华为手机扫描识别文字:脑部肿瘤的自身供血系统

Tumors are notoriously hard to kill. Attack them with chemotherapy, and they develop drug resistance; surgically remove them, and they may have already metastasized to other parts of the body. Now scientists have found that tumors have yet another trick up their sleeve: They can create their own blood supply by morphing into blood vessels. The observations, reported by two separate teams online today in Nature, could explain why drugs designed to choke off blood to brain tumors often fail.

        肿瘤向来以难以清除而臭名昭著。化疗虽可破坏，它们却可以生发出抗药性；手术虽可切除， 它们却可能已经转移到身体的其他部位了。近期，科学家们发现肿瘤的另一个诡计：它们可以形成血管来为自己供血。这一由两个不同的团队提出的发现今天被《自然》杂志在线报道，这也许可以解释为什么试图切断脑部肿瘤血液供应的药物并不起作用。

The researchers drew the link between tumor cells and blood vessel cells with a series of experiments on glioblastomas—fast-growing brain tumors that contain tufts of thin, abnormal blood vessels. Neurosurgeon and stem cell scientist Viviane Tabar and colleagues at Memorial Sloan-Kettering Cancer Center in New York City first took glioma samples from the operating room and looked for chromosomal abnormalities in the endothelial cells lining the tumor's blood vessels. They found patterns exactly like those in cells from the tumor itself, suggesting that at least some of the blood vessel cells came from the tumor.

        研究者们通过在胶质母细胞瘤上的一系列实验归纳出了肿瘤细胞和血管细胞的联系。其中，胶质母细胞瘤是一种生长很快的脑部肿瘤，伴随有簇生的薄而异常的血管。作为神经外科医生，同时是干细胞研究专家的维维恩 塔巴和其在纽约的斯隆-凯特琳癌症中心的同事最先从手术室中获取神经胶质瘤样本，并且检视了肿瘤血管边沿的内皮细胞的染色体异常情况。他们发现，那些染色体的形态和肿瘤自身细胞的完全相同，说明至少一些血管细胞是来自肿瘤内部的。

The researchers then sorted glioma cells into different types using antibodies that stick to specific proteins on a cell's surface. They showed that the cells that give rise to blood vessels are an immature cancer cell, known as a stemlike cancer cell. Finally, the researchers injected these cancer stem cells into the brains of mice with weakened immune systems and then examined the blood vessels within the resulting tumors. The vessels stained positive for antibodies to human endothelial cells, again showing that some of the cells had to come from the tumor.

        研究者们接下来通过特异性结合细胞表面蛋白质的抗体将神经胶质瘤细胞分成不同的类型。他们证明形成了血管的细胞是不成熟的癌细胞，常被称为干细胞样癌细胞。最后，研究者们将这些癌症干细胞注射到免疫低下的小鼠脑部并检测生成的肿瘤中的血管。这些血管对人类内皮细胞抗体呈阳性，再一次证明了一些血管细胞来自肿瘤自身。

The bottom line: "There is plasticity within the tumor, and it can make its own blood vessels," says Tabar. She says that this could explain why cancer drugs aimed at choking off a tumor's blood supply by blocking growth signals, known as angiogenesis inhibitors, usually stop working within about 6 months. When her team added one of the antiangiogenesis drugs to a culture of the cancer cells, the drug stopped immature blood vessel cells from maturing but didn't block the stem cells from developing into the immature blood vessel cells. Because tumor cells are genetically unstable, they may easily find ways to bypass the antiangiogenesis drugs, Tabar says.

        塔巴表示，研究证明肿瘤内部具有可塑性，它可以形成自己的血管。她说这也就可以解释为什么试图通过血管生成抑制因子来阻断血管生长信号而阻断肿瘤血液供应的药物通常在六周内失去作用。当她的团队将一种抗血管生成的药物加入到培养的癌细胞中时，药物可以终止不成熟的血管细胞的成熟过程，但却不能阻止干细胞发展成为不成熟的血管细胞。塔巴表示，由于肿瘤细胞在遗传上的不稳定性，它们可以轻易躲过抗血管生成药物的攻击。

A separate team led by Ruggero De Maria at the Istituto Superiore di Sanità in Rome published a similar set of experiments today. Both teams suggest that combining antiangiogenesis drugs with another drug that stops the stem cells from maturing might be a way to overcome resistance in gliomas and perhaps other cancers.

        另一个位于罗马的国家卫生研究所的研究组也发表了一套类似的实验。两个研究组都提到，通过结合使用抗肿瘤生成药物和另一种可以阻断干细胞成熟的药物也许可以解决神经胶质瘤以及其他癌症出现的抗性的问题。

Other papers have hinted that cancer cells might give rise to blood vessel cells, but the two studies reporting essentially the same result confirm that suspicion, says angiogenesis researcher David Cheresh of the University of California, San Diego. "These two papers will put the controversy to rest."

        其他的文章曾经暗示，癌症干细胞有可能生发出血管细胞，这两份研究的报告证实了这个假设。加州大学圣迭戈分校研究血管生成的大卫 查莱仕指出，这两份报告将会停息这些争论了。