Susan G Komen  
I've Been Diagnosed With Breast Cancer Someone I Know Was Diagnosed Share Your Story Join Us And Stay Informed Donate To End Breast Cancer
    Home > Research & Grants > Grants Program > Research Grants > Research Grants Awarded > Abstract
    Awarded Grants
    Thermal Enhancement of Natural Killer Cell Recognition and Killing of Breast Tumors

    Scientific Abstract:
    Thermal Enhancement of Natural Killer Cell Recognition and Killing of Breast Tumors. Background: Natural killer (NK) cells are important effectors of the innate immune system because of their ability to kill virally infected cells and tumor cells. The recognition of these target cells by NK cells is done by surface receptors, one of which is the activating receptor NKG2D. It is proposed that NKG2D, which is upregulated upon NK cell activation, is involved in innate immune surveillance of tumor cells. Known ligands of the NKG2D receptor are MIC A, MIC B and ULBP in humans and Rae-1, H60 and Mult1 in mice. Immune recognition of tumor cells by NK cells has in some cases been found to depend on the capacity of NK cells to recognize “induced-self” ligands such as Rae1/H60 and MIC proteins. Importantly, some forms of cellular stress have been observed to regulate the expression of these ligands. Elements in the promoter region of MICA/B are similar to that of heat shock protein genes and permit the upregulation of these proteins in stressed tissues, but not healthy, normal tissues. Previous studies from our group have shown that a mild fever like whole body heating of tumor bearing mice on its own can temporarily delay the growth of breast tumors. The anti-tumor effect of elevated temperatures appeared to be dependent on NK cells, as determined using antibodies that block NK activity in vivo. Together these pieces of information suggest that NK cells may function in the thermal control of breast tumor growth. Preliminary data of our group suggests that the mRNA levels of the NKG2D ligands on tumor cells are also increased with this mild thermal stress. Even though there is indication of stress induction of the human NK activation receptor ligands, no research done before has directly addressed physiologically relevant heat-related upregulation of mouse ligands and NKG2D itself. Hypothesis: We hypothesize that the expression of NKG2D on NK cells and its ligands on breast tumor cells is thermally sensitive, and fever like temperatures will enhance the levels of these molecules on cell surfaces resulting in better breast tumor recognition and killing by NK cells. Specific Aims and Study Design: To test this hypothesis, Aim 1 will investigate the ability of mild thermal stress to increase NKG2D expression on mouse and human NK cells, and determine whether this correlates with the activation of NK cells. Here we will compare heated and non-heated NK cells for their mRNA and protein expression levels of NKG2D as well as other more classical markers of NK cell activation. Aim 2 will then determine whether the expression of ligands for NKG2D (mouse and human) increases on breast tumor cells with our mild thermal stress protocol. Both mRNA and protein expression levels of MICA or MICB on human breast tumor cells and the mouse homologues on murine breast tumor cells will be analyzed. Lastly, Aim 3 will examine the effects of thermal stress on the interaction of NK cells and tumor targets, and test whether thermally induced NK mediated tumor growth control in vitro and in vivo depends upon NKG2D recognition of its ligands. The cellular interactions will be measured using different fluorescent probes on NK cells and targets, where a double fluorescent signal will indicate the formation of a NK cell-target cell complex. The tumor cell lysis that results from such interactions will also be analyzed by LDH and/or flow cytometric assays. Antibody blocking studies will then help determine the specific contribution of the NKG2D receptor-ligand interaction on the thermal regulation of NK-target cell interactions and/or NK mediated lytic activity in vitro and tumor growth control in vivo. Significance: The proposed work will allow better understanding of NK-tumor cell interactions, and will help provide the necessary information to explain the immunological effects of mild physiological thermal stress in controlling breast tumor growth. These results will help define the most rational use of thermal therapy in the breast cancer clinic.

    Lay Abstract:
    Thermal Enhancement of Natural Killer Cell Recognition and Killing of Breast Tumors Increased attention is being devoted to finding ways to enhance a breast cancer patient’s immune response against her own tumor. Natural killer (NK) cells are important cells of the immune system because of their ability to recognize and kill tumor cells. NK cells have many surface receptors specific for binding to ligands on tumor cells but the details underlying this interaction (which are needed for identifying ways to enhance the killing of tumor cells by NK cells) are still largely unknown. This research proposal focuses on analyzing the interaction between receptors on NK cells and the tumor cell surface molecules (or ligands) that it recognizes and asking whether conditions such as fever-like hyperthermia will increase this interaction, and as a result, increase tumor cell killing. Our group has been interested in investigating the potential use of mild thermal stimuli to support the therapies of breast cancer patients. Importantly, our previous studies have shown that a physiologically relevant, mild fever-like whole body heating can temporarily delay breast tumor growth in mice. The anti-tumor effect of elevated temperatures appeared to be dependent on NK cells, as determined by blocking NK activity in these mice and observing the loss of the tumor growth delay. Together these pieces of information suggest several potential mechanisms by which thermally regulated NK cells may function to control breast tumor growth. The predoctoral proposal described here hypothesizes that fever range temperatures results in better tumor recognition and killing by NK cells in part through the thermal regulation of both the recognition receptors on NK cells and its counterpart ligand molecules on tumor cells. The first aim of this project is to determine if the expression of the NK cell receptor NKG2D is thermally regulated. The second aim will then determine whether or not expression of the corresponding NKG2D ligands on tumor cells is also regulated by mild thermal stress (not just classic heat shock protocols). As a final aim, we will correlate these changes with tumor recognition and killing by NK cells, examining the effects of mild thermal stress on the interaction of NK cells and tumor targets, and whether any effect is lost when the specific receptor-ligand complex formation is blocked. Our ultimate goal is to provide insight on how to better target breast tumors for immune recognition, potentially through the clinical use of thermal therapy as a novel complimentary or alternative treatment for breast cancer patients. The proposed work will first allow a better understanding of NK cell-tumor cell interactions. This proposal will also help to define the cellular mechanisms by which mild physiological thermal therapies aid to control breast tumor growth.