The Tumor Biomarker Series: ATRX

Alpha Thalassemia/Mental Retardation Syndrome X-linked (ATRX) is a gene that encodes a protein involved in chromatin remodeling. ATRX mutations are a marker of astrocytic lineage among the IDH-mutant gliomas and are mutually exclusive with 1p/19q codeletion. Present in 57% of secondary GBMs, ATRX mutations are uncommon in primary glioblastomas. Nearly all diffuse gliomas with IDH and ATRX mutations also have TP53 mutation and are associated with the Alternative Lengthening of Telomeres (ALT) phenotype. Immunohistochemistry for ATRX demonstrates loss of protein expression in neoplastic cells harboring the inactivating mutations, while expression is retained within non-neoplastic internal controls (such as endothelial cells).