A Phase II Trial of the DNA Methyl Transferase Inhibitor, Guadecitabine (SGI-110), in Children and Adults With Wild Type GIST,Pheochromocytoma and Paraganglioma Associated With Succinate Dehydrogenase Deficiency and HLRCC-associated Kidney Cancer

Background: Wild-type gastrointestinal stromal tumor (GIST) is a cancer in the esophagus, stomach, or intestines. It does not respond well to standard chemotherapy or radiation therapy. Most people with GIST are treated with imatinib. But it may not work in many children with GIST. Researchers think the drug SGI-110 may help treat people with GIST, pheochromocytoma and paraganglioma (PHEO/PGL), or kidney cancer related to hereditary leiomyomatosis and renal cell carcinoma (HLRCC). Objective: To learn if SGI-110 causes GIST tumors to shrink or slows their growth. Also to test how it acts in the body. Eligibility: People ages 12 and older who have GIST, PHEO/PGL, or HLRCC that has not responded to other treatments Design: Participants will be screened with: * Physical exam * Urine tests * Computed tomography (CT) or magnetic resonance imaging (MRI), or fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan: A machine takes pictures of the body. * Blood tests Participants will be injected with SGI-110 under the skin each day for 5 days. This cycle will repeat every 28 days. The cycles repeat until their side effects get too bad or their cancer gets worse. Participants will have tests throughout study: * Physical exam and blood and urine tests before each cycle * Blood tests on days 1, 7, 14, and 28 of the first cycle. * Scans before cycle 1 and then every other cycle. * Questionnaires about their pain and quality of life * Tumor biopsy for those 18 and older: A needle removes a small piece of tumor. After they stop treatment, participants will have a final visit. This includes an evaluation of their health, pain, and quality of life. ...