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        A stealthy way to

        combat tumors

        Biologists show that helper immune cells disguised as cancer cells can help
        rejuvenate T cells that attack tumors

              nder the right circumstances,
              the body’s T cells can detect
       Uand destroy cancer cells.
        However, in most cancer patients,
        T cells become disarmed once they
        enter the environment surrounding
        a tumor.
        Scientists are now trying to find
        ways to help treat patients by
        jumpstarting those lackluster
        T cells. Much of the research
        in this field, known as cancer
        immunotherapy, has focused on
        finding ways to stimulate those T
        cells directly. MIT researchers have
        now uncovered a possible new way
        to indirectly activate those T cells,   Image source:
        by recruiting a population of helper
        immune cells called dendritic cells.
                                             help to enhance the effectiveness   Dendritic cells are known to help
        In a new study, the researchers      of cancer immunotherapy, she says.   activate tumor-fighting T cells, but
        identified a specific subset of      In a study of mice, the researchers   there are many different subtypes of
        dendritic cells that have a unique   showed that stimulating these       dendritic cells, and their individual
        way of activating T cells. These     dendritic cells slowed the growth of   roles in T cell activation are not fully
        dendritic cells can cloak themselves   melanoma and colon tumors.        characterized. In this study, the MIT
        in tumor proteins, allowing them                                         team wanted to investigate which
        to impersonate cancer cells and      Spranger is the senior author of the   types of dendritic cells are involved
        trigger a strong T cell response.    study, which appears today in the   in T cell responses that successfully
                                             journal Immunity. The lead author of   eliminate tumors.
        “We knew that dendritic cells        the paper is MIT graduate student
        are incredibly important for the     Ellen Duong.                        To do that, they found a tumor
        antitumor immune response, but we                                        cell line, from a type of muscle
        didn’t know what really constitutes   Spontaneous regression             tumor, that has been shown to
        the optimal dendritic cell response                                      spontaneously regress in mice.
        to a tumor,” says Stefani Spranger,   When tumors begin to form, they    Such cell lines are difficult to find
        the Howard S. and Linda B. Stern     produce cancerous proteins that     because researchers usually don’t
        Career Development Professor at      T cells recognize as foreign.       keep them around if they can’t form
        MIT and a member of MIT’s Koch       This sometimes allows T cells to    tumors, Spranger says.
        Institute for Integrative Cancer     eliminate tumors before they get
        Research.                            very large. In other cases, tumors   Studying mice, they compared
                                             are able to secrete chemical signals   tumors produced by that regressive
        The results suggest that finding     that deactivate T cells, allowing
        ways to stimulate that specific      the tumors to continue growing                                8
        population of dendritic cells could   unchecked.

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