Oct 3, 2014 — What is genome sequencing? How is it different from other kinds of genetic testing? And what can it really tell you about your health? Wendy Kohlmann, a genetic counselor at the Huntsman Cancer Institute at the University of Utah, answers these questions and explains who should get it done, and where the technology is heading.

Interview

Interviewer: Maybe you've heard the term, genome sequencing; what exactly is it and should we all be demanding that we have it done?

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Interviewer: I'm with Wendy Kohlmann, a genetic counselor at the Huntsman Cancer Institute at the University of Utah. Ms. Kohlmann, describe what genome sequencing is and how it's different from say a routine genetic test.

Ms. Kohlmann: Genome sequencing refers to really evaluating the genetic code of our entire genome. We kind of think about genome sequencing, and there are two different types. One would be looking at what we call our exome. That would be analyzing the genetic code of really just the areas of our genetic material that contain genes. We have lots of filler genetic material in between all those genes, so there's a second technology called whole genome sequencing, which involves analyzing everything, including the areas that are outside of specific genes.

Interviewer: And we're learning more and more that this so-called filler DNA is actually important as well.

Ms. Kohlmann: Right, we think it is. So that's why some clinical and research applications are looking even more broadly.

Interviewer: So do you see this as becoming more common in the future, that patients will have their entire genome or their exome sequence?

Ms. Kohlmann: Genetic testing technology is rapidly evolving. In the past we used to very carefully evaluate families and try to pick the best gene that we thought fit what maybe was going on with the particular patient or a particular family history, because testing in one gene was very expensive. Technology is now making it so it's possible to sequence the whole exome or whole genome now for a few thousand dollars as opposed to the billion dollars that it took to do the first whole genome sequence. You may have heard this mentioned before, we're moving toward the idea of the thousand-dollar genome.

Interviewer: Right.

Ms. Kohlmann: But with that goes the million dollar interpretation. So actually analyzing all of that data and making meaningful sense of all the millions of variations that there are between humans and figuring out the ones that actually are providing meaningful information about that person's health, that's really where the challenge of implementing this technology into actual clinical care comes into play.

Interviewer: Is genome sequencing something that's covered by insurance at this point? Do you know?

Ms. Kohlmann: I can be in certain circumstances. The first area that was really introduced into clinical care was in a pediatric setting, where we can have very sick newborns where time is crucial in making a diagnosis. And going through this process of, well maybe it's this gene, maybe it's that gene, maybe it's that gene; that's just a luxury that those babies don't have. And so whole exome or whole genome sequencing might be an approach to trying to as quickly as possible evaluate the child to see if a genetic cause of their illness could be identified.
Coverage in general of all genetic tests is a little bit all over the board. We have some insurers who readily cover genetic testing. We have others who exclude even very well established tests. So I think with whole genome or whole exome sequencing the coverage will depend on if that's something covered by the plan, then also if a good case can be made as to why that expensive of a test is really the best approach for that situation.

Interviewer: And you would think that it could be a good thing to have your whole genome tested. After all, knowledge is power, right?

Ms. Kohlmann: I generally agree with that statement. I think that knowledge is power, but I think that there are a lot of misunderstandings about what our genetic code can tell us about ourselves. It is not if you have gene A that equals future B. It's much more complex than that. And we are still so in the beginning stages of identifying and understanding all the genetic factors that contribute to disease. What if a change is found in a gene that predisposes to cardiovascular disease? But what if you have a variation in another gene that is associated with being protective against cardiovascular disease? What does having those two results mean for any given person?
It's not that a genetic code comes with this roadmap of at 65 you'll get a colon polyp and at 70 you'll have a heart attack. It's very much more ambiguous than that. And right now it's a lot of money to spend on something that is likely to provide information that we really can't interpret or actually put into action at this point.

Interviewer: Something else you wanted to bring up is sequencing tumors. Can you explain what the difference is between sequencing a tumor and sequencing an individual's DNA?

Ms. Kohlmann: Genetic testing technology; we often think of it being used to make a diagnosis in a person or to help predict who is at risk for diseases. But genetic testing can also be used in other settings and one of the areas that we're using it more and more frequently is in the area of cancer. All cancers arise due to a series of genetic mutations. And so while we may think of something as being breast cancer or colon cancer, every cancer is actually a little bit different because of the different pathways of mutations occurred to create that cancer.
The same technology that I was describing to look at whole genomes or exomes or panels of targeted genes is now being applied to tumors to help more specifically say not just is this a breast cancer, but exactly what type of breast cancer it is. What mutations have occurred, and by looking at those mutations and knowing what role they are playing in a cell can we then pick a specific chemotherapy that may work better for this person. So this is a new area where this technology is really being applied, and an exciting area where the hope is more personalized and more effective cancer treatments.
But just like I was saying with using this testing for predicting disease risk, there are still limitations, you know. When we look at so many changes we don't necessarily know what every change is doing in the cancer cell. We don't always have a chemotherapy that may be targeting that particular mutation. But this certainly is a developing area of genetic technology.

Announcer: Interesting, informative, and all in the name of better health. This is The Scope Health Sciences Radio.


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