Elevated interleukin-6 and G-CSF in human pancreatic cancer cell conditioned medium suppress dendritic cell differentiation and activation.
Although dendritic cell (DC) function is impaired in pancreatic cancer patients, the underlying mechanisms are unknown. This study analyzed the soluble factors released by pancreatic cancer cells responsible for inhibiting DC differentiation and activation. Medium conditioned by a highly metastatic human pancreatic cancer cell line BxPC-3 [BxPC-3 conditioned medium (BxCM)] was mainly used for the study. Both CD34+ hematopoietic progenitor cell-derived and CD14+ monocyte-derived immature DCs and mature DCs (mDCs) were inhibited by BxCM. Allostimulation of CD4+ and CD8+ T cells by BxCM-treated mDCs was inefficient and resulted in production of lower levels of Th1 and Th2 cytokines. Antigen-specific T-cell activation capability was also reduced in BxCM-treated mDCs. Addition of exogenous interleukin-6 (IL-6) and granulocyte colony-stimulating factor (G-CSF), which were present in high amounts in BxCM, mimicked the inhibitory effect of BxCM on DC differentiation and maturation. IL-6 was able to suppress DC differentiation and G-CSF mainly acted on the suppressing allostimulatory capacity of DCs. In addition, pancreatic cancer patient sera were able to inhibit DC differentiation of CD14+ monocytes obtained from healthy donors. Depleting IL-6 or G-CSF from BxCM could reverse the DC-inhibitory properties of BxCM. Furthermore, BxCM, IL-6, or G-CSF led to the activation of signal transducer and activator of transcription 3 (STAT3) in CD14+ monocytes to different degrees. Blocking BxCM-induced STAT3 activation also reversed the inhibitory effect of BxCM on DC differentiation. Therefore, IL-6 and G-CSF in BxCM represent two main factors responsible for suppression of DC differentiation, maturation, and antigen presentation, and this suppression of DC functions may be due to the aberrant activation of STAT3 by BxCM.
Bharadwaj
Uddalak
U
Molecular Surgeon Research Center, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas 77030, USA.
Li
Min
M
Zhang
Rongxin
R
Chen
Changyi
C
Yao
Qizhi
Q
D017951:Antigen Presentation; D018952:Antigens, CD34 / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology*; D016179:Granulocyte Colony-Stimulating Factor / Q000172:deficiency / Q000276:immunology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology; D006801:Humans; D015850:Interleukin-6 / Q000276:immunology*; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008213:Lymphocyte Activation; D009000:Monocytes / Q000166:cytology / Q000276:immunology; D010190:Pancreatic Neoplasms / Q000276:immunology* / Q000473:pathology; D050796:STAT3 Transcription Factor / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology; D020032:Tyrphostins / Q000494:pharmacology
D018952:Antigens, CD34; D017077:Culture Media, Conditioned; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D016179:Granulocyte Colony-Stimulating Factor; C507924:JAK2 protein, human; D053614:Janus Kinase 2