KRAS–O-GlcNAc Axis Drives CLDN18.2 Resistance in PDAC : Gut | June 2026

Introduction:

Introduction: Claudin 18.2 (CLDN18.2) has emerged as an important therapeutic target in gastrointestinal malignancies, with encouraging results in gastric and gastroesophageal cancers. Its expression in pancreatic ductal adenocarcinoma (PDAC) has generated considerable interest for targeted therapies. However, clinical responses in PDAC have been less impressive than anticipated, suggesting that tumor-specific biological mechanisms may limit treatment efficacy.

Problem Statement:

Problem Statement: The reasons underlying the modest activity of CLDN18.2-targeted therapies in PDAC remain poorly understood. Given the near-universal prevalence of KRAS mutations and the frequent coexistence of metabolic dysfunction and hyperglycemia in pancreatic cancer, identifying mechanisms that alter CLDN18.2 localization and therapeutic accessibility is critical for improving treatment outcomes.

Summary:

Summary: This comprehensive translational study investigated the impact of O-linked N-acetylglucosaminylation (O-GlcNAcylation) on CLDN18.2 biology using patient samples, patient-derived organoids, patient-derived xenografts, orthotopic models, and genetically engineered mouse models.

The investigators identified a previously unrecognized mechanism whereby KRAS mutations and hyperglycemia cooperate to induce O-GlcNAcylation of CLDN18.2 at the T204 residue. This post-translational modification altered CLDN18.2 subcellular trafficking, causing accumulation within the cytoplasm rather than on the cell membrane.

Because CLDN18.2-targeted therapies require membrane surface expression for effective target engagement, cytoplasmic sequestration substantially reduced therapeutic susceptibility.

Beyond therapeutic resistance, O-GlcNAcylated CLDN18.2 actively promoted tumor aggressiveness. Increased O-GlcNAcylation enhanced cancer cell migration, invasion, and metastatic potential, indicating that this modification is not merely a biomarker of resistance but a functional driver of disease progression.

Mechanistically, O-GlcNAcylation disrupted CLDN18.2 interaction with PTP1B, resulting in enhanced tyrosine phosphorylation. This facilitated recruitment and activation of Src kinase through SH2-domain interactions, triggering downstream oncogenic signaling pathways associated with invasion and metastasis.

Importantly, both genetic inhibition and pharmacologic suppression of O-GlcNAcylation restored CLDN18.2 membrane localization and attenuated tumor progression.

A particularly important therapeutic finding was the effect of low-dose MRTX1133, a KRASG12D inhibitor. Treatment reduced CLDN18.2 O-GlcNAcylation, restored membrane expression, and significantly enhanced the efficacy of CLDN18.2-targeted therapy in KRAS-mutant PDAC models while maintaining a favorable toxicity profile.

The study establishes a direct mechanistic link between oncogenic KRAS signaling, metabolic dysregulation, glycosylation biology, and therapeutic resistance. It also provides a biological explanation for why CLDN18.2-directed approaches have underperformed in pancreatic cancer despite target expression.

From a clinical perspective, these findings have several implications. Hyperglycemia may influence responsiveness to CLDN18.2-targeted therapies, suggesting a potential role for metabolic optimization in treatment strategies. Assessment of CLDN18.2 membrane localization, rather than total expression alone, may become important when selecting patients for targeted therapy. Furthermore, combining KRAS inhibition with CLDN18.2-directed agents may represent a rational precision oncology approach for KRAS-mutant PDAC.

This work is particularly significant because it converts a major resistance mechanism into a therapeutic opportunity. Rather than abandoning CLDN18.2 as a target in PDAC, the study demonstrates that modifying its cellular localization can restore drug sensitivity.

Overall, the study identifies KRAS-driven O-GlcNAcylation of CLDN18.2 as a central mechanism linking tumor progression and therapeutic resistance in pancreatic cancer and provides a strong preclinical rationale for combining KRASG12D inhibition with CLDN18.2-targeted therapies to improve outcomes in this highly lethal disease.