Full Interview: Dr. Eric Klein of the
Cleveland Clinic Talks about XMRV Research
January 7th, 2011 www.cfidsreport.com
Dr. Eric A. Klein, MD is the Chairman of the Glickman Urological & Kidney Institute at the Cleveland Clinic. As part of a research team at the Cleveland Clinic that originally published an association with cancer and the novel retrovirus XMRV in 2006, Klein is a knowledgeable and engaging researcher on the topic of XMRV. In the following interview with the CFS Report's Craig Maupin, conducted January 7th, 2010, Klein answers a series of questions about XMRV, recent research, future plans of his clinic, and the media coverage of four studies in Retrovirology on December 21st, 2010.
Maupin: As a primer of your clinic's interest in XRMV, how did you and your clinic become involved in XMRV research?
Dr. Klein: In 1996, a group led by some investigators at Hopkins and the National Cancer Institute published some findings that suggested that there was a gene that predisposes men to cancer on the long-arm of chromosome one. About four years later, members of that same group contacted a colleague of mine, Bob Silverman, and suggested that gene that pre-disposes men to cancer was a gene that he had cloned about ten years earlier -- a gene called Rnase L. That gene is a gene that fights off virus infections. We all have it and any typical virus infection we get, that gene will get turned on, and that helps limit the spread of the virus and helps keep us from getting sick.
In the background of that observation, as well as a lot of epidemiologic data that suggested that cancer might be associated with some prior history of prostatitis and sexually-transmitted infections -- there was a hypothesis that it may be a sexually-transmitted disease. We asked a very simple question, which is, whether or not cancer may be caused by a virus.
So, again the logical link there was cancer occurs at a higher rate of frequency in men with a history of infections, and a gene that normally assists in fighting off virus infections, when mutated, may increase the risk of cancer. So, with this information, we asked: Could cancer be caused by a virus?
So, we collaborated with some folks at the University of California at San Francisco. And, we sent them fresh prostrate tumor, directly from the operating room, in men who were having their prostrate removed for cancer. They used a unique discovery tool called the Virochip, and screened the tumors for the presence of viruses -- and what they found was this novel virus, which we eventually named XMRV. Admittedly, that is fifteen years of science work summarized in a few sentences.
Maupin: Do you see XMRV becoming a player in the diagnosis and treatment of cancer, in the clinical setting, eventually?
Klein: Well, right now we don't know that for sure. No one who knows about the field has suggested that we know XMRV causes any known human disease, whether it is cancer or chronic fatigue syndrome. That has not been proven, in any way, shape or form.
But, it is pretty fascinating, that XMRV was isolated in men from cancer. And that it grows in cell culture, preferentially, in cancer cells or prostrate epithelial cells -- benign or malignant. And, the reason for that is the part of the virus that fuels its growth, it has a segment that responds to testosterone. The prostrate has more testosterone in it than any other organ. So, the virus does have a predilection for the prostrate.
Furthermore, we have under review at the Journal of Virology, a series of experiments where we injected XMRV into some monkeys (rhesus macaques ) and we found the virus in the epithelium, the part of the gland that eventually can turn into cancer, seven days after IV injection into monkeys.
So, it is possible, not proven, that XMRV plays a role in cancer.
If it does play a role, though at this time not proven, how could we exploit that? One way would be to develop screening tests to test for the presence of the virus. If you have the virus, you can find a way to specifically look at prostatic secretions (and we are working on that). If you have the virus, you might be at higher risk for cancer or it might indicate the need for a biopsy. There is some data that suggests that XMRV may be associated with higher grade cancer. So, that would make it important to develop accurate screening tests. We are looking in patient urine samples now after massaging the prostrate and we can find the virus in those secretions. So, [screening] is one way.
The second way would be that drugs that possibly work against XMRV might have a therapeutic effect against cancer, if that link is proven. That said, I don't want anyone with cancer out there taking AIDS drugs. That is not the appropriate thing to do at this point.
Finally, the bigger and more exciting picture is if we prove this link, we might be able to develop a vaccine that prevents cancer caused by XMRV, just as there is a vaccine against HPV that causes certain types of cervical cancer. So, those are the exciting possibilities about it.
Maupin: In August of this year, your clinic published a study detailing antibody response of rhesus monkeys to XMRV. Meanwhile, PCR has been the favored method of many of the researchers critical of the idea of XMRV has a human pathogen. How do you envision the future test for XMRV? What may it look like? And, at this point, is PCR an effective and reliable method of detecting XMRV?
Klein: Every lab test, has its advantages and its imprecisions. And, whether it is PCR based, or monoclonal antibody based, or a chemical reaction. Often, the public is mislead into believing that any blood test that they have coming back reported with an exact value is "carved in stone "as their value without any variability in there.
So, this is not a knock on PCR. PCR has been a very powerful tool for detecting all sorts of bits of DNA, RNA, and nucleic acid, and it has been essential in a lot of major discoveries since it was first discovered back in the early 80s. That is not the issue.
The issue is, with respect to XMRV, if you are not careful, and if in your laboratory you have some mouse DNA around, you can get some false positives. You must be very scrupulous about being sure that you don't have that contamination. Our mouse contamination studies in our lab have all been negative.
If you read the [scientific] literature, the contamination can come from the initial blood specimen and how it is handled. It can come from which specific lab reagents you use, because there is one polymerase, one enzyme, that is used for PCR that seems to be contaminated with some mouse DNA because it was made with mouse monoclonal antibodies. Or it could come from other general lab contaminants.
So, these papers (December 21st, 2010, Retrovirology) that have been published don't refute the fact that XMRV exists as a virus. They don't challenge the previously positive studies. All they say is that you have to be careful that when you are testing for XMRV using PCR that you don't have any mouse DNA contaminating things, because if you do, you can come to the wrong conclusion.
I would also point out that there are a lot of other studies, many of which are published, some of which aren't. These studies used other standard virological methods which are not PCR-based, that have found XMRV in patients. So, if you go back to the original Science paper that showed the presence of XMRV in patients with chronic fatigue syndrome, you'll find there were five different methods used, four of which are not PCR-based. So, that was what was lost in the publicity of these papers in Retrovirology.
Maupin: I'd like to cycle through some of the findings/criticisms in those papers, and gather your response.
Maupin: One criticism was that contamination affected the PCR reagents employed in testing kits.
Klein: Yes. We noticed that and we did some experiments with that reagent a few years ago, so we knew that was a problem and we stopped using it because of it. So, that is a cautionary tale: don't use that reagent. That is the only thing you can draw from that paper.
Maupin: What about the idea that previously-described XMRV sequences are derivatives of sequences in human cell line 22rv1?
Klein: That paper does not prove that. Because, it did not show that the XRMV that we found in radical ctomy specimens came from 22rv1. All it showed was that all the isolates of XMRV, whether they are from that cell line or from patient samples are pretty similar in sequence. And, that they are all pretty similar to related xenotropic mouse viruses. So what?
The other point of that paper is that there are only --if I counted correctly -- six patient samples in that paper. I wouldn't make any conclusions about the diversity of XMRV in the human population based on six human samples. I think that is an overreach.
So, what we take from that paper is that XMRV is similar to what was found in that cell line. We don't know which came first. That cell line was established by taking prostrate tissue from a patient and injecting it into a nude mouse. And the authors of that paper, concluded, inappropriately, that the virus came from the mouse and infected the cell line, and that everything else that XMRV has been found in must be a contaminate from that cell line. That is a possibility. But, there is also a possibility -- of equal chance -- that the patient had the XMRV and it was propagated in the nude mouse, and then it became established in the cell line.
Maupin: One of the studies found no evidence of XMRV using serology methods.
Klein: There have been a couple of negative studies that have looked for antibodies against XMRV in patient samples. There are already some that have been published, both in chronic fatigue syndrome, and I don't know if anyone has looked very hard in cancer.
However, there are some studies, in cancer, and there is one from Emory University, that did find antibodies in serum to XMRV in a pretty substantial portion of patients with cancer. So, we do not know of those discrepancies are differences in patient population. Or, are they differences in assays and so forth?
Maupin: In regard to the December 21st articles, there was a great deal of media coverage of those studies. A press release was released in concert with those articles. As you know, media coverage has a significant effect -- long term and short term-- on public opinion and even opinions in the scientific community. Given that some of the statement in those press releases were extremely negative -- especially regarding the idea that XMRV could be a human pathogen -- could this media coverage affect the pace, the progress, the funding, or collaborations in the future?
Klein: Yes. It certainly could.
In the end, it depends on the influence that the coverage has on the individuals who make those decisions. So, yes it could. Will it? I don't know, and that remains to be seen.
Maupin: Due to HIV, we often conceptualize retroviruses as affecting the functioning and effectiveness of white blood cells. Is there any nascent or developing knowledge about how XMRV may affect white blood cells.
Klein: At this point, I am not sure that anyone has proven that XMRV affects the function of white blood cells. In regard to the Whittemore-Peterson Institute and the chronic fatigue syndrome studies published in Science, if they can detect it in the white blood cells, I can tell you that in our monkey studies, that we can also detect it in white blood cells early on.
To my knowledge, I have not seen any data on how XMRV may affect the function of white blood cells or the immune system. So, I am just unaware of any data looking at it. That does not mean that it does or does not affect the immune system, at this point.
Maupin: Rnase L, particularly low molecular weight Rnase L, has been one of the more unique areas of CFS research. Does it remain a line of inquiry or topic of interest at your clinic?
Klein: Yes. Rnase L is a major focus here, because Bob Silverman, my collaborator cloned Rnase L. He is one of the world's experts on it. It remains a focus and we continue to study it in the context of XMRV, cancer, and a lot of other diseases.
Maupin: Is your clinic working on -- or planning -- any clinical studies yet, with regard XMRV.
Klein: Our current work is to see if we can develop a clinic-based screening test for XMRV in men with cancer. In fact, we have a pretty substantial amount of data that we can detect it in the prostatic secretions of men with cancer. We have already published that.
We can also detect XMRV in the urine of men with cancer after their is massaged. We are not ready to publish that data yet. It is not a secret. We just don't have enough data yet, and we are also not in a position to conclude one way or another whether or not that will be a useful screening test. We'll see.
Maupin: Beyond what has already been discussed, what will your lab continue to work on in 2011?
We are going to continue to study the biology of XMRV, so that we can continue to understand how that it affects cells that it infects. That is the main focus. We also want to understand how it could be a pathogen.
Maupin: Will collaborations with CFS researchers or clinics continue?
Absolutely. We collaborate with a number of labs around the world. Not everything that we have collaborated on is ready for 'prime time' or to be shared with the public. But, I assure you, there is a lot of work still going on.
And we are still quite excited by that work and the whole field. We are excited by the idea that XMRV may infect the human population and it may be something important. We haven't proven that, but we still believe that is a serious possibility and we continue to work on it.