Suppression of cellular O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) can repress prolifera-tion and migration of various cancer cells,which opens a new avenue for cancer therapy.Based on the regulation of insulin gene transcription,we designed a cell-based fluorescent reporter capable of sensing cellular O-GlcNAcylation in HEK293T cells.The fluorescent reporter mainly consists of a reporter (green fluorescent protein (GFP)),an internal reference (red fluorescent protein),and an operator (neuronal differentiation 1),which serves as a "sweet switch" to control GFP expression in response to cellular O-GlcNAcylation changes.The fluorescent reporter can efficiently sense reduced levels of cellular O-GlcNAcylation in several cell lines.Using the fluorescent reporter,we screened 120 natural products and obtained one compound,sesamin,which could markedly inhibit protein O-GlcNAcylation in HeLa and human colorectal carcinoma-116 cells and repress their migration in vitro.Altogether,the present study demonstrated the development of a novel strategy for anti-tumor drug screening,as well as for con-ducting gene transcription studies.