Cancer’s Fusion Dance

A new study reported by The Scientist and presented at the American Society for Cell Biology Annual Meeting this week, has shown that mouse cancer cells can fuse with immune macrophages to form hybrids capable of rapid growth. When cultured together outside of the body, colon tumor cells and macrophages fused, combining the genetic material of both cells to form a new cell type that has unique adhesion abilities and shows enhanced tumor growth when injected back into mice.

Tumor cells from mice are able to fuse with macrophages, yielding hybrids sporting speedier tumor growth (Image source:

I’ve talked about cancer research on here before and the general message has been that cancer is infinitely clever, and that the main obstacle in beating it is having to be smarter than our own bodies. Few stories demonstrate that principle better than this.

Macrophages are immune cells that literally eat bodily invaders by enveloping them in the cell membrane and forming an internal bubble to contain them (called a vesicle) then digesting them with some potent oxidative compounds. They are able to circulate through the body quickly and exit the bloodstream easily, thanks in large part to a complex process of adhesion that allows them to slow down as they pass over the walls of blood vessels, stop, and then slip out. Combine this ability with the inherent dangers of cancer and you have a terrifying possibility for expanding cancer’s reach within the body, a new means of rapid and widespread metastasis.

This is a macrophage (in purple) eating a cancer cell (in yellow). Imagine the macrophage’s surprise when its plan backfires and it finds itself bodysnatched and working to destroy the body it had once sworn to protect (Image source:

While this study did show that the fusion of macrophages and tumor cells causes a change in the behavior of these cells, proving that they grow faster than unfused tumors, it did not address whether or not the hybrids are able to hijack the macrophage’s adhesion process to diffuse quicker throughout the body. The study’s lead author, Alain Silk, told The Scientist that the group’s next goal is to determine whether or not this fusion can help speed up transportation on top of speeding up tumor growth.

Other researchers quoted in The Scientist’s article argued that the next question to be asked should be whether or not this is a phenomenon that can happen in vivo, that is, in the body itself. Since the fusion occurred when the group cultured the two cells types together outside of mice, they need to now prove that the cells are able to combine while inside the body. If not, then these hybrids won’t pose much of a threat, but instead be nothing more than lab-based oddities.

The idea that cancer cells can fuse with macrophages isn’t new. In fact, it’s been around for over a hundred years now, as both the study itself and the news article point out. Most scientists didn’t think it was possible though, as no serious research had been done to confirm it and no solid evidence existed to support it (the possibility had only been hypothesized back in 1911, but apparently there was no real evidence that supported the idea). Recently though, new studies have been showing that this old idea deserves some new attention. This is the first study to show that these newly discovered hybrids have altered phenotypes in vivo, that they behave differently as a result of the genetic recombination during fusion. Assuming it holds up to more scrutiny, this is a remarkable find that could help researchers to design new ways to combat the spread of cancer.

Original articles:

(I also got the NIH papers from The Scientist’s story. Just fyi and whatnot)


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