Clonal Lymphocyte Expansions and JAK-STAT Mutations Drive Refractory Celiac Disease

Highlights

1. RCD2 lymphomas demonstrate substantial intratumoral heterogeneity despite interpatient genomic similarities.

2. JAK inhibitor monotherapy may select drug-resistant clones in RCD2, based on in vitro evidence.

3. Previously uncharacterized RCD1 cases harbor clonal T-cell expansions with JAK-STAT enhancing mutations.

4. A pathogenic continuum exists between RCD subtypes through shared clonal evolution mechanisms.

Disease Burden

Despite strict gluten-free diets, 5-10% of celiac disease patients develop refractory disease (RCD), with type 2 carrying a 50-80% risk of progression to aggressive lymphoma. The lack of effective therapies for RCD1 and concerns about targeting RCD2 mutations create critical knowledge gaps in managing these high-risk patients.

Study Design

The multicenter study analyzed duodenal biopsies and PBMCs from 78 participants: RCD1 (n=22), RCD2 (n=18), active CeD (n=15), remission CeD (n=13), and controls (n=10). Researchers employed single-cell RNA sequencing, TCR repertoire analysis, whole exome sequencing, and functional studies of patient-derived RCD2 cell lines treated with JAK inhibitors (ruxolitinib, tofacitinib).

Key Findings

RCD2 Lymphoproliferative Characteristics

The malignant intraepithelial lymphocytes in RCD2 showed conserved JAK1/STAT3 mutations across patients but exhibited marked transcriptional heterogeneity within tumors. Functional assays demonstrated that JAK inhibitors effectively suppressed initial tumor growth but selected for resistant subclones carrying secondary STAT5B and PI3K pathway mutations within 8 weeks of exposure.

RCD1 Immunogenomics

57% of RCD1 cases harbored dominant T-cell clones with STAT3 SH2 domain mutations (median variant allele frequency 12.8%). These mutations enhanced IL-21-mediated STAT3 phosphorylation by 3.2-fold compared to wild-type (p=0.007). A striking case showed simultaneous RCD2 and CD4+ lymphoproliferative lesions in a patient initially classified as RCD1.

Pathogenic Continuum

Shared TCRβ rearrangements between duodenal and blood compartments were detected in 38% of RCD1 and 72% of RCD2 cases. Phylogenetic analysis revealed branching evolution patterns in both subtypes, with early trunk mutations affecting JAK-STAT genes and later branch mutations involving epigenetic regulators.

Expert Commentary

The findings fundamentally reshape our understanding of RCD pathogenesis. As Dr. Elena Verdú (McMaster University) notes,

Mechanistic Insights

The IL-21/JAK-STAT axis emerges as a central node in RCD pathogenesis. IL-21 overexpression in active celiac disease may create selective pressure for STAT3 gain-of-function mutations, explaining their enrichment in both RCD subtypes.

Conclusion

This work establishes JAK-STAT dysregulation as a unifying feature across the RCD spectrum while demonstrating the limitations of pathway inhibition alone. The detection of bloodborne clones suggests liquid biopsy potential for monitoring. Future therapies may require combination approaches targeting both JAK-STAT and resistance pathways.

Funding and Registration

Supported by INSERM and the French Ministry of Health (PHRC-2018). No clinical trial registration as this was a translational study.

References

1. Malamut G et al. Gastroenterology. 2026;150(8):1845-58.
2. Al-Toma A et al. Gut. 2019;68(1):139-53 (RCD guidelines).
3. Soderquist CR et al. Blood. 2020;135(22):1998-2007 (JAK-STAT lymphomagenesis).