Since cancer is the leading cause of death in Japan, we need to develop novel strategies to cure it. Tumor consists of not only cancer cells but also the non-cancerous cells including fibroblast, immune cells and cells that comprise the blood and lymphatic vessels. We aim to elucidate the mechanisms how cancer cells become malignant by the various cytokines in cancer microenvironment in order to develop novel therapeutic strategies targeting multiple components of cancer microenvironment.
(1) Understanding the molecular mechanisms underlying endothelial-mesenchymal transition (EndMT)
Endothelial cells undergo differentiation into mesenchymal cells during not only various physiological processes including heart valve formation but also pathological processes including cancer progression, heart failure and diabetes. However, the molecular mechanisms that regulate such endothelial-mesenchymal transition (EndMT) remain to be elucidated. We aim to study the molecular mechanisms underlying EndMT in order to identify novel targets and attempt to develop therapeutic strategies for EndMT-related diseases.
(2) Elucidation of the molecular mechanisms underlying tumor angio- and lympangiognesis
Tumor angiogenesis and lymphangiogenesis are key features of tumor progression and metastasis. While multiple signaling pathways have been implicated in the formation of blood and lymphatic vessels, the molecular mechanisms underlying these processes have not yet fully elucidated. Recent findings revealed that members of the transforming growth factor-β (TGF-β) family play pivotal roles on in angiogenesis and lymphangiogenesis, and that abnormalities in TGF-β family signaling lead to development of certain vascular disorders, including hereditary hemorrhagic telangiectasia (HHT), pulmonary arterial hypertension, Marfan syndrome and Loeys-Dietz syndrome. We attempt to elucidate the molecular mechanisms how TGF-β family signals regulate antiogenesis and lymphaniogenesis in tumor microenvironment. In addition, we elucidated the molecular mechanism for anti-angiogenesis by vasohibin-1 (VASH1). We are conducting basic research aimed at suppressing tumor progression through the functional analysis of VASH1.
(3) Understanding the molecular mechanisms underlying metastasis of cancer cells
Epithelial-mesenchymal transition (EMT) plays important roles in various physiological and pathological processes, and is regulated by signaling pathways mediated by cytokines including TGF-β. Using various types of in vitro cultured oral carcinoma cells and in vivo systems, we aim to identify the molecules involved in the acquisition of invasive properties of cancer cells, in order to develop novel therapeutic strategies.
(4) Structural and functional mapping of lysosomal membranesc
Lysosomes are ubiquitous organelles rich in hydrolytic enzymes, responsible for the degradation of macroBio- Matrix molecules derived from the extracellular space through endocytosis or phagocytosis, and from the cytoplasm through autophagy. These processes are vital to acquire energy source and essential materials, to defend against pathogen, and to clear unnecessary or potentially harmful intracellular obstacles. Furthermore, accumulating evidence has revealed that the lysosome surface is a crucial site for the activation of mammalian or mechanistic target of rapamycin complex 1 (mTORC1), a master regulator of cell growth and metabolism. mTORC1. Clinically, impairment of lysosome function gives rise to progressive and ultimately serious damages in widespread tissue and organ, particularly in brain, bones and connective tissues. Lysosome-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2) have a large, heavily glycosylated luminal domain composed of the two subdomains, and are the most abundant protein components in lysosome membranes. LAMP-1 and LAMP-2 have distinct functions, and the presence of both proteins together is required for the vital essential regulation of autophagy to avoid embryonic lethality. However, the structural aspects of LAMP-1 and LAMP-2 haves not been elucidated. Here, we demonstrated that the subdomains of LAMP-1 and LAMP-2 have adopt the unique β-prism fold. Furthermore, we found that the N-domain of the LAMP-1 is necessary, whereas that of LAMP-2 is repressive, for the organization of a multimeric assembly of the LAMPs. Accordingly, the present study suggests for the first time that the assembly modes of LAMP-1 and LAMP-2 are different, which may underlie their distinct functions [ Biochemical and Biophysical Research Communications 479, 489-495 (2016)] .
(5) Heparan sulfate proteoglycan-dependent cellular logistics
Heparan sulfate proteoglycans (HSPGs) are one of the basic constituents of plasma membranes and have ability to interact with a number of the extracellular ligands. HSPGs have been suggested to mediate the tra trafficking of various macromolecules from the cell surface. Growth factors, cytokines, lipoproteins, cell penetrating peptides, polycation-nucleic acid complexes, along with exosomes, and pathogens enter cells through HSPG-dependent endocytosis. HSPGs-dependent endocytic events have been involved in tumor progression, stressing the importance of the identi identification of HSPG species participating in a formation of various endocytic complexes. We have characterized the intracellular trafficking complexes formed in the presence of HSPGs in a rat C6 glioma cell line model. Successful isolation of HSPG-positive transport vesicles followed by detailed proteomic analysis allowed us the identification of over eighty proteins related to vesicular transport; i.e. endocytosis or recycling. Part of HSPGs in glioma cells found to be internalized through clathrin-dependent endocytosis and underwent recycling. Further characterization of HSPG-rich vesicular compartments will help us understand the nature of HSPG-ligand interactions and to design the tools for targeted delivery of ligands into the cells (reported in Cancer Genomics & Proteomics, 2016, 13, 443-452).
(6) Posture, behavior, and motion sickness of common marmosets in low gravities.
In planetary development projects such as manned Mars exploration that will take longer than 3 years, longterm biological adaptation to weightlessness and partial-gravity environments is a critical issue. Since rodents of short lifespan (rats and mice) cannot survive in such a long-term flight, other animals of longer lifespan must be used alternatively so as to conduct appropriate studies on posture and exploration as well as voice communication and social behaviors of animals that have some relevance to long-term manned spaceflight. Common marmoset belonging to the same anthropoid with humans has a lifespan of 15 years is characterized by unique social behavior resembling humans with abundant squealing. In parabolic flight experiment carried out in February 2016, we first examined the adaptation and social behavior of common marmoset under such conditions as Moon and Mars simulation or weightlessness. We have gained new knowledge on the response and behavior of primates in partial gravities.
(7) Unraveling of the physiological role of VASH1 as a detyrosination enzyme on α-tubulin
VASH1, which is induced expression by VEGF stimulation in endothelial cells, also works as an enzyme of detyrosination. Detyrosination is one of the post-translational modification of microtubules, it is known that detyrosinated microtubules play key role for several physiological phenomena, such as a chromosome partition in mitosis or a functional beating of heart. We have revealed the molecular mechanism that VASH1 inhibits VEGF/VEGFR2- or FGF2/FGFR1-signaling through the blockage of receptor endocytosis by the increase of detyrosinated α-tubulin, and thereby exerting anti-angiogenic effects (reported in Angiogenesis, 2021, 24, 159-176). Now, we are conducting basic research aimed at molecularly elucidating of role as a detyrosination enzyme in the various physiological function of VASH1.