Stimulator of interferon genes (STING) is an endoplasmic reticulum adaptor transmembrane protein that plays a pivotal role in innate immune system. STING agonists, such as endogenous cyclic dinucleotide (CDN) cyclic GMP-AMP (cGAMP), have been used in diverse clinical research for immunogenic tumor clearance, antiviral treatments and vaccine adjuvants. CDNs containing noncanonical mixed 3′-5′ and 2′-5′ phosphodiester linkages show higher potency in the activation of the STING pathway. In this study, a series of 2′3′-CDNs were designed and synthesized through a modified one-pot strategy. We then established a surface plasmon resonance (SPR)-based binding assay to quantify the binding affinities of synthesized CDNs for human STING, which requested a minuscule amount of sample without any pretreatment. Using this assay, we identified compound 8d (K_D = 0.038 μM), a novel CDN that showed higher binding affinity with hSTING than cGAMP (K_D = 0.543 μM). Cellular assays confirmed that 8d could trigger the expression of type I IFNs and other proinflammatory cytokines more robust than cGAMP. 8d also exhibited more resistant than cGAMP to enzymatic cleavage in vitro, indicating the successful improvement in drug availability. These findings provide guidelines for the design and structural optimization of CDNs as STING agonists.

The aim of this study is to investigate the gene biomarkers and metabolites for esophageal squamous cell carcinoma (ESCC) or cisplatin (DDP)-resistance ESCC through integrated analysis of transcriptome and metabolome. A total of 6130 differentially expressed genes (DEGs) and 326 differentially expressed metabolites (DEMs) were identified in KYSE30 compared to HEEC, while compared to KYSE30, there were totally 1179 DEGs and 224 DEMs in KYSE30/DDP. Profile #6 depicted the mRNA characteristics of KYSE30 obviously. Genes in profile #6 were mainly involved in platinum drug resistance, ferroptosis, and glutathione metabolism. In addition, the associated TCGA dataset identified APOBEC3B as a critical gene involved in inhibiting ferroptosis by activating PD-L1 to suppress CD8⁺T cells. In vitro experiments demonstrated that knockdown of APOBEC3B enhanced ferroptosis and inhibited the glutathione metabolism signaling pathway in KYSE30/DDP. Moreover, in vivo experiments further confirmed that knockdown of APOBEC3B suppressed PD-L1, thereby activating CD8⁺T cells and promoting ferroptosis. These findings indicate the critical role of ferroptosis and glutathione metabolism in the development and progression of ESCC. Meanwhile, APOBEC3B may serve as a promising therapeutic target for cisplatin-resistant ESCC cells.