Scientists at Johns Hopkins have determined how the characteristic shedding of fatty substances, or lipids, by ovarian tumors allows the cancer to evade the body's immune system, leaving the disease to spread unchecked. Ovarian cancer is considered to be one of the most aggressive malignancies, killing more than 70 percent of diagnosed women within five years, including an estimated 15,000 this year.
In a two-year series of lab experiments, a team of researchers from the Johns Hopkins University School of Medicine and its Sidney Kimmel Comprehensive Cancer Center showed that fluid secretions from tumors, called ascites, which contain lipids and collect in the space surrounding cancerous ovaries, can totally suppress the action of natural killer T cells in the immune system.
Known as NKTs for short, these special T cells must be activated to do their job of jump-starting the immune response and signaling other kinds of white blood cells to rid the body of diseases or leave healthy tissue alone.
As part of the study, researchers collected lipid-filled ascites from 25 women with ovarian cancer and then exposed the lipid samples to an immune system test to see if they blocked activation of NKT cells.
In a report set to appear in the Dec.1 issue of the journal Clinical Cancer Research, the research team also found this evasive blocking tactic to be virtually exclusive to a specific protein, called CD1d, needed to activate the NKT cells.
Their experiments specifically showed that NKT activation was blocked between 10 percent and 100 percent after test cultures of cells that stimulate NKT cells were exposed to increasing concentrations of tumor-derived ascites.
Disrupted or stalled T cell action has been known to play a key role in the spread of several kinds of cancer, the scientists say. But until now, there was no firm evidence that tied a specific T cell in the body's defensive immune system to ovaria
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| Contact: David March dmarch1@jhmi.edu 410-955-1534 Johns Hopkins Medical Institutions Source:Eurekalert |