Signal Substances in Cancer Pain Discovered

Researchers at the University of Heidelberg have discovered two signal substances released by tumors that may explain why cancer patients suffer from pain that cannot often be relieved with conventional medication.

During the study, led by Dr. Rohini Kuner, professor, Pharmacology Institute at Heidelberg, the researchers found two molecules in tissue samples taken from mice that had only before been known as growth factors for blood-forming stem cells. When the researchers tested nerve activity of these molecules with electricity, the researchers discovered that the nerve cells surrounding the cancerous tissue became much more sensitive to pressure. According to the researchers, the cancer cells also “use the growth factors for their own growth and spread through the nerve pathways and blood vessels to the rest of the organism,” which explains why even the growth of tumor cells can be painful.

“The findings are consistent with descriptions of cancer patients who say that merely touching the affected area is painful,” said Kuner.

In their study, published in Nature Medicine, the researchers said that the specific growth factors examined, granulocyte- and granulocyte-macrophage colony-stimulating factors, were “important in tumor-nerve interactions” and that “their receptors on primary afferent nerve fibers constitute potential therapeutic targets in cancer pain.”

This discovery may lead to the development of new treatments for cancer pain, the researchers noted. In the next step of the study, they injected proteins that blocked “the contact sites for cancer signal substances on the nerve cells,” which lessened the sensitivity of nerve cells and tumor growth.

Research must now be conducted to see if the same effect can be achieved in human tissue, the researchers said. If this can be done, “it would be conceivable to inject these Œprotein blockers directly into the tumor and thus reduce pain and side effects for the patient.”