title: Tumor-associated macrophage-derived IL-6 and IL-8 enhance invasive activity of LoVo cells induced by PRL-3 in a KCNN4 channel-dependent manner.
abstract: BACKGROUND
  Tumor-associated macrophages (TAMs) are known to promote cancer progression and metastasis through the release of a variety of cytokines. Phosphatase of regenerating liver (PRL-3) has been considered as a marker of colorectal cancer (CRC) liver metastasis. Our previous research suggests that PRL-3 can enhance the metastasis of CRC through the up-regulation of intermediate-conductance Ca2+-activated K+ (KCNN4) channel, which is dependent on the autocrine secretion of tumor necrosis factor-alpha (TNF-α). However, whether TAMs participate in the progression and metastasis of CRC induced by PRL-3 remains unknown.
  
  
  METHODS
  We used flow cytometry, coculture, western blotting, invasion assays, real-time quantitative PCR, chromatin immunoprecipitation, luciferase reporter assays, and immunofluorescence staining to determine the effect of TAMs on the ability of PRL-3 to promote invasiveness of CRC cells.
  
  
  RESULTS
  In this study, we found that TAMs facilitated the metastasis of CRC induced by PRL-3. When TAMs were cocultured with CRC cells, the expression of KCNN4 was increased in TAMs and the invasion of CRC cells was enhanced. Furthermore, cytokines that were secreted by TAMs, such as IL-6 and IL-8, were also significantly increased. This response was attenuated by treating TAMs with the KCNN4 channel-specific inhibitor, 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34), which suggested that KCNN4 channels may be involved in inducing the secretion of IL-6 and IL-8 by TAMs and improving CRC cell invasiveness. Moreover, the expression of KCNN4 channels in TAMs was regulated through the NF-κB signal pathway, which is activated by TNF-α from CRC cells. Immunofluorescence analysis of colorectal specimens indicated that IL-6 and IL-8 double positive cells in the stroma showed positive staining for the TAM marker CD68, suggesting that TAMs produce IL-6 and IL-8. Increased numbers of these cells correlated with higher clinical stage.
  
  
  CONCLUSIONS
  Our findings suggested that TAMs participate in the metastasis of CRC induced by PRL-3 through the TNF-α mediated secretion of IL-6 and IL-8 in a paracrine manner.
authors.forename: Heyang
authors.initials: H
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Lai
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.forename: Xingxi
authors.initials: X
authors.lastname: Luo
authors.forename: Yujie
authors.initials: Y
authors.lastname: Zeng
authors.forename: Heng
authors.initials: H
authors.lastname: Wu
authors.forename: Qiusheng
authors.initials: Q
authors.lastname: Lan
authors.affiliation: Department of Gastroenteropancreatic Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, P,R, China. sumschuzhonghua@hotmail.com.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Chu
mesh_terms: D001665:Binding Sites; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D018920:Coculture Techniques; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000473:pathology; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D016209:Interleukin-8 / Q000378:metabolism*; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D016328:NF-kappa B / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000378:metabolism*; D019899:Paracrine Communication; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D059016:Tumor Microenvironment; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C508606:CXCL8 protein, human; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; D016328:NF-kappa B; D009363:Neoplasm Proteins; D026902:Potassium Channel Blockers; D014409:Tumor Necrosis Factor-alpha; C484730:PTP4A3 protein, human; D017027:Protein Tyrosine Phosphatases