title: Timing is critical for an effective anti-metastatic immunotherapy: the decisive role of IFNγ/STAT1-mediated activation of autophagy.
abstract: BACKGROUND
  Immunotherapy is often recommended as an adjuvant treatment to reduce the chance of cancer recurrence or metastasis. Interestingly, timing is very important for a successful immunotherapy against metastasis, although the precise mechanism is still unknown.
  
  
  RESULTS
  Using a mouse model of melanoma metastasis induced by intravenous injection of B16-F10 cells, we investigated the mechanism responsible for the diverse efficacy of the prophylactic or therapeutic TLR4 and TLR9 agonist complex against metastasis. We found that the activation of TLR4 and TLR9 prevented, but did not reverse, metastasis because the potency of this combination was neither sufficient to overcome the tumor cell-educated immune tolerance nor to induce efficacious autophagy in tumor cells. The prophylactic application of the complex promoted antimetastatic immunity, leading to the autophagy-associated death of melanoma cells via IFNγ/STAT1 activation and attenuated tumor metastasis. IFNγ neutralization reversed the prophylactic benefit induced by the complex by suppressing STAT1 activation and attenuating autophagy in mice. However, the therapeutic application of the complex did not suppress metastasis because the complex could not reverse tumor cell-induced STAT3 activation and neither activate IFNγ/STAT1 signaling and autophagy. Suppressing STAT3 activation with the JAK/STAT antagonist AG490 restored the antimetastatic effect of the TLR4/9 agonist complex. Activation of autophagy after tumor inoculation by using rapamycin, with or without the TLR4/9 agonist complex, could suppress metastasis.
  
  
  CONCLUSIONS
  Our studies suggest that activation of IFNγ/STAT1 signaling and induction of autophagy are critical for an efficacious anti-metastatic immunotherapy and that autophagy activators may overcome the timing barrier for immunotherapy against metastasis.
authors.affiliation: Molecular Immunology and Pharmacology Laboratory, State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.forename: Zi-Yan
authors.initials: ZY
authors.lastname: Wang
authors.forename: Hong-Zhen
authors.initials: HZ
authors.lastname: Yang
authors.forename: Han-Zhi
authors.initials: HZ
authors.lastname: Liu
authors.forename: Su
authors.initials: S
authors.lastname: Mi
authors.forename: Xiao-Xi
authors.initials: XX
authors.lastname: Lv
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Fu
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Yan
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Zhang
authors.forename: Qi-Min
authors.initials: QM
authors.lastname: Zhan
authors.forename: Zhuo-Wei
authors.initials: ZW
authors.lastname: Hu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001343:Autophagy / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D007167:Immunotherapy / Q000379:methods*; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism*; D008168:Lung / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008545:Melanoma / Q000150:complications / Q000628:therapy; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D009362:Neoplasm Metastasis / Q000517:prevention & control / Q000628:therapy; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D050794:STAT1 Transcription Factor; D007371:Interferon-gamma