{"entity":{"id":"aromatase","kind":"target","name":"Aromatase (CYP19A1)","aka":[],"tldr":"The enzyme that turns androgens into oestrogen in fat, muscle and breast tissue after the menopause. Aromatase inhibitors remove the oestrogen that drives most breast cancers in post-menopausal women.","summary":"Aromatase, the product of the CYP19A1 gene, converts androstenedione and testosterone into oestrone and oestradiol. After the menopause the ovaries stop making oestrogen and aromatase in peripheral fat, muscle and the breast itself becomes the main source, so inhibiting it with letrozole, anastrozole or exemestane lowers circulating oestrogen to very low levels and deprives hormone receptor-positive breast cancer of its growth signal. Aromatase inhibitors are the standard endocrine partner for CDK4/6 inhibitors in advanced disease and a standard adjuvant treatment in early disease; joint pain and bone loss are their characteristic side effects.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/Aromatase","links":[{"label":"UniProt P11511: CYP19A1","url":"https://www.uniprot.org/uniprotkb/P11511/entry"}],"tags":[],"related":[],"cancers":["breast-hr-positive"],"sections":[],"technologies":[],"targets":[],"drugs":["letrozole","exemestane"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"CYP19A1","role":[],"sources":[],"specificity":"tumour-associated","distribution":"one-type","specificityNote":"Tumour-associated overexpression: HPA finds the RNA cancer enhanced in cancer (Glioblastoma Multiforme (TCGA)) and tissue enriched in normal placenta, so the tumour and the normal tissue it comes from share the target and the medicine relies on the difference in level. HPA CYP19A1: RNA tissue enriched (placenta 117 nTPM); high antibody staining in 1 normal tissue. Distribution: 1 cancer family in the corpus carries a prevalence row, label threshold or catalogue link for it (Breast cancer (all types)); approvals of single-target medicines aimed at it also list Ovarian cancer, Endometrial cancer, not counted; Open Targets associates it with 2 specific cancer types at or above 0.5 (breast cancer, breast carcinoma); the corpus evidence decides and the Open Targets list is quoted for comparison. (Rule 7 of scripts/fetch-target-specificity.ts.)","specificitySources":[{"label":"Human Protein Atlas CYP19A1 tissue","url":"https://www.proteinatlas.org/ENSG00000137869-CYP19A1/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas CYP19A1 pathology","url":"https://www.proteinatlas.org/ENSG00000137869-CYP19A1/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000137869 associations","url":"https://platform.opentargets.org/target/ENSG00000137869/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:2594","ensembl":"ENSG00000137869","uniprot":"P11511","entrez":"1588","firstDescribed":1986,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Evans C.T. et al, Proc. Natl. Acad. Sci. U.S.A, 1986, \"Isolation and characterization of a complementary DNA specific for human aromatase-system cytochrome P-450 mRNA\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/3018730/","biology":"Cytochrome P450 enzyme that aromatises the A ring of androgens to form oestrogens; expressed in adipose tissue, muscle, bone, brain and breast tumour stroma.","whereFound":["Hormone receptor-positive breast cancer in post-menopausal women"],"targetClass":"enzyme","prevalence":[{"cancerId":"breast-hr-positive","pct":"about 70","measure":"Share of breast cancers that are hormone receptor-positive, the population aromatase inhibitors treat","source":"https://www.cancer.org/cancer/types/breast-cancer/understanding-a-breast-cancer-diagnosis/breast-cancer-hormone-receptor-status.html"}]},"route":"/targets/aromatase/","neighbours":{"cancer":[{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"}],"drug":[{"id":"aminoglutethimide","kind":"drug","name":"Aminoglutethimide","route":"/drugs/aminoglutethimide/"},{"id":"anastrozole","kind":"drug","name":"Anastrozole","route":"/drugs/anastrozole/"},{"id":"exemestane","kind":"drug","name":"Exemestane","route":"/drugs/exemestane/"},{"id":"formestane","kind":"drug","name":"Formestane","route":"/drugs/formestane/"},{"id":"letrozole","kind":"drug","name":"Letrozole (and other aromatase inhibitors)","route":"/drugs/letrozole/"}],"target":[{"id":"cyp11a1","kind":"target","name":"CYP11A1 (cholesterol side-chain cleavage enzyme)","route":"/targets/cyp11a1/"}]}}