Cancer patients often suffer from severe pain that cannot be treated effectively with traditional drugs. Scientists at the Institute of Pharmacology at the University of Heidelberg have now discovered the potential reason for the severe pain associated with several forms of cancer: tumours release two specific signalling substances that render the nerve cells particularly sensitive at the same time as enhancing tumour growth. In animal experiments, the researchers blocked the effect of these signalling substances on the nerve cells and found that both the sensitivity of the nerve cells and the growth of the tumour decreased.
The research results of the international group of researchers led by Professor Dr. Rohini Kuner show a new approach for the development of effective painkillers for cancer patients. The study was pre-published in the online version of the well-known journal "Nature Medicine".
Strong pain is one of the most severe and debilitating symptoms associated with cancer. The reasons for the strong pain are barely known. Pain associated with cancer does not react well to treatment with traditional painkillers, for example those of the opioid group. High doses are necessary in order for the painkillers to have any effect, which leads to major side effects and habituation. "We urgently need drugs specifically targeted at alleviating the pain experienced by cancer patients," said pharmacologist Professor Dr. Rohini Kuner who is particularly interested in clarifying the mechanisms associated with chronic pain.
In their current study, Kuner and her team have been investigating the blood serum and tissue of mice. They have discovered certain signalling substances that are released by tumours, including two molecules that had previously only been known as growth factors for haematopoietic stem cells. In their investigations of nerve activity using electrodes, the researchers were able to show that nerve cells in the environment of cancer tissue become far more pressure sensitive when they are in contact with the two molecules. “The findings are consistent with the observations of cancer patients who report that just touching the affected areas is very painful,” explains Professor Dr. Kuner.But it is not only touch that causes severe pain, the growth of the tumour also causes pain due to the fact that expanding tissue exerts pressure. It appears that the cancer cells use the growth factors for their own growth and dissemination in the organisms by way of nerve tracts and blood vessels. Injections for the treatment of tumour-associated pain?The discovery by the Heidelberg researchers opens up new perspectives in the fight against tumour-associated pain: in a subsequent step, the researchers injected mice with antibodies that block cancer signalling substances in the nerve cells’ receptors. The researchers found that both the sensitivity of the nerve cells and the tumour growth decreased.Further research will now have to be undertaken in order to show whether this application is also effective in human tissue. It would then be feasible to inject such “protein blockers” locally at the tumour site, which could lead to more effective pain relief and fewer side effects.
Contact:Professor Dr. Rohini KunerInstitute of PharmacologyUniversity of HeidelbergTel.: +49 (0)6221/54 82 89E-mail: rohini.kuner(at)pharma.uni-heidelberg.de