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寨卡病毒或可治療腦癌
07/09/2017

馮維維

圖片來源:SHERBROOKE CONNECTIVITY IMAGING LAB/SCIENCE PHOTO LIBRARY

 

寨卡病毒會導致嬰兒出生後存在嚴重腦損傷,但人們或可利用這種病毒抵抗成年人腦瘤。

 

寨卡病毒約在4年前從波利尼西亞到達南美洲,它在懷孕女性中尤為危險。它會導致頭小畸形(異常的小頭癥),並與母親懷孕時感染病毒的嬰兒出現神經問題存在關聯,此外還會導致更高的流產率。

 

寨卡病毒之所以如此,是因為它與大多數微生物不同,會從血液進入大腦,並在那裏感染及殺死幹細胞,對發育大腦造成嚴重負面影響。

 

但寨卡病毒影響大腦幹細胞的能力已被證實或對抵抗致命腦癌具有幫助,很多腦癌是由於幹細胞變異造成的。

 

美國加州大學聖疊戈分校的Jeremy Rich和團隊通過惡性膠質瘤(最常見的腦癌)測試了寨卡病毒。惡性膠質瘤是最難治愈的癌癥之一,即便在經過手術和其他治療之後,它通常還會在一年內導致病人死亡。

 

該團隊發現,將生長在培養皿中的惡性膠質瘤的樣本暴露給寨卡病毒之後,會損傷癌癥幹細胞。通常這些幹細胞會導致病人死亡,因為它們對所有可獲得的療法具有抵抗力。

 

當該團隊在未罹患癌癥的成年人的普通腦細胞上驗證寨卡病毒後,他們發現該病毒並不會影響組織,這或許可以解釋為什麼寨卡病毒鮮少在成年人中致病。

 

接下來,該團隊在植入惡性膠質瘤的小鼠體內驗證了該病毒。通常,這一類老鼠會在1個月內死亡,然而那些註射了寨卡病毒的小鼠生命會更長,9只小鼠中有4只小鼠在兩個月後依然存活。

 

Rich表示,目前尚不清楚這種機制在人體中會如何轉化,因為該疾病對小鼠的影響不同於人類。

 

研究人員並未計劃在患有腦癌的人中間驗證寨卡病毒,因為他們擔心它會被傳播給孕婦:美國一些區域發現了攜帶寨卡病毒的蚊蟲,該病毒可以通過性傳播。與此相對,該團隊計劃了解是否可以對該病毒進行基因編輯,使其變得更加安全,同時在研究將其作為腦癌的潛在療法。

 

 

 

Zika virus used to treat aggressive brain cancer

 

Brain tumourImage copyrightGETTY IMAGES

A harmful virus that can cause devastating brain damage in babies could offer up a surprising new treatment for adult brain cancer, according to US scientists.

Until now, Zika has been seen only as a global health threat - not a remedy.

But latest research shows the virus can selectively infect and kill hard-to-treat cancerous cells in adult brains.

Zika injections shrank aggressive tumours in fully grown mice, yet left other brain cells unscathed.

Human trials are still a way off, but experts believe Zika virus could potentially be injected into the brain at the same time as surgery to remove life-threatening tumours, the Journal of Experimental Medicine reports.

The Zika treatment appears to work on human cell samples in the lab.

a virus in the brainImage copyrightGETTY IMAGES
Image captionThe virus would need to be delivered directly to where it is needed in the brain

There are many different types of brain cancer. Glioblastomas are the most common in adults and one of the trickiest to treat.

They are fast growing and diffuse, meaning they spread through the brain, making it difficult to see where the tumour ends and the healthy tissue begins.

Radiotherapy, chemotherapy and surgery may not be enough to remove these invasive cancers.

But the latest research, in living mice and donated human brain tissue samples, shows Zika therapy can kill cells that tend to be resistant to current treatments.

It is thought that these glioblastoma stem cells continue to grow and divide, producing new tumour cells even after aggressive medical treatment.

Different, healthy stem cells are found in abundance in baby brains, which probably explains why regular Zika can be so damaging to infants, say the researchers.

Adult brains, however, have very few stem cells. This means Zika treatment should destroy only the cancer-causing brain stem cells without causing much collateral damage.

As an extra safety precaution, the team, from Washington University School of Medicine and the University of California San Diego School of Medicine, have already begun modifying the virus to make it more tame than regular Zika.

Researcher Dr Michael Diamond said: "Once we add a few more changes, I think it's going to be impossible for the virus to overcome them and cause disease.

"It looks like there's a silver lining to Zika. This virus that targets cells that are very important for brain growth in babies, we could use that now to target growing tumours."

He hopes to begin human trials within 18 months.

Using viruses to fight cancer is not a new idea, but using Zika as the weapon of choice is.

UK scientists at the University of Cambridge are beginning similar trials with Zika.

Dr Catherine Pickworth, from Cancer Research UK, said: "This promising research shows that a modified version of the Zika virus can attack brain tumour cells in the lab.

"This could one day lead to new treatments for this particularly hard to treat type of cancer."


Zika

Baby with microcephalyImage copyrightREUTERS
Image captionZika infections in pregnancy have been linked to cases of microcephaly in newborns
  • Zika is a virus people can catch if they are bitten by an infected mosquito
  • Most people will have few or no symptoms, but the disease can pose a serious threat to babies in the womb
  • Affected infants have been born with abnormally small heads and underdeveloped brains - a condition known as microcephaly
  • The infection has been linked to severe birth defects in almost 30 countries
  • Although Zika is no longer "an international medical emergency", the World Health Organization says it is closely monitoring the infection

 

http://www.bbc.com/news/health-41146628

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