Opioid painkillers may stimulate cancer growth

Dec 1, 2009

Two studies were presented at “Molecular Targets and Cancer Therapeutics” in Boston, Massachusetts that highlighted the mu opiate receptor as a potential therapeutic topic. This was a joint meeting of the National Cancer Institute, the American Association for Cancer Research and the European Organization for Research and Treatment of Cancer.

The mu opiate receptor is where morphine works, a painkiller commonly used to treat chronic cancer pain. Several years ago, a drug called methylnaltrexone (MNTX) was found to block morphine from crossing the brain barrier without interfering with pain relief, and a study published in February 2009 indicated that patients who took MNTX lived longer than expected. This led to further research.

In the two studies that were presented in Boston, the researchers focused on the mu opiate receptor as it related to regulation of tumor growth and metastasis and examined how MNTX can attenuate the effects. Using bronchioloalveolar carcinoma cells in a cell culture model, one study found that MNTX prevented tumor cell proliferation and migration and blocked oncogenic signaling. The other study looked at Lewis lung carcinoma cells in mice. Mice without the mu opiate receptor didn’t develop tumors when injected with the cancer cells, but normal mice did. The researchers also found that the use of MNTX reduced the proliferation of cancer cells in normal mice by 90 percent. The authors of the second study concluded that the mu opioid receptor promoted tumor growth, angiogenesis and metastasis of Lewis lung cancer in mice, and that MNTX attenuated these effects.

It is important to note that these findings have not yet been proven in human clinical trials, only in cell culture studies and in mice. If they are confirmed clinically, the use of opioid antagonists like MNTX may become more important in the treatment of cancer pain.

For the full story, go to Science Daily.

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