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Researchers have found a way to target elusive cells that suppress immune response, depleting them with peptides that spare other important cells and shrink tumors in preclinical experiments. 

"We've known about these cells blocking immune response for a decade, but haven't been able to shut them down for lack of an identified target," said the paper's senior author, Larry Kwak, M.D., Ph.D., chair of Lymphoma/Myeloma and director of the Center for Cancer Immunology Research at The University of Texas MD Anderson Cancer Center, in the press release. 

The cells, dubbed myeloid-derived suppressor cells (MDSCs), are found in the microenvironment around tumors and are created with other blood cells in the bone marrow. They interfere with activation of T cells which are immune system's attack cells. These cells were observed in mouse models accelerating cancer progression and metastasis. 

"This is the first demonstration of a molecule on these cells that allows us to make an antibody, in this case a peptide, to bind to them and get rid of them," Kwak said. "It's a brand new immunotherapy target."

Researchers developed anti-cancer therapeutic vaccines that sparked an immune system attack against tumors. However the effectiveness was compromised by factors such as MDSCs that stifle immune response. "The key to taking cancer vaccines to another level is combining them with immunotherapies that target the tumor microenvironment," Kwak said.

Peptide antibodies developed by Kwak and co-discoverer, Hong Qin, Ph.D., assistant professor of Lymphoma/Myeloma, wipe out MDSCs in the blood, spleen and tumor cells of mice without binding to other white blood cells or dendritic cells involved in immune response, the press release added.

"That's really exciting because it's so specific for MDSCs that we would expect few, if any, side effects," Kwak said.

Researchers said they were working to develop the same target for use in humans.

The research has been published in the journal Nature Medicine.