Bisphenol A (BPA) is an organic synthetic compound belonging to the group of diphenylmethane derivatives and bisphenols. It is widely used in the manufacture of polycarbonate plastics and epoxy resins. BPA is known to exhibit estrogen-mimicking, hormone-like properties, which have raised concerns about its presence in consumer products and potential impact on health, particularly in vulnerable populations like pregnant women, infants, and children. People are primarily exposed to BPA through dietary sources due to its use in food containers. BPA has been associated with various health risks, including reproductive disorders, developmental problems in children, cardiovascular diseases, and diabetes. In response to these concerns, some countries and regions have restricted or banned the use of BPA in certain products, particularly those intended for infants and young children, there has also been a growing market for BPA-free products.
To explore the intersection between environmental chemicals and hormonal pathways in the context of breast cancer, a new study published in the Journal of Biochemical and Molecular Toxicology and led by Dr. Masahiro Ogawa, Mr. Junya Kitamoto, Mr. Takeo Takeda, and Dr. Megumi Terada from the Life Science Research Institute at Kumiai Chemical Industry Co. Ltd., the researchers conducted a comprehensive analysis investigating the effects of BPA on progesterone (P4) signaling and the expression of Tripartite motif‐containing 22 (TRIM22) and TP53 in human breast carcinoma MCF‐7 cells.
The research team selected MCF-7 breast cancer cell line for their studies because it is known for its estrogen receptor positivity. The cells were cultured in Dulbecco’s Modified Eagle Medium (DMEM) with high glucose, supplemented with fetal bovine serum, penicillin, and streptomycin for maintenance. To study the effects of P4 and Estradiol (E2), the cells were transferred to a phenol red-free DMEM high glucose, which is essential to eliminate any estrogenic activity from the media, thus ensuring that the observed effects are solely due to the experimental treatments.
P4 a key hormone in female reproductive biology, plays a vital role in various physiological processes. The study aimed to understand how P4 influences TRIM22 expression and apoptosis in MCF-7 cells. To achieve this, cells were treated with different concentrations of P4, and the mRNA levels of TRIM22 were measured using qRT-PCR. This method allows for precise quantification of specific mRNA levels, offering insights into the gene expression changes induced by P4. The study also employed esiRNA to silence the progesterone receptor (PGR), assessing the role of PGR in mediating the effects of P4 on TRIM22 expression.
The researchers treated the MCF-7 cells with various concentrations of BPA in the presence of P4. This approach was designed to observe how BPA modulates the effects of P4 on cell viability and apoptosis. The concentration-dependent effects of BPA were carefully monitored to understand its interaction with P4 signaling pathways.
A critical aspect of the study was assessing the transcriptional activity of the P4 receptor. The researchers used a luciferase assay, where MCF-7 cells were transfected with a plasmid containing the progesterone response element (PRE) linked to a luciferase reporter gene. This technique allows for the measurement of PGR activity based on the luciferase activity, providing a quantifiable readout of the effects of P4 and BPA on PGR transactivation.
To investigate the molecular changes, the authors utilized quantitative real‐time reverse transcription‐polymerase chain reaction (qRT‐PCR). This method was used to quantify the mRNA expression levels of PGR, TRIM22, TP53, and GAPDH (as an internal control) in the treated cells. The precision of qRT-PCR enabled the researchers to quantify minute changes in gene expression, essential for understanding the cellular response to BPA and P4.
The researchers conducted MTT assay which is a colorimetric assay for assessing cell metabolic activity, was employed to evaluate the cytotoxic effects of the test substances on MCF-7 cells. This assay provided insights into the viability of the cells post-treatment. Additionally, they used an Annexin V-FITC Apoptosis Detection Kit to measure the rate of apoptosis in the cells. The technique involved staining the cells with annexin V and propidium iodide and analyzing them via flow cytometry, offering a detailed view of the apoptotic processes in response to the treatments. To understand how BPA interferes with P4 signaling, the authors investigated how BPA affected P4-induced apoptosis and viability changes in the MCF-7 cells. They analyzed the concentration-dependent effects of BPA on the P4-induced cellular responses, illuminating the interactions between these compounds within the cellular environment. Moreover, Dr. Masahiro Ogawa and colleagues found that P4 increased TRIM22 mRNA levels in a dose-dependent manner, indicating its role in P4-mediated cellular processes in MCF‐7 cells. TRIM22, known for its involvement in apoptosis, was significantly affected by P4, as its knockdown altered cell viability and apoptotic responses. The study also revealed that P4 increased TP53 mRNA expression, which is integral to cellular apoptosis and survival pathways. Additionally, they demonstrated that BPA significantly decreased P4-induced TRIM22 and TP53 mRNA expression in a dose-dependent manner.
In conclusion, the authors’ study represents a methodologically robust and scientifically significant effort to understand the complex dynamics between environmental chemicals and hormonal pathways in breast cancer. By employing a range of sophisticated techniques, from cell culturing to molecular biology assays, the researchers have provided valuable insights into the potential mechanisms through which BPA interferes with P4 signaling in breast cancer cells. According to the authors, TRIM22 can potentially be used as a biomarker for assessing chemical disruptions in hormonal signaling for more targeted and effective breast cancer treatments. The implications of this research are far-reaching, highlighting the importance of considering environmental factors in the context of cancer biology and treatment.
Ogawa M, Kitamoto J, Takeda T, Terada M. Bisphenol A prevents MCF-7 breast cell apoptosis via the inhibition of progesterone receptor transactivation. J Biochem Mol Toxicol. 2023 ;37(7):e23367. doi: 10.1002/jbt.23367.