title: Interleukin-6 is a potential therapeutic target in interleukin-6 dependent, estrogen receptor-α-positive breast cancer.
abstract: BACKGROUND
  Interleukin-6 (IL-6) is an important growth factor for estrogen receptor-α (ERα)-positive breast cancer, and elevated serum IL-6 is associated with poor prognosis.
  
  
  METHODS
  The role of the phosphorylated signal transducer and activator of transcription 3 pathway was investigated in ERα-positive breast cancer. A panel of cell lines was treated with exogenous IL-6. An IL-6 specific gene signature was generated by profiling ten ERα-positive breast cancer cell lines alone or following treatment with 10 ng/mL recombinant IL-6 or human marrow stromal cell-conditioned media, with or without siltuximab (a neutralizing anti-IL-6 antibody) and grown in three-dimensional tumor microenvironment-aligned cultures for 4 days, 5 days, or 6 days. The established IL-6 signature was validated against 36 human ERα-positive breast tumor samples with matched serum. A comparative MCF-7 xenograft murine model was utilized to determine the role of IL-6 in estrogen-supplemented ERα-positive breast cancer to assess the efficacy of anti-IL-6 therapy in vivo.
  
  
  RESULTS
  In eight of nine ERα-positive breast cancer cell lines, recombinant IL-6 increased phosphorylation of tyrosine 705 of STAT3. Differential gene expression analysis identified 17 genes that could be used to determine IL-6 pathway activation by combining their expression intensity into a pathway activation score. The gene signature included a variety of genes involved in immune cell function and migration, cell growth and apoptosis, and the tumor microenvironment. Validation of the IL-6 gene signature in 36 matched human serum and ERα-positive breast tumor samples showed that patients with a high IL-6 pathway activation score were also enriched for elevated serum IL-6 (≥10 pg/mL). When human IL-6 was provided in vivo, MCF-7 cells engrafted without the need for estrogen supplementation, and addition of estrogen to IL-6 did not further enhance engraftment. Subsequently, we prophylactically treated mice at MCF-7 engraftment with siltuximab, fulvestrant, or combination therapy. Siltuximab alone was able to blunt MCF-7 engraftment. Similarly, siltuximab alone induced regressions in 90% (9/10) of tumors, which were established in the presence which were established in the presence of hMSC expressing human IL-6 and estrogen.
  
  
  CONCLUSIONS
  Given the established role for IL-6 in ERα-positive breast cancer, these data demonstrate the potential for anti-IL-6 therapeutics in breast cancer.
authors.affiliation: Janssen Research and Development, Beerse, Belgium, USA.
authors.forename: Tineke
authors.initials: T
authors.lastname: Casneuf
authors.affiliation: Janssen Research and Development, Spring House, PA, USA.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Axel
authors.affiliation: Janssen Research and Development, Spring House, PA, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: King
authors.affiliation: Janssen Research and Development, Spring House, PA, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Alvarez
authors.affiliation: LabConnect LLC, Seattle, WA, USA.
authors.forename: Jillian L
authors.initials: JL
authors.lastname: Werbeck
authors.affiliation: Janssen Research and Development, Beerse, Belgium, USA.
authors.forename: Tinne
authors.initials: T
authors.lastname: Verhulst
authors.affiliation: Janssen Research and Development, Beerse, Belgium, USA.
authors.forename: Karin
authors.initials: K
authors.lastname: Verstraeten
authors.affiliation: Janssen Research and Development, Spring House, PA, USA.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Hall
authors.affiliation: Janssen Research and Development, Spring House, PA, USA.
authors.forename: A Kate
authors.initials: AK
authors.lastname: Sasser
keywords: breast cancer; estrogen receptor; gene signature; paracrine IL-6; siltuximab