In addition to its association with cancer, hormonal problems, liver abnormalities, diabetes, and heart disease, exposure to bisphenol A (BPA)—the chemical the U.S. Food and Drug Administration (FDA) has deemed safe—has now also been found to reduce the effectiveness of chemotherapy treatments, according to University of Cincinnati (UC) scientists.
UC’s Nira Ben-Jonathan, PhD, led the study that found BPA induces a protein group that protect cancer cells from chemotherapy. “Resistance to chemotherapy is a major problem for cancer patients, especially those with advanced or metastatic disease,” says Ben-Jonathan, professor of cancer and cell biology at UC who has studied BPA for over 10 years. “Finding out what contributes to that resistance can give us an idea of what to target in order to make chemotherapy as effective as possible.”
BPA is used extensively in food and drink containers and baby bottles; is found in drinking water, dental sealants, and household dust; and can be found in the systems of nearly every American. In recent months, pressure has been mounting for government and corporate action, partly because BPA is so ubiquitous it is nearly impossible to avoid. Some governmental lawmakers have worked to ban BPA from children’s products and some companies, such as Wal-Mart, Toys R Us, and Naglene, are either not producing or selling BPA products or banning its use in its products.
And, yet, despite continuing and mounting evidence that BPA poses a danger to humans, the FDA—the agency charged with protecting Americans from such dangers—continues to maintain and defend BPA’s safety, instead of working toward a ban. “Right now, our tentative conclusion is that it’s safe, so we’re not recommending any change in habits,” said Laura Tarantino, head of the FDA’s office of food additive safety. Unfortunately, the FDA only seems to be listening to reports developed by industry and refuses to heed warnings issued by nonindustry-connected scientists.
Researchers suspect that BPA could play a role in cancer because of its structural similarities to a cancer-promoting compound called diethylstilbestrol (DES). “BPA does not increase cancer cell proliferation like DES does,” she says. “It’s actually acting by protecting existing cancer cells from dying in response to anti-cancer drugs, making chemotherapy significantly less effective.” Ben-Jonathan’s team studied human breast cancer cells, dosing them with low BPA levels consistent with levels found in the blood of human adults. The team found that BPA is acting in cancer cells similar to the way estrogen does—by inducing proteins that protect the cells from chemotherapy agents. Estrogen’s protein-inducing action has been linked to chemotherapy resistance; however, researchers have been unable to explain why this resistance occurs in some patients with less estrogen. Ben-Jonathan says her team’s research has important implications for this subgroup of patients.
“Patients with less circulating estrogen—post-menopausal women, for example—can also suffer from chemotherapy resistance,” she says. “Linking BPA to this problem gives us one more avenue to explore in terms of preventing chemotherapy resistance.”
“These data,” study authors write, “provide considerable support to the accumulating evidence that BPA is hazardous to human health.”
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