Project Summary/Abstract The advanced colon cancer with organ invasion and liver metastasis are the most common cause of colon cancer death in part due to the resistance to current standard therapies. The ultimate goal of this project is to develop small-molecule degraders of small ubiquitin-related modifier 1 (SUMO1) as the first-in-class anticancer drugs for treatment of advanced colon cancers. To achieve this goal, we have already identified SUMO1 as a cancer drug target, developed cancer cell-based drug screen, identified the hit compound, and optimized the more potent lead compounds through chemical modification of the hit compound. Investigating the drug-targeted pathway, we have identified the compound binding cytoplasmic activation/proliferation-associated protein-1 (CAPRIN1) and revealed the CAPRIN1-CUL1 ubiquitin ligase complex. Upon the binding of CAPRIN1, SUMO1 degraders induce the recruitment of SUMO1 to CAPRIN1-CUL1 ligase for SUMO1 ubiquitination and degradation in cancer cells. Using genetically characterized human colon cancer cell lines, 3-dimensional (3D) organoids and patient’s derived xenografts (PDXs), we have provided the proof-of-principle that targeting SUMO1 by its degraders is a safe and effective therapy for colon cancer. The objective of this project is to investigate the mechanism and therapeutic efficacy of SUMO1 degraders in treatment of advanced colon cancer, alone and in combination of the standard chemotherapy. To achieve this, we will first evaluate the therapeutic efficacy of the lead compounds in treatment of advanced colon cancer in Aim 1. To this end, we will test the in vivo toxicity, target engagement biomarker and therapeutic efficacy of the lead compounds using genetically characterized advanced colon cancer PDX models. Next, we will determine how SUMO1 degraders drive metabolic reprograming of glycolysis and glutaminolysis in advanced colon cancer for the anticancer activity (Aim 2). We will reveal the mechanism on how the degraders regulate the sumoylation of the transcription of the metabolic StAR-related lipid transfer domain protein-7 (STARD7) in advanced colon cancer. Finally, we will determine the mechanism and therapeutic efficacy of the combination of the lead compounds and standard chemotherapy in treatment of advanced colon cancer in Aim 3. In particular, we will determine whether the metabolic enzyme G6PD (glucose-6-phosphate dehydrogenase) is conjugated by SUMO1 and thus SUMO1 degraders eliminates its conjugation and functions and sensitize colon cancers to the standard chemotherapy. Next, we will evaluate the therapeutic efficacy of the combination of the degraders and chemotherapy in treatment of a large panel of genetically characterized 3D organoid and PDX models. Upon completion, we expect that this preclinical project will provide solid scientific foundation for development of SUMO1 degraders as the first-in-class anticancer drugs for treatment of advanced colon cancer, a deadly human...