Catechol estrogen quinones as initiators of breast and other human cancers: implications for biomarkers of susceptibility and cancer prevention.
Level 5 - mechanism / opinion, no new human data
Narrative review of in vitro, animal, and preliminary mechanistic human data
PubMed 16675129 · doi:10.1016/j.bbcan.2006.03.001
What was done
This narrative review synthesized biochemical, cell culture, animal model, and human biomarker evidence examining how estrogen metabolism leads to cancer initiation. It assessed the reaction of catechol estrogen-3,4-quinones (CE-3,4-Q) with DNA, mutagenic profiles in rat mammary models and mouse skin (lacI and Harvey-ras reporter assays), neoplastic transformation in estrogen receptor-alpha-negative MCF-10F cells xenografted into SCID mice, tumor development in ER-alpha knockout mice (ERKO/Wnt-1), and preliminary detection of depurinating adducts and unbalanced estrogen-activating enzymes in human breast tissue and prostate cancer urine samples.
What was found
The depurinating adducts 4-OHE1(E2)-1-N3Ade and 4-OHE1(E2)-1-N7Gua accounted for more than 99% of the total DNA adducts formed by CE-3,4-Q. In animal models, 4-OHE2 and E2-3,4-Q induced A→G and G→A mutations within 6 to 12 hours after exposure. In vitro, E2, 4-OHE2, and 2-OHE2 induced neoplastic transformation of ER-alpha-negative MCF-10F cells even in the presence of the antiestrogen ICI-182,780, forming poorly differentiated adenocarcinomas when injected into SCID mice. In human samples, unbalanced estrogen metabolism was noted in breast cancer biopsy tissue compared to controls, and 4-OHE1(E2)-1-N3Ade was detected in the urine of prostate cancer patients but not in healthy controls (no quantitative rates or sample sizes reported in the abstract).
Why it matters
This work outlines an estrogen receptor-independent, genotoxic pathway for estrogen-induced carcinogenesis driven by reactive quinone metabolites. It identifies specific depurinating adducts and unbalanced estrogen-metabolizing enzymes as potential targets for cancer risk assessment and chemoprevention.
Limits
The abstract describes a narrative review combining disparate preclinical in vitro and animal models with qualitative human observations; it provides no sample sizes, effect sizes, confidence intervals, or systematic search methodology for the human data cited.
Cited by
- supports The estrogen metabolite 4-hydroxyestrone can form DNA adducts and is genotoxic.