KOSEN 한인과학기술자네트워크

Natural killer (NK) cells are large granular lymphocytes capable of clearing both virus-infected and transformed cells. NK cell cytotoxicity is controlled by the integration of activating and inhibitory receptor signaling at the NK cell immune synapse (IS) formed between NK and target cells. NK cells can also respond by producing cytokines, e.g., interferon-γ (IFN-γ) or tumor necrosis factor-α (TNF-α), and are known to be activated by cytokines like interleukin (IL)-2, IL-12, and IL-15. Activating receptors, such as DNAM-1, NKp44, and KLRB1, are upregulated, while inhibitory receptors, like KIR2DL2 and KIR3DL3, are downregulated after exposure to IL-2. In addition, increased cell-cell adhesion has been directly coupled to cytotoxicity. NK cells are able to lyse target cells but require the right combination of activating signals, and, therefore, seem more tightly regulated than IL-2-activated NK cells.

In our lab, we are focusing on the identification of cytotoxic dynamics of NK cells. Using time-lapse imaging, we examine "cytotoxic dynamics", such as killing behavior, contact dynamics, motility and directionality of NK cells as well as dying process of cancer cells.

Mesenchymal stem cells (MSCs) are present in diverse tissues and organs, including bone marrow, umbilical cord, adipose tissue, and placenta. MSCs can expand easily in vitro and have regenerative stem cell properties and potent immunoregulatory activity. They inhibit the functions of dendritic cells, B cells, and T cells, but enhance those of regulatory T cells by producing immunoregulatory molecules such as transforming growth factor-β, hepatic growth factors, prostaglandin E2, interleukin-10, indolamine 2,3-dioxygenase, nitric oxide, heme oxygenase-1, and human leukocyte antigen-G. These properties make MSCs promising therapeutic candidates for the treatment of autoimmune diseases. However, the detailed mechanisms by which MSCs exert their immunomodulatory functions are still incompletely understood.

In our lab, we focus on identifying the immunoregulatory mechanisms of MSCs. Our hypothesis is that MSCs might regulate the functions of immune cells (T cells, B cells, dendritic cells, and so on) via producing soluble mediators and direct cell-cell contact. To prove it, two strategies are established. First, we are trying to identify cell-type-specific soluble mediator. Second, using time-lapse imaging, we are studying the cell type-specific contact dynamics, such as contact duration, contact frequency, motility speeds, directionality, and their relevance with chemokine axis.

Our lab has assay systems to evaluate the efficacy of immunomodulators (stimulants and suppressants). In enzymatic assay, we general identify the direct molecular target of compounds by using kinase assay. In cellular assay, we generally test the effect of compounds on viability, proliferation and Ab production of B cells, proliferation and cytokine production of T cells, maturation of dendritic cells (6 assay parameters), and cytokine production of macrophages. In addition, we examine the effect of compounds on signaling pathways downstream from TCR, BCR, TLRs, and cytokine receptors. In animal assay, we have syngeneic tumor model (tumor growth and metastasis) to develop immunostimulants and inflammation models (lupus and rheumatoid arthritis) to develop anti-inflammatory drugs.

We also have assay systems to evaluate the efficacy and mechanisms of anti-cancer drug candidates. In enzymatic assay, we general identify the direct molecular target of compounds by using kinase assay. In cellular assays, we examine the cytotoxic potential of compounds on more than 60 human cancer cell lines by using SRB, MTT, and SRB assay (for tumor growth inhibitor). We also examine the invasion and migration of endothelial cells (for angiogenesis blocker) and cancer cells (for metastasis inhibitor). We used qRT-PCR to examine the effects of compounds on gene expression and WB on protein expression/phosphorylation. In animal assay, we have syngeneic murine tumor model, xenograft human tumor model (nude mice), and lung metastasis models.