Powering up radiotherapy

A way to boost the effectiveness of radiotherapy and protect patients and even astronauts from the effects of radiation exposure has been discovered by scientists atOslo University.

Radiotherapy causes side effects because the dose of radiation needed to destroy sufficient numbers of cancers cells also causes significant damage to healthy tissue. But the dose cannot be reduced or delivered in smaller amounts over time because radiation exposure also causes and effect called "radiation resistance" in the surviving cells, whereby subsequent doses of radiation are much less effective.

But now Erik Pettersen and Nina Edin at Oslo University have discovered the chemical basis of this resistance effect, meaning that if it can be selectively deactivated in cancer cells, or conversely boosted in healthy tissue, then the side effects of radiotherapy could be minimised by cutting down the dose.

They made the discovery by showing that growth medium from cells exposed to radiation can confer radio-resistance upon second batch of non-irradiated cells. This was the initial proof that a chemical signal of some kind must be being secreted by radiation-exposed cells. In the context of a human body exposed to radiation, this means that, paradoxically, radiation-exposed healthy tissue can also end up protecting the cancer cells by secreting the same signals.

Now they've identified the factor responsible, a signal called TGF-beta-3, which locks cells into a resistant state. Removing it from a tumour renders it vulnerable again, whilst elevating the signal in healthy tissue can lead to protection.

The potential benefits don't stop there though. As the researchers point out, the same trick could be exploited to protect humans from incidental radiation exposure - such as astronauts and high-altitude fliers - as well as patients undergoing high-dose x-ray investigations like CT scans...