OVER THE past two decades Alexander Szalay, an astronomer at Johns Hopkins University in Baltimore, has helped create the most detailed maps of the cosmos yet made. His raw material comes from the Sloan Digital Sky Survey, which began in 2000. So far, this project has charted a third of the heavens and observed nearly 1 bn astronomical objects.
过去二十年，巴尔的摩的约翰・霍普金斯大学的天文学家亚历山大・萨莱（Alexander Szalay）协助绘制了迄今为止最详尽的宇宙地图。他的原始材料来自于自 2000 年启动的斯隆数字化巡天项目（Sloan Digital Sky Survey）。到目前为止，这个项目已经测绘了整个天空的三分之一，观测了近 10 亿个天体。
The survey’s telescope, which sits on a mountain top in New Mexico, collects its data by recording the arrival of photons of light on a charge-coupled device. This turns them into an electrical signal that Dr Szalay and his confrères translate into a representation of reality by winnowing out the noise and determining, from what remains, what sorts of objects the telescope is looking at and how far away they are.
Now, Dr Szalay has added a microscope to his telescope. In collaboration with Janis Taube, a colleague at Johns Hopkins who is a pathologist, he is developing AstroPath. This is a project that combines his knowledge of astronomy with hers of pathology into a system which does for images of cancer cells and tissues what the Sloan survey does for images of the universe.
现在，萨莱又在他的望远镜上加上了一台显微镜。他正与约翰・霍普金斯大学的同事、病理学家詹尼斯・陶贝（Janis Taube）合作，开发 AstroPath。这个项目将萨莱的天文学知识和陶贝的病理学知识融合起来，打造一个系统来测绘癌细胞和癌组织，就像斯隆项目绘制宇宙的图像一样。
Dr Szalay, ever handy with an astronomical analogy, compares the most common current approach to the examination of images of cancers—which is to look in great detail, but at only a few tumours—to studying the universe using the Hubble Space Telescope. This instrument can focus on only a restricted area of the sky, but is then able to record what it sees with immense precision by spending lots of time taking long exposures.
As a consequence, the Hubble has surveyed only 45 of the 41,253 square degrees which constitute the celestial sphere. By contrast, the Sloan survey has so far covered, in a more cursory manner, about 15,000 square degrees of that sphere. This sweeping approach lets astronomers understand the universe’s large-scale structure by seeing entire clusters of galaxies and the relationships between them.
也因此，哈勃只观测了天球 41253 平方度总面积中的 45 平方度。相比之下，斯隆项目采用的方法更粗略，目前为止覆盖了天球的大约 15000 平方度。借助这种笼统而全面的方法，天文学家可以观察整个星系团以及它们之间的关系，从而在宏观层面了解宇宙的结构。
Both methods are valuable. But because fewer cancer biologists use the second than the first, AstroPath is designed to fill the gap. The specialised microscopes the project uses capture images of broad slices of tumours, and do so in multiple wavelengths. These images are then subjected to data-analysis techniques developed as part of the Sloan survey.
In particular, AstroPath employs a technique called immunofluorescence to make its images. This works by using antibodies to attach fluorescent tags to specific sorts of protein molecules. That permits the distributions of these proteins throughout a tumour to be mapped cell by cell. So far, AstroPath can do this simultaneously for between 20 and 30 proteins. Dr Taube’s long-term goal is to do likewise for hundreds of individual tumours of more than 20 different types, enabling comparisons to be made both within and between types.
具体来讲，AstroPath 采用了一种叫做免疫荧光的方法来生成图像，方法是用抗体将荧光标签附着到特定种类的蛋白质分子上。这样就可以将这些蛋白质在整个肿瘤中的分布情况绘制出来，精确到每个细胞。AstroPath 目前可以同时对二三十种蛋白质进行这样的操作。陶贝的远期目标是对 20 多种、数量达几百个的肿瘤开展类似的成像操作，以便对同类型和不同类型的肿瘤做比较。
Currently, AstroPath has scanned more than 226m cells from three types of tumour—lung cancer and two skin cancers, melanoma and Merkel-cell carcinoma. Dr Szalay points out that dealing with these three alone meant processing more pixels than the whole Sloan survey to date. But this is only a start. Eventually, he and Dr Taube aspire to collect and process 1,000 times more data than this.
目前，AstroPath 已经扫描了超过 2.26 亿个细胞，它们来自三种肿瘤——肺癌，以及黑色素瘤和默克尔细胞癌这两种皮肤癌。萨莱指出，光是测绘这三种肿瘤要处理的像素就比整个斯隆项目迄今为止已处理的像素还要多。但这还只是个开始。他和陶贝希望最终能收集和处理的数据会是现在的 1000 倍。
For herself, Dr Taube particularly hopes AstroPath will flag up molecules that will help her develop blood tests for melanoma and lung cancer, and will improve her understanding of how tumours respond to a form of treatment called immunotherapy. Some cancers are able to put the brakes on the immune system’s anti-tumour activity. Disable this ability and the immune system can return to the fray. She hopes to identify markers, such as the levels of a substance called PD-1, a so-called immune checkpoint protein, that will be able to predict whether a patient will respond to such therapy—and, if so, precisely which sort of it.
陶贝则尤其希望 AstroPath 能够标记出一些分子来帮助她开发针对黑色素瘤和肺癌的血液测试，并让她更好地了解肿瘤如何对免疫疗法这种治疗形式做出反应。有些癌症能够抑制免疫系统的抗肿瘤活性。如果能阻止它们发挥这种能力，免疫系统就可以重返战场。她希望能够识别出一些标记物，例如一种叫做 PD-1 的物质的水平。PD-1 是一种所谓的免疫检查点蛋白，能够预测患者是否会对免疫疗法有反应，以及如果有的话，确切来说是哪一种免疫疗法。
The project’s wider aim, though, is to make the results available to the world as a cancer atlas in a format similar to Google Maps. Then, any interested oncologist can take a look and draw conclusions relevant to his or her own area of interest and expertise. If that can be done, it really will enable cancer researchers to reach for the stars.