We adopted a spirocyclization-based strategy to design γ-glutamyl hydroxymethyl selenorhodamine green (gGlu-HMSeR) as a photo-inactive compound that would be specifically cleaved by the tumor-associated enzyme γ-glutamyltranspeptidase (GGT) to generate the potent photosensitizer HMSeR. gGlu-HMSeR has a spirocyclic structure and is colorless and does not show marked phototoxicity toward low-GGT-expressing cells or normal tissues upon irradiation with visible light. In contrast, HMSeR predominantly takes an open structure, is colored, and generates reactive oxygen species upon irradiation. The γ-glutamyl group thus serves as a tumor-targeting moiety for photodynamic therapy (PDT), switching on tumor-cell-specific phototoxicity. To validate this system, we employed chick chorioallantoic membrane (CAM), a widely used model for preliminary evaluation of drug toxicity. Photoirradiation after gGlu-HMSeR treatment resulted in selective ablation of implanted tumor spheroids without damage to healthy tissue.

To achieve highly selective ablation of lacZ-positive cells in a biological milieu in vivo, we developed an activatable photosensitizer, SPiDER-killer-βGal, targeted to β-galactosidase encoded by the lacZ reporter gene. Hydrolysis of SPiDER-killer-βGal by β-galactosidase simultaneously activates both its photosensitizing ability and its reactivity to nucleophiles, so that the phototoxic products generated by light irradiation are trapped inside the lacZ-positive cells. The combination of SPiDER-killer-βGal and light irradiation specifically killed lacZ-positive cells in coculture with cells without lacZ expression. Furthermore, β-galactosidase-expressing cells in the posterior region of cultured Drosophila wing discs and in pupal notum of live Drosophila pupae were selectively killed with single-cell resolution. This photosensitizer should be useful for specific ablation of targeted cells in living organisms, for example, to investigate cellular functions in complex networks.

LCs existing around or within biliary epithelial layers are important as periductal antigen-presenting cells in PBC and the migration of LCs into bile ducts is closely associated with the periductal cytokine milieu and biliary innate immunity in PBC.

It seems possible that increased bile ductules expressing cellular senescence markers and chemokines are at least partly involved in the progressive portal and bridging fibrosis in NAFLD.