There is a growing interest in the cancer risk posed by endocrine-disrupting chemicals (EDCs)in our environment. Steroidal EDCs interfere with the normal function of the endocrine system and have been associated with cancer. Currently, detection and monitoring of water sources for steroidal contamination of water relies on a laborious analysis of their chemical structures. Considering that many natural steroids are rapidly metabolized, their derivatives are frequently not present in the currently existing libraries and thus cannot be identified. In addition, it is unclear whether EDCs detected by chemical methods can elicit specific biological responses in mammalian systems.
Scientists at the National Cancer Institute's Laboratory of Receptor Biology and Gene Expression developed a high-throughput assay for testing biological activity of EDCs using mammalian cells that express GFP-tagged nuclear steroid receptor constructs. This automated assay is based on translocation of a fluorescent marker from the cytoplasm to the nucleus in the presence of a ligand that interacts with a specific receptor. The workflow utilizing for image-based screening of environmental contaminants with glucocorticoid activity using Perkin Elmer Opera Image Screening System is shown below:
Using this assay and studies of transcriptional activation, NCI scientists screened water samples collected from 14 states in the US and found androgen activity in 35% of samples, and a previously unrecognized glucocorticoid (GC) activity in 27% of the samples. Androst-4-en-3,6-dione was identified in one of the samples. Androgen receptor (AR)-dependent nuclear translocation and transcriptional activation was confirmed for two AR-responsive genes, NKX3.1 and RHOU. NKX3.1 is a homeobox gene frequently deleted in prostate cancers, and RHOU is implicated in epidermal growth factor receptor signaling and cell migration. Glucocorticoid receptor (GR)-dependent transcriptional activation was detected using several targets. Induction of a circadian rhythm gene, Per1, was confirmed at concentrations equal to those present in a water sample. This water site was positive in a sample obtained by extraction of a filter (POCIS membranes), as well as a grab water sample obtained several years later.
- Automated, highly reproducible, and low cost assay detects biologically active steroidal EDCs and is suitable for wide application in testing water samples.
- Testing for biological activity of many other steroid EDCs has not been previously performed
- Biological activity is determined more efficiently than chemical analysis
- High Specificity and selectivity
Stavreva D, et al. Prevalent glucocorticoid and androgen activity in US water sources. [PMID: 23226835]
- U.S. Patent Issued: U.S. Patent Number US 9,921,211, Issued 20 Mar 2018
- Foreign Issued: - Patent Number JP 6546311, Issued 28 Jun 2019