New breast cancer drug destroys deadliest tumors — even after they spread

CHAMPAIGN, Ill. — A new drug that wipes out the deadliest breast tumors may do things others can’t, a groundbreaking study reveals. In experiments on mice, a team from the University of Illinois reports this new approach to breast cancer treatment kills between 95 and 100 percent of diseased cells – even after they spread to the bone, brain, liver, and lungs.

Researchers are hopeful the small molecule, called ErSO, will be just as effective in human patients. The drugs works against estrogen-receptor-positive breast cancers. These account for up to eight in 10 cases of the disease, which predominantly affects women.

Illinois researchers on the study include, from front left, research scientist Chengjian Mao and graduate students Matthew Boudreau, Darjan Duraki and Ji Eun Kim. In the back row, from left, are molecular and integrative physiology professor Erik Nelson, chemistry professor Paul Hergenrother and biochemistry professor David Shapiro.

“Even when a few breast cancer cells do survive, enabling tumors to regrow over several months, the tumors that regrow remain completely sensitive to retreatment with ErSO,” says research co-leader and biochemistry professor David Shapiro in a university release.

“It is striking that ErSO caused the rapid destruction of most lung, bone and liver metastases and dramatic shrinkage of brain metastases, since tumors that have spread to other sites in the body are responsible for most breast cancer deaths.”

How does ErSO work?

Study authors explain that the drug relies on a protein called the estrogen receptor. When ErSO binds to this protein, it starts regulating the pathway in cells that preps cancer cells for growth and protects them from stress. The pathway, called the anticipatory Unfolded Protein Response (a-UPR), drives the production of proteins that protects cancer cells from damage.

“The a-UPR is already on, but running at a low level, in many breast cancer cells,” Shapiro explains. “It turns out that this pathway shields cancer cells from being killed off by anti-cancer drugs.”

“Because this pathway is already on in cancer cells, it’s easy for us to overactivate it, to switch the breast cancer cells into lethal mode,” adds graduate student and first author Darjan Duraki.

Different from any other breast cancer medication

The team notes their new approach to fighting breast cancer attacks the problem in a completely unique way.

“This is not another version of tamoxifen or fulvestrant, which are therapeutically used to block estrogen signaling in breast cancer,” Shapiro says.

Although ErSO binds to the same receptor as other treatments, it targets a different area of the estrogen receptor and sends the cellular pathways haywire.

“Since about 75% of breast cancers are estrogen-receptor positive, ErSO has potential against the most common form of breast cancer,” Matthew Boudreau adds. “The amount of estrogen receptor needed for ErSO to target a breast cancer is very low, so ErSO may also work against some breast cancers not traditionally considered to be ER-positive.”

The study shows mice taking ErSO did not experience any harm to their reproductive systems. It also resulted in few side-effects at doses well above those that doctors would prescribe to cancer patients.

German pharmaceutical giant Bayer AG has licensed ErSO with a goal of trying it on women with ER positive breast cancers. The researchers are also exploring if it’s effective against other cancers that feed off estrogen, such as those in the bowel.

The findings appear in the journal Science Translational Medicine.

SWNS writer Mark Waghorn contributed to this report.