June 24, 2013  A promising new  treatment for breast cancer being developed at Virginia  Commonwealth University Massey Cancer Center and the VCU  Institute of Molecular Medicine (VIMM) has been shown in cell  culture and in animal models to selectively kill cancer stem  cells at the original tumor site and in distant metastases with  no toxic effects on healthy cells, including normal stem cells.  Cancer stem cells are critical to a cancer's ability to recur  following conventional chemotherapies and radiation therapy  because they can quickly multiply and establish new tumors that  are often therapy resistant.
    The study, published in the International Journal of    Cancer, focuses on a gene originally cloned in the    laboratory of primary investigator Paul B. Fisher, M.Ph., Ph.D.    The gene, melanoma differentiation associated gene-7 (mda-7),    also known as interleukin (IL)-24, has been shown to directly    impact two forms of cell suicide known as apoptosis and toxic    autophagy, regulate the development of new blood vessels and    also play a role in promoting cancer cell destruction by the    immune system. In the present study, the researchers used a    recombinant adenovirus vector, an engineered virus with    modified genetic material, known as Ad.mda-7 to deliver the    mda-7/IL-24 gene with its encoded protein directly to the    tumor.  
    "Therapy with the mda-7/IL-24 gene has been shown to be safe in    a phase I clinical trial involving patients with advanced    cancers, and prior studies in my laboratory and with    collaborators have shown that the gene could also be effective    against breast, prostate, lung, colorectal, ovarian, pancreatic    and brain cancers," says Fisher, Thelma Newmeyer Corman Endowed    Chair in Cancer Research and co-leader of the Cancer Molecular    Genetics program at VCU Massey, chairman of VCU School of    Medicine's Department of Human and Molecular Genetics and    director of the VCU Institute of Molecular Medicine. "Our study    demonstrates that this therapy may someday be an effective way    to eradicate both early and advanced stage breast cancer, and    could even be used to reduce the risk of cancer recurrence."  
    The researchers found that infection of human breast cancer    cells with the adenovirus decreased the proliferation of breast    cancer stem cells without affecting normal breast stem cells.    It was also shown to induce a stress response in the cells that    led to apoptosis by disrupting Wnt/B-catenin signaling, a    process cells rely upon to transmit signals that initiate    biological functions critical to survival. In mouse models, the    therapy profoundly inhibited the growth of tumors generated    from breast cancer stem cells and also killed cancer cells in    distant, uninjected tumors.  
    Since discovering the mda-7/IL-24 gene, Fisher and his team    have worked to develop better ways to deliver it to cancer    cells, including two cancer "terminator" viruses known as    Ad.5-CTV and Ad.5/3-CTV. Cancer terminator viruses are unique    because they are designed to replicate only within cancer cells    while delivering immune-modulating and toxic genes such as    MDA-7/IL-24. Coupled with a novel stealth delivery technique    known as ultrasound-targeted microbubble destruction (UTMD),    researchers can now systemically deliver viruses and    therapeutic genes and proteins directly to tumors and their    surrounding tissue (microenvironment) at both primary and    metastatic tumor sites. UTMD uses microscopic, gas-filled    bubbles that can be paired with viral therapies, therapeutic    genes and proteins, and imaging agents and can then be released    in a site and target-specific manner via ultrasound. Fisher and    his colleagues are pioneering this approach and have already    reported success in experiments utilizing UTMD technology and    mda-7/IL-24 gene therapy in prostate and colorectal cancer    models.  
    "We are hopeful that this targeted gene therapy could be safely    combined with conventional chemotherapies to significantly    improve outcomes for patients with breast cancer and    potentially a variety of other cancers," says Fisher. "When    paired with promising new delivery techniques such as UTMD,    physicians may one day be able to better target site-specific    cancers and also monitor the effectiveness of these types of    therapies in real time."  
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Targeted viral therapy destroys breast cancer stem cells in preclinical experiments