title: Constitutive and treatment-induced CXCL8-signalling selectively modulates the efficacy of anti-metabolite therapeutics in metastatic prostate cancer.
abstract: BACKGROUND
  The current study was undertaken to characterize the effect of anti-metabolites on inducing CXCL8 signaling and determining whether the constitutive and/or drug-induced CXCL8 signaling in metastatic prostate cancer (CaP) cells modulates their sensitivity to this class of agent.
  
  
  METHODS
  The response of metastatic CaP cells to 5-Fluorouracil (5-FU), Pemetrexed or Tomudex was determined using cell count assays, flow cytometry and PARP cleavage analysis. Quantitative-PCR, ELISA and immunoblots were employed to determine effects of drugs or CXCL8 administration on target gene/protein expression.
  
  
  RESULTS
  Administration of 5-FU but not pemetrexed potentiated CXCL8 secretion and increased CXCR1 and CXCR2 gene expression in metastatic PC3 cells. Consistent with this, the inhibition of CXCL8 signaling using a CXCR2 antagonist, AZ10397767, increased the cytotoxicity of 5-FU by 4-fold (P<0.001), and increased 5-FU-induced apoptosis in PC3 cells (P<0.01). In contrast, while administration of AZ10397767 had no effect on the sensitivity of pemetrexed, the CXCR2 antagonist exerted the greatest effect in increasing the sensitivity of PC3 cells to Tomudex, a directed thymidylate synthase (TS) inhibitor. Subsequent experiments confirmed that administration of recombinant human CXCL8 increased TS expression, a response mediated in part by the CXCR2 receptor. Moreover, siRNA-mediated knockdown of the CXCL8-target gene Bcl-2 increased the sensitivity of PC3 cells to 5-FU.
  
  
  CONCLUSIONS
  CXCL8 signaling provides a selective resistance of metastatic prostate cancer cells to specific anti-metabolites by promoting a target-associated resistance, in addition to underpinning an evasion of treatment-induced apoptosis.
authors.affiliation: Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Wilson
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Maxwell
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Longley
authors.forename: Richard H
authors.initials: RH
authors.lastname: Wilson
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Johnston
authors.forename: David J J
authors.initials: DJ
authors.lastname: Waugh
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D045744:Cell Line, Tumor; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D023062:Receptors, Interleukin-8A / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D023063:Receptors, Interleukin-8B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics
chemical_list: D000964:Antimetabolites, Antineoplastic; C508606:CXCL8 protein, human; D016209:Interleukin-8; D009363:Neoplasm Proteins; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B