Highly read on jem.rupress.org in December.

Chemotherapy kills cancer cells, but in colorectal cancer it can also stimulate their growth by activating cells called fibroblasts in the connective tissue.

Matthew Kalady and Jeremy Rich at the Cleveland Clinic in Ohio and their colleagues analysed tumours from patients with colorectal cancer before and after chemotherapy. The researchers found that the abundance of cancer-associated fibroblasts increased after treatment, and that these cells enhanced the ability of a subset of cancer cells to initiate tumour growth. The fibroblasts seem to do this by secreting signalling proteins, including one called IL-17A.

The findings suggest that chemotherapy can trigger drug resistance by changing the tumour's microenvironment. Disrupting this mechanism could be a way of improving cancer therapies, the authors say.

J. Exp. Med. 210, 2851–2872 (2013)