ARSD (arylsulfatase D) is an X-linked gene localized to Xp22.3 that encodes an arylsulfatase enzyme with arylsulfatase activity functioning in the endoplasmic reticulum lumen 1. As a female-biased gene escaping X-chromosome X, ARSD expression is regulated by estrogen receptor alpha (ERα) and lineage-specific transcription factors (FOXA1, GATA3) in luminal breast cancer cells 1. ARSD functions as a tumor suppressor: ectopic overexpression inhibits breast cancer cell proliferation and migration by activating the Hippo/YAP signaling pathway 1, while ARSD downregulation correlates with higher tumor grade and poorer prognosis 2. In chrX lymphocytic leukemia, ARSD overexpression associates with unmutated IGVH status and shorter time to therapy initiation, establishing it as a novel prognostic factor 3. In glioblastoma, ARSD promotes glycolysis and temozolomide resistance through β-catenin pathway activation; TRIM67-mediated ARSD degradation suppresses these oncogenic effects 4. Paradoxically, ARSD overexpression in breast epithelial cells triggers amyloidosis-associated gene expression changes potentially linked to Alzheimer's disease pathology 5. These findings indicate ARSD functions as a context-dependent regulator of cancer progression and metabolic reprogramming with dual relevance for cancer therapy and neurodegenerative disease.