To investigate the diagnostic value of endoscopic sign of light blue crest (LBC) capsuling papillary lesion (LCPL) for high-risk intestinal metaplasia (IM).

A total of 314 patients (352 biopsy specimens) who underwent endoscopic examination and biopsy in Department of Gastroenterology of Army Medical Center of PLA from January 2021 to June 2023 were recruited, and HE and HID-AB staining (the golden standard of high-risk IM) were apllied to detect the histological types and IM types. The samples were subsequently divided into chronic inflammation group, low-risk IM group, high-risk IM group, well-differentiated intestinal-type gastric cancer group, and poorly-differentiated intestinal-type gastric cancer group. The positive rate of LCPL in each group and its diagnostic efficacy were analyzed based on endoscopic images of the biopsy sites. Logistic regression analysis was used to investigate the relationship between LCPL sign and high-risk IM, as well as the clinical and pathological features associated with LCPL sign. Receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic efficacy of LCPL for high-risk IM, using indicators such as sensitivity, specificity, Youden index and area under the curve (AUC).

The positive rate of the LCPL sign in high-risk IM group was 75.70%, significantly higher than that of the other groups (all P<0.001). Logistic regression analysis showed that LCPL sign was significantly correlated with high-risk IM (OR=30.286, 95%CI: 13.528~67.804, P<0.001). When the sign was employed in diagnosing high-risk IM, the sensitivity was 69.84%, the specificity was 93.75%, the Youden’s index was 0.636, and the AUC value was 0.818 (95%CI: 0.773~0.857). Besides sensitivity, all above parameters of LCPL sign showed significantly better diagnostic efficacy than those of traditional LBC sign, which is used as a sign for diagnosing IM (P<0.001). Moreover, recognition of LCPL sign was not easily affected by age (OR=1.130, 95%CI: 0.709~1.800, P=0.607), lesion site (Angular incisure: OR=2.360, 95%CI: 0.732~7.613, P=0.151; Autrum: OR=2.257, 95%CI: 0.756~6.744, P=0.145), and presence of peptic ulcers (OR=1.085, 95%CI: 0.208~5.652, P=0.923). Significantly, 94.12% of positive and 66.94% of negative LCPL signs could be rapidly recognized within 3 s (OR=4.536, 95%CI: 1.372~14.997, P=0.013).

LCPL sign shows high efficacy and potential clinical application value for high-risk IM in gastric mucosa of endoscopic diagnosis.

Recent evidence shows that Streptococcus anginosus (S. a) promotes the development of gastric cancer (GC). However, its role in GC progression, particularly its impact on tumor immune microenvironment (TIME), remains unclear. This study aims to investigate the role of S. a in advanced GC and test the hypothesis that S. a upregulates PD-L1 expression in GC cells, thereby inhibiting CD8⁺ T cell function.

Based on in-house RNA sequencing (RNA-seq) raw data (n=98), a computational pipeline was established to determine the relative abundance of S. a (S. a score). In parallel, a machine learning-based signature gene model was constructed to infer S. a abundance from gene expression matrices of public cohorts. Using these approaches, GC patients were stratified into S. a-high (S. a^high) and S. a-low (S. a^low) groups according to the median abundance. Single-cell RNA sequencing (scRNA-seq) data (n=23) were integrated to analyze differences in cellular composition within the TIME between the 2 groups. For in vitro validation, human (NUGC-3) and murine (TKM) GC cell lines were treated with S. a for 8 h, followed by quantification of PD-L1 expression via qPCR and Western blotting. Cytotoxic function of CD8⁺ T cells against S. a-pretreated GC cells was evaluated by flow cytometry in co-culture systems. where S. a-pretreated cancer cells were incubated with CD8⁺ T cells, and cytotoxicity was measured by flow cytometry. For in vivo validation, a C57BL/6 mouse orthotopic GC model was established; the experimental group received S. a bacterial suspension via oral gavage, while the control group received sterile culture medium, with continuous intervention for 6 weeks (n=6). Tumor burden was evaluated by in vivo imaging, tumor volume, and stomach weight.

The abundance of S. a was significantly higher in GC tissues than in normal gastric mucosa (P=0.000850), and high abundance was associated with poor prognosis (HR=1.49, 95%CI: 1.09 to 2.04, P=0.0139). Analysis of the TIME using scRNA-seq data revealed distinct cellular compositions between GC tissues with varying S. a levels. Notably, S. a^high GC tissues exhibited a significant increase in CD8⁺ T cell infiltration (P<0.0001), yet these cells predominantly displayed an exhausted phenotype (P<0.0001). Further analysis identified a subset of GC cells whose abundance is correlated positively with both S. a levels (Spearman’s rho=0.288, P<0.0001) and proportion of exhausted CD8⁺ T cells (Spearman’s rho=0.522, P<0.0001), suggesting their potential roles in modulating CD8⁺ T cell function. Mechanistically, S. a treatment significantly upregulated PD-L1 expression in GC cells (P<0.0001). In co-culture assays, S. a-pretreated cancer cells impaired the cytotoxic function of CD8⁺ T cells (P=0.000526). In vivo results demonstrated that the mice in the S. a gavage group exhibited significantly higher tumor bioluminescence intensity (P=0.0306), larger tumor volume (P=0.0453), and increased stomach weight (P=0.0306) compared to the control group.

Enriched S. a abundance not only reshapes the TIME of GC, but also mediates CD8⁺ T cell exhaustion and facilitates tumor immune evasion by inducing high PD-L1 expression in GC cells.