March 27, 2012

Link Between Opioids and Cancer Growth

(Ivanhoe Newswire) -- Opioid-based painkillers, such as morphine, have been the standard treatment of postoperative and chronic cancer pain for over 200 years. Two new studies show that opioid drugs may stimulate the spread and growth of tumors!

"Epidemiologic findings suggest that the type of anesthesia we do for cancer surgery influences recurrence rate, and laboratory studies demonstrate that opioids influence tumor progression and metastasis. These studies have caused anesthesiologists to re-evaluate how best to do anesthesia and pain control for cancer patients," Jonathan Moss, M.D., PH.D., professor of anesthesiology and critical care at the University of Chicago Medicine and co-author was quoted as saying.

One study led by Patrick Singleton, Ph.D., assistant professor of medicine at the University of Chicago Medicine, found that opioids that are already present in the body can enhance malignant tendencies of lung cancer cells transplanted in mice.

Researchers found that cells from human lung cancers have five to ten times as many opioid receptors as non-cancerous lung cells. Dr. Singleton's team mapped out two biochemical pathways, Akt and mTOR (both targets for chemotherapeutics), that are triggered by contact between the receptors and endogenous opioids.

In this study, human lung cancer cells with added opioids receptors grew more than twice as fast as tumor cells that lacked extra receptors. Also, they were 20 times more likely to spread to other parts of the body. Medications that are supposed to block opioids receptors, like naloxone, reduced tumor growth and spread, suggesting mu opioids receptor may be a therapeutic target.

The other study led by Andrey Bortsov, M.D., Ph.D., assistant professor of anesthesiology at the University of North Carolina, used human data to study the opioid-cancer link. Researchers observed survival rates from an earlier study of 2,000 breast cancer patients. The women being treated had a tiny genetic mutation that caused them to be less sensitive to opioids and were more likely to survive another ten years after treatment. Women with one copy of the mutation were twice as likely to have survived and those with two copies were four times more likely.

"The results of this study provide support for the hypothesis that endogenous and/or exogenous opioids, acting via the mu opioids receptor, may influence cancer outcomes," Dr. Bortsov was quoted as saying.

SOURCE: Anesthesiology, March 2012