Murine gammaretroviruses in prostate cancer cell lines

23 June 2011

nude mouseThe retrovirus XMRV arose during passage of a human prostate tumor in nude mice. The genomes of these mice contain two different proviral DNAs related to XMRV, pre-XMRV-1 and pre-XMRV-2, that recombined to produce XMRV that has been isolated from humans. Two other prostate cancer cell lines also contain mouse gammaretroviruses that are not XMRV. These viruses may have entered the prostate tumor cells during xenograft passage in immunocompromised mice.

The discovery of infectious XMRV in the prostate tumor cell line 22Rv1 prompted the examination of other prostate tumor cell lines for the presence of murine gammaretroviruses. Antisera against Moloney murine leukemia virus were used to screen 72 cell lines by immunohistochemistry for the presence of murine gammaretroviruses. Three human prostate tumor cell lines (22Rv1, LAPC4, and VCaP) and one lung carcinoma cell line (EKVX) reacted with the antisera.

Polymerase chain reaction and nucleotide sequencing analysis revealed that these viruses are not XMRV. The virus in the EKVX cell line is a xenotropic MLV similar to a virus previously isolated from a human B-lymphoblastoid cell line. The virus from the LAPC4 and VCaP cell lines is the murine xenotropic retrovirus Bxv-1. A different sample of VCaP cells obtained from the ATCC were also positive for Bxv-1, as were LAPC4 cells obtained from a different laboratory. Replication-competent viruses were detected in all three cell lines.

How did these human prostate cancer cell lines become contaminated with murine gammaretroviruses? The authors believe this is a consequence of passage of the tumors through immunocompromised mice. In support of this hypothesis, the retrovirus Bxv-1 is present in nude mice, and passage of tumors in these mice can lead to infection with xenotropic MLVs. In contrast to the origin of XMRV, recombination was not needed to produce these viruses.

These findings led the authors to examine two other prostate cancer cell lines, present in their laboratory, DU145 and LNCaP, for the presence of gammaretroviruses. They found these cell lines to be contaminated with XMRV, likely obtained from 22RV1 cells in use in the laboratory. Fresh aliquots of the DU145 and LNCaP cells obtained from other sources were not contaminated. The authors conclude that if

CWR22Rv1 cells are routinely cultured in a typical biomedical research laboratory setting (e.g. using standard Class II biosafety cabinets and procedures for cell culture in which two different cell lines are never present under the hood at the same time), that XMRV can infect and contaminate other cell lines.

Karen Sandell Sfanos, Amanda L. Aloia, Jessica L. Hicks, David M. Esopi, Jared P. Steranka, Wei Shao, Silvia Sanchez-Martinez, Srinivasan Yegnasubramanian, Kathleen H. Burns, Alan Rein, & Angelo M. De Marzo (2011). Identification of Replication Competent Murine Gammaretroviruses in Commonly Used Prostate Cancer Cell Lines PLoS One : 10.1371/journal.pone.0020874

  • PseudoAnonymous

    Professor,

    XMRV isolate S-162 (prostate cancer) is clearly not from a contaminated cell line. It sort of hangs out on its own on a phylogenetic tree.

    Your input would be appreciated.

    http://www.ncbi.nlm.nih.gov/nuccore/FR872816.1

  • PseudoAnonymous

    Also, there is an interesting (provision) PDF titled “Phylogeny-directed search for murine leukemia virus – like retroviruses in vertebrate genomes, and in patients suffering from Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Prostate Cancer” here (if it’s of interest for any of your shows):

    http://www.hindawi.com/journals/av/aip/341294/

  • John

    “Antisera against Moloney murine leukemia virus were used to screen 72 cell lines by immunohistochemistry for the presence of murine gammaretroviruses.”

    Could these Moloney MLV antisera be used to examine CFS patient samples for murine gammaretroviruses since XMRV-specific antibodies were not able to find XMRV? 

  • John

    Or are these antisera similar to the Aloia prostate cancer study which didn’t find any XMRV/MLV’s?

    Aloia et al. XMRV: A New Virus in Prostate Cancer?
    http://cancerres.aacrjournals.org/content/70/24/10028.abstract

  • Guest

    So which came first, the chicken or the egg?  Did the gammaretroviruses found in these cell lines cause cancer? Or did the cancer cells pick up the viruses by accident after they were cultured outside of the patients they came from?  Or since these viruses show an affinity to this tissue – did both happen?

  • Anonymous

    Sorry Professor, but there is only a hypothesis that the HGRV strain XMRV arose from a human prostate cancer cell line.   I’m sure others will revisit this in the future and see whether there is evidence to support such an idea, but for now the paper Paprotka et al. failed to do so.   A good start would have been to have confirmed the existence of the virus Paprotka chose to arbitrarily call PreXMRV-1.   I’m surprised that giving a political name to a virus is not frowned upon.   The sooner someone uses an appropriate assay to look for XMRV in mice, the easier it will be to begin to understand the origin of HGRVs.  

       

  • Ronnie

    I would appreciate if you could do another TWiV on this subject, but instead of focusing on one or two studies, give us a picture of the whole story. Based on over a hundred studies (that number is just a wild guess) so far, what do we know by now? What questions are still not answered. Do we have a definitive conclusion already? or should we really wait for Lipkin?

  • Anonymous

    That isolate cannot have come from 22Rv1 and therefore 22Rv1 cannot be the source.

  • PseudoAnonymous

    The provisional PDF I posted a link to has 215 citations, and is a great resource if you want to see the big picture + much more.

  • Guest

    why dont have you just have Frank Ruscetti on your show, it would answer a million questions.
    all the questions which you and everyone wants to know!

  • PseudoAnonymous

    I would like to back up what I said with evidence:

    22Rv1 Alignment (this has the most identical): http://codeviewer.org/view/code:1c28

    22Rv1 – Identities = 7847/8212 (96%), Gaps = 69/8212 (1%)

    Phylogenetic tree: http://i.imgur.com/9OzXF.png

  • Anonymous

    There are many more obvious explanations for the paragraph below, but that is not what people seem to want everyone to be aware of.  Why is that?

    “These findings led the authors to examine two other prostate cancer cell lines, present in their laboratory, DU145 and LNCaP, for the presence of gammaretroviruses. They found these cell lines to be contaminated with XMRV, likely obtained from 22RV1 cells in use in the laboratory. Fresh aliquots of the DU145 and LNCaP cells obtained from other sources were not contaminated. ”

  • Karin

    Wow, XMRV and other murine gamma retroviruses sure seem to have no problem infecting human cell lines… The problem seem to be the opposite: how to prevent them from infecting cell lines and contaminating everything in the labs.

    And we should rest assured that these retroviruses cannot infect humans? I am still worried about this, even after hearing the explanation that serum complement quickly clears XMRV from the blood. That sure is reassuring, but on the other hand, how about mucosal tissues, could these be a back-door entrance for the infection? How about lungs, intestinal mucosa, genital mucosa, etc… How about oral and airborne contamination? Sexual contamination? Vertical transmission?

    I am very concerned, I must say, because the rates of autoimmune disease and cancers are rising, and we still don’t have a clue why. Here is a new class of retroviruses capable of infecting human cell lines, that have been around for a few decades, and that we know cause cancers, immune problems and neurological problems in mice, so I feel that we should invest some resources into researching whether or not these gamma retroviruses can cause disease in humans, cancer, autoimmune, neurological, or otherwise…

  • James

    dear prof like the other poster I would be interested in your view on the lithuanian isolate..maybe you missed his question but its a very interesting question becuase the whole sequence has been published, many thanks

  • Gerwyn

    Gob987 — what are your qualifications — a virologist, a retrovirologist, have you ever done any PCR testing — to address these issues.  It just seems you don’t know what you are talking about.

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