生体直交性プローブと改変酵素による高精度ながん蛍光可視化の実現 ――背景ノイズを低減し、高いコントラストでのがん部位特異的検出に成功――

2026-02-27 東京大学

開発したがんイメージング系の概要。メタゲノム由来糖加水分解酵素 Td2F2 を、指向性進化によって改変した新たなレポーター酵素をがんに集積させ、β-D-フコースを有する生体直交性のプローブを投与することで、がん細胞を鮮明に可視化できる。

＜関連情報＞

• https://www.u-tokyo.ac.jp/content/400281166.pdf
• https://pubs.acs.org/doi/10.1021/jacs.5c14173

バイオ直交蛍光プローブと標的部位を有する改変レポーター酵素を用いた低バックグラウンド癌イメージング Low-Background Cancer Imaging with a Bioorthogonal Fluorescence Probe and Engineered Reporter Enzyme Bearing a Targeting Moiety

Ziyi Wang,Ryosuke Kojima,Rikuki Kiji,Kyohhei Fujita,Ryo Tachibana,Reiko Tsuchiya,Taku Uchiyama,Yoshihiro Minagawa,Tadahaya Mizuno,Kiyohiko Igarashi,Hiroyuki Noji,Mako Kamiya,and Yasuteru Urano
Journal of the American Chemical Society  Published: February 27, 2026
DOI:https://doi.org/10.1021/jacs.5c14173

Abstract

Combinatorial use of an antibody–reporter enzyme conjugate and a fluorescence probe activated by the enzyme is a powerful strategy for fluorescence-guided cancer surgery. However, conventional probes for typical reporter enzymes lack sufficient bioorthogonality, leading to high background signals in nontarget tissues. We screened a library of HMRef (rhodol derivative)-based fluorescence probes with various sugar moieties and found that HMRef-β-d-Fucose is bioorthogonal in mammalian systems but is activated by a metagenomic glycosidase, Td2F2. Directed evolution generated a mutant with a k_cat/K_m of 3.3 × 10⁵/M/sec, 7.3 times higher than wild-type Td2F2 and comparable to β-galactosidase (LacZ) with its corresponding probe. Theoretical calculation suggested the E296G mutation facilitates probe access to the enzyme’s active site. In a proof-of-concept study, SKOV-3 cells, which endogenously express HER2, were visualized with minimal background in the mesentery of a mouse model using HMRef-β-d-Fucose and engineered Td2F2 conjugated or fused to a HER2-binding antibody or nanobody.