# CYP1B1

Source: https://onco.cc/targets/cyp1b1/  
OnCo record `cyp1b1` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

CYP1B1 (Cytochrome P450 1B1) is an enzyme. In the public catalogues the evidence so far is association rather than a proven role. Tied to Skin cancer, Melanoma and Basal cell carcinoma.

## Summary

A cytochrome P450 monooxygenase involved in the metabolism of various endogenous substrates, including fatty acids, steroid hormones and vitamins. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (NADPH--haemoprotein reductase). Exhibits catalytic activity for the formation of hydroxyestrogens from estrone (E1) and 17beta-estradiol (E2), namely 2- and 4-hydroxy E1 and E2.

Open Targets scores its association with cancer at 0.60 (direct and indirect evidence; datatypes literature 0.98, animal model 0.68, genetic association 0.74).

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: cytochrome P450 family 1 subfamily B member 1; Cytochrome P450 1B1; CP1B; GLC3A
- Tags: cancer-genes-wave
- Symbol: CYP1B1
- Class: enzyme
- Biology: A cytochrome P450 monooxygenase involved in the metabolism of various endogenous substrates, including fatty acids, steroid hormones and vitamins. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (NADPH--haemoprotein reductase). Exhibits catalytic activity for the formation of hydroxyestrogens from estrone (E1) and 17beta-estradiol (E2), namely 2- and 4-hydroxy E1 and E2. Displays a predominant hydroxylase activity toward E2 at the C-4 position. Metabolises testosterone and progesterone to B or D ring hydroxylated metabolites. May act as a major enzyme for all-trans retinoic acid biosynthesis in extrahepatic tissues. Location: Endoplasmic reticulum membrane; Microsome membrane; Mitochondrion (UniProt). Locus 2p22.2 (HGNC).
- Where found: Skin cancer: Open Targets association 0.55 with skin cancer (MONDO_0002898); Melanoma: Open Targets association 0.56 with melanoma (MONDO_0005105); Basal cell carcinoma: Open Targets association 0.55 with basal cell carcinoma (MONDO_0020804)

## Notes

- Written by scripts/fetch-cancer-genes.ts from CIViC, Open Targets, IntOGen, HGNC and UniProt; the function text is UniProt's, condensed and in UK spelling. Roles: none stated by the sources. Evidence tier "association-only" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:2597: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:2597
- UniProt Q16678: https://www.uniprot.org/uniprotkb/Q16678/entry
- NCBI Gene 1545: https://www.ncbi.nlm.nih.gov/gene/1545
- Ensembl ENSG00000138061: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000138061

## Connected records

- collections: [Open Targets Platform](https://onco.cc/collections/open-targets/)
- cancers: [Basal cell carcinoma](https://onco.cc/cancers/basal-cell-carcinoma/), [Melanoma](https://onco.cc/cancers/melanoma/), [Skin cancer (all types)](https://onco.cc/cancers/skin-cancer/)
- pathways: [Chemical carcinogenesis - receptor activation](https://onco.cc/pathways/chemical-carcinogenesis-receptor-activation/)

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JSON: https://onco.cc/api/v1/entities/cyp1b1.json