Primary tumour cells that have been starved of oxygen have been shown to have a survival advantage when spreading to different parts of the body to form new tumours.

Over 90% of solid tumours are oxygen deprived. Known as hypoxia, this is associated with poorer prognosis for patients. This was thought to be due to the increased tendency of oxygen deprived cells to leave the primary tumour and move into the bloodstream. In a process known as metastasis, the cancer cells can circulate until they are able to colonise another tissue and multiply to form a secondary tumour.

The researchers used a fluorescence switch to light up cancer cells exposed to oxygen concentrations lower than 0.5%. They were then able to track the movement of both oxygen deprived cancer cells and normal cancer cells away from primary breast cancer tumours, in both miniature organ and mouse models.

It was found the cancer cells subjected to hypoxia were four times more likely to become viable tumour circulating cells, enhancing their metastatic ability. It was also found that hypoxia induced genetic changes within the cancer cells that help them survive the oxidative stress that they may experience travelling through the bloodstream. Some of the cells even retained these genetic changes after being reoxygenated.

Further research will investigate if hypoxic cells are more resistant to chemotherapy.

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