Pancreatic ductal adenocarcinoma (PDAC) is most aggressive among all gastrointestinal tumors. The complex intra-tumor heterogeneity and special tumor microenvironment in PDAC bring great challenges for developing effective treatment strategies. We aimed to delineate dynamic changes of tumor microenvironment components during PDAC malignant progression utilizing single-cell RNA sequencing. A total of 11 samples (4 PDAC I, 4 PDAC II, 3 PDAC III) were used to construct expression matrix. After identifying distinct cell clusters, subcluster analysis for each cluster was performed. New cancer associated fibroblasts (CAFs) subset was validated by weighted gene co-expression network analysis, RNA in situ hybridization and immunofluorescence. We found that ductal cells were not dominant component while tumor infiltrating immune cells and pancreatic stellate cells gradually accumulated during tumor development. We defined several new Treg and exhausted T cell signature genes, including DUSP4, FANK1 and LAIR2. The analysis of TCGA datasets showed that patients with high expression of DUSP4 had significantly worse prognosis. In addition, we identified a new CAFs subset (complement-secreting CAFs, csCAFs), which specifically expresses complement system components, and constructed csCAFs-related module by weighted gene co-expression network analysis. The csCAFs were located in the tissue stroma adjacent to malignant ductal cells only in early PDAC. We systematically explored PDAC heterogeneity and identified csCAFs as a new CAFs subset special to PDAC, which may be valuable for understanding the crosstalk inside tumor. This study was supported by The Natural Science Foundation of China (NO.81572339, 81672353, 81871954) and the Youth Clinical Research Project of Peking University First Hospital (2018CR28).

Metabolic reprogramming provides tumors with an energy source and biofuel to support their survival in the malignant microenvironment. Extensive research into the intrinsic oncogenic mechanisms of the tumor microenvironment (TME) has established that cancer-associated fibroblast (CAFs) and metabolic reprogramming regulates tumor progression through numerous biological activities, including tumor immunosuppression, chronic inflammation, and ecological niche remodeling. Specifically, immunosuppressive TME formation is promoted and mediators released via CAFs and multiple immune cells that collectively support chronic inflammation, thereby inducing pre-metastatic ecological niche formation, and ultimately driving a vicious cycle of tumor proliferation and metastasis. This review comprehensively explores the process of CAFs and metabolic regulation of the dynamic evolution of tumor-adapted TME, with particular focus on the mechanisms by which CAFs promote the formation of an immunosuppressive microenvironment and support metastasis. Existing findings confirm that multiple components of the TME act cooperatively to accelerate the progression of tumor events. The potential applications and challenges of targeted therapies based on CAFs in the clinical setting are further discussed in the context of advancing research related to CAFs.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the complex tumor microenvironment (TME), consisting of an abundance of stromal cells. Among them, tumor infiltrating T cells play a pivotal role in tumor progress. To identify the full spectrum and developmental trajectory of T cells and their crosstalk with tumor cells in PDAC, we conducted scRNA-seq analysis based on multiple datasets from our institution and open databases. We delineated the cellular landscape and transcriptional dynamics of T cells in PDAC. Through the inferCNV analysis and known tumor markers, the malignant ductal cells were identified. The inter-patients heterogeneity of tumor cells was also identified. After integrating T cells and malignant ductal cells, we found the CCL5-SDC1/4 receptor-ligand interactions between them. Furthermore, we demonstrated that CCL5 promoted tumor cells migration via interacting with SDC1 in vitro. Our findings pave the way for characterizing the heterogeneity and development trajectory of T cells, and cell-to-cell communications in TME of PDAC, which might provide a new target for immunotherapy.

Purpose: Most patients with pancreatic ductal adenocarcinoma (PDAC) have vascular invasion and metastasis, leading to low surgical resection rate and dismal prognosis. Tumor angiogenesis is related to vascular invasion and metastasis. However, anti-angiogenesis therapeutic effects in PDAC are limited. Therefore, it is imperative to explore molecular mechanism of angiogenesis in PDAC.

Hedgehog (Hh) signaling is crucially involved in tumorigenesis. This study aimed to assess the role of Hh signaling in the regulation of epithelial-mesenchymal transition (EMT), stemness properties and chemoresistance of human pancreatic Panc-1 cancer stem cells (CSCs). Panc-1 cells were transfected with recombinant lentiviral vectors to silence SMO and serum-free floating-culture system was used to isolate Panc-1 tumorspheres. The expression of CSC and EMT markers was detected by flow cytometry, real-time RT-PCR and Western blot analysis. Malignant behaviors of Panc-1 CSC were evaluated by tumorigenicity assays and nude mouse lung metastasis model. We found that tumorspheres derived from pancreatic cancer cell line Panc-1 possessed self-renewal, differentiation and stemness properties. Hh pathway and EMT were active in Panc-1 tumorspheres. Inhibition of Hh signaling by SMO knockdown inhibited self-renewal, EMT, invasion, chemoresistance, pulmonary metastasis, tumorigenesis of pancreatic CSCs. In conclusion, Hh signaling contributes to the maintenance of stem-like properties and chemoresistance of pancreatic CSC and promotes the tumorigenesis and metastasis of pancreatic cancer. Hh pathway is a potential molecular target for the development of therapeutic strategies for pancreatic CSCs.