ISYNA1 encodes inositol-3-phosphate synthase 1, the rate-limiting enzyme in myo-inositol biosynthesis that catalyzes the conversion of glucose 6-phosphate to myo-inositol 1-phosphate 1. This enzyme is essential for de novo inositol synthesis, as demonstrated by the "inositol-less death" phenotype observed in ISYNA1 knockout cells when deprived of inositol 1. The gene plays a paradoxical role in cancer, functioning as both a tumor suppressor and oncogene depending on cellular context 2. ISYNA1 exhibits tumor-suppressive properties in ovarian cancer by suppressing stemness through Notch1 pathway inhibition 3 and in pancreatic cancer through p21/ZEB-1 signaling 4. However, it is overexpressed in bladder cancer where it promotes proliferation and inhibits apoptosis 5. In acute myeloid leukemia, ISYNA1 is frequently silenced through DNA hypermethylation, creating a synthetic lethal dependency on the myo-inositol transporter SLC5A3 6. The enzyme's expression is regulated by E2F1 transcription factor 7, and genetic polymorphisms may influence spina bifida risk through interactions with glucose metabolism 8. Inositol depletion affects phospholipid metabolism and activates stress signaling pathways 1.