Bone cancer pain, caused by the destruction of bone by cancerous cells, may be relieved by a new treatment, according to US researchers at the University of Minnesota.
Osteoclasts, the cells which absorb bone material, are responsible for most cancer-induced bone destruction. They are present in increased numbers in cancerous bone and their formation is known to be blocked by osteoprotegerin (OPG), a protein related to the tumour necrosis factor receptor family.
The researchers report the effects of treatment with OPG on bone cancer and bone cancer pain in a study using a mouse model of bone cancer pain (Nature Medicine 2000;6:521). They injected OPG or vehicle into the femora of mice with induced bone cancer, and found that treatment with OPG eliminated the destructive osteoclasts from the site of the cancer and also reduced bone destruction and pain.
In addition, the researchers found that OPG inhibited the neurochemical changes in the spinal cord that are thought to be involved in the generation and maintenance of cancer pain. In the study, all mice were assessed for behavioural responses. Parameters of ongoing pain included activity-induced guarding and the number of spontaneous flinches. The number of palpation-induced fights and flinches were also determined. Activity-induced guarding decreased by 73.5+/-7.9 per cent with OPG treatment. The number of spontaneous flinches decreased by 44.5+/-7.7 per cent. In addition, treatment with OPG significantly reduced palpation-induced pain behaviours.
In an accompanying article (ibid, p504), Dr Stephen Thompson and Dr David Tonge of Guy's, King's & St Thomas's school of medicine, London, describe the study as "an exciting development for the treatment of a widespread and distressing symptom of cancer" and comment that the data have "consequences for the mechanisms that may underlie bone cancer pain and the therapeutic application of OPG."