Hyperinsulinemia Promotes Pancreatic Cancer Fibrosis via Tumor-Derived Exosomal TNFAIP8-Mediated STAT1 Ubiquitination in CAFs
Abstract:
Background:Diabetes-associated hyperinsulinemia is a recognized risk factor for pancreatic ductal adenocarcinoma (PDAC) and is known to exacerbate stromal fibrosis in other solid tumors, such as breast and liver cancers. However, whether and how elevated systemic insulin levels contribute to the development of the dense fibrotic stroma in PDAC remain poorly understood.
Methods: We combined histopathological analysis of PDAC tissue microarrays (TMAs), bioinformatics of TCGA and public single-cell RNA sequencing (scRNA-seq) datasets, and in vitro functional assays using isolated primary cancer-associated fibroblasts (CAFs) and insulin-responsive PDAC cell lines (PANC-1, MIA PaCa-2). Conditioned medium (CM), co-culture systems, proteomic profiling, immunoprecipitation, immunofluorescence, and a xenograft mouse model were employed to investigate how insulin influences exosome-mediated tumor–CAF crosstalk and stromal remodeling.
Results: Histological and transcriptomic analyses showed that diabetic PDAC patients exhibited higher insulin levels and increased stromal fibrosis compared to non-diabetic cases. In vitro, insulin significantly enhanced tumor cell proliferation but had no direct effect on CAFs. Instead, conditioned medium from insulin-treated tumor cells markedly promoted CAF proliferation, indicating a tumor-mediated paracrine effect. Further proteomic profiling identified tumor-derived exosomal TNFAIP8 as a key upregulated cargo in response to insulin stimulation. Mechanistically, exosomal TNFAIP8 was taken up by CAFs, where it recruited E3 ligase TRIM21 to promote STAT1 ubiquitination and degradation, thereby relieving STAT1-mediated suppression of fibrotic gene expression. Functionally, this drove the transition of antigen-presenting CAFs (apCAFs) to myofibroblastic CAFs (myCAFs), enhancing α-SMA and Collagen I production. In vivo, inhibition of TNFAIP8 in tumor-derived exosomes attenuated CAF activation and stromal fibrosis, supporting its functional role in remodeling the tumor microenvironment.
Conclusions: Our study reveals that hyperinsulinemia remodels the PDAC stroma by driving tumor-derived exosomal TNFAIP8 secretion, which promotes STAT1 ubiquitination-dependent activation and phenotypic conversion of CAFs. Targeting this metabolic–fibrotic axis may offer new therapeutic avenues to alleviate fibrosis and improve drug delivery in PDAC