Can an existing drug win against aggressive breast cancer?

Triple-negative breast cancer, which is a particularly aggressive form of the disease, often has very poor outcomes; it is resilient in the face of current treatments. But scientists now say that an existing form of antimicrobial therapy is where we should look next in the fight against this form of breast cancer.

According to recent studies, breast cancers are the second most commonly diagnosed type of cancer among women in the United States.

Triple-negative breast cancer is a resilient and especially aggressive subtype, accounting for approximately 15 percent of all diagnoses of breast cancer.

Triple-negative breast cancer is resistant to the commonest type of therapy currently applied: chemotherapy. This is partly due to the sheer endurance of stem-like cancer cells, which promote the formation of new tumors.

For this reason, scientists are permanently on the lookout for better, more effective treatment options that will prevent the migration of cancer cells within the body.

Now, researchers at the Case Comprehensive Cancer Center at Case Western Reserve University School of Medicine in Cleveland, OH, have revealed that triple-negative breast cancer cells may respond to an existing therapy used to treat other conditions, including multiple sclerosis (MS), called interferon-β.

"We demonstrate that interferon-β reverses some of the more aggressive features of triple-negative breast cancer, which are responsible for metastasis and therapy-failure. "

First study author Mary Doherty, graduate student at Case Western Reserve School of Medicine

"Moreover," she adds, "we found that evidence of interferon-β in triple-negative breast cancer tumors correlates with improved patient survival following chemotherapy."

The researchers' findings have recently been published in the journal PNAS.

Interferon-β targets cancer stem cells

Interferon-β is a cytokine, which is a type of protein involved in cell signaling. It has an antimicrobial effect and a complex immune-regulatory impact, which is why it has, so far, been used in the treatment of autoimmune diseases such as MS.

Doherty now explains that interferon-β also acts on the stem-like properties of breast cancer cells, impairing their ability to migrate and thus preventing the formation of metastatic tumors.

"While chemotherapy kills the majority of tumor cells, it fails to eliminate a subset of cancer cells, called cancer stem cells," Doherty explains.

"The survival of these cancer stem cells following therapy is believed to be responsible for therapy failure in patients," she notes. This is why interferon-β's suppression of these cells' activity could lead to improved treatment outcomes in the future.

In an in vitro study using human triple-negative cancer tissue, the team noted that interferon-β targeted cancer stem-like cells directly. The cytokine had a marked effect on the cancer tissue exposed to it, even after the researchers interrupted the exposure.

For the cancerous tissue that was treated with interferon-β in vitro, the migrating cells had halved, compared with the control tissues that had not been exposed to this treatment.

Moreover, cancer cells treated with interferon-β had a significantly reduced tendency for tumor sphere formation.

Analyzing data sourced from cancer tissue databases, the team also notes that, post-treatment, the breast cancer patients with the longest survival rates, as well as the lowest tumor recurrence rates, exhibited high levels of interferon-β.

More specifically, individuals with high interferon-β levels had an approximately 25 percent lower risk of tumor recurrence compared with the individuals with low levels of interferon-β.

Next steps on path to new treatment

Following these promising findings, Doherty and team are taking a closer look at the role played by interferon-β in immune-regulation, targeting its potential in boosting the body's immune response against cancer.

They are also hoping to start clinical trials for a possible interferon-β therapy and explore its effects on its own, or as a complementary pathway to chemotherapy.

One challenge that the scientists will face will be that of finding an effective way of delivering the interferon-β.

"Our future studies will examine improved methods of interferon-β delivery to the tumor site incorporating nanoparticle technology," Doherty explains.

The recent advances in medical technology, paired with the scientists' search for ever more effective treatments, deliver fresh hope in the fight against aggressive forms of cancer.