No evidence for a role of xenotropic murine leukaemia virus-related virus and BK virus in prostate cancer of German patients

False Alarm: XMRV, Cancer, and Chronic Fatigue Syndrome

Xenotropic murine leukemia virus (MLV)-related virus (XMRV) was first described in 2006 in some human prostate cancers. But it drew little attention until 2009, when it was also found, as infectious virus and as MLV-related DNA, in samples from people suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This discovery was rapidly followed by efforts of the international research community to understand the significance of the association and its potential to spread widely as an important human pathogen. Within a few years, efforts by researchers worldwide failed to repeat these findings, and mounting evidence for laboratory contamination with mouse-derived virus and viral DNA sequences became accepted as the explanation for the initial findings. As researchers engaged in these studies, we present here a historical review of the rise and fall of XMRV as a human pathogen, and we discuss the lessons learned from these events.

Prevalence of Human Polyomavirus BK Virus in Prostate Cancer Patients and Benign Prostatic Hyperplasia: A Cross-sectional Study on Prostate Patients Referred to Imam Khomeini Hospital in Ahvaz Between 2015 and 2017

Background: Human polyomavirus BK virus (BKV) belongs to the Polyomaviridae family and seems to be a drastic virus in prostate cancer (PCa) etiology. BK virus induces oncogenesis via the expression of large tumor antigen (LTAg) and small tumor antigen (stAg). Also, BKV infection seems to play an essential role in prostate cancer development. Objectives: In this study was aimed to study the prevalence of BKV in benign and cancerous prostate tissues. Methods: In this study, 100 formalin-fixed paraffin-embedded tissues of PCa specimens and benign prostatic hyperplasia (BPH) were collected. The DNA was extracted from tissue samples, and the BKV DNA was investigated using a semi-nested polymerase chain reaction (PCR). The MEGA 6.0 software was used for phylogenetic analysis to assemble the viral genome. A phylogenetic tree was constructed by neighbor-joining analysis with 1,000 replicates of the bootstrap resampling test. Results: The BKV DNA was found in 66% (33/50) of patients with PCa and 36% (18/50) of patients with benign prostatic hyperplasia (BPH) (P = 0.003). The frequency of BKV DNA in different classes of Gleason score (5 - 10) was not significant (0.094). The distribution of BKV DNA among different age groups was not significant (P = 0.086). Conclusions: High frequency of BKV infection was detected in patients with PCa compared to patients with BPH (P = 0.003), and the coexistence of BKV DNA was confirmed in 51% (51/100) of tissue samples, which were confirmed to be subtype 1 of BKV infection.

Epstein-Barr and BK virus in cancerous and noncancerous prostate tissue

Aim: We conducted a case–control study to examine the presence of BK virus (BKV) and Epstein barr virus (EBV) genome in prostate specimens of benign prostatic hyperplasia (BPH) and prostate cancer (PCa) in Iran. Materials & methods: 64 paraffin-embedded PCa specimens were included as case subjects and 57 paraffin-embedded BPH specimens as control. DNA extraction was carried out by phenol–chloroform technique and PCR for detection of BKV and EBV. Results: 90 (73%) out of 121 specimens were collected by prostatectomy and 31 (27%) by transurethral resection of the prostate. BKV was not detected in any of the samples and one positive EBV was reported. Conclusion: These findings provide further evidence against a causative role of BKV and EBV in the development of PCa.

Viral infections in prostate carcinomas in Chilean patients

BACKGROUND

A few viruses have been detected in prostate cancer, however their role in the development of this malignancy has not been determined. The aim of this study was to analyze the presence and functionality of human papillomavirus (HPV) and polyomaviruses (BKPyV and JCPyV) in prostate carcinomas in Chilean patients.

METHODS

Sixty-nine primary prostate carcinomas were analyzed for the presence of HPV, BKPyV and JCPyV using standard polymerase chain reaction protocols. In addition, when samples were positive for HPyV, large T antigen (TAg) transcripts were analyzed using reverse transcriptase PCR.

RESULTS

HPV and JCPyV were not detected in any specimens (0/69, 0 %); whereas, BKPyV was detected in 6/69 PCas (8.7 %). We did not find a statistically significant association between the presence of BKPyV and age (p = 0.198) or Gleason score (p = 0.268). In addition, 2/6 (33 %) BKPyV positive specimens showed detectable levels of TAg transcripts.

CONCLUSIONS

There was no association between HPV or JCPyV presence and prostate cancer development. The presence of BKPyV in a small subset of prostate carcinomas in Chilean patients could indicate that this virus plays a potential role in prostate cancer development and requires further investigation.

Polyomavirus BK and prostate cancer: an unworthy scientific effort?

The Polyomavirus BK (BKV) has been proposed to be one of the possible co-factors in the genesis of prostate cancer (PCa) but, so far, the only convincing suggestion is the hypothesis of a “hit and run” carcinogenic mechanism induced by the virus at early stages of this disease. To support this hypothesis we conducted an updated systematic review on previous studies regarding the association between BKV and PCa, in order to interpret the contrasting results and to explore whether there might be a significant virus-disease link. This updated analysis provides evidence for a significant link between BKV expression and PCa development, particularly between the BKV infection and the cancer risk. Forthcoming scientific efforts that take cue from this study might overcome the atavistic and fruitless debate regarding the BKV-PCa association.

The saga of XMRV: a virus that infects human cells but is not a human virus

Xenotropic murine leukemia virus-related virus (XMRV) was discovered in 2006 in a search for a viral etiology of human prostate cancer (PC). Substantial interest in XMRV as a potentially new pathogenic human retrovirus was driven by reports that XMRV could be detected in a significant percentage of PC samples, and also in tissues from patients with chronic fatigue syndrome (CFS). After considerable controversy, etiologic links between XMRV and these two diseases were disproven. XMRV was determined to have arisen during passage of a human PC tumor in immunocompromised nude mice, by activation and recombination between two endogenous murine leukemia viruses from cells of the mouse. The resulting XMRV had a xentropic host range, which allowed it replicate in the human tumor cells in the xenograft. This review describes the discovery of XMRV, and the molecular and virological events leading to its formation, XMRV infection in animal models and biological effects on infected cells. Lessons from XMRV for other searches of viral etiologies of cancer are discussed, as well as cautions for researchers working on human tumors or cell lines that have been passed through nude mice, includingpotential biohazards associated with XMRV or other similar xenotropic murine leukemia viruses (MLVs).

Evidence supporting the association of polyomavirus BK genome with prostate cancer

Prostate cancer (PCA) is the most frequent cancer in men. Exposure to infectious agents has been reported to have a putative role in tumorigenesis. Among the infectious agents, convincing evidence has been accumulated about the human polyomavirus BK (BKV). Tissue fresh specimens, serum, and urine samples were collected from 124 consecutive patients, 56 with PCA and 68 with benign prostatic hyperplasia (BPH). Quantitative PCR assays were used to assess the presence of BKV and JC virus (JCV) genomes. BKV-positive tissue specimens were found in 32.1 and 22.1 % of PCA and BPH patients, respectively; in PCA group the number of positive BKV specimens/patients was significantly higher than in BPH group (3.06 vs. 1.73, p = 0.02). JCV genome was found in the biopsies collected from 28.1 and 24.2 % of PCA and BPH patients, respectively, with no significant difference in the rate of JCV specimens/patients between PCA and BPH groups. Our results support the putative causal association between BKV genome and PCA. Further studies are required to demonstrate the direct pathogenetic role of BKV in the PCA occurrence and progression in order to clear the tempting way of vaccine prophylaxis.

Recombinant origin, contamination, and de-discovery of XMRV

The discovery and de-discovery of the xenotropic murine leukemia virus-related virus (XMRV) has been a tumultuous roller-coaster ride for scientists and patients. The initial associations of XMRV with chronic fatigue syndrome and prostate cancer, while providing much hope and optimism, have now been discredited and/or retracted following overwhelming evidence that (1) numerous patient cohorts from around the world are XMRV-negative, (2) the initial reports of XMRV-positive patients were due to contamination with mouse DNA, XMRV plasmid DNA, or virus from the 22Rv1 cell line and (3) XMRV is a laboratory-derived virus generated in the mid 1990s through recombination during passage of a prostate tumor xenograft in immuno-compromised mice. While these developments are disappointing to scientists and patients, they provide a valuable road map of potential pitfalls to the would-be microbe hunters.

Susceptibility of human lymphoid tissue cultured ex vivo to xenotropic murine leukemia virus-related virus (XMRV) infection

BACKGROUND

Xenotropic murine leukemia virus-related virus (XMRV) was generated after a recombination event between two endogenous murine leukemia viruses during the production of a prostate cancer cell line. Although the associations of the XMRV infection with human diseases appear unlikely, the XMRV is a retrovirus of undefined pathogenic potential, able to replicate in human cells in vitro. Since recent studies using animal models for infection have yielded conflicting results, we set out an ex vivo model for XMRV infection of human tonsillar tissue to determine whether XMRV produced by 22Rv1 cells is able to replicate in human lymphoid organs. Tonsil blocks were infected and infection kinetics and its pathogenic effects were monitored

RESULTS

XMRV, though restricted by APOBEC, enters and integrates into the tissue cells. The infection did not result in changes of T or B-cells, immune activation, nor inflammatory chemokines. Infectious viruses could be recovered from supernatants of infected tonsils by reinfecting DERSE XMRV indicator cell line, although these supernatants could not establish a new infection in fresh tonsil culture, indicating that in our model, the viral replication is controlled by innate antiviral restriction factors.

CONCLUSIONS

Overall, the replication-competent retrovirus XMRV, present in a high number of laboratories, is able to infect human lymphoid tissue and produce infectious viruses, even though they were unable to establish a new infection in fresh tonsillar tissue. Hereby, laboratories working with cell lines producing XMRV should have knowledge and understanding of the potential biological biohazardous risks of this virus.

Restricted replication of xenotropic murine leukemia virus-related virus in pigtailed macaques

Although xenotropic murine leukemia virus-related virus (XMRV) has been previously linked to prostate cancer and myalgic encephalomyelitis/chronic fatigue syndrome, recent data indicate that results interpreted as evidence of human XMRV infection reflect laboratory contamination rather than authentic in vivo infection. Nevertheless, XMRV is a retrovirus of undefined pathogenic potential that is able to replicate in human cells. Here we describe a comprehensive analysis of two male pigtailed macaques (Macaca nemestrina) experimentally infected with XMRV. Following intravenous inoculation with >10(10) RNA copy equivalents of XMRV, viral replication was limited and transient, peaking at ≤2,200 viral RNA (vRNA) copies/ml plasma and becoming undetectable by 4 weeks postinfection, though viral DNA (vDNA) in peripheral blood mononuclear cells remained detectable through 119 days of follow-up. Similarly, vRNA was not detectable in lymph nodes by in situ hybridization despite detectable vDNA. Sequencing of cell-associated vDNA revealed extensive G-to-A hypermutation, suggestive of APOBEC-mediated viral restriction. Consistent with limited viral replication, we found transient upregulation of type I interferon responses that returned to baseline by 2 weeks postinfection, no detectable cellular immune responses, and limited or no spread to prostate tissue. Antibody responses, including neutralizing antibodies, however, were detectable by 2 weeks postinfection and maintained throughout the study. Both animals were healthy for the duration of follow-up. These findings indicate that XMRV replication and spread were limited in pigtailed macaques, predominantly by APOBEC-mediated hypermutation. Given that human APOBEC proteins restrict XMRV infection in vitro, human XMRV infection, if it occurred, would be expected to be characterized by similarly limited viral replication and spread.