Retroviruses cause cancer.
Like how HPV causes cancer, its not really ‘on purpose’, its just a side-effect of their life-cycle– insert DNA randomly into a genome enough times, and eventually youre going to plop somewhere you aint supposed to be, and cause cancer.
Thus I am terribly amused when Creationists bawww about how ERVs are perfect and special (not junk!)… cause if those ERVs werent rendered junk by mutagenesis or epigenetics, we would all be dead (technically, never born).
Found a paper in Nature Cancer Gene Therapy that kinda turns this issue upside down:
Theyre exploring ways to use envelope (from ERVs and retroviruses) to kill cancer!
Heres what they did–
Know how we got HeLa cells? There are lots of other cell lines we use in the lab that we got this way too. One of those is H322. Its a cell line we got from a fellow with lung cancer in 1981 (his cancer cells have been multiplying in labs for almost 30 years).
If you inject these cells into mice with no adaptive immune system, the mice get this ‘human’ cancer.
One of the features of this cancer is that it takes up exogenous DNA (!!!). So instead of needing a virus to deliver the genes youre interested in, you can just inject these mice with DNA, and the tumor will suck it up all on its own (again, !!!).
So, they injected the mice with DNA that contained different retroviral envelope genes. Once this DNA is in the tumors, the tumor will start making the envelope proteins. What does envelope like to do?… SYNCYTIA!!
Cells expressing Env fuse with surrounding cells, and they fuse with surrounding cells, on and on till you get 50-100 nuclei in one big cell… and then it dies. They also spit out stuff that kills surrounding cells (bystander effect), which is kinda just fine when youre talking about a tumor.
Their treatments didnt totally obliterate the tumors, but in the absence of any chemo/radiation, they stopped/slowed the tumors growth. This could end up being another weapon in our arsenal against some kinds of cancers (this only worked because of features of H322, not all lung cancers will have these features).
An unexpected, really neat weapon!