XML Feed for RxPG News   Add RxPG News Headlines to My Yahoo!   Javascript Syndication for RxPG News

Research Health World General
 
  Home
 
 Latest Research
 Cancer
  Breast
  Skin
  Blood
  Prostate
  Liver
  Colon
  Thyroid
  Endometrial
  Brain
  Therapy
  Risk Factors
  Esophageal
  Bladder
  Lung
  Rectal Cancer
  Pancreatic Cancer
  Bone Cancer
  Cervical Cancer
  Testicular Cancer
  Gastric Cancer
  Ovarian Cancer
  Nerve Tissue
  Renal Cell Carcinoma
 Psychiatry
 Genetics
 Surgery
 Aging
 Ophthalmology
 Gynaecology
 Neurosciences
 Pharmacology
 Cardiology
 Obstetrics
 Infectious Diseases
 Respiratory Medicine
 Pathology
 Endocrinology
 Immunology
 Nephrology
 Gastroenterology
 Biotechnology
 Radiology
 Dermatology
 Microbiology
 Haematology
 Dental
 ENT
 Environment
 Embryology
 Orthopedics
 Metabolism
 Anaethesia
 Paediatrics
 Public Health
 Urology
 Musculoskeletal
 Clinical Trials
 Physiology
 Biochemistry
 Cytology
 Traumatology
 Rheumatology
 
 Medical News
 Health
 Opinion
 Healthcare
 Professionals
 Launch
 Awards & Prizes
 
 Careers
 Medical
 Nursing
 Dental
 
 Special Topics
 Euthanasia
 Ethics
 Evolution
 Odd Medical News
 Feature
 
 World News
 Tsunami
 Epidemics
 Climate
 Business
Search

Last Updated: Aug 19th, 2006 - 22:18:38

Prostate Channel
subscribe to Prostate newsletter

Latest Research : Cancer : Prostate

   DISCUSS   |   EMAIL   |   PRINT
Human infections documented with a native rodent retrovirus
Mar 31, 2006, 12:51, Reviewed by: Dr. Priya Saxena

The search for the new virus began when Silverman and his colleagues provided samples of a rare familial prostate cancer in which the viral-defense gene, RNASEL, had been mutated in a specific way.

 
Howard Hughes Medical Institute researchers and their colleagues have discovered a new retrovirus in humans that is closely related to a cancer-causing virus found in mice. Their findings describe the first documented cases of human infection with a retrovirus that is native to rodents.

The researchers discovered the virus in patients with a rare type of prostate cancer. The patients in the study have a genetic mutation that compromised some of their natural defenses against viral infection. Thus, the researchers said their discovery raises the possibility that increased susceptibility to viral infection may play a role in development of some cancers. However, they emphasized that their findings by no means implicate the virus, dubbed XMRV, in causing prostate cancer. The virus may well have flourished as a result of the failure of the defense mechanism; and other factors such as chronic inflammation may play a more direct role in the cancer.

The discovery of the new virus was made by an interdisciplinary research team led by Robert Silverman of Cleveland Clinic and HHMI investigators Joseph DeRisi and Don Ganem, both at the University of California at San Francisco. The search for the new virus began when Silverman and his colleagues provided samples of a rare familial prostate cancer in which the viral-defense gene, RNASEL, had been mutated in a specific way. This mutation compromised the function of the enzyme produced by RNASEL, which normally shreds viral genetic material. Infected cells carrying the shredded viral genetic material are usually targeted for destruction by the immune system. While some scientists believe that such vulnerability to viral infection is connected to prostate cancer in these rare cases, others have presented evidence contesting that theory.

To screen for viruses in the prostate tissue samples, DeRisi and Ganem used the Virochip, which was invented by DeRisi and his colleagues. The Virochip consists of a microarray of some 20,000 characteristic gene sequences — called oligonucleotides — representing a vast array of known viruses. The oligonucleotides are deposited as tiny spots on a small glass chip.

To detect viruses from tissue samples, the researchers isolated genetic material from each sample and tagged the genetic material with a fluorescent tracer. They then applied the fluorescently tagged genetic material to the microarray chip. Since genes tended to adhere to those with a complementary genetic sequence, any viral gene sequences in the sample would attach themselves to corresponding viral sequences on the chip. The telltale fluorescence on spots on the chip signaled the presence of viral genetic material in the sample.

Although the Virochip contains only sequences from known viruses, DeRisi said it can also detect new viruses because they invariably contain sequences that have been conserved in their evolution from related viruses.

The initial screen of the RNASEL-mutant prostate cancers revealed the presence of a genetic sequence that closely resembled that of a mouse virus called murine leukemia virus (MuLV). Murine leukemia virus is known as an endogenous virus because it normally exists as an integrated part of the mouse genome, rather than as independent, infective particle. The RNA is then reverse transcribed into DNA that is integrated into the DNA of the host cell the virus is infecting.

When the researchers isolated and sequenced the genome of the virus, they found that it was a xenotropic virus - one that can only grow in foreign cells other than mouse cells. Thus, they named the virus, Xenotropic MuLV-related virus, or XMRV.

According to DeRisi, the Virochip made it possible to analyze these samples without preconceived biases about what viruses might be present. “We would never have looked for this class of virus if it wasn't for the virus chip.”

Importantly, the researchers found that prostate cancers in which both copies of the RNASEL gene were crippled by mutation showed much more frequent XMRV infection than did those cancers that still had one normal copy of the RNASEL gene.

“This link between the virus and RNASEL is the second finding that is important and is firmly established in this study,” noted Ganem. “We don't see the infection in people who don't have the RNASEL mutation, which suggests strongly RNASEL is an important part of the defense against retroviral infection. DeRisi pointed out that detailed comparison of samples of the virus between people found that - although all were XMRV - they showed tiny genetic variations. Ganem cautioned that any link between XMRV and prostate cancer is tenuous at best. “First, the genetic variant we studied occurs in familial clusters that constitute only a very small sliver of prostate cancers,” he said. “And secondly, there are many reasons to believe that the virus might not relate to prostate cancer.”

For example, he pointed out, analysis of prostate tissue by Silverman and his colleagues indicated that the virus appears only in a small percentage of connective tissue cells, called stromal cells, rather than in the tumors themselves. “So, one interpretation could be that the infection is entirely incidental to prostate cancer,” said Ganem. Clearly XMRV is not a classic oncogenic virus.”

Nevertheless, said Ganem, an indirect link to cancer cannot be ruled out, since “in cancer research these days, there is a lot of interest in the stroma as the soil in which cancer arises.” He added that the chronic inflammation from infection of stromal tissues may play a role in triggering such cancers.

This initial finding raises many questions. How is the virus passed from person to person? And are people the natural reservoir of this virus, or is it some other organism?”

DeRisi and Ganem said they are planning studies to explore whether XMRV is restricted to prostate cancers or whether it is more widespread in the body and in other segments of the human population.
 

- A paper describing the findings was published on March 31, 2006, in the journal, Public Library of Science Pathogens.
 

www.hhmi.org

 
Subscribe to Prostate Newsletter
E-mail Address:

 



Related Prostate News

Gene therapy study takes aim at prostate cancer
Pain associated with prostatic biopsy is related to the site biopsied
Admixture mapping reveals locus for prostate cancer risk
Diet modification and stress reduction may attenuate progression of prostate cancer
Prostatic Irradiation Doesn’t Lead To Any Appreciable Increase in Rectal Cancer Risk
Pomegranate Juice Slows PSA Acceleration Rate
Pomegranate juice could kill cancer cells
Early estrogen exposure leads to later prostate cancer risk
JHDM2A enzyme induced H3K9 demethylation offers new look at male hormone regulation
What is the appropriate age to stop prostate cancer screening?


For any corrections of factual information, to contact the editors or to send any medical news or health news press releases, use feedback form

Top of Page

 

© Copyright 2004 onwards by RxPG Medical Solutions Private Limited
Contact Us