New Osteoporosis Drug Curbs the Growth of Breast Cancer Cells Even in Resistant Tumors

A new drug approved in Europe to cure Osteoporosis displays other side benefits - the drug stops the growth of breast cancer cells.

In the past few generations breast cancer treatments have come a long way. Breast cancer is treated with radiation therapy, chemotherapy and hormonal therapy, all of which  have significant side effects. There are times when the breast cancer cells get resistant to the targeted therapies. For such cases a new drug approved in Europe offers a new hope to the cancer victims.

A latest finding by researchers at the Duke Cancer Institute found that a new drug called bazedoxifene not only arrests estrogen from fueling breast cancer cells growth but also marks the receptors of estrogen for destruction. This drug works even if the cancer has become resistant to the targeted therapies.

 "We found bazedoxifene binds to the estrogen receptor and interferes with its activity, but the surprising thing we then found was that it also degrades the receptor; it gets rid of it," senior author Donald McDonnell, PhD, chair of Duke's Department of Pharmacology and Cancer Biology, said in a press statement.

Tests were conducted on animal and cell cultures and the researchers noticed that the drug repressed growth not only in estrogen dependent breast cancer cells but also in those cells that were resistant to the tamoxifen and aromatase inhibitors that are widely used drugs to treat cancer.

The new pill Bazedoxifene belongs to a class of drugs called specific estrogen receptor modulators (SERMs). What makes this drug different is its capacity to play the role of estrogen in some tissue and blocking estrogen activity in other tissues. This drug is slightly different from the drug tamoxifen as it has properties of a new drug; the selective estrogen receptor degraders or SERDs that have the ability to target the estrogen receptor for destruction.

"Because the drug is removing the estrogen receptor as a target by degradation, it is less likely the cancer cell can develop a resistance mechanism because you are removing the target," said lead author Suzanne Wardell, PhD, a research scientist working with McDonnell's lab.

Dr Wardell states that it was earlier believed that if the breast cancer cells develop resistance to tamoxifen, then they will be resistant to the other drugs as well that target estrogen receptor. But in this latest study it was noticed that even if the cancer cells develop resistance to tamoxifen the estrogen receptor remains a good target.

The findings were presented on 15 June 2013, at the annual Endocrine Society meeting in San Francisco.