{"entity":{"id":"cyp11a1","kind":"target","name":"CYP11A1 (cholesterol side-chain cleavage enzyme)","aka":[],"tldr":"CYP11A1 is the first enzyme in making every steroid hormone from cholesterol; the historic breast cancer drug aminoglutethimide blocked it, cutting oestrogen and adrenal steroids, before aromatase inhibitors made that approach precise.","summary":"CYP11A1 converts cholesterol to pregnenolone inside mitochondria, the rate-limiting first step for cortisol, aldosterone, androgens and oestrogens. Aminoglutethimide, introduced for advanced breast cancer and Cushing's syndrome in the 1960s and 1970s, inhibited CYP11A1 and aromatase, producing a medical adrenalectomy that required cortisol replacement; it was displaced by the selective aromatase inhibitors anastrozole, letrozole and exemestane. Blocking steroid synthesis further downstream at CYP17A1 with abiraterone is the modern equivalent in prostate cancer. The enzyme is also a marker of adrenocortical carcinoma.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/Cholesterol_side-chain_cleavage_enzyme","links":[{"label":"UniProt P05108: CYP11A1","url":"https://www.uniprot.org/uniprotkb/P05108/entry"},{"label":"HGNC:2590 CYP11A1","url":"https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:2590"},{"label":"ChEMBL target CHEMBL2033","url":"https://www.ebi.ac.uk/chembl/explore/target/CHEMBL2033"}],"tags":["chembl-gap"],"related":["cyp17a1","aromatase"],"cancers":["breast-hr-positive","prostate"],"sections":[],"technologies":[],"targets":[],"drugs":["aminoglutethimide"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"CYP11A1","role":[],"sources":[],"specificity":"tumour-associated","distribution":"few-types","specificityNote":"Tumour-associated overexpression: HPA finds the RNA cancer enhanced in cancer (Kidney Chromophobe (TCGA)) and tissue enriched in normal adrenal gland, so the tumour and the normal tissue it comes from share the target and the medicine relies on the difference in level. HPA CYP11A1: RNA tissue enriched (adrenal gland 991 nTPM); blood lineage lineage enriched (granulocytes 10 nTPM); high antibody staining in 3 normal tissues. Distribution: 2 cancer families in the corpus carry a prevalence row, label threshold or catalogue link for it (Breast cancer (all types), Prostate cancer); Open Targets associates it with 2 specific cancer types at or above 0.5 (Congenital adrenal insufficiency with 46, XY sex reversal OR 46,XY disorder of sex development-adrenal insufficiency due to CYP11A1 deficiency, adrenal cortex carcinoma). (Rule 7 of scripts/fetch-target-specificity.ts.)","specificitySources":[{"label":"Human Protein Atlas CYP11A1 tissue","url":"https://www.proteinatlas.org/ENSG00000140459-CYP11A1/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas CYP11A1 pathology","url":"https://www.proteinatlas.org/ENSG00000140459-CYP11A1/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000140459 associations","url":"https://platform.opentargets.org/target/ENSG00000140459/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:2590","ensembl":"ENSG00000140459","uniprot":"P05108","entrez":"1583","firstDescribed":1986,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Chung B.-C. et al, Proc. Natl. Acad. Sci. U.S.A, 1986, \"Human cholesterol side-chain cleavage enzyme, P450scc: cDNA cloning, assignment of the gene to chromosome 15, and expression in the placenta\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/3024157/","biology":"A mitochondrial cytochrome P450 of adrenal cortex, gonads and placenta; it requires adrenodoxin and adrenodoxin reductase to receive electrons from NADPH.","whereFound":["Adrenal cortex, ovary, testis and placenta","Adrenocortical carcinoma and steroid-producing tumours"],"targetClass":"enzyme","prevalence":[{"cancerId":"breast-hr-positive","pct":"host","measure":"Host target: first enzyme of steroid synthesis. Not a tumour alteration, so no prevalence applies; the drug acts on normal tissue or on symptoms."}]},"route":"/targets/cyp11a1/","neighbours":{"target":[{"id":"aromatase","kind":"target","name":"Aromatase (CYP19A1)","route":"/targets/aromatase/"},{"id":"cyp17a1","kind":"target","name":"CYP17A1 (17-alpha-hydroxylase/17,20-lyase)","route":"/targets/cyp17a1/"}],"cancer":[{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"drug":[{"id":"aminoglutethimide","kind":"drug","name":"Aminoglutethimide","route":"/drugs/aminoglutethimide/"}]}}