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Reovirus may be a Novel Approach to Prostate Cancer Treatment

March 9, 2010

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• Therapeutic activity demonstrated in vitro and in vivo.
• Virus’ effect is selective for prostate cancer; not normal tissue.
• Safety and efficacy shown in early-stage prostate cancer.

PHILADELPHIA — Researchers in Canada have detected a novel oncolytic viral therapy against prostate cancer with use of a virus called the reovirus, according to study results published in Cancer Research, a journal of the American Association for Cancer Research.

The respiratory, enteric, orphan virus (commonly known as reovirus) is a non-attenuated, environmental virus that has shown oncolytic potential against many types of cancer, specifically lymphoid, ovarian, breast, pancreatic and high grade glioma cancer, according to the study. This is the first time the virus has been studied against prostate cancer.

“The reovirus is a very common, ubiquitous virus that most people are exposed to. As far as we know, it doesn’t cause any significant illness in humans, even though when someone is exposed to it, it manifests, at most, as a mild respiratory infection or mild diarrhea,” said researcher Don Morris, M.D., Ph.D., medical oncologist in the Department of Oncology at the Tom Baker Cancer Center in Alberta, Canada.

“For the treatment of localized prostate cancer, we found that the reovirus is safe and has evidence of specific tumor vs. normal prostate cell efficacy,” added Morris.

Using preclinical and clinical settings, Morris and colleagues examined the efficacy of the reovirus as an experimental therapeutic for prostate cancer in vitro and in vivo. Among the six patients who participated in the study, all had early-stage, organ-confined prostate cancer. Each patient underwent a single intralesional virus injection into a suitable prostate cancer nodule via transrectal ultrasound guidance. Three weeks later, Morris and colleagues removed the prostate as part of the patient’s standard treatment for correlative science analysis.

Findings showed safety and efficacy with minimal toxicity and no viral replication in the normal parts of the prostate, according to Morris. Cancer cell death was evident in the prostate. Studies to date have suggested that the virus’ side effects are relatively modest, consisting of mild, self-limiting, flu-like symptoms.

“Our results are a stepping stone into future prostate cancer clinical trials with another category of cancer therapeutics,” he said.

Robert Clarke, Ph.D., D.Sc., professor of oncology at Lombardi Comprehensive Cancer Center at Georgetown University and an editorial board member of Cancer Research, agreed, stating that he believes this study is worthy of subsequent clinical trials of the reovirus as a possible way of treating some prostate cancers.

“People have known of this application of the reovirus in trials, but no one to my knowledge has conducted studies in prostate cancer,” said Clarke, who was not associated with this study. “I think this is an interesting approach. There is not a lot done in oncolytics, but clearly it is an area that is getting increasing attention, and we need everything we can get our hands on to make a difference in these patients.”

Funding for this research was provided by the Alberta Cancer Foundation, Oncolytics Biotech Inc. and the Prostate Cancer Research Foundation of Canada.

Download photos of the researchers:
Don Morris, M.D., Ph.D.
Robert Clarke, Ph.D., D.Sc.

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The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, the AACR is the world’s oldest and largest professional organization dedicated to advancing cancer research. The membership includes 30,000 basic, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and nearly 90 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants, research fellowship and career development awards. The AACR Annual Meeting attracts more than 16,000 participants who share the latest discoveries and developments in the field. Special conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care. The AACR publishes six major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; and Cancer Prevention Research. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists. CR provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship and advocacy.

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One Comment leave one →
  1. Liting Song permalink
    March 9, 2010 11:29 pm

    We believe that activated Ras or an activated element of Ras pathway is not the determinant of a cell’s sensitivity to reovirus infection; Rather, lack of reovirus receptor(s) on the cell’s surface should be the essential reason for a cell’s resistance to reovirus infection just as most other viruses, and as van Houdt et al (Cancer Gene Ther 2008; 15: 284-292), van den Wollenberg et al (Gene Ther 2008; 15: 1567-1578), and Antar et al ( Cell Host Microbe 2009; 5:59-71) reported recently (Song et al. Cancer Gene Ther 2009; 16: 382. Epub 2008 Oct 24; and Song et al. Proc Am Assoc Cancer Res 2000; 41: 350).

    Reoviruses were replicated in cell cultures in the lab for more than 50 years using normal monkey and mouse cells. Reovirus can cause cytopathic effect (CPE) on normal monkey kidney LLC-MK2 cells and mouse L929 cells, and after a few days, reovirus will destroy and kill the cells it infected eventually in vitro.

    In my opinion, the key point is that reovirus is not special at all, just like most other viruses, it can infect and kill both normal cells and cancer cells if the cells have reovirus receptors. Therefore, revirus is unlikely to be a practical and effective anticancer agent.

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