In a small, early-stage clinical trial, an antibody seems to slow the growth of tumours by decreasing the number of cancer-boosting immune cells in and near the tumours.

Some immune cells known as macrophages promote tumour growth and are regulated by a protein, CSF-1, and its receptor. Carola Ries at Roche in Penzberg, Germany, and her colleagues produced an antibody that blocks this receptor and tested it in seven patients with a rare cancer of the joints. The researchers found that the antibody lowered the number of macrophages in one patient from whom a biopsy was taken, and shrank tumours in five of the patients. In people with other types of tumours, the antibody also depleted tumour-associated macrophages and shifted the ratio of another type of immune cell, T cells, towards those that fight tumours.

Targeting macrophages, in combination with other chemo- or immunotherapies, could improve treatment, but further testing in humans is needed, the authors say.

Cancer Cell http://doi.org/s3m (2014)