In the rare inherited human disease, ataxia-telangiectasia (A-T), a mutation is present in a gene encoding a protein that normally activates cellular responses to DNA damage. The mutation in the ATM gene leads to decreased ability to repair damaged DNA, and an increased sensitivity to ionising radiation and other DNA damaging agents. This highlights the ATM pathway as a potential target to increase the sensitivity of tumour cells to radiotherapy or chemotherapy. The ATM protein demonstrates kinase activity and a selective, small molecule inhibitor of this kinase, CP466722, has now been shown to enhance the sensitivity of tumour cells grown in vitro to ionising radiation.
Inhibition of ATM kinase activity is rapid, and is completely and rapidly reversed on wash-out; further experiments suggested that inhibition of ATM for a short period of time may be sufficient to sensitise tumour cell to radiotherapy. Because CP466722 is effective in murine cells as well as human cells, it may be possible to use mouse models to further explore the potential of using ATM inhibitors to increase the effectiveness of radiotherapy.