Eva Domènech-Moreno

Peutz‐Jeghers syndrome (PJS) is associated with early‐onset gastrointestinal polyposis caused by hereditary inactivating pathogenic variants in the tumor suppressor gene STK11 (LKB1). Due to lack of prophylactic therapies, management of PJS polyps requires frequent surveillance. Interestingly, studies in mouse models have revealed that stromal cells drive the polyp formation, but detailed understanding of the cell types and interactions involved has been lacking. Using single‐cell RNA sequencing of PJS mouse model polyps, we here identify a polyp‐enriched crypt top fibroblast (pCTF) cluster characterized by a transcriptional signature also enriched in PJS patient polyps. The pCTF signature was also noted in primary fibroblasts in vitro following acute STK11 loss. Targeted deletion of Stk11 in crypt top fibroblasts using Foxl1‐Cre led to upregulation of the pCTF signature genes and later to polyposis. pCTFs displayed similarity to inflammation‐associated fibroblasts, and polyposis was exacerbated by inflammation. Cell–cell communication analysis identified interleukin 11 (IL‐11) as a potential pCTF inducer, and consistent with this, IL‐11 was required for fibroblast reprogramming toward pCTFs following STK11 loss. Importantly, a neutralizing IL‐11 antibody efficiently reduced polyp formation in a PJS model indicating a key, targetable role for IL‐11 in polyp development. Together the results characterize pCTFs as a PJS polyp‐enriched fibroblast subset and identify IL‐11 as a key mediator of fibroblast reprogramming and a potential therapeutic target in PJS. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Inactivating germline mutations in the tumor suppressor kinase LKB1 (STK11) predispose to Peutz-Jeghers Syndrome (PJS) with increased cancer risk and early-onset development of gastrointestinal polyps requiring regular surveillance. Studies using PJS mouse models have indicated fibroblasts as drivers of polyp formation. Here, we use single-cell RNA sequencing to investigate the fibroblast heterogeneity and tumorigenic mechanisms in a PJS mouse model. We identify five distinct gastric fibroblast subsets, including a polyp-enriched ST2 (Il1rl1)-expressing crypt top fibroblast (CTF) cluster, and show that the polyps arise from Foxl1-expressing CTFs. The transcriptional signature of the ST2⁺ fibroblasts overlapped with the effects seen by LKB1 loss in vitro and in vivo. The ST2⁺ fibroblasts also shared similarities with inflammation-associated fibroblasts, and inflammation exacerbated polyposis. Interestingly, the tumorigenic ST2⁺ fibroblasts showed a distinct signaling pattern, including high expression of interleukin 11 (IL-11). Notably, IL-11 was required for the LKB1 loss-induced transcriptional changes in fibroblasts, and treatment with an IL-11 neutralizing antibody substantially reduced the tumor burden in the PJS mouse model, suggesting therapeutic value. In summary, our study uncovers a critical mechanism underlying PJS polyposis and suggests that PJS patients could benefit from anti-IL-11 therapy.

Growth factors secreted by stromal fibroblasts regulate the intestinal epithelium. Stroma-derived epidermal growth factor (EGF) family ligands are implicated in epithelial regeneration and tumorigenesis, but their specific contributions and associated mechanisms remain unclear. Here, we use primary intestinal organoids modeling homeostatic, injured and tumorigenic epithelia to assess how the fibroblast-derived EGF family ligands neuregulin 1 (NRG1) and epiregulin (EREG) regulate the intestinal epithelium. NRG1 was expressed exclusively in the stroma, robustly increased crypt budding and protected intestinal epithelial organoids from radiation-induced damage. NRG1 also induced regenerative features in the epithelium, including a fetal-like transcriptome, suppression of the Lgr5+ stem cell pool and remodeling of the epithelial actin cytoskeleton. Intriguingly, unlike EGF and EREG, NRG1 failed to support the growth of pre-tumorigenic intestinal organoids lacking the tumor suppressor Apc, commonly mutated in human colorectal cancer (CRC). Interestingly, high expression of stromal NRG1 was associated with improved survival in CRC cohorts, suggesting a tumor-suppressive function. Our results highlight the power of stromal NRG1 in transcriptional reprogramming and protection of the intestinal epithelium from radiation injury without promoting tumorigenesis.

Supplementary Materials and Methods

Purpose:Mutations in STK11 (LKB1) occur in 17% of lung adenocarcinoma (LUAD) and drive a suppressive (cold) tumor immune microenvironment (TIME) and resistance to immunotherapy. The mechanisms underpinning the establishment and maintenance of a cold TIME in LKB1-mutant LUAD remain poorly understood. In this study, we investigated the role of the LKB1 substrate AMPK in immune evasion in human non—small cell lung cancer (NSCLC) and mouse models and explored the mechanisms involved.Experimental Design:We addressed the role of AMPK in immune evasion in NSCLC by correlating AMPK phosphorylation and immune-suppressive signatures and by deleting AMPKα1 (Prkaa1) and AMPKα2 (Prkaa2) in a KrasG12D-driven LUAD. Furthermore, we dissected the molecular mechanisms involved in immune evasion by comparing gene-expression signatures, AMPK activity, and immune infiltration in mouse and human LUAD and gain or loss-of-function experiments with LKB1- or AMPK-deficient cell lines.Results:Inactivation of both AMPKα1 and AMPKα2 together with Kras activation accelerated tumorigenesis and led to tumors with reduced infiltration of CD8+/CD4+ T cells and gene signatures associated with a suppressive TIME. These signatures recapitulate those in Lkb1-deleted murine LUAD and in LKB1-deficient human NSCLC. Interestingly, a similar signature is noted in human NSCLC with low AMPK activity. In mechanistic studies, we find that compromised LKB1 and AMPK activity leads to attenuated antigen presentation in both LUAD mouse models and human NSCLC.Conclusions:The results provide evidence that the immune evasion noted in LKB1-inactivated lung cancer is due to subsequent inactivation of AMPK and attenuation of antigen presentation.

Purpose:Mutations in STK11 (LKB1) occur in 17% of lung adenocarcinoma (LUAD) and drive a suppressive (cold) tumor immune microenvironment (TIME) and resistance to immunotherapy. The mechanisms underpinning the establishment and maintenance of a cold TIME in LKB1-mutant LUAD remain poorly understood. In this study, we investigated the role of the LKB1 substrate AMPK in immune evasion in human non—small cell lung cancer (NSCLC) and mouse models and explored the mechanisms involved.Experimental Design:We addressed the role of AMPK in immune evasion in NSCLC by correlating AMPK phosphorylation and immune-suppressive signatures and by deleting AMPKα1 (Prkaa1) and AMPKα2 (Prkaa2) in a KrasG12D-driven LUAD. Furthermore, we dissected the molecular mechanisms involved in immune evasion by comparing gene-expression signatures, AMPK activity, and immune infiltration in mouse and human LUAD and gain or loss-of-function experiments with LKB1- or AMPK-deficient cell lines.Results:Inactivation of both AMPKα1 and AMPKα2 together with Kras activation accelerated tumorigenesis and led to tumors with reduced infiltration of CD8+/CD4+ T cells and gene signatures associated with a suppressive TIME. These signatures recapitulate those in Lkb1-deleted murine LUAD and in LKB1-deficient human NSCLC. Interestingly, a similar signature is noted in human NSCLC with low AMPK activity. In mechanistic studies, we find that compromised LKB1 and AMPK activity leads to attenuated antigen presentation in both LUAD mouse models and human NSCLC.Conclusions:The results provide evidence that the immune evasion noted in LKB1-inactivated lung cancer is due to subsequent inactivation of AMPK and attenuation of antigen presentation.

Supplementary Materials and Methods