Peter Mac tests tumour-cell zapper

Researchers at Melbourne's Peter MacCallum Cancer Centre have begun testing a high-precision, antibody-mediated system to deliver short-range radionuclides to cancerous cells.

Lead researcher Dr Tom Karagiannis said the experimental therapy involved conjugating a class of radionuclides called auger-electron emitters to the monoclonal antibody therapy Cetuximab, which binds to tumour cells that over-express epidermal growth factor (EGF).

The monoclonal delivers a lethal package comprising a Hoechst DNA-intercalating drug, conjugated to the radioisotope iodine-125, or the shorter-lived iodine-123 radionuclide, produced by the Australian Nuclear Science and Technology Organisation at its Lucas Heights reactor.

The decaying iodine radioisotopes emit low-energy ionising radiation that operate at extremely short range, damage the tumour cells' DNA, and inducing programmed cell death -- apoptosis.

Karagiannis said the ionising radiation's damaging effects are limited to a volume of a millionth of a cubic millimeter, so there is virtually no damage to surrounding, health tissues that do not over-express EGF receptors.

So far the new technique, which Karagiannis describes as the most specific and precise yet developed for treating cancer, has been tested only in cellular systems, on a cancerous cell lines that over-express the EGF receptor, and another that over-expresses the iron-transport protein transferring.

Karagiannis said the technique, if successful, should be particularly suited to killing metastatic cells liberated from primary tumours, established, metastatic micro-tumours, and residual cancerous deposits missed by surgery.