P0118 A novel subset of TNIP3+ OLR1+ AQP9+ inflammatory monocytes drives resistance to multiple biologics in ulcerative colitis
Authors: Saifuddin A , Cozzetto D , Olbei M , Korcsmaros T , Hart A , Powell N 
Published: January 2025

Abstract

Background
We previously reported that the pre-treatment mucosal enrichment of a 325-transcript-long module, TM1, predicts resistance to ustekinumab and anti-TNF therapy in moderate-to-severe ulcerative colitis (UC). Only 5% of patients with high TM1 expression achieved week 8 mucosal healing with ustekinumab and no patients with high expression had week 6 histo-endoscopic remission in two infliximab-treated cohorts. We explored which cell populations might be driving this phenomenon to guide potential therapeutic perspectives.

Methods
We used gene set variation analysis (GSVA) to calculate the enrichment score of TM1 in transcriptionally profiled single cells from mucosal biopsies from patients with active UC [1]. We sub-clustered cell populations of interest, which were defined based on the ranked fold changes of differentially expressed genes between these groups, and investigated their molecular phenotype. Transcriptomic signatures were defined using the top 20 markers of each population. We employed the LiANA tool to predict likely cell-cell interactions and Ingenuity Pathway Analysis upstream regulator analysis (IPA, Qiagen, US) to identify inhibitory drugs. Analyses were performed in R (v 4.2.2, Vienna) and GraphPad Prism (US, v 10.3).

Results
GSVA revealed that TM1 was particularly enriched in the myeloid compartment and most highly in inflammatory monocytes (IMs). Further analyses defined three subpopulations named IM0, IM1 and IM2. These were PKIB+ SNX17+ NDUFB5+, TNIP3+ OLR1+ AQP9+ and CLLU1OS+ LAD1+ CXCL5+, respectively. IM1 cells also differentially expressed TREM1 and ETS2, which have been previously associated with anti-TNF resistance and disease severity [2]. Eleven of the top 20 IM1 transcripts were present in TM1 compared to 2/20 from IM2 and 0/20 for IM0. Enrichment of IM1 marker genes in pre-treatment UC biopsy samples also correlated highly with TM1 enrichment (ρ=0.92, p&lt;0.0001). Ligand-receptor analysis suggested that these IM sub-populations interacted with myeloid, lymphoid, mesenchymal and epithelial cells, particularly involving the IM1 receptors CD44, CD4 and LILRB2, and ligands S100A8, IL1β and S100A9. Common interactions included S100A8/9 from IM1 and IM0 binding TLR4 and CD36 on IM1s, and FN1 from mesenchymal cells stimulating PLAUR, C5AR1 and CD44 on IM1s. IPA highlighted MEK inhibitors U0126 and SB203580 as potential drugs that could counteract the effect of IM1 functions.

Conclusion
A population of TNIP3+ OLR1+ AQP9+ IMs appears to be involved in resistance to ustekinumab and anti-TNF medications in UC, which augments previous findings about treatment resistance. MEK inhibitors may offer a novel IBD drug class to target these cells in refractory disease.

References
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