26 October 2016

Helpers of metastases

Immune DNA networks help cancer metastasize

Kirill Stasevich, "Science and Life", based on Cold Spring Harbor Laboratory: Our most common infection-fighting white blood cells can be hijacked to support cancer spread

Among the rich "weapons" arsenal that immune cells use against infections, there is a rather strange method of catching bacterial cells in DNA networks created by neutrophil cells.

We recalled these immune networks relatively recently when we talked about the results of experiments by researchers from the University of Salzburg – they found out that dying neutrophils release a DNA strand from themselves, fix it on the surface and then crawl away, like some spider weaving a web. Other neutrophils that stumble upon DNA also begin to "weave a network", so that as a result, even a small number of cells can "weave" a relatively large space. Bactericidal proteins sit on the DNA, which kill bacteria trapped in the network.


However, DNA networks have a downside. Mikala Egeblad and her colleagues from the Laboratory in Cold Spring Harbor and other research centers in the United States and South Korea found out that this kind of way to fight infection has learned to use cancer cells for their own purposes. Generally speaking, neutrophils relatively rarely enjoy the attention of those who deal with the relationship between immunity and cancer, the usual "stars" here are macrophages and T–lymphocytes, which are directly at war with malignant cells. But at the same time, neutrophils often turn out to be a collateral victim of chemotherapy, and the patient is forced to take drugs that increase the level of these cells. So sooner or later, but someone had to think about whether neutrophils play any significant role in the development of cancer.

In experiments, mice were transplanted with human breast tumor cells. There were two types of cancer, the first was mildly aggressive, the second was prone to metastasis. It turned out that metastatic cells attract neutrophils to themselves, moreover, neutrophils that have come to metastatic cells are especially prone to weave their DNA networks (although there is no bacterial infection in this case). Further, when we took a closer look at the tumor samples taken from the operated patients, it turned out that both the primary tumor and secondary tumor metastases in the lungs provoke immune cells to create a DNA network, and the more aggressive the tumor, the more likely it is that it will acquire such a network.

And, finally, the most important thing: in an article in Science Translational Medicine (Park et al., Cancer cells induce metastasis-supporting neutrophil extracellular DNA traps), the authors write that neutrophil trapping networks somehow helped metastatic tumor cells to penetrate healthy tissues. When nanoparticles with proteins that destroy DNA strands of networks were injected into mice with a tumor, the probability of cancer spreading, the probability that secondary tumors would appear in the body, decreased markedly - the lungs of mice, where breast cancer metastases usually go, remained healthy.

Exactly how the immune trapping nets contribute to metastases is still unclear. It's probably all about the enzymes that sit on DNA strands - some of them are able to break down other proteins, and although they should attack bacteria, they can also damage our own tissue proteins, so as a result, it becomes easier for cancer cells to penetrate such slightly corroded tissue.

Anyway, now it's time to think about how to somehow stop neutrophilic assistance to metastases, especially since the authors of the study even showed how to do it - you just need to destroy the DNA networks woven by neutrophils in a timely manner.

Portal "Eternal youth" http://vechnayamolodost.ru  26.10.2016

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