Intratumor Lactobacillus reuteri D-lactate drives ESCC ferroptosis resistance via STAT3 K631 lactylation
Background
Esophageal squamous cell carcinoma (ESCC) ranks among the most lethal gastrointestinal malignancies, characterized by poor prognosis due to challenges in early diagnosis, molecular heterogeneity, and therapeutic resistance. Current standard-of-care often falls short, necessitating novel biomarkers and therapeutic targets. Emerging research highlights tumor-resident microbiota as active components of the tumor ecosystem, capable of reshaping cancer cell stress responses. However, the precise mechanisms by which intratumor bacteria influence ESCC cell survival and therapeutic resistance, particularly concerning ferroptosis, remain largely undefined.
Study Design
Researchers performed 16S rRNA gene sequencing on 102 multiregional tissue blocks from 27 patients with ESCC, integrating this with untargeted metabolomics, RNA sequencing, and mass spectrometry. Mechanistic studies were conducted using ESCC cell lines and nude-mouse xenografts. They investigated the impact of Lactobacillus reuteri and its metabolites, specifically D-lactate, on cancer cell behavior. Key interventions included disrupting bacterial D-lactate production using a ldhD-deficient L. reuteri mutant and blocking host STAT3 lactylation using STAT3-knockout cells reconstituted with wild-type STAT3 or lactylation-defective STAT3 K631R.
Results
The study identified Lactobacillus, particularly Lactobacillus reuteri, as a tumor-enriched taxon significantly associated with adverse survival in ESCC patients. Mechanistic investigations revealed a distinct dynamic: in contrast to host-derived L-lactate, L. reuteri-derived D-lactate induced site-specific STAT3 lactylation at lysine 631. This modification promoted STAT3 dimerization and subsequent nuclear translocation. This host signaling rewiring led to the upregulation of the ferroptosis suppressors GPX4 and FTH1. Consequently, cancer cells exhibited reduced ferroptotic vulnerability and enhanced ESCC growth both in vitro and in vivo. > Disrupting bacterial D-lactate production using a ldhD-deficient L. reuteri mutant or blocking host STAT3 lactylation using STAT3 K631R abolished these pro-tumor and anti-ferroptotic effects, confirming the critical role of this microbe-metabolite-host signaling axis.
Key Findings
- Intratumor
Lactobacillus reuteriis enriched in ESCC and associated with adverse patient survival. L. reuteri-derived D-lactate induces site-specificSTAT3lactylation at lysine 631.STAT3lactylation promotes its dimerization, nuclear translocation, and upregulation of ferroptosis suppressorsGPX4andFTH1.- This mechanism reduces ferroptotic vulnerability and enhances ESCC growth in vitro and in vivo.
- Blocking D-lactate production or
STAT3lactylation abolishes these pro-tumor and anti-ferroptotic effects.
Why It Matters
This research defines a novel tumor-resident microbe-metabolite-host signaling axis, linking intratumor Lactobacillus to ferroptosis escape in ESCC. It provides a new mechanistic framework that extends beyond the classical Warburg effect, offering fresh avenues for developing biomarkers and therapeutic strategies. Targeting STAT3 lactylation or sensitizing ESCC cells to ferroptosis could represent a potent therapeutic approach. Furthermore, these translatable results emphasize the critical need for context-specific evaluation of Lactobacillus-containing probiotic supplementation, particularly in patients with ESCC, as certain strains may inadvertently promote tumor progression rather than confer health benefits.