Researchers at the University of Michigan Rogel Cancer Center have determined cancer cells seize control of the metabolic pathways within specific immune cells to suppress the immune system and accelerate tumor growth.

Immune suppressor cells that exist in cancerous tumors block the body’s natural defense system, and a high volume of these immune suppressor cells can render the immune system ineffective at fighting tumor growth.

Previously, researchers had little understanding of what caused the development of immune suppressor cells but did recognize the necessity of a healthy immune system in the battle against cancer. Immunotherapy, which harnesses a patient's own immune system to fight cancer, has been very successful for survivors of certain cancers.

“Immunotherapy includes treatments that work in different ways,” the American Cancer Society states on its website. “Some boost the body’s immune system in a very general way. Others help train the immune system to attack cancer cells specifically.”

The limited understanding of the immune-suppressing cells makes it difficult to treat certain types of cancers using immunotherapy. Cancers, such as triple-negative breast cancer – the cancer cell line used in this research because of its prominent immune suppressor cells – are especially difficult to treat. Triple-negative breast cancer lacks three common receptors that stimulate tumor growth, making it harder to treat.

“Since the tumor cells lack the necessary receptors, common treatments like hormone therapy and drugs that target estrogen, progesterone, and HER-2 are ineffective,” the National Breast Cancer Foundation states on its website. Chemotherapy is often a triple-negative breast cancer patient’s only option.

Weiping Zou, a renowned professor of surgery and primary researcher in the study, explained the issue with current immunotherapy treatment.

“Immunotherapy works very well for some patients, but not everyone is responsive to the treatment,” Zou said. “Through this study we hope to improve the current treatment to make it better for more people.”

During the project, the researchers studied the tumors’ growth in mice, approved by the committee on Use and Care of Animals at the University of Michigan. They were able to measure the growth of the tumors and find the factors that caused the processes within them. The researchers also studied cultivated cells separately. Extensive measurements were taken during the experiment on tumor growth and cell production which were then analyzed using various data analytical techniques.

Dr. Inka Kryczek, Research Assistant Professor of Surgery, summarized the various parts of the process they studied.

“We looked at the metabolic pathways, the immunosuppressive cells themselves, and the biology of the tumor. It proved to be a very comprehensive study.” said Kryczek.

The new research sheds some light on what could be causing the development of the immune suppressor cells. A link found between the metabolic production of glycolysis and the number of the immune suppressor cells present in the tumor showed a direct correlation between an increase in glycolysis and an increase in immune suppressor cells.

Zou believes the discovery can lead to new treatments for patients that exhibit high numbers of the immune suppressor cells.

“We hope we can manipulate the metabolic pathways to develop an immunotherapy approach to help these patients,” Zou said.

Zou also anticipates the research will inspire other researchers to develop better techniques for treatment.

“It is important for people to hear this message," Zou said. "We are working very hard to help as many patients as possible.”

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