On Language, Scientific Metaphor, and Endocrine Disruption: An Interview with Feminist Scientist Ana Soto

In the late 1980s, Professor of Immunology Ana Soto accidentally discovered the presence of synthetic estrogens in her lab equipment. Her lab had designed an experiment to test the effect of estrogen on the proliferation of human breast cancer cells (MCF7). Based on previous findings, Soto and her research partner Carlos Sonnenschein believed that, contrary to popular wisdom, the introduction of estrogen would not directly induce the proliferation of the cells, but would instead interfere with a naturally occurring inhibitor in the blood. But the control setup containing positive and negative controls (used in the past without problem) was now producing odd readings: although no estrogenic compound had been introduced, the cancer cells were still proliferating. Soto and Sonnenschein methodically removed each item in the control setup that might be producing the estrogen-like result. When they discovered that the estrogenic activity leached from the plastic centrifuge tubes used to store components of the cell culture medium, they called the manufacturer to find out what could have changed. The manufacturer let them know that the constituent materials of the tubes had recently been modified in order to reduce the possibility of breakage during centrifugation but declined to reveal what specific changes had been made. So Soto’s lab turned to studying the tubes themselves. After a year of further research, they concluded that the estrogenic activity was due to the additive that had been introduced by the manufacturer—nonylphenol, an antioxidant used in numerous other applications, some of which are meant for human use (e.g., spermicide) and the synthesis of detergents. Soto and Sonnenschein’s assay is called E-SCREEN and has been enormously influential; in fact, most of the environmental estrogens discovered in the 1990s rely on it. Conducted by Gracen Brilmyer at UCLA during the Chemical Entanglements Symposium, this 2017 interview with Soto highlights her experiences of sexism in the sciences and how those experiences have shaped her thinking on language, science, and scholarship