She believes XMRV isn't in ME/CFS patients but that there's evidence for the retrovirus in prostate cancer
CFS Central emailed University of Utah's Dr. Ila Singh about her new XMRV study, which found no evidence of XMRV in ME/CFS patients. In 2009, Singh found evidence of the retrovirus in prostate-cancer tissue.
CFS Central: Will you revisit your prostate-cancer XMRV findings in light of this XMRV negative CFS study? From what you’ve learned in this latest CFS study, do you now believe that the XMRV that you found in prostate cancer is a human infection or just contamination?
Dr. Ila Singh: Prostate cancer and chronic fatigue syndrome are completely different illnesses. I recognize that recent studies have cast doubts on the prostate cancer association as well, but there is still considerable data supporting the link to prostate cancer that cannot be easily explained by contamination. We will present some of this work at the Cold Spring Harbor meeting later this month. But clearly more work needs to be done before that question can be settled.
CFS Central: Do you believe scientists should be looking for XMRV in CFS patients’ tissues instead of blood?
Singh: The original study by Mikovits' group reported finding XMRV only from blood. They did not examine other tissues. So blood is where the focus should be. Now if one found it in blood, then of course you'd be interested in finding out where else the virus is. And then it would be interesting to look at tissues. But looking at tissues is not trivial and not something to be attempted without good evidence of the virus being present in the body first.
CFS Central: Did you test the new assays/methods used in the new study against any XMRV positive samples from your prostate-cancer study?
Singh: Our prostate cancer study was entirely on prostate tissues. These were archived in tissue banks in a de-identified manner, so there was no way to go back to those patients and obtain blood samples. So, we could not test some of the new tests we developed on our material from prostate cancer patients.
CFS Central: In your new study it says that “2 positive controls were also included” (line 349 of your study). Were the two positive controls clones or clinical samples from prostate-cancer studies or from Mikovits’s positive CFS patients?
Singh: The samples from Mikovits' patients were all tested in a completely blinded fashion. We did not know which of them were positive, so could not use them as positive controls. But more accurately, there are no real patient 'positive controls' for XMRV. In order to use patient samples as controls, you'd have to first be absolutely certain that these patients have XMRV. How could you do that right now? So we used what you call a 'clone' for our PCR studies. But remember, this clone was isolated from a patient (a prostate cancer patient). And this is over 99% identical to the isolates from CFS patients described in Lombardi et al. For the viral culture studies, we used very small amounts of titrated virus that was grown in the lab as positive controls. And all of these positive controls were always positive.
CFS Central: You grew XMRV in the prostate-cancer cell line LNCaP and the breast-cancer cell line MCF-7 in your study “Raltegravir is a potent inhibitor of XMRV, a virus implicated in prostate cancer and chronic fatigue syndrome.” It’s unclear to me why the new study didn’t culture XMRV from those two positives.
Singh: Yes, we did. And these grew just fine. Apologies for not being clearer in the paper. None of the patient samples tested positive, but the positive controls were always positive.
CFS Central: Some patients on the forums find this sentence from the new study problematic: “We are forced to conclude that prescribing antiretroviral agents to CFS patients is insufficiently justified and potentially dangerous.” The Science and the Alter/Lo studies have reported XMRV and related MLVs in CFS patients. CFS patients are very ill, many for decades, and there are no approved treatments. They believe the decision to try antiretroviral drugs should be between a patient and his or her doctor. Why did you feel the need to put that statement in the study and press release?
Singh: The patient and their doctor did not make the decision to try antiretroviral drugs in a vacuum. It was based on reports of finding XMRV in CFS patients. We are now convinced that there is no XMRV in CFS patients--so the reason for starting those drugs does not exist. And there is no good evidence for continuing to use drugs that could lead to serious side effects of liver or bone-marrow failure.
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I wrote to Singh to ask her to clarify two of her answers:
CFS Central: In your prostate-cancer study, “XMRV is present in malignant prostatic epithelium and is associated with prostate cancer, especially high-grade tumors,” you found 4 percent of healthy controls with evidence of XMRV. If you’re finding a background rate in controls in your prostate-cancer studies, why do you think you didn’t find a background rate in CFS patients and controls?
CFS Central: To clarify one of my previous questions, beginning on line 347 of your new study, it states: “We inoculated LNCaP cells with 100 [microliters] of plasma from 31 patients and 34 healthy volunteers, and passaged the cells weekly for 6 weeks. 13 negative controls and 2 positive controls were also included. Only one culture was handled at a time to prevent any cross-contamination. After weeks 2, 4 and 6, cultures were lysed and analyzed by Western blots (Fig. 4) and by qPCR for XMRV. No XMRV protein or DNA was detected in any of the cultures. [emphasis added]
My question is this: Is the bolded sentence correct, or did the 2 positive controls grow in these cultures and/or did the positive samples continue to test positive in culture? If the positive controls didn’t grow or if the positives controls didn’t test positive in culture, why didn’t they? You grew XMRV in the prostate-cancer cell line LNCaP and the breast-cancer cell line MCF-7 in your study “Raltegravir is a potent inhibitor of XMRV, a virus implicated in prostate cancer and chronic fatigue syndrome.”
Singh: That was our poor wording in the paper (the words in bold). All positive controls grew XMRV--as one would expect. None of the samples from the healthy controls or CFS patients grew any virus in culture. And of course the negative controls did not grow any XMRV.