We are currently investigating these resistant cells for known mechanisms of chemotherapy and radiation resistance. We are also investigating how cells treated with radiotherapy become resistant to chemotherapy and the cellular response pathways involved.

We believe these unique cellular models will provide valuable insight into the relationship between chemotherapy and radiotherapy resistance.

Cancers that do not respond to chemotherapy usually do not respond to radiotherapy and similarly, cancers that are unresponsive to radiotherapy are also unresponsive to chemotherapy.

There is also evidence that cancers previously treated with radiotherapy show a reduced chemotherapy response compared to those not previously treated with radiotherapy.

Little is known about the relationship between radiation and chemotherapy resistance. A better understanding of this relationship is essential if we are to maximise the effectiveness of combined chemotherapy and radiotherapy. We have established cellular models in which to study this relationship.

Both human leukaemia cells and human small cell lung cancer cells have been treated with fractionated radiation using a similar schedule as that used in the clinic. This produced cell sublines that had increased resistance to radiation. This was accompanied by increased resistance to some chemotherapeutic drugs and increased levels of MRP1.