PROM1 (prominin 1) encodes a five-transmembrane domain glycoprotein that serves critical roles in stem cell biology, retinal development, and cellular homeostasis 1. The protein localizes to membrane protrusions and is widely recognized as a biomarker for cancer stem cells, including brain tumor-initiating cells where CD133+ populations demonstrate enhanced tumorigenicity and radioresistance 23. In retinal tissue, PROM1 undergoes tissue-specific alternative splicing with exon 4 inclusion crucial for photoreceptor development and maturation 4. Exon 4 skipping leads to decreased protein expression, cone photoreceptor defects, and abnormal cellular distribution, correlating with late-onset maculopathy 4. PROM1 also plays essential roles in retinal pigment epithelium (RPE) homeostasis, where knockdown results in abnormal RPE morphology, subretinal fluid accumulation, and secondary photoreceptor loss resembling atrophic AMD 5. The protein contributes to DNA damage response and repair mechanisms in glioma stem cells, conferring radioresistance that can be therapeutically targeted 3. Additionally, PROM1 participates in stem cell signaling networks, including a positive feedback loop with SOX9 in colorectal cancer that maintains stemness while blocking differentiation 6. Its expression patterns vary across cancers, with overexpression generally associated with poor prognosis 7.