Autophagy mediates survival of pancreatic tumour-initiating cells in a hypoxic microenvironment.

Involvement of dysregulated autophagy in cancer growth and progression has been shown in different tumour entities, including pancreatic ductal adenocarcinoma (PDA). PDA is an extremely aggressive tumour characterized by a small population of highly therapy-resistant cancer stem cells (CSCs) capable of self-renewal and migration. We examined whether autophagy might be involved in the survival of CSCs despite nutrition and oxygen deprivation typical for the hypoxic tumour microenvironment of PDA. Immunohistochemistry revealed that markers for hypoxia, CSCs and autophagy are co-expressed in patient-derived tissue of PDA. Hypoxia starvation (H/S) enhanced clonogenic survival and migration of established pancreatic cancer cells with stem-like properties (CSC(high)), while pancreatic tumour cells with fewer stem cell markers (CSC(low)) did not survive these conditions. Electron microscopy revealed more advanced autophagic vesicles in CSC(high) cells, which exhibited higher expression of autophagy-related genes under normoxic conditions and relative to CSC(low) cells, as found by RT-PCR and western blot analysis. LC3 was already fully converted to the active LC3-II form in both cell lines, as evaluated by western blot and detection of accumulated GFP-LC3 protein by fluorescence microscopy. H/S increased formation of autophagic and acid vesicles, as well as expression of autophagy-related genes, to a higher extent in CSC(high) cells. Modulation of autophagy by inhibitors and activators resensitized CSC(high) to apoptosis and diminished clonogenicity, spheroid formation, expression of CSC-related genes, migratory activity and tumourigenicity in mice. Our data suggest that enhanced autophagy levels may enable survival of CSC(high) cells under H/S. Interference with autophagy-activating or -inhibiting drugs disturbs the fine-tuned physiological balance of enhanced autophagy in CSC and switches survival signalling to suicide.

Rausch V ，Liu L ，Apel A ，Rettig T ，Gladkich J ，Labsch S ，Kallifatidis G ，Kaczorowski A ，Groth A ，Gross W ，Gebhard MM ，Schemmer P ，Werner J ，Salnikov AV ，Zentgraf H ，Büchler MW ，Herr I ... -  《-》

Inhibition of glucose turnover by 3-bromopyruvate counteracts pancreatic cancer stem cell features and sensitizes cells to gemcitabine.

Isayev O ，Rausch V ，Bauer N ，Liu L ，Fan P ，Zhang Y ，Gladkich J ，Nwaeburu CC ，Mattern J ，Mollenhauer M ，Rückert F ，Zach S ，Haberkorn U ，Gross W ，Schönsiegel F ，Bazhin AV ，Herr I ... -  《Oncotarget》

Aspirin counteracts cancer stem cell features, desmoplasia and gemcitabine resistance in pancreatic cancer.

Zhang Y ，Liu L ，Fan P ，Bauer N ，Gladkich J ，Ryschich E ，Bazhin AV ，Giese NA ，Strobel O ，Hackert T ，Hinz U ，Gross W ，Fortunato F ，Herr I ... -  《Oncotarget》

Microenvironmental hCAP-18/LL-37 promotes pancreatic ductal adenocarcinoma by activating its cancer stem cell compartment.

The tumour stroma/microenvironment not only provides structural support for tumour development, but more importantly it provides cues to cancer stem cells (CSCs) that regulate their self-renewal and metastatic potential. This is certainly true for pancreatic ductal adenocarcinomas (PDAC), where tumour-associated fibroblasts, pancreatic stellate cells and immune cells create an abundant paracrine niche for CSCs via microenvironment-secreted factors. Thus understanding the role that tumour stroma cells play in PDAC development and CSC biology is of utmost importance. Microarray analyses, tumour microarray immunohistochemical assays, in vitro co-culture experiments, recombinant protein treatment approaches and in vivo intervention studies were performed to understand the role that the immunomodulatory cationic antimicrobial peptide 18/LL-37 (hCAP-18/LL-37) plays in PDAC biology. We found that hCAP-18/LL-37 was strongly expressed in the stroma of advanced primary and secondary PDAC tumours and is secreted by immune cells of the stroma (eg, tumour-associated macrophages) in response to tumour growth factor-β1 and particularly CSC-secreted Nodal/ActivinA. Treatment of pancreatic CSCs with recombinant LL-37 increased pluripotency-associated gene expression, self-renewal, invasion and tumourigenicity via formyl peptide receptor 2 (FPR2)- and P2X purinoceptor 7 receptor (P2X7R)-dependent mechanisms, which could be reversed by inhibiting these receptors. Importantly, in a genetically engineered mouse model of K-Ras-driven pancreatic tumourigenesis, we also showed that tumour formation was inhibited by either reconstituting these mice with bone marrow from cathelicidin-related antimicrobial peptide (ie, murine homologue of hCAP-18/LL-37) knockout mice or by pharmacologically inhibiting FPR2 and P2X7R. Thus, hCAP-18/LL-37 represents a previously unrecognised PDAC microenvironment factor that plays a critical role in pancreatic CSC-mediated tumourigenesis.

Sainz B Jr ，Alcala S ，Garcia E ，Sanchez-Ripoll Y ，Azevedo MM ，Cioffi M ，Tatari M ，Miranda-Lorenzo I ，Hidalgo M ，Gomez-Lopez G ，Cañamero M ，Erkan M ，Kleeff J ，García-Silva S ，Sancho P ，Hermann PC ，Heeschen C ... -  《-》

Marker-free lineage tracing reveals an environment-instructed clonogenic hierarchy in pancreatic cancer.

Effective treatments for pancreatic ductal adenocarcinoma (PDAC) are lacking, and targeted agents have demonstrated limited efficacy. It has been speculated that a rare population of cancer stem cells (CSCs) drives growth, therapy resistance, and rapid metastatic progression in PDAC. These CSCs demonstrate high clonogenicity in vitro and tumorigenic potential in vivo. However, their relevance in established PDAC tissue has not been determined. Here, we use marker-independent stochastic clonal labeling, combined with quantitative modeling of tumor expansion, to uncover PDAC tissue growth dynamics. We find that in contrast to the CSC model, all PDAC cells display clonogenic potential in situ. Furthermore, the proximity to activated cancer-associated fibroblasts determines tumor cell clonogenicity. This means that the microenvironment is dominant in defining the clonogenic activity of PDAC cells. Indeed, manipulating the stroma by Hedgehog pathway inhibition alters the tumor growth mode, revealing that tumor-stroma crosstalk shapes tumor growth dynamics and clonal architecture.

Lodestijn SC ，Miedema DM ，Lenos KJ ，Nijman LE ，Belt SC ，El Makrini K ，Lecca MC ，Waasdorp C ，van den Bosch T ，Bijlsma MF ，Vermeulen L ... -  《Cell Reports》