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Stem Cells Change Man's DNA
An anonymous reader writes "After receiving umbilical cord stem cells to replace bone marrow as treatment for non-Hodgkin's lymphoma, Greg Graves temporarily had three different sets of DNA. Eventually, one of the two sets of cells transplanted into his bone marrow took root, leaving him different DNA in his blood from the rest of his body: 'If you were to do a DNA test of my blood and one from my skin, they'd be different,' Graves said. 'It's a pretty wild thing.'"
It's ok. Calm down. Deep breath. This is actually not a terribly uncommon event when bone marrow transplants are used. The news seems to be that instead of transplanted bone marrow, he had stem cells from two different donors infused, and for a while both were found in his blood, but after a period of time only one of the lines seemed to survive. The "news" seems to be that this used stem cells which differentiated into new bone marrow for the patient.
If it had been a "traditional" bone marrow transplant, he would STILL have had a second set of DNA found in his blood. This is becasue for this therapy to work, all of his native bone marrow is destroyed, completely. He will be physically incapable of making his own red, white, and platelet cells. The donor donated marrow is then given to him in the hopes that it will "take root" where his now-ablated marrow once was, and will take that function. It's just like a kidney or heart transplant, just much wetter.
As for offspring due to the implanted cells, not gonna happen. The Gonads are very well protected from things like this, and just like with a transplanted solid organ, this only affects the somatic cells, not the germ cells created in his testes.
So, just remember, think of the bone marrow and blood as another organ, and this is just another organ transplant. His biggest concern would be the effects of his chemo and radiation on his gonads, not the transplanted cells. Make sense?
No he is not, for several reasons.
First, he is not the first to have two sets of DNA due to a bone marrow transplant (although he might be one of the first with 3 sets). Anyone who has had an allogeneic (as opposed to autologous) bone marrow transplant like his has that, as do any other transplant recipients.
In fact, the differences between those DNA is both one of the best things and one of the worst things about alloBMTs to treat blood cancers. The new blood system sets itself up and sees the cancer cells as "foreign" and attacks them, what would be called "rejecting" them in a solid organ transplant. This is called "Graft Versus Leukemic Effect" in leukemia patients, for example. That's the good part. The bad part is that the new blood system looks at the rest of the body and sees it as foreign as well. "All this has to go" is the reaction, also called "Graft Versus Host Effect", or GVHD. That can kill you. Cord blood stem cells make this less likely to happen, because the cord blood cells are not quite sure what the other cells are supposed to look like yet.
The second reason he is not the first man-made chimera is that he is not a chimera. A chimera is when the second set of DNA comes from another species. That has been done before (organ transplants from pigs, for example), but is not the case in this story.
The real story here is that he had a stem cell transplant using cord blood from two different donors.
I am a pediatric blood and marrow transplant physician. After every successful bone marrow transplant (BMT), peripheral blood stem cell transplant (PBSCT), or umbilical cord blood transplant (UCBT) in which the donor is not the patient or an identical twin, the recipient becomes genetic chimera. The DNA in cells derived from the bone marrow stem cells is different from the DNA in the rest of the recipient's body.
As others have pointed out, this isn't anything new. Significant clinical use of BMT dates back to the 1970's. PBSCT and UCBT came into widespread use in the late 1980's and early 1990's.
My group performed a BMT on a patient with relapsed leukemia a few years ago. The patient unfortunately suffered liver and kidney damage as a result of the BMT. He had a liver transplanted from one donor and later a kidney from another donor. Fortunately, he recovered and has remained leukemia free. He is essentially back to being a normal kid, although he will need to take immunosuppressive mediations to prevent rejection indefinitely. That patient permanently has DNA from 4 different sources (bone marrow, liver, kidney, and his original genotype in all other parts of his body).