Loss of PBRM1 accelerates pancreatic cancer progression by inducing acquisition of mesenchymal phenotype and inflammatory cancer-associated fibroblasts reprogramming.
BACKGROUND: PBRM1 is an important subunit of the SWI/SNF complex, which broadly regulates gene transcription by chromatin remodeling. Genomic alterations of PBRM1 have been found in patients with pancreatic ductal adenocarcinoma (PDAC), but its molecular functions remain unclear. METHODS: Clinical relevance of PBRM1 was analyzed by using human PDAC samples and public genomic datasets. Mice with concomitant pancreas-specific Pbrm1 deletion in Kras-driven genetic PDAC models were generated. Single-cell transcriptomics were performed to determine tumor phenotype and microenvironment reprogramming. RESULTS: Reduction of PBRM1 expression was observed in human PDAC tissues and correlated with poor prognosis and metastasis. Pbrm1 loss promoted ductal metaplasia and delayed epithelial recovery in mice with caerulein-induced pancreatic injury. In PDAC model with either mutant Kras alone or in combination with Trp53 mutation, lack of Pbrm1 markedly accelerated tumor development and progression. Bulk transcriptomics and scRNA-seq identified reprogramming of both tumor compartment with mesenchymal phenotype acquisition and stroma compartment with inflammatory cancer-associated fibroblasts (iCAFs) transformation. Mechanistically, Pbrm1 deletion induced Zeb1 upregulation through epigenetic chromatin remodeling, thereby enhancing epithelial-mesenchymal and basal-like subtype transition. CONCLUSIONS: These findings indicated a tumor-suppressing role of PBRM1 in PDAC. PBRM1-deficient PDAC constitutes a specific subgroup of patients with aggressive phenotype and prognostic significance.