Cancer cells can evolve by combining

Cancer cells are notoriously tricky; despite treatments designed to kill them, they can keep returning by quickly evolving or diversifying their genetics. Mutation is one way that cancer cells can switch up their genetics. Now, a group led by Andriy Marusyk of the University of South Florida has found another mechanism, one that looks a lot like sex. In in vivo and in vitro tests, Marusyk’s team found that a small number of cancer cells can combine their DNA by fusing together, taking on characteristics of both parent cells (Nat. Ecol. Evol. 2021, DOI: 10.1038/s41559-020-01367-y). Researchers have seen cancer cells fuse before, but it wasn’t clear if there was a benefit to the cells. Marusyk’s team wondered if parasexual recombination—combining two cells to create one new one—might be happening. To find out, the researchers made two populations of breast cancer cells, each modified to produce a different fluorescent label. Using microscopy, the researchers saw cells combine, creating cells with both colorful tags. Some of those double-tagged cells resulted from processes such as one cell engulfing another, while other times two cells fused to produce a new, genetically different cell. The team cultured the new cells and found they could multiply and proliferate, passing on new traits. The researchers’ modeling suggests this type of genetic recombination could promote evolution in cancer cells. Further research is needed to understand if this new mechanism could complicate treatment plans or be clinically relevant in other ways, the team says.