May 29th 2008
From The Economist print edition
It may become possible to vaccinate against brain tumours
CERVICAL cancer is caused by a virus. That has been known for some time and it has led to a vaccine that seems to prevent it. Since then, researchers have been looking for other cancers that may be caused by viruses, to see if they too can be prevented. And they seem to have found one—one of the most feared of all. A piece of research expected to be unveiled on June 1st by Duane Mitchell of Duke University in North Carolina, at a meeting of the American Society of Clinical Oncology, hints that glioblastomas, the most lethal form of brain tumour, may also be susceptible to vaccination.
子宫颈癌由病毒引起的事实已知多时，并由此诞生了似乎能避免子宫颈癌的疫苗。从那时起， 科研人员一直在寻找由病毒引起的其它癌症，来看是否它们也能因此而被阻止。并且他们似乎找到了一种最令人恐惧的癌症的解决方法。这项研究成果预计将在六月 一日由位于北卡罗来纳杜克大学的Duane Mitchell在美国临床肿瘤学会的会议上公布。这项成果显示胶质母细胞瘤这种脑肿瘤中最致命的一种或许也会对疫苗敏感。
The story began a few years ago when Charles Cobbs of the California Pacific Medical Centre Research Institute in San Francisco found something odd about glioblastomas. He noticed they usually have a form of herpes, called cytomegalovirus, active within them. It is not that catching cytomegalovirus automatically causes a brain tumour—the virus is found, inactive, in about 80% of the population. Nevertheless, there is clearly some connection between virus and tumour, a connection reinforced by Dr Cobbs’s discovery that the virus appears to dwell inside the tumour but not in the healthy tissue surrounding it. This led him to speculate that the virus may be creating the tumour as a safe haven to support its own existence.
这个故事始于几年前，位于旧金山的加州太平洋医学中心研究所 的Charles Cobbs发现了胶质母细胞瘤的一些不寻常的地方。他注意到在这种肿瘤中活跃着一种叫做巨细胞病毒的疱疹病毒。这并不是说感染了巨细胞病毒会自动引起脑肿 瘤。这种存在于百分之八十人群中的病毒呈休眠状态。Cobbs医生的研究清楚的表明了这种病毒和肿瘤之间显而易见的关系。这种病毒寄居于肿瘤之中，但并不 存在于四周的健康组织。这个事实让他猜想也许这种病毒创造了肿瘤，使之成为支持其自身存在的安全之所。
After learning about Dr Cobbs’s work, Dr Mitchell and his colleagues first confirmed the basic findings. They discovered cytomegalovirus in the tumours of more than 90% of those people with glioblastoma whom they examined, but not in healthy brain tissue, nor in non-malignant brain tumours. They then began an experiment on 21 patients who had been diagnosed with glioblastoma.
得知Cobbs医生的工作之后，Mitchell医生和他的同事首先证实了这项基础的发现。他们发现了在他们检查的罹 患胶质母细胞瘤的病人当中有超过百分之九十的人的肿瘤中存在巨细胞病毒，但这种病毒并不存在于正常的脑组织或者是非恶性的脑肿瘤中。接下来他们在诊断患有 胶质母细胞瘤的二十一个病人中开展了一项实验。
Their intention was to encourage those patient’s immune systems to attack the tumours by training them to recognise the signs of active cytomegalovirus infection. To do that, they drew blood from their patients and exposed the immune-system cells within each sample to bits and pieces of cytomegalovirus, in order to encourage those cells to develop the power to identify the pathogen. The cells were then injected back into the patients they had come from, in the hope that those patients’ immune systems would react to cytomegalovirus as if they had encountered it naturally within the body.
他 们的打算是通过训练病人免疫系统来识别活跃的巨细胞病毒感染的特征来达到促使免疫系统攻击肿瘤的目的。为了做到这一点，他们抽取病人的血液，并使每个血样 中的免疫细胞接触到巨细胞病毒的碎片，从而达到促使这些细胞产生识别病原体的能力。接下来这些细胞被注射回相应的病人体内，并寄希望于那些病人的免疫系统 能够对在体内自然存在的巨细胞病毒产生反应。
The results are encouraging. The normal prognosis for glioblastoma is death within two years, even if a patient is treated with chemotherapy and radiation. Such treatment by itself is reckoned to slow the tumour’s growth by between six and eight months. When Dr Mitchell added his crude vaccine to the traditional treatment, this figure rose to more than a year—and in some people the tumours have stopped growing for more than two years, an observation that opens the door to work on a proper vaccine.
得到的结果振奋人心。胶质母细胞瘤通常的预后是即使病人接受化疗和 放疗也会在两年内死亡。这种疗法自身就能使肿瘤的生长减缓六个月到八个月。当Mitchell医生将他的初级疫苗加入到传统的治疗方法中，这个数字增加到 了多于一年，并且在一些人中肿瘤停止生长的时间超过了两年。这个发现为开发一种合适疫苗的工作开启了大门。
Just why active cytomegalovirus is associated with glioblastoma is still unclear. The virus may cause the tumour, as Dr Cobbs suspects, or the tumour may simply provide the virus with a congenial home. From the vaccine-maker’s point of view it hardly matters. If a vaccine causes the immune system to destroy infected cells, the cancer will be killed anyway. And that would be very good news indeed.
活跃的巨细胞病毒和胶质母细胞瘤相联系的原 因还不清楚。像Cobbs医生怀疑的那样，这种病毒或许引起了肿瘤，或者是肿瘤仅仅是为病毒提供了一个适宜的空间。从疫苗生产者的角度来看这几乎是无关紧 要的。如果一种疫苗能够使免疫系统破坏受感染的细胞，那么癌症总归能够被杀死。并且这的确将是一个非常好的消息。