'Traitor' white blood cells aid cancer spread

White blood cells, key defenders in the body's immune system, help activate cancer cells and aid their spread, a new study has found.

The study, led by investigators at the Research Institute of the McGill University Health Centre (RI-MUHC) in Canada, reveals that infection-fighting white blood cells play a role in activating cancer cells and facilitating their spread to secondary tumours.

"We are the first to identify this entirely new way that cancer spreads," said senior author Dr Lorenzo Ferri, MUHC director of the Division of Thoracic Surgery and the Upper Gastrointestinal (GI) Cancer Programme.

"What's equally exciting is medications already exist that are being used for other non-cancer diseases, which may prevent this mechanism of cancer spread or metastasis," Ferri said.

"Our first clue of this association was from our previous research, which showed that severe infection in cancer patients after surgery results in a higher chance that patients will have the cancer return in the form of cancer metastasis.

"This led us to investigate the cellular players in the infection, notably neutrophils, the first and most numerous of the white blood cells that are used by the immune system fight off infections," he said.

Ferri and his colleagues from McGill University and the University of Calgary used both cultured cells and mouse models of cancer to show that there is a relationship between infection, a white blood cell response (inflammation) and metastasis.

A web-like network called Neutrophils Extracellular Traps (NETs), is produced by white blood cells (neutrophils) in response to an infection and this normally traps and kills invading pathogens, such as bacteria.

"We demonstrated that in the case of infected animals with cancer, the neutrophil web (NETs) also trapped circulating cancer cells," said Dr Jonathan Cools-Lartigue, first author of the study, from the LD MacLean Surgical Research Laboratories at McGill University.

"Instead of killing the cancer cells, these webs activated the cancer cells and made them more likely to develop secondary tumours, or metastasis," Cools-Lartigue said.

The researchers went one step further and showed that breaking down the neutrophil web is achievable by using certain medication.

Furthermore, in mice with cancer, markedly less tumour growth and metastasis occurred after the medication was administered.

This finding was true for a number of different cancer types, suggesting that neutrophil webs may be a common pathway involved in the spreading of many cancers.The study was published in the Journal of Clinical Investigation.