Opposing Roles of Immune Cells in Breast Cancer

Immune system cells play polar opposite roles when it comes to breast cancer, new research suggests.

In a study published in Nature, investigator Kelly Kersten found that some immune cells contribute to metastasis, while others are activated to improve the effects of chemotherapy.

Kersten used mouse models with an invasive form of breast cancer that is comparable to metastasizing breast cancer in humans.

“We saw that the primary tumor caused an infectious response in the whole body, which makes it easier for metastases to occur,” Kersten said.

The investigators found that the immune cell neutrophil plays an active role, and the infectious response caused by the tumor results in the production of neutrophils, which begin to accumulate.

“We’ve known for some time that some immune system cells, T cells, work against the cancer, slowing down tumor growth,” Kersten explained. “It’s these favorable cells that are switched off by the neutrophils, which then makes it easier for the tumor to spread.”

The results of the study showed that the neutrophils are led by the domino effect of different immune reactions. The findings pushed Kersten to determine what it meant for the treatment of breast cancer.

“A lot of successful results have been achieved in patients using immunotherapy, where the person’s own immune system is activated to remove the tumor,” Kersten said. “This is already part of the treatment for lung and skin cancer, but not yet for breast cancer. So we tested a particular kind of immunotherapy in the same kind of mice. We didn’t see very much effect from the immunotherapy alone, but we did see a change in combination with specific types of chemotherapy.”

Combining chemotherapy with immunotherapy caused an anti-tumor immune reaction that slowed the growth of tumors in mice, according to the study.

“This immune reaction is in fact the whole cascade of responses,” Kersten said. “We have now looked at the first steps in the cascade in patients.”

Kersten found that there was a positive correlation between different signal substances from this cascade in the tissue of patients with breast cancer.

“There is a particular link, also in humans, which could indicate that the casual relationship that we found in mice between this immune reaction and the metastases also applies in humans,” Kersten said.

Despite the positive findings, Kersten said more research needs to be done.

Currently, the Netherlands Cancer Institute is conducting clinical trials of immunotherapy in patients with breast cancer. According to Kersten, the treatment also tests the combination of chemo-immunotherapy.

“I am very curious about the outcome of this study,” Kersten said. “What I have found in my PhD research is very promising, but it is still a mouse and not a human being. More research is needed to determine whether our results can be translated to the clinical environment.”