Elucidating Oncogenic Mechanisms Underlying Wilms Tumor Using Kidney Organoids

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PROJECT SUMMARY/ABSTRACT Wilms tumor is the most common pediatric kidney cancer. Blastemal-predominant tumors are classified as high-risk and have demonstrated resistance to chemotherapeutic treatments, drastically increasing the likelihood for relapse compared to other subtypes. Current treatment consists of removal of the entire affected kidney followed by chemotherapy, or vice versa. Pediatric chemotherapy increases the risk for developing secondary cancers, while kidney removal eliminates up to 50% of a patient’s functioning nephrons. Clearly, safer and more effective targeted therapeutic strategies for blastemal-predominant Wilms tumor are needed to reduce or eliminate relapse while simultaneously retaining precious functional kidney tissue to mitigate the potential for chronic health issues. The goal of my proposed research is to elucidate the oncogenic mechanisms underlying blastemal-predominant Wilms tumor formation to identify novel candidate factors for the development of targeted therapies. These tumors express markers normally restricted to the nephron progenitor niche during fetal kidney development, including the transcription factor SIX1 which plays a critical role in establishing this niche. Sequencing of blastemal-predominant tumors identified a recurring missense mutation, Q177R, at a known DNA base-contacting residue within the evolutionary-conserved DNA binding homeodomain of SIX1. I hypothesize this mutation alters direct SIX1 regulatory interactions disrupting downstream networks, driving aberrant gene expression, obstructing nephron progenitor differentiation, and promoting a pro-oncogenic state. Utilizing cutting-edge technologies including CRISPR-Cas9 genome editing and human induced pluripotent stem cell-derived kidney organoids to model blastemal-predominant Wilms tumor in vitro, I aim to: 1) identify oncogenic phenotypes resulting from SIX1-Q177R through differentiation analysis, cell cycle profiling, proliferation, and migration assays and 2) define regulatory network disruptions downstream of SIX1-Q177R through ChIP-seq, RNA-seq and immunoprecipitation-mass spectrometry. Integration of genomic and proteomic data will pinpoint target genes directly regulated by SIX1-Q177R that are potentially contributing to oncogenic phenotypes. This pioneering work will provide a substantial foundation for understanding the molecular mechanisms contributing to the development of blastemal-predominant Wilms tumor, guiding the investigation of novel targeted therapies. Furthermore, this research will contribute vital knowledge to advance our fundamental understanding of the transcriptional control of human kidney development. This research will take place in a supportive and collaborative laboratory environment under the direction of my sponsor Dr. Lori L. O’Brien, an expert in kidney development and the regulatory control of nephron progenitor cell fate. With additional training provided by my co-sponsor Dr. Albert S. Baldwin, a leader in the field of NF-kB transcriptional networks and their roles in cancer, completion of this research and execution of my training plan will strengthen conceptual and experimental research skills and enhance professional development.