Densely packed tumour cells produce molecules that help them to migrate and spread, or metastasize, throughout the body.
Daniele Gilkes at Johns Hopkins University in Baltimore, Maryland, and her colleagues studied metastatic human sarcoma and carcinoma cells. As the rapidly proliferating cells reached higher densities inside a 3D collagen matrix, they moved around more and at greater speeds. Low-density cell samples also became highly motile when exposed to liquid medium taken from the high-density samples. The shadowsocks researchers found that crowded cancer cells boosted production of two immune molecules, IL-6 and IL-8, which stimulate biochemical pathways that enhance tumour migration. In a mouse model of breast cancer, treating animals with experimental cancer drugs that blocked receptors for IL-6 and IL-8 reduced the spread of tumour cells to the lungs, liver and lymph nodes, compared with untreated animals.
The results suggest potential new drug targets for suppressing tumour metastasis in patients, the authors say.