Viruses - The New Cancer Hunters

Main Category: Cancer / Oncology
Article Date: 30 Jan 2006 - 0:00 PDT

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Researchers from the Hebrew University have succeeded in isolating a variant of the Newcastle Disease Virus (NDV-HUJ), which usually affects birds, in order to specifically target cancer cells. The research, which has already cleared the first phase of clinical trials, is already patented and if all goes well it might receive an approval for clinical use, changing the way we think about viruses forever.

Professors Amos Panet and Zichria Zakay-Rones, from the Department of Virology at the Hebrew University Hadassah Medical School, have been involved during the past five years in research that could create a new and effective weapon in the fight against cancer, as well as change the way we look at viruses. As an obligatory parasitic entity with no independent life of its own, a virus must enter a living cell in order to multiply.

The viral life-cycle begins when the virus inserts its genetic material into the host's cell, forcing it to replicate the virus' components, and eventually leading to the death of the cell. The NDV-HUJ virus, discovered by the Hebrew University in Jerusalem team, acts in a similar way, except for its outstanding preference for infecting cancerous cells. NDV-HUJ is a natural variant of NDV (Newcastle Disease Virus) which usually affects birds. Being an attenuated variant (e.g., weakened virus), it is innately preferentially targets and replicates in certain types of tumor cells, leaving normal cells almost unaffected.

A plausible (though not yet proved) explanation suggested by the researchers for this interesting behavior might be linked to some deficiencies of the Interferon-system inside cancerous cells. Interferon is a natural anti-viral substance which serves as the body's first line of defense against viruses. As opposed to the activation of the immune system and antibodies production, the Interferon system is activated immediately after the infection process has taken place, and acts to diminish the viral replication. Thus, deficiencies in this system make the cancerous cells more vulnerable to viral infections such as the NDV-HUJ. Chemotherapy, the current main weapon against cancer is non-selectively effective against proliferating cells and thus is severely harmful to healthy tissues, such as the hair, skin, digestive and immune systems. Using the NDV-HUJ virus will enable doctors to specifically target cancer cells without the risk of severely affecting the patient.

Viro-therapy is not a new idea. Its roots could be found in the mid 20th Century, when a number of physicians noticed an interesting phenomenon: some of their patients, who suffered from cancer and had an incidental viral infection, or subjected to vaccination, were now improving, experiencing a remission from their symptoms. In the 40's and 50's, studies were conducted in animal models to evaluate the use of viruses in the treatment of tumors, and in 1956, one of the first human clinical trials with an oncolytic virus ("onco" meaning cancer, "lytic" meaning "killing") was conducted in patients with advanced-stage cervical cancer. Nevertheless, systematic research of this field was delayed for years, due to lack of more advanced technologies. In recent years the research in the field of oncolytic viruses began to move forward more quickly. Last year it was reported that researchers from the Ohio State University Medical Center have been trying to use a genetically engineered herpes virus against one type of brain tumor in mice. The Ohio State researchers have modified one of the herpes genes so it will be active only in cells that made a protein called nestin. The results of the mice research were encouraging and some of the mice who received the treatment lived a few days more than the control group who did not receive the treatment…. (continues, click below)

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