Involvement of IL-8 in COX-2-mediated bone metastases from breast cancer

J Surg Res. 2006 Jul;134(1):44-51. doi: 10.1016/j.jss.2006.03.018. Epub 2006 May 6.

Abstract

Background: Cyclooxygenase-2 (COX-2) overexpression by a primary tumor correlates with poor prognosis in breast cancer, including early spread to bone. Interleukin-8 (IL-8) stimulates osteoclastogenesis and resorption of bone, and elevated IL-8 levels predict early metastatic spread of breast cancer. The purpose of this study was to test our hypothesis that tumors that overexpress COX-2 induce IL-8 production.

Materials and methods: We cotransfected MCF-10A (nonmalignant breast epithelial) cells, as well as MDA-231 (highly metastatic human breast cancer) cell lines with a pSG5-COX-2 vector and pEF1a-Luc-IRES-Neo vector (luciferase reporter). COX-2 overexpression was confirmed by Western blot and PGE2 (a product of the COX-2 pathway) immunoassay. IL-8 production was measured by immunoassay. In vivo testing used a nude mouse model to measure COX-2 and IL-8 production from breast cancer cells that had metastasized to bone (bone-seeking clones (BSCs)). Long bone metastases were localized and quantified by luciferase imaging (Xenogen IVIS system) and X-ray. BSCs were isolated and cultured and then tested for the production of PGE2 and IL-8.

Results: COX-2 overexpression caused a 4- to 5-fold increase in IL-8 production in both MCF-10A and MDA-231 cells in vitro. In vivo, we observed that the MDA-231-BSC (metastatic cells isolated from bone metastases) produced significantly greater levels of both PGE2 and IL-8 compared to the parental MDA-231 cells (P < 0.01). In contrast to the results obtained with these estrogen receptor-negative cell lines, COX-2 expression failed to induce IL-8 in the MCF-7 estrogen receptor-positive breast cancer cell line. Treatment with the COX-2 inhibitor NS-398 at a low 1-mu[scap]M dose reduced the production of IL-8 in COX-2-transfected MDA-231 cells by 30%, thus confirming the involvement of COX-2 in IL-8 induction.

Conclusion: COX-2 expression induced formation of PGE2 and IL-8 in breast cancer cells. Since PGE2 and IL-8 stimulate osteoclasts to resorb bone, COX-2 inhibition is a potential target for treatment to prevent bone metastases.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bone Neoplasms / secondary*
  • Breast Neoplasms / pathology*
  • Cell Line, Tumor
  • Cyclooxygenase 2 / physiology*
  • Cyclooxygenase 2 Inhibitors / pharmacology
  • Female
  • Humans
  • Interleukin-8 / biosynthesis
  • Interleukin-8 / physiology*
  • Mice
  • Mice, Nude
  • Protein Processing, Post-Translational

Substances

  • Cyclooxygenase 2 Inhibitors
  • Interleukin-8
  • Cyclooxygenase 2