In vitro screening of inhibition of PPAR-γ activity as a first step in identification of potential breast carcinogens
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Published on: May 20, 2015
T I Kopp1, J Lundqvist2, R K Petersen3
1National Food Institute, Technical University of Denmark, Søborg, Denmark tinis@food.dtu.dk.
Abstract:
Alcohol consumption and increased estrogen levels are major risk factors for breast cancer, and peroxisome proliferator-activated receptor γ (PPAR-γ) plays an important role in alcohol-induced breast cancer. PPAR-γ activity is inhibited by ethanol, leading to increased aromatase activity and estrogen biosynthesis ultimately leading to breast cancer. If other organic solvents inhibit PPAR-γ activity, they should also lead to increased oestrogen biosynthesis and thus be potential breast carcinogens. Ten commonly used hydrophilic organic solvents were first tested in a cell-based screening assay for inhibitory effects on PPAR-γ transactivation. The chemicals shown to inhibit PPAR-γ were tested with vectors encoding PPAR-γ with deleted AB domains and only the ligand-binding domain to rule out unspecific toxicity. Next, the effects on biosynthesis of estradiol, testosterone and oestrone sulphate were measured in the H295R steroidogenesis assay after incubation with the chemicals. Ethylene glycol, ethyl acetate, and dimethyl sulphoxide inhibited PPAR-γ transactivation in a dose-dependent manner. The inhibitory effect on PPAR-γ was specific for PPAR-γ since the AB domain of PPAR-γ was required for the inhibitory effect. In the second step, ethylene glycol significantly increased production of oestradiol by 19% (p < 0.05) and ethyl acetate inhibited production of testosterone (p < 0.05). We here show that screening of 10 commonly used organic solvents for the ability to inhibit PPAR-γ transactivation followed by a well-established steroidogenesis assay for production of sex hormones in exposed H295 R cells may provide a screening tool for potential breast carcinogens. This initial screening thus identified ethylene glycol and possibly ethyl acetate as potential breast carcinogens.
Insights
Certain organic solvents may pose breast cancer risks by inhibiting peroxisome proliferator-activated receptor γ (PPAR-γ), potentially increasing estrogen production. Ethylene glycol and ethyl acetate were identified as potential carcinogens in this study.
Area of Science:
- Endocrinology
- Toxicology
- Molecular Biology
Background:
- Alcohol consumption and elevated estrogen levels are key breast cancer risk factors.
- Peroxisome proliferator-activated receptor γ (PPAR-γ) is implicated in alcohol-induced breast cancer, as ethanol inhibits its activity, increasing estrogen biosynthesis.
- This inhibition mechanism suggests other organic solvents inhibiting PPAR-γ could also be potential breast carcinogens.
Purpose of the Study:
- To screen commonly used organic solvents for their ability to inhibit PPAR-γ transactivation.
- To assess if inhibition of PPAR-γ by organic solvents leads to increased sex hormone biosynthesis.
- To identify potential breast carcinogens among hydrophilic organic solvents.
Main Methods:
- A cell-based screening assay was used to test 10 hydrophilic organic solvents for PPAR-γ transactivation inhibition.
- Chemicals showing inhibition were further tested using PPAR-γ vectors with deleted AB domains to confirm specificity and rule out unspecific toxicity.
- The H295R steroidogenesis assay was employed to measure the effects of solvents on estradiol, testosterone, and estrone sulfate biosynthesis.
Main Results:
- Ethylene glycol, ethyl acetate, and dimethyl sulfoxide demonstrated dose-dependent inhibition of PPAR-γ transactivation.
- The inhibitory effect was specific to PPAR-γ, requiring its AB domain.
- Ethylene glycol significantly increased estradiol production (19%), and ethyl acetate inhibited testosterone production.
Conclusions:
- Screening for PPAR-γ inhibition and subsequent steroidogenesis assays can identify potential breast carcinogens.
- Ethylene glycol and ethyl acetate are identified as potential breast carcinogens due to their effects on PPAR-γ and sex hormone biosynthesis.
- This approach provides a valuable screening tool for assessing the carcinogenic potential of organic solvents.
