Starlinger, Patrick

PURPOSE Deficient mismatch repair/microsatellite instability (dMMR, MSI-H) in biliary tract cancers (BTCs) is observed in 1%-5% of tumors. MSI-H across solid tumors has demonstrated durable response to immune checkpoint inhibitors (ICIs) regardless of the anatomic location. Here, we describe clinical outcomes and surgical conversion of MSI-H BTC treated with ICIs. Patients and Methods We conducted a multicenter, retrospective analysis of BTC patients with dMMR/MSI-H between 2017 and 2024 at Mayo Clinic, University of Michigan, and University Hospitals Seidman Cancer Center. Outcomes of interest were surgical resection rate, rate of pathologic response, 2-year overall survival (OS; time from initiation of treatment to death/last follow-up), and time to treatment discontinuation (TTD; time from initiation of treatment to cessation because of any cause). Analyses were descriptive. RESULTS Thirty patients with MSI-H BTC were identified: 19 with cholangiocarcinoma, three with gallbladder cancer, and 8 with BTC undefined. The median age at diagnosis was 61.5 years (range, 26-86). Twenty-six (86.7%) patients had advanced stage at diagnosis. Twenty-seven patients (90%) received first-line systemic therapy, and 13 (48.1%) continued onto second line. Six patients (23.1%) were restaged to resectable from advanced disease after ICI therapy and underwent resection; all remained recurrence-free at last follow-up. Of these six patients, 3 (50%) achieved a pathologic complete response. Among those receiving first-line therapy, the median TTD was 9.9 months (95% CI, 5.7 to 14.5 months) and the 2-year OS was 73% (95% CI, 56% to 94%). CONCLUSION ICI therapy in patients with MSI-H BTC demonstrated durable response and downstaged some BTC to a resectable stage. dMMR/MSI-H should be performed up-front to guide treatment decisions.

Background and Aims: Unresolved inflammation and fibrosis are defining features of metabolic dysfunction–associated steatohepatitis (MASH), a progressive form of steatotic liver disease that can advance to cirrhosis and hepatocellular carcinoma. While innate immune mechanisms in MASH have been extensively characterized, the role of CD4 + T cells remains poorly understood despite their central function in orchestrating immune responses through effector and regulatory mechanisms. Approach and Results: Integrated single-cell proteomic, transcriptomic, and functional analyses were used to investigate the CD4 + T-cell landscape in murine and human MASH. We delineated a profound shift in the differentiation of intrahepatic and peripheral CD4 + T cells toward Th1, regulatory, and cytotoxic phenotypes in murine and human MASH. Notably, hepatic CD4 + T cells exhibited heightened effector activity and elevated secretion of proinflammatory cytokines, thus amplifying inflammatory signaling cascades. The CD4 + T-cell reprogramming in MASH also included the induction of the co-stimulatory receptor OX40. In parallel, OX40 ligand (OX40L)-expressing monocyte-derived macrophages and dendritic cells accumulated in MASH livers, establishing a feed-forward CD4 + T cell-myeloid activation loop. Therapeutic blockade of the OX40–OX40L axis, in turn, reversed liver pathology in mice with established MASH and reduced disease markers in an ex vivo human liver model. Furthermore, genetic depletion or functional inhibition of CD4 + T cells attenuated fibrosis, accompanied by decreased infiltration of monocyte-derived macrophages. Conclusions: These studies provide a comprehensive single-cell proteogenomic atlas of CD4 + T cells in MASH and identify an OX40-dependent CD4 + T cell-macrophage axis as a promising therapeutic target for the treatment of MASH and liver fibrosis.