Cellular and molecular characteristics of stromal Lkb1 deficiency‐induced gastrointestinal polyposis based on single‐cell RNA sequencing

Abstract Liver kinase B1 (Lkb1), encoded by serine/threonine kinase ( Stk11 ), is a serine/threonine kinase and tumor suppressor that is strongly implicated in Peutz–Jeghers syndrome (PJS). Numerous studies have shown that mesenchymal‐specific Lkb1 is sufficient for the development of PJS‐like polyps in mice. However, the cellular origin and components of these Lkb1‐associated polyps and underlying mechanisms remain elusive. In this study, we generated tamoxifen‐inducible Lkb1 flox/flox ; Myh11‐Cre/ERT2 and Lkb1 flox/flox ; PDGFRα‐Cre/ERT2 mice, performed single‐cell RNA sequencing (scRNA‐seq) and imaging‐based lineage tracing, and aimed to investigate the cellular complexity of gastrointestinal polyps associated with PJS. We found that Lkb1 flox/+ ; Myh11‐Cre/ERT2 mice developed gastrointestinal polyps starting at 9 months after tamoxifen treatment. scRNA‐seq revealed aberrant stem cell‐like characteristics of epithelial cells from polyp tissues of Lkb1 flox/+ ; Myh11‐Cre/ERT2 mice. The Lkb1‐associated polyps were further characterized by a branching smooth muscle core, abundant extracellular matrix deposition, and high immune cell infiltration. In addition, the Spp1–Cd44 or Spp1–Itga8/Itgb1 axes were identified as important interactions among epithelial, mesenchymal, and immune compartments in Lkb1‐associated polyps. These characteristics of gastrointestinal polyps were also demonstrated in another mouse model, tamoxifen‐inducible Lkb1 flox/flox ; PDGFRα‐Cre/ERT2 mice, which developed obvious gastrointestinal polyps as early as 2–3 months after tamoxifen treatment. Our findings further confirm the critical role of mesenchymal Lkb1/Stk11 in gastrointestinal polyposis and provide novel insight into the cellular complexity of Lkb1‐associated polyp biology. © 2024 The Pathological Society of Great Britain and Ireland.