{"entity":{"id":"cyp17a1","kind":"target","name":"CYP17A1 (17-alpha-hydroxylase/17,20-lyase)","aka":[],"tldr":"The enzyme that makes androgens in the testes, the adrenal glands and prostate tumours themselves. Abiraterone blocks it, cutting androgen production below what castration alone achieves.","summary":"CYP17A1 catalyses two steps, 17-alpha-hydroxylation and 17,20-lyase cleavage, that convert pregnenolone and progesterone into DHEA and androstenedione, the precursors of testosterone and dihydrotestosterone. Because castration-resistant prostate cancer keeps making androgens from adrenal precursors and inside the tumour, blocking CYP17A1 with abiraterone lowers androgens further than castration and restores control in many patients. Blocking the enzyme also diverts steroid synthesis towards mineralocorticoids, which is why abiraterone is given with prednisone or prednisolone.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/CYP17A1","links":[{"label":"UniProt P05093: CYP17A1","url":"https://www.uniprot.org/uniprotkb/P05093/entry"}],"tags":[],"related":["androgen-receptor"],"cancers":["prostate","prostate-mcrpc"],"sections":[],"technologies":[],"targets":[],"drugs":["abiraterone"],"companies":[],"institutions":[],"pathways":[],"terms":["castration-resistance","mcrpc-mhspc"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":["paper-taplin-ar-mutation-androgen-independent-prostate-nejm-1995"],"journals":[],"dependsOn":[],"notes":["Prostate cancer: the reason the AR L702H allele matters. L702H makes the receptor responsive to glucocorticoid, and abiraterone, a CYP17A1 inhibitor, is given with prednisone or prednisolone to offset mineralocorticoid excess, so the steroid given with the drug can in principle feed a receptor carrying that allele."],"symbol":"CYP17A1","role":[],"sources":[],"specificity":"tumour-associated","distribution":"one-type","specificityNote":"Tumour-associated overexpression: HPA finds the RNA cancer enhanced in cancer (Liver Hepatocellular Carcinoma (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 CYP17A1: RNA tissue enriched (adrenal gland 8,353 nTPM); high antibody staining in 2 normal tissues. Distribution: 1 cancer family in the corpus carries a prevalence row, label threshold or catalogue link for it (Prostate cancer); Open Targets associates it with 2 specific cancer types at or above 0.5 (17,20-lyase deficiency, isolated, prostate cancer); 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 CYP17A1 tissue","url":"https://www.proteinatlas.org/ENSG00000148795-CYP17A1/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas CYP17A1 pathology","url":"https://www.proteinatlas.org/ENSG00000148795-CYP17A1/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000148795 associations","url":"https://platform.opentargets.org/target/ENSG00000148795/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:2593","ensembl":"ENSG00000148795","uniprot":"P05093","entrez":"1586","firstDescribed":1987,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Chung B.-C. et al, Proc. Natl. Acad. Sci. U.S.A, 1987, \"Cytochrome P450c17 (steroid 17 alpha-hydroxylase/17,20 lyase): cloning of human adrenal and testis cDNAs indicates the same gene is expressed in both tissues\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/3025870/","biology":"Cytochrome P450 enzyme of the adrenal cortex, testis and prostate cancer cells; the rate-limiting step of androgen synthesis from pregnenolone.","whereFound":["Prostate cancer, including intratumoral androgen synthesis in castration-resistant disease"],"targetClass":"enzyme","prevalence":[{"cancerId":"prostate","pct":"nearly all","measure":"Androgen-driven at diagnosis; abiraterone acts on androgen synthesis in almost every prostate cancer, resistance develops later","source":"https://www.cancer.gov/types/prostate/hp/prostate-treatment-pdq"}]},"route":"/targets/cyp17a1/","neighbours":{"target":[{"id":"srd5a2","kind":"target","name":"5-alpha-reductase type 2 (SRD5A2)","route":"/targets/srd5a2/"},{"id":"androgen-receptor","kind":"target","name":"Androgen receptor","route":"/targets/androgen-receptor/"},{"id":"cyp11a1","kind":"target","name":"CYP11A1 (cholesterol side-chain cleavage enzyme)","route":"/targets/cyp11a1/"}],"cancer":[{"id":"prostate-mcrpc","kind":"cancer","name":"Metastatic castration-resistant prostate cancer","route":"/cancers/prostate-mcrpc/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"drug":[{"id":"abiraterone","kind":"drug","name":"Abiraterone acetate","route":"/drugs/abiraterone/"},{"id":"galeterone","kind":"drug","name":"Galeterone","route":"/drugs/galeterone/"},{"id":"orteronel","kind":"drug","name":"Orteronel","route":"/drugs/orteronel/"}],"term":[{"id":"castration-resistance","kind":"term","name":"Castration-resistant prostate cancer (CRPC)","route":"/terms/castration-resistance/"},{"id":"mcrpc-mhspc","kind":"term","name":"mCRPC and mHSPC (castration-resistant vs hormone-sensitive prostate cancer)","route":"/terms/mcrpc-mhspc/"}],"paper":[{"id":"paper-taplin-ar-mutation-androgen-independent-prostate-nejm-1995","kind":"paper","name":"Mutation of the androgen-receptor gene in metastatic androgen-independent prostate cancer","route":"/key-papers/paper-taplin-ar-mutation-androgen-independent-prostate-nejm-1995/"}],"trial":[{"id":"armor3-sv","kind":"trial","name":"ARMOR3-SV","route":"/trials/armor3-sv/"},{"id":"elm-pc-4-orteronel","kind":"trial","name":"ELM-PC 4","route":"/trials/elm-pc-4-orteronel/"}],"biomarker":[{"id":"ar-ligand-binding-domain-mutation","kind":"biomarker","name":"AR ligand-binding-domain mutation (L702H, W742C, H875Y, T878A, F877L)","route":"/biomarkers/ar-ligand-binding-domain-mutation/"}]}}