Exposure to bisphenol A, a chemical commonly found in plastic food containers, may reduce the effectiveness of chemotherapy treatments, according to researchers who studied the effects on human breast cancer cells.

Resistance to chemotherapy is a major problem, especially for people with advanced cancer. The researchers aimed to find what contributes to resistance in the hopes of improving how well chemotherapy works.

Scientists have suspected that BPA may play a role in cancer since the chemical is structurally similar to a cancer-promoting compound called diethylstilbestrol or DES. But the high doses of BPA used in many studies has produced conflicting results.

In Wednesday's online issue of the journal Environmental Health Perspectives, Nira Ben-Jonathan, a professor of cancer and cell biology at the University of Cincinnati, and her colleagues, said they found BPA doesn't actually mimic the action of DES.

Boosting immortality of cancer cells

"BPA does not increase cancer cell proliferation like DES does," Ben-Jonathan said. "It's actually acting by protecting existing cancer cells from dying in response to anti-cancer drugs, making chemotherapy significantly less effective."

To come to that conclusion, the team exposed human breast cancer cells to low levels of BPA similar to those found in the blood of adults.

"BPA at environmentally relevant doses reduces the efficacy of chemotherapeutic agents," the study's authors concluded. "These data provide considerable support to the accumulating evidence that BPA is hazardous to human health."

BPA acted in a similar way to estrogen, leading proteins to be produced that protect cells from chemotherapy.

The findings may help explain why some women with less estrogen, such as post-menopausal women, become resistant to chemotherapy, Ben-Jonathan said.