Extracellular lumican augments cytotoxicity of chemotherapy in pancreatic ductal adenocarcinoma cells via autophagy inhibition

• Published in: Oncogene Vol. 35; no. 37; pp. 4881 - 4890
• Main Authors: Li, X, Roife, D, Kang, Y, Dai, B, Pratt, M, Fleming, J B
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.09.2016; Nature Publishing Group
• Subjects: 13; 13/1; 13/106; 13/2; 13/31; 13/95; 631/67; 631/67/1059/99; 82; 82/80; 96; 96/35; 96/95; Adenocarcinoma; AMP-Activated Protein Kinases - genetics; Animals; Antineoplastic agents; Antineoplastic Combined Chemotherapy Protocols - administration & dosage; Antitumor activity; Apoptosis; Apoptosis - drug effects; Autophagy; Autophagy - drug effects; Cancer therapies; Carcinoma, Pancreatic Ductal - drug therapy; Carcinoma, Pancreatic Ductal - genetics; Carcinoma, Pancreatic Ductal - pathology; Cell Biology; Cell culture; Cell Line, Tumor; Cell Proliferation - drug effects; Chemotherapy; Chloroquine; Cytochrome c; Cytotoxicity; Deoxycytidine - administration & dosage; Deoxycytidine - analogs & derivatives; Deoxyribonucleic acid; DNA; DNA damage; Extracellular matrix; Gemcitabine; Growth inhibition; Health aspects; Human Genetics; Humans; Internal Medicine; Lactates; Lactic acid; Lumican - administration & dosage; Medicine; Medicine & Public Health; Mice; Microenvironments; Microtubule-Associated Proteins - biosynthesis; Microtubule-Associated Proteins - genetics; Mitochondria; Oncology; original-article; Pancreatic cancer; Proteoglycans; Reactive oxygen species; Reactive Oxygen Species - metabolism; Secretion; Signal transduction; Signal Transduction - drug effects; Stellate cells; Tumors; Vascular endothelial growth factor; Xenograft Model Antitumor Assays; Xenografts
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2016.20

Lumican, an extracellular matrix proteoglycan overexpressed by pancreatic stellate cells (PSCs) and pancreatic ductal adenocarcinoma cells (PDACs), drives the formation of a tumor-specific microenvironment. We recently showed that extracellular lumican inhibits pancreatic cancer cell growth and is associated with prolonged survival after surgery. Here we investigated the role of extracellular lumican in chemotherapy-mediated cancer therapy. Lumican secretion was increased by chemotherapeutic agents in PDAC, and especially in PSCs, and appeared to be linked to the extent of cells’ response to chemotherapy-induced growth inhibition. In multiple PDAC models, including cell lines, patient-derived xenografts and lumican knockout mice, lumican significantly increased antitumor effect of chemotherapy. This effect was associated with DNA damage, apoptosis and inhibition of cell viability, glucose consumption, lactate production and vascular endothelial growth factor secretion. In PDAC cells, chemotherapeutic agents triggered autophagosome formation and increased LC3 expression through the reactive oxygen species-mediated AMP-activated kinase (AMPK) signaling pathway. Inhibition of gemcitabine-induced autophagy in cancer cells by treatment with AMPK inhibitor compound C, lysosomal inhibitor chloroquine or autophagy inhibitor 3MA enhanced gemcitabine-induced apoptosis, suggesting that autophagy is a protective cellular response to gemcitabine treatment. Importantly, lumican dramatically decreased AMPK activity, inhibiting chemotherapy-induced autophagy in both in vitro and in vivo PDAC models. Co-treatment of PDAC cells with lumican and gemcitabine increased mitochondrial damage, reactive oxygen species (ROS) production and cytochrome c release, indicating that lumican-induced disruption of mitochondrial function may be the mechanism of sensitization to gemcitabine. Together, our findings demonstrate that extracellular lumican augments cytotoxicity of chemotherapy in PDAC cells through inhibition of chemotherapeutic agent-induced autophagy.