The metabolites in the kynurenine (KYN) pathway which is a main metabolic pathway of tryptophan (TRP) are closely related with a lot of life phenomena and pathophysiology of the various diseases. There are 3 steps in KYN pathway; KYN generation from TRP, 3-hydroxyanthranilic acid (3HAA) generation from KYN, and the metabolism of 3HAA. Kynureninase, tryptophan 2,3-dioxygenase in the liver, and indoleamine 2,3-dioxygenase (IDO) in the extrahepatic organs are the rate‐limiting enzymes, and the differences of function between IDO1 and IDO2 have been focused in some diseases. The importance of KYN pathway has been shown mainly in the field of cranial neuropathy. It has been recently shown to be related with cancer, infection, and inflammatory diseases, and some clinical applications started in these fields. We review the correlation between TRP metabolism and some skin diseases, especially focusing on one of representative inflammatory skin diseases, psoriasis, in this article.

Natural product-derived chemical probes have played essential roles in facilitating direct target identification and engagement analysis. Despite the biomedical significance, designing appropriate probes with necessary functional groups for effectively capturing and enriching proteins for target analysis remains challenging. In this review, recent progress in the development of covalent and non-covalent chemical probes for exploring targets of natural products is highlighted. Novel gold-nanoparticle probes that multivalently display both natural product ligands and protein reactive groups are presented as promising tools for a streamlined analysis of target proteins and their scopes and characteristics are discussed.

Exosomes, tiny vesicles secreted by all cells, were first thought to function only as cellular garbage disposal. However, it has been discovered that they also function as a cell-cell communication tool. Due of this very important function, exosomes are now thought to be linked to a variety of diseases including cancer.

We have previously shown that cancer cells send “exosomes” to the future site of metastasis to alter the environment to a favorable place where cancer cells can successfully metastasize. In this article, we will explain how exosomes can determine the future metastatic site and prepare the microenvironment, and furthermore, discuss the role of exosomes in the potential diagnosis of cancer.

Cancer treatment is becoming increasingly specialized. It is hence important to develop diagnostic imaging tools that will guide the making of appropriate treatment decisions. Diffusion MRI allows the observation of the diffusion of water molecules in a living body, reflecting the tissue microstructure. We are developing new quantitative markers from diffusion MRI, which will be useful for the diagnosis of cancer recurrence and for assessing the prognosis. Another important issue is the standardization of the quantitative values obtained from diffusion MRI. This paper introduces state-of-the-art cancer imaging research, developments concerning Diffusion MRI and our efforts toward its standardization.