Modulation of CXCR3 ligand secretion by prostaglandin E2 and cyclooxygenase inhibitors in human breast cancer

Abstract

IntroductionIn murine breast cancer models, the two interferon-gamma (IFN-γ) inducible chemokines and CXC-chemokine receptor 3 (CXCR3) receptor ligands, monokine induced by γ-interferon (CXCL9) and interferon-γ-inducible protein-10 (CXCL10) impair tumor growth and metastasis formation through recruitment of natural killer (NK) cells and tumor-suppressive T lymphocytes. In human breast cancer, CXCL9 mRNA overexpression correlates with the number of tumor infiltrating lymphocytes and predicts response to different chemotherapeutic regimens. Raising the intratumoral CXCR3 ligand concentration is therefore a possible way to enhance immune intervention in breast cancer. Little is known, however, about expression levels and regulation of these chemokines in human breast cancer. Since the inhibition of cyclooxygenases (COX) has been shown to reduce tumor growth and incidence of metastases in a lymphocytic and IFN-γ dependent manner, we argued that COX isoenzymes are a pharmacologic target to increase intratumoral CXCR3 ligand concentration in human breast cancer.MethodsCXCL9 was visualized in breast cancer specimens by immunohistochemistry, expression levels of CXCL9 and cyclooxygenases were determined by ELISA and western blotting, respectively. For regulation studies, Michigan Cancer Foundation-7 (MCF-7) and M.D. Anderson - Metastatic Breast 231 (MDA-MB 231) breast cancer cells were stimulated with IFN-γ with or without prostaglandin E2 (PGE2) or COX inhibitors (indomethacin, acetylsalicylic acid (ASA), celecoxib). CXCR3 ligand release from cells was measured by ELISA.ResultsWithin the tumor microenvironment, cancer cells are the major source of CXCL9. PGE2 impairs IFN-γ mediated CXCL9 and CXCL10 release from MCF-7 and MDA-MB 231 cells, and inhibition of endogenous cyclooxygenases by indomethacin or ASA correspondingly increases this secretion. Otherwise, high concentrations of the Cyclooxygenase-2 (COX-2) specific antagonist celecoxib have opposite effects and impair CXCL9 and CXCL10 release. In human breast cancer tissue specimens there is an inverse correlation between COX-2 overexpression and CXCL9 concentration, suggesting that the observed in vitro effects are of importance in vivo as well.ConclusionsSuppressing endogenous PGE2 synthesis by cyclooxygenase inhibition increases CXCL9 and CXCL10 release from breast cancer cells and is therefore a pharmacologic candidate to enhance intratumoral immune infiltration. Yet, to this end the unselective COX inhibitors ASA and indomethacin seem preferable to celecoxib that at higher concentrations reduces CXCR3 ligand release most probably due to COX independent mechanisms.

Aspirin and NSAIDs for breast cancer chemoprevention

“…In addition, previous evidence has shown that inhibition of cyclooxygenases reduces tumor growth and incidence of metastases in a lymphocytic and IFN-γ-dependent manner. Thus, in a recently published study, Bronger et al (2012) hypothesized that the COX isoenzymes could be a pharmacologic target for the increase of intratumoral CXCR3 ligand concentration in human breast cancer. In that study, MCF-7 or MDA-MB-231 cells were treated with IFN-γ with or without PGE 2 or the COX inhibitors indomethacin, acetylsalicylic acid, and celecoxib.…”

Identification of Potential Therapeutic Targets Among CXC Chemokines in Breast Tumor Microenvironment Using Integrative Bioinformatics Analysis

“…We found that high transcription levels of CXCL9 conferred an overall survival advantage in all BC patients, consistent with previous findings. Some researchers have already discovered that IFN-γ exhibits a powerful influence on the secretion and expression of CXCL9 and CXCL10 [41, 42]. The GeparSixto trial revealed that as an immune-activating factor, CXCL9 shows a positive correlation with PD-1 [43].…”

The Role of CXCR3/Ligand Axis in Cancer

“…The significance of CXCR3/ligand axis in cancer is further strengthened by the observations that COX-inhibitors increased CXCL9/CXCL10 expression [56] and promoted anti-tumor effects in breast cancer [57]. Bronger et al [56] demonstrated that suppressing endogenous PGE2 synthesis by cyclooxygenase inhibition increased CXCL9 and CXCL10 release from breast cancer cells and enhanced intra-tumoral immune infiltration.…”

“…Bronger et al [56] demonstrated that suppressing endogenous PGE2 synthesis by cyclooxygenase inhibition increased CXCL9 and CXCL10 release from breast cancer cells and enhanced intra-tumoral immune infiltration. In this study, the unselective COX inhibitors aspirin and indomethacin were preferable in increasing CXCL9/CXCL10 in comparison to celecoxib that at higher concentrations reduced ligand release from breast cancer cells.…”

“…In this study, the unselective COX inhibitors aspirin and indomethacin were preferable in increasing CXCL9/CXCL10 in comparison to celecoxib that at higher concentrations reduced ligand release from breast cancer cells. The decrease in ligand release from breast cancer cells at high concentrations of celecoxib was attributed to COX independent mechanisms [56].…”