Study: Morphine Stimulates Breast Cancer Growth in Mice

Morphine, a common treatment for severe cancer pain, has been shown to stimulate the growth of breast tumors in mice, according to researchers at the University of Minnesota.

Morphine stimulates signals in endothelial cells that spur the growth of tumors in mice, according to the study published in Cancer Research. Researchers said there is currently no scientific evidence that indicates that morphine will lead to increased growth of cancers in humans.

The mice in the study were given doses of morphine similar to what is given to cancer patients. The drug activates a signaling pathway in human endothelial cells (cells that form blood vessels). The signaling pathway promotes endothelial cell multiplication and angiogenesis (formation of new blood vessels). Angiogenesis can promote tumor growth by providing nutrients to the tumors and transporting cancer cells from a tumor to other areas of the body.

However, morphine did not promote initial or early growth of tumors, said Kalpna Gupta, PhD, assistant professor in the department of medicine and lead author of the study.

Researchers also discovered that morphine promotes the survival of endothelial cells by activating a key survival-signaling pathway inside these cells. Endothelial cell survival is critical to the process of the formation of new blood vessels.

"Despite the widespread use of morphine to treat pain in many medical conditions like cancer, little was known about how this drug affects blood vessels or cancer," said Gupta. "Our study shows that morphine stimulates the formation of new blood vessels inside the tumor, which in turn allows increased growth of tumors in mice."

Researchers are hopeful that their findings will lead to new treatments to manage cancer pain that do not stimulate the formation of new blood vessels.

Other sources: University of Minnesota