In this research, we will make full use of innovative in vivo imaging technology with medaka as the model organism, in which whole-body high-resolution fluorescence imaging is possible, to identify target molecules for suppressing and treating cancer metastasis and to elucidate the underlying mechanisms. Specifically, as the model organism for cancer, we will develop transgenic medaka lines in which the onset of fluorescence-labeled pancreatic cancer can be observed by the pancreas-specific forced expression of human cancer genes and fluorescent proteins. Furthermore, we will create immune-deficient medaka using genome editing techniques, and by transplanting fluorescence-labeled human cancer cells, we will develop medaka models that enable optically detailed observation of the in vivo kinetics of human cancer cells. As a base for these medaka models, we will use transgenic lines that have already been developed, in which in vivo visualization of the vascular system, including blood vessels and lymphatic vessels, is possible. This will allow us to investigate the relationship between cancer metastasis and the vascular system.
As for the whole-body observation of medaka cancer models described above, we will develop a light-sheet microscope that takes advantage of active optical devices based on liquid crystals (LCs). This microscope will allow us to construct 3D images over a wide field of view without unevenness of illumination light. Furthermore, improvements of LC optical devices will be made to achieve adaptive optics function that enables higher-order correction of not only spherical aberration but also asymmetric coma aberration and astigmatism. By applying these to the light source of a multi-photon excitation microscope, we will develop a microscope that can correct refractive index differences that arise from the heterogeneity of living tissues, and improve z-axis spatial resolution, in particular, thereby making it possible to observe fluorescence in the deep tissues of medaka.
We will integrate innovative medaka cancer models, fluorescence imaging technology, and optogenetic techniques to analyze the process of metastasis in a temporally and spatially dynamic fashion over a wide range or at high resolution, with the aim of identifying target cells and molecules that can be effective in preventing or suppressing cancer metastasis among the various molecules involved in metastasis formation. To perform detailed analysis of the signal transduction mechanisms, we will carry out compound screening by adding low molecular weight compounds into the breeding aquarium of medaka cancer models, and by using a light-sheet microscope to perform macro-level observation of kinetic changes in cancer cells. Moreover, as a means to inactivate identified target molecules in certain cells, we will use optogenetic techniques.