Background: Common treatments for metastatic/unresectable HER2‐negative gastric cancer include chemotherapy, immune checkpoint inhibitor monotherapy and chemotherapy plus immune checkpoint inhibitor. However, significant drug resistance exists regardless of the treatment regimen.Methods: Patients with metastatic/unresectable HER2‐negative gastric/gastroesophageal junction adenocarcinoma were enrolled. All patients were divided into three groups according to the treatment regimen and were further divided into responders and non‐responders according to efficacy evaluation. Metagenomics sequencing were performed to analyze gut microbiome signature of patients receiving different treatments at baseline and throughout treatment.Results: One hundred seventeen patients with HER2‐negative advanced gastric or gastroesophageal junction adenocarcinoma receiving chemotherapy alone, anti PD‐1/PD‐L1 immunotherapy alone or combined regimen were included in this study. Microbiome signatures related to clinical response are distinct among the three treatment groups. Among which, 14, 8 and 13 species were significantly different between responders and non‐responders in immunotherapy, immunotherapy plus chemotherapy and chemotherapy group, respectively. Patients with higher relative abundance of Lactobacillus possessed higher microbiome diversity and significantly better response to anti‐PD‐1/PD‐L1 immunotherapy and had a trend to achieve better progression‐free survival. Another cohort of 101 patients has been used as an external validation set to confirm the stability and reliability of these findings.Conclusions: Gut microbiome affects response of treatments in HER2‐negative advanced gastric cancer in a treatment‐specific way, immunotherapy plus chemotherapy did not equal to a simple superposition of immunotherapy and chemotherapy. Lactobacillus is expected to become a novel choice as an adjuvant agent in promoting the efficacy of immunotherapy in gastric cancer.

Intestinal ischemia–reperfusion (IIR) is a life-threatening clinical event with damaging signals whose origin and contents are unclear. Here we observe that IIR significantly affect the metabolic profiles of most organs by unbiased organ-wide metabolic analysis of gut contents, blood, and fifteen organs in rats (n = 29). Remarkably, correlations between gut content metabolic profiles and those of other organs are the most significant. Gut contents are also the only ones to show dynamic correlations during IIR. Additionally, according to targeted metabolomics analysis, several neurotransmitters are considerably altered in the gut during IIR, and displayed noteworthy correlations with remote organs. Likewise, metagenomics analysis (n = 35) confirm the effects of IIR on gut microbiota, and identify key species fundamental to the changes in gut metabolites, particularly neurotransmitters. Our multi-omics results establish key roles of gut contents in IIR induced remote injury and provide clues for future exploration.

The occurrence and progression of gastric cancer (GC) are closely associated with dysbiosis of the gastric microbiota and alteration in host microenvironments. However, the interaction between intratumoral bacteria and gastric microenvironments remains incompletely understood. In this study, we characterized the biological profiles of intratumoral bacteria, metabolome, and proteome in 20 GC tumors and paired non-tumor tissues, in combination with 6 independent datasets (comprising 477 gastric tissue biopsies and 534 normal tissues), as well as mucosal tissues from 10 individuals without GC. We found that the diversity and richness of gastric microbiota were significantly higher in tumor tissues than in non-tumor tissues. In contrast, the lowest biodiversity, at both the genus and species levels, was found in the microbiota of individuals without GC. Specifically, tumors were enriched with Bacteroides thetaiotaomicron, Lactobacillus parabrevis, Brevundimonas nasdae, and Brevundimonas vesicularis. We also identified 39 human immunity-related proteins, particularly in the tryptophan metabolic pathway, which were differentially expressed across various microenvironments (tumor and non-tumor). Furthermore, we found that several pathways involved in the human immune system and associated with the gastric microbiota, such as thiazole biosynthesis II, pyrimidine deoxyribonucleoside salvage, superpathway of pyrimidine deoxyribonucleoside salvage, and superpathway of heme biosynthesis from uroporphyrinogen-III, hold potential as biomarkers for early detection of GC. Our results provide a comprehensive framework for investigating the complex interactions between the tumor immune microenvironment and intratumoral bacterial community.

Background: Small-cell lung cancer (SCLC) represents an aggressive malignancy associated with a poor prognosis, underscoring the critical demand for enhanced monitoring methodologies. Circulating tumor DNA (ctDNA) constitutes a promising non-invasive biomarker; however, reports employing highly sensitive tumor-informed assays in SCLC remain scarce. This investigation aimed to assess the clinical utility of a personalized ctDNA monitoring strategy for predicting therapeutic outcomes and resistance in SCLC patients. Methods: This prospective observational study enrolled patients diagnosed with unresectable SCLC. Whole exome sequencing was conducted on baseline tumor specimens to design customized 16-plex multiplex polymerase chain reaction (PCR) panels. Serial blood samples were obtained at baseline, at six-week intervals during treatment, and upon disease progression. Detection of ctDNA-based minimal residual disease (MRD) was performed using a tumor-informed assay (Huajianwei^® bespoke MRD) with ultra-deep sequencing. Results: Among seven evaluable patients, the baseline ctDNA-MRD positivity rate was 100%. A significant positive correlation was observed between the baseline ctDNA levels and radiographic tumor burden (r = 0.821, 95% confidence interval [CI] 0.179–0.973, p = 0.034). Longitudinal analysis indicated that patients exhibiting an early decline in MRD levels demonstrated a non-significant trend toward superior progression-free survival (PFS) compared to those with an MRD increase. Though this between-group difference did not reach conventional statistical significance, it represented a trend-level finding (p = 0.0665, hazard ratio [HR] = 0.24, 95% CI: 0.02–3.19), with no definitive prognostic association confirmed in this pilot cohort. Notably, an elevation in MRD preceded radiographic progression by as much as 135 days in certain instances. Conclusions: This study shows that dynamic tumor-informed ctDNA-based MRD monitoring reflects tumor burden changes and may correlate with clinical outcomes in SCLC, supporting its potential to guide personalized treatment and facilitate earlier therapeutic interventions compared to conventional imaging techniques. Prospective multicenter validation is needed to confirm its clinical utility.