Here is a nice open access review article on ERVs and their association with cancer:
Human endogenous retroviruses and cancer prevention: evidence and prospects
While thats wonderfully interesting, what I want to focus on is a bit at the end. More information I have never heard before--
An amino acid sequence similar to HERV-K-MEL, recognized to cause a significant protective effect against melanoma, is shared by the antigenic determinants expressed by some vaccines such as BCG, vaccinia virus and the yellow fever virus.
...
A recent epidemiological study provided provisional evidence of how melanoma risk could possibly be reduced if the yellow fever virus vaccine (YFV) were received at least 10 years before, possibly preventing tumor initiation rather than culling melanoma cells already compromised.
Wait, WAT?? All those vaccines (bacterial and viral) are associated with lower melanoma rates? WAT??
HERV-K-MEL is a pseudogene inside of an ERV (junk within junk!). It has been shown to be expressed in melanomas and 'sarcoma, lymphoma, bladder, breast and ovarian cancer'. By chance, it appears as if some of the proteins in TB, Small Pox, and Yellow Fever vaccines have a similar enough structure that our immune system can be trained to see 'Yellow Fever', but can also see HERV-K-MEL, a cancer marker, too!
This wasnt done on purpose at all!
The connection between vaccines and lower risk of certain kinds of cancers was hypothesized in the early 1990s, and strengthened in 2003.
HERV-K-MEL wasnt discovered until 2002!
And we didnt make the connection between vaccine, molecular mimicry, ERV expression, and cancer until 2005!
I think that is relatively fast to connect some WEIRD dots!
Its 2013 and I am just now learning about this, and still amazed, myself!
Edward Jenner, 1796, uses cowpox as a vaccine against small pox. 1939 we realize that our 'cowpox' vaccine evolved into something else, we name it 'vaccinia' and just roll with it. 2005 we notice it has a protective effect against some kinds of cancers (just kinda protective, we arent doing it on purpose, here! its a side-effect!), which have a messed up active ERV.
Mind blown.
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I am dubious about the ERV-link. Infections have a strong relationship to cancer, with somewhere between 25% and 50% of cancers being due to infections. Proven mechanisms of action are the transfer of viral oncogenes into cells (HPV, EBV) and inflammation-induced mutagenesis through the production of ROS. Vaccination can prevent/reduce both of those, for specific pathogens.
I'm especially dubious about the claims of antigen cross-reactivity. Table 2 in the paper shows the "shared" amino acid sequences - which vary greatly, carry mutations on what would be the anchor residues for MHC binding, and whose differences in amino acid composition often substitutes highly different amino acids (i.e. small hydrophobic for bulky, etc); typically, that equals non-cross reactivity of antibodies...
That's super cool! Too bad it's *those* vaccines. YFV vaccine is nothing to screw around with (though it seems to last forever). Neither is vaccinia (had it, and it sucked), which is also contagious and has some potential nasty side effects. And I was under the impression that BCG doesn't work for it's intended purpose (TB).
It would be awesome if it were a vaccine that everyone gets, like polio. Though I guess if a super-common vaccine prevented melanoma we would have seen a shift in melanoma rates by now.
JustaTech, you had vaccinia? How old are you?
@ Rob: Not that old! I had it as part of a research program I worked on. I'd guess that I'm one of very few people of my generation.