorigenesis in part by creating aberrant nuclear speckle-related biomolecular condensates that dysregulate mRNA splicing. This project will address 2 aims in order to support an R01 resubmission. Aim 1: We will interrogate the composition and dynamic properties of cellular biomolecular condensates composed of EWSR1 or EWS::FLI1. Translated: we will look for new, key, partner proteins. Aim 2: We will monitor mRNA splicing in cells by direct visualization of biomolecular condensate markers, comparing splicing alterations and protein localization from EWSR1 with EWS::FLI1. Translated: we will investigate where the interactions are happening and begin to think about future new treatments to block those interactions.