Cancer cells in neuroblastoma contain a molecule that breaks down a key energy source for the body's immune cells, leaving them too physically drained to fight the disease, according to new research.

Scientists have discovered that the cells in neuroblastoma - a rare type of childhood cancer that affects nerve cells - produce a molecule that breaks down arginine, one of the building blocks of proteins and an essential energy source for immune cells. 
Around 90 cases of neuroblastoma are diagnosed each year in the UK, mostly in children under five years old.

This molecule - called 'arginase' - creates a huge dip in the level of arginine found in the area around the tumor. As soon as the body's immune cells get close to the cancer, the sudden lack of their favorite energy source makes them lethargic and ineffective.

Neuroblastoma cells have a molecule on their surface that marks them out as different from healthy cells. This had led to hopes that the immune system might be trained to recognize and destroy them. But this new research may explain why early attempts to harness the immune system in this way have so far been unsuccessful.

Dr Francis Mussai, study author at the University of Birmingham, said, "We've known for a while that harnessing the power of the immune system could be an effective way to treat neuroblastoma. But we didn't know why the immune cells were having such difficulty recognizing and destroying the tumour.

"Armed with this new knowledge about the role of arginine, we may be able to activate the immune system to attack cancer cells."

Dr Carmela De Santo, co-study author from the University of Birmingham, said, "Now the challenge is to develop new drugs which stop neuroblastoma from using arginine, and may make immune therapy more effective."

Citation: Mussai, F., et al, Neuroblastoma arginase activity creates an immunosuppressive microenvironment that impairs autologous and engineered immunity. Cancer Research, 2015. DOI: 10.1158/0008-5472.CAN-14-3443