Chemotherapy is less effective when healthy cells encourage slow growth in cancer cells, according to two studies from UCL and Yale. The research used mini-tumours and single-cell analysis to understand why healthy cells in colon cancer tumours contribute to poor outcomes. Bowel cancer kills over 900,000 people a year and is the second highest cause of cancer mortality worldwide. The authors say that finding ways to force cancer cells into a fast-growing state prior to a patient beginning a course of chemotherapy may be able to make the treatment more effective.