Sachiko Karaki

Development and validation of algorithms for measuring G-protein coupled receptor activation in cells using the LSC-based imaging cytometer platform.

A cell‐based assay system (Transfluor) has been developed for measurement of G‐protein coupled receptor (GPCR) activity by using cells transfected to express a fusion protein of arrestin plus green fluorescent protein (GFP) and the target GPCR. Upon agonist stimulation, the arrestin‐GFP translocates to and binds the activated GPCR at the plasma membrane. The receptor/arrestin‐GFP complexes then localize in clathrin‐coated pits and/or intracellular vesicles. This redistribution of arrestin‐GFP into condensed fluorescent spots is useful for visually monitoring the active status of GPCRs and its quantitation is possible with certain types of digital image analysis systems.

Characterization of beta-tricalcium phosphate as a novel immunomodulator

Calcium phosphate (CaP) ceramics including hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) have been widely used for bone substitution in orthopedic, maxillofacial and dental surgery, as well as in tumor resections. CaP particles are also known to cause inflammatory responses, which are thought to be an unfavorable characteristic of prosthetic coating materials. On the other hand, the immunostimulatory effect of β-TCP induces an anti-tumor effect in xenograft tumor models in athymic mice. To date, in depth analysis of the biological effects of β-TCP has not been studied in mice. In the present study, in vivo biological effects of β-TCP were investigated by subcutaneously injecting β-TCP particles into mice. This induced extensive migration of immune cells to the area surrounding the injection. In addition, we found that in vitro treatment with β-TCP in murine monocyte/macrophage cells (J774A.1) induced up-regulation of surface expression of CD86, and increased production of TNF-α, MIP-1α, and sICAM-1. Furthermore, conditioned medium from J774A.1 cells treated with β-TCP facilitated migration of murine splenocytes in a transwell migration assay. These findings clarify that β-TCP induces an immunostimulatory effect in mice, and suggest a potential for β-TCP as a novel adjuvant for cancer therapy.

Innate Immunity-Based Immunotherapy of Cancer

The immune system protects against invading pathogens and transformed cells, including cancer. Mammalian immune system is divided into two major categories, i.e., innate and adaptive immunity. Innate immunity consists of cellular and biochemical defense mechanisms that respond in the early phase after harmful events, such as encounters with microbes or transformed cells. The cellular components of innate immunity include dendritic cells (DCs), macrophages and monocytes, polynuclear cells (e.g. neutrophils and mast cells), natural killer (NK) cells, ┛├ T cells and natural killer T (NKT) cells. Adaptive immunity consists of T and B lymphocytes and their humoral mediators, including cytokines and antibodies, and achieves excellent antigen specificity by somatic rearrangement of the antigen receptor genes of each lymphocyte lineage; T cell receptor for T lymphocytes and immunoglobulin for B lymphocytes, respectively. Furthermore, another excellent characteristic of adaptive immunity is a “memory system” to maintain antigenspecific lymphocytes in a functionally quiescent or slowly cycling state for many years. The memory system enables host organisms to respond to the second and subsequent exposure to the same or related antigens in a more rapid and effective manner.