ABSTRACT
Tumor-associated macrophages (TAMs) are abundant population of inflammatory cells which play an essential role in remodeling tumor microenvironment and tumor progression. Previously, we found the high density of TAMs was correlated with lymph node metastasis and poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Therefore, this study was designed to investigate the mechanisms of interaction between TAMs and PDAC. THP-1 monocytes were the exposure to conditioned media (CM) produced by PDAC cells; then, monocyte recruitment and macrophage differentiation were assessed. CM from PDAC attracted and polarized THP-1 monocytes to tumor-driven like macrophages. mRNA expression cytokine profiling and ELISA identified the IL-8 secretion was increasing in tumor-driven like macrophages, and STAT3 pathway was involved. Addition of exogenous recombinant human IL-8 promoted PDAC cells motility in vitro and metastasis in vivo via upregulating Twist expression, which mediated epithelial-mesenchymal transition in cancer cells. What is more, IL-8 expression level in tumor stroma by immunohistochemical analysis was related to lymph node metastasis, the number of tumor CD68 but not CD163 positive macrophages and patient outcome. Taken together, these findings shed light on the important interplay between cancer cells and TAMs in tumor microenvironment and suggested that IL-8 signaling might be a potential therapeutic target for PDAC.
Subject(s)
Carcinoma, Pancreatic Ductal/pathology , Interleukin-8/genetics , Interleukin-8/metabolism , Macrophages/metabolism , Monocytes/cytology , Pancreatic Neoplasms/pathology , Animals , Carcinoma, Pancreatic Ductal/genetics , Carcinoma, Pancreatic Ductal/metabolism , Cell Differentiation/drug effects , Cell Line, Tumor , Cell Movement/drug effects , Culture Media, Conditioned/pharmacology , Epithelial-Mesenchymal Transition , Gene Expression Regulation, Neoplastic , Humans , Macrophages/pathology , Mice , Monocytes/drug effects , Monocytes/metabolism , Neoplasm Metastasis , Neoplasm Transplantation , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/metabolism , STAT3 Transcription Factor/metabolism , Signal Transduction , THP-1 Cells , Tumor Microenvironment , Up-Regulation , Pancreatic NeoplasmsABSTRACT
It is critical to understand the pathogenesis of preinvasive stages of pancreatic duct adenocarcinoma (PDAC) for developing novel potential diagnostic and therapeutic targets. The polycomb group family member B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi1) is overexpressed and involved in cancer progression in PDAC; however, its role in the multistep malignant transformation of human pancreatic duct cells has not been directly demonstrated. In this study, we stably expressed Bmi1 in a model of telomerase-immortalized human pancreatic duct-derived cells (HPNE) and showed that Bmi1 promoted HPNE cell proliferation, migration, and invasion but not malignant transformation. We then used mutant KRASG12D as a second oncogene to transform HPNE cells and showed that it further enhanced Bmi1-induced malignant potential. More importantly, coexpression of KRASG12D and Bmi1 caused anchorage-independent growth transformation in vitro but still failed to produce tumors in nude mice. Finally, we found that mutant KRASG12D induced HPNE-Bmi1 cells to undergo partial epithelial-mesenchymal transition (EMT) likely via upregulation of snail. Knockdown of KRASG12D significantly reduced the expression of snail and vimentin at both the messenger RNA (mRNA) and protein level and further impaired the anchorage-independent growth capability of invasive cells. In summary, our findings demonstrate that coexpression of Bmi1 and KRASG12D could lead to transformation of HPNE cells in vitro and suggest potential new targets for diagnosis and treatment of PDAC.