Breakthrough allows drugs across blood brain barrier

Scientists from the University of Oxford have developed a way of delivering drugs more effectively to treat cancers in the brain (Journal of the National Cancer Institute).

Research with in mice and tissue samples took a protein called TNF that can track down sites in the brain where cancer has spread by recognising a marker found only on tumour blood vessels.

The scientists found that TNF can home in on these sites and temporarily open the blood-brain barrier allowing drugs to pass from the blood system into the tumour.
Normally, the barrier acts as a shield preventing toxic compounds and organisms such as bacteria entering the brain. Not surprisingly, this same shield stops cancer drugs reaching tumours that have spread to the brain. A number of natural compounds are however known to easily cross the same shield.

Interestingly, the TNF protein only broke down the barrier in the blood vessels that pass through the tumour, leaving the healthy parts of the brain undamaged by potentially toxic drugs.  For example, the research shows that when TNF is injected into the bloodstream the breast cancer drug herceptin, which is not normally able to cross the blood-brain barrier, can reach cancer cells in the brain.

As well as preventing drugs reaching tumours in the brain, the same barrier prevents the early diagnosis of the tumour’s spread to the brain as the dyes used to highlight the tumour cannot penetrate the barrier. This new approach will also allow diagnostic dyes to access the tumour and enable earlier diagnosis.

Study author Dr Nicola Sibson said: “Treatments that work very well against the original site of the cancer lose their effectiveness when the cancer spreads to the brain – as these drugs are prevented from getting to the tumour because of the blood-brain-barrier.

A number of attempts have been made to open up the blood-brain barrier but they’ve all struggled because they’re either not specific enough to open the BBB only at the site of the tumour or not effective enough to allow the drug across to kill the cancer.”

Potentially, this new work is a game changer.

 

July - Oct 2013 Cancer Watch
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