吗啡可促进肿瘤增长

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吗啡可促进肿瘤增长

据路透社芝加哥电，美国研究人员周三声称，越来越多的证据表明：通常用于止痛的吗啡可加速癌症增长，但是，一种新研制的药物可防止吗啡的这个副作用，且阻止肿瘤扩散。他们说，Progenics制药公司出品的药物Relistor,以往用于治疗镇痛药如吗啡等引起的便秘，现在被发现，可改善小鼠肺癌导致的肿瘤不适反应。
“这确实是一项惊人的发现！”芝加哥大学医学中心的帕特里克.苏灵顿在一次波士顿癌症会议说，他在两项研究中的得到了该发现，同时在电话采访中表示：该药物可以有效阻断肺癌的进展！”，并且说多项研究结果已开始提示，镇痛药物促进肿瘤细胞生长、加速癌症扩散。
在2002年一项关键性研究显示：脊椎给予吗啡的癌症病人的生存期远长于全身给药的病人。最近在爱尔兰的两项研究中也发现，乳腺癌和前列腺癌病人进行局部镇痛治疗后，其肿瘤复发机率远比全身治疗要小。
苏灵顿和乔纳森莫斯大学的前期研究表明：吗啡可以提高肿瘤的生长速度，抑制机体免疫反应。吗啡促进新生血管生长即血管生成，并使血管脆性增加，这会导致血管内肿瘤细胞向全身扩散的机会增加。在最新研究中，研究小组特别观察了药物Relistor以及甲基纳曲酮用于癌症细胞在阻断阿片受体或者分子通道时的作用。在实验器皿中，甲基纳曲酮可以阻断肺癌细胞的扩散。转基因老鼠因缺乏阿片受体，当它们注射入癌症细胞后不会发展为肿瘤，而正常的老鼠则会演变为肿瘤。
百分之九十的影响
他们还表示该药物对于90%的正常老鼠可以减低肿瘤细胞的扩散速度。苏灵顿说：“这些研究都表明一个非常有趣的事实，即多种类型的肺癌，均可过表达阿片受体，且它们与癌症的扩散、转移、入侵有关。而药物甲基纳曲酮看起来能够阻断肿瘤的生长和入侵。该药物不能够改变麻醉作用，但是确实改善了阿片类的副作用。而另一方面的作用会被证实，在癌症进程中非常重要。苏灵顿说，下一步将研究该药物对人体肿瘤的影响。
上月，于2005年在惠氏公司获得药物合格认证的Progenics与惠氏母公司达成协议，重新获得全球范围内的Relistor的专利权，并确认在一年过度期后的未来发展和销售权。

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Pain drug morphine may accelerate cancer growth
止痛药物吗啡可促进癌细胞生长

CHICAGO (Reuters) – Evidence is mounting that morphine, commonly used to manage pain, may accelerate cancer growth, but a newly-approved drug that blocks its side effects could also keep tumors from spreading, U.S. researchers said on Wednesday.
They said the Progenics Pharmaceuticals Inc drug Relistor, which is used to treat constipation caused by pain drugs like morphine, appeared to reverse some of the tumor-causing effects in mice and in lung cancer cells.
"It's a surprising finding, really," said Patrick Singleton of the University of Chicago Medical Center, who presented findings from two studies at a cancer meeting in Boston.
"This drug might actually inhibit the progression of lung cancer," Singleton said in a telephone interview.
He said several studies have begun to show that opiate-based pain drugs stimulate cancer cell growth and foster the spread of cancers.
A key study in 2002 showed that cancer patients who were given morphine delivered to the spine, rather than releasing the drug throughout the body, tended to live longer.
And two recent studies in Ireland found that breast and prostate cancer patients who got regional rather than general anesthesia were less likely to have their cancer return.
Prior lab studies by Singleton and colleague Jonathan Moss have shown that morphine can boost tumor cell growth and inhibit the immune response.
They also found that opiates promote the growth of new blood vessels, a process called angiogenesis, and can make blood vessels leaky, which could increase the chances that tumor cells in the blood can spread in the body.
In the latest studies, the team looked specifically at the effects of blocking opiate receptors or molecular doorways on cancer cells with the drug Relistor, or methylnaltrexone.
Methylnaltrexone prevented lung tumor cells from spreading in lab dishes. Mice genetically altered to lack the opiate receptor called mu did not develop tumors when they were injected with cancer cells, but normal mice did.
90 PERCENT EFFECT
They also showed that the drug reduced the spread of cancer cells by 90 percent in normal mice.
"One very interesting thing these studies are showing is that many types of lung cancer have overexpression of these opiate receptors and they seem to be involved in cancer proliferation, migration and invasion," Singleton said.
"And the drug methylnaltrexone seems to inhibit cancer growth and invasion."
Singleton said the drug does not alter the effect of the anesthesia, but it does alter some of the side effects of opiates. "One of the side effects may turn out to be very important in terms of cancer progression," he said.
Singleton said the next step is to see how the drug affects cancer in people.
Last month, Progenics, which had licensed the drug to Wyeth in 2005, reached a deal with Wyeth parent Pfizer Inc to regain worldwide rights to Relistor and assume control of future development and sales after a one-year transition.

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