Bacteria boost the spread of cancer

Now, are bacteria aiding and abetting the spread of cancer? That’s the conclusion of a new study this week from scientists at Westlake University in China, where they have found that tumours pick up bacteria from the bloodstream and take them inside their cells where they somehow boost the strength of the cancer cells so they can better withstand travelling through the bloodstream to create secondary tumours elsewhere in the body. Eric Rahrmann is a cancer biologist at Cancer Research UK; he wasn’t involved in the new study but works in this same general area. Chris asked him to take a look at the results…

Eric - A couple years ago, some major papers came out demonstrating that in human tumours we see bacteria actually within the cells and that they're having some sort of contribution to tumour development. What this particular group out of Wakefield has demonstrated is that not only are bacteria cells present, they help to support the dissemination or trafficking of cells from the primary tumour throughout the body in the process that we call metastasis.

Chris - How do they do it? How did they show that (A) the microbes are there and (B) that they're making an active contribution to making the cancer spread?

Eric - They used some really cool mouse models of memory tumour development, and coupled that with some microscopy. Through genetic labelling of bacterial strains, basically a fluorescent protein or colour so you can follow where the bacteria strains go within the tumour, they can see these green labelled bacterial strains within the primary tumour cells. And they can see that these green bacteria are retained within the primary tumour cells when they leave their site, traffic in the peripheral blood, and then seed at a distant organ. What this group has been able to uncover is that different strains of bacteria have different profound impacts on the ability of cells to travel or spread throughout the body.

Chris - And what, if you remove those bacteria, the tumour spreads less well or is less likely to take up residence at a distant site in the body.

Eric - Yes, that's right. Through a number of different combinations of antibiotic treatments, they were able to selectively kill the bacteria within the tumour cells themselves. When they did this, they identified that certain strains that were obliterated reduced the ability of the cancer cells to seed and create metastases.

Chris - Where do these microbes come from in the first place? How do they get into the cancer to start with?

Eric - Our bodies are composed of large, diverse microbiome phyla. Most well-characterized within the colorectal intestinal tissues. Through many years of research, we've see that many of our other organs also have this relationship with bacterial strains within our body that are normally there. So, these are normal residents. I think a big question out there is, 'How do the bacteria that are in the surrounding environment actually get into the cell itself? There's a number of bits of research to understanding this, but I think we're really just getting at the surface of this process, of this, in a way, I guess, symbiotic relationship of the bacteria going intracellularly to the cancer cells, promoting their survival.

Chris - And what do those microbes do so that when the cancer cells do break away from the primary tumor, where the disease begins, and start to travel around the body, they are more likely to spread somewhere else. What's the role of the microbes in that happening?

Eric - This is where this particular study, I thought, really sparked my interest, here. What they're able to demonstrate is that when the microbiome occur intracellularly, that makes them more healthy. One example that they looked at is sheer stress. Imagine fluid is flowing through our peripheral veins and arteries, and that's really harsh conditions on cells and there's some membranes. So, if you're not in the right structure or formation, you will die. They've demonstrated that the microbiome helps to reprogram the cell to survive these conditions.

Chris - How do we use this knowledge?

Eric - What I think is really beneficial from this study that's coming out is that we need to start looking at how we treat metastatic cancer differently than we are currently. We should start considering how to target these different strains. And it's not just what's happening at the cellular genetic level, but other contributing factors as well.