LIKE treading on a hose with your foot, multiplying tumour cells could squash blood and lymph vessels and block the passage of anti-cancer drugs, scientists said yesterday.
The effect could help explain why some cancer treatments do not work as well as they should.
The American scientists at Massachusetts General Hospital in Boston studied the squashing effect by grafting human cancer cells into mice.
When the animals were treated with diphtheria toxin, which preferentially kills human rather than mouse cells, the tumours began to die off.
Analysis of the toxin-treated tumours showed that both blood and lymphatic vessels looked much more open than those in untreated tumours.
The experiment showed that taking the pressure off vessels by removing cancer cells could reopen them. However, although the treated blood vessels appeared to be functioning nearly normally again, treated lymphatic vessels were still not functional.
Professor Rakesh Jain, who led the study reported in the journal Nature, said work was still at an early stage.
The scientists warned that opening blood and lymph vessels may improve the efficiency of drug delivery, but would also enhance access for nutrients that can fuel a cancer.