A tumour's response to chemotherapy is shaped by interactions between the tumour and its microenvironment.

Mikala Egeblad at Cold Spring Harbor Laboratory in New York and her colleagues used in vivo microscopy to monitor tumours' responses to the chemotherapy drug doxorubicin in mice. They found that the drug is more effective in a mouse model of breast cancer with intermediate tumours rather than precancerous changes or late-stage tumours, and in animals that lack the enzyme MMP9, which acts on the protein matrix surrounding cells and tumours.

The improved drug response seemed to be linked to increased leakage from tumour blood vessels, which facilitates drug access. Moreover, mice lacking a receptor called CCR2 responded more strongly to doxorubicin than did mice with the receptor. Immune cells that express the CCR2 receptor are attracted to tumours as a result of doxorubicin treatment — this can promote tumour regrowth.

Drugs that inhibit MMP9 and CCR2 could be combined with traditional chemotherapies to boost cancer treatment success, the authors suggest.

Cancer Cell 21, 488–503 (2012)