Intratumoral COX‐2 inhibition enhances GM‐CSF immunotherapy against established mouse GL261 brain tumors

Abstract

Immunotherapy has shown effectiveness against experimental malignant brain tumors, but the clinical results have been less convincing most likely due to immunosuppression. Prostaglandin E 2 (PGE 2 ) is the key immunosuppressive product of cyclooxygenase-2 (COX-2) and increased levels of PGE 2 and COX-2 have been shown in several tumor types, including brain tumors. In the current study, we report enhanced cure rate of mice with established mouse GL261 brain tumors when immunized with granulocyte macrophage-colony stimulating factor (GM-CSF) secreting tumor cells and simultaneously treated with the selective COX-2 inhibitors parecoxib systemically (5 mg/kg/day; 69% cure rate) or valdecoxib intratumorally (5.3 mg/kg/day; 63% cure rate). Both combined therapies induced a systemic antitumor response of proliferating CD4 1 and CD8 1 T cells, and further analysis revealed T helper 1 (T h 1) cell supremacy. The GL261 tumor cell line produced low levels of PGE 2 in vitro, and co-staining at the tumor site demonstrated that a large fraction of the COX-2 1 cells were derived from CD45 1 immune cells and more specifically macrophages (F4/80 1 ), indicating that tumor-infiltrating immune cells constitute the primary source of COX-2 and PGE 2 in this model. We conclude that intratumoral COX-2 inhibition potentiates GM-CSF immunotherapy against established brain tumors at substantially lower doses than systemic administration. These findings underscore the central role of targeting COX-2 during immunotherapy and implicate intratumoral COX-2 as the primary target.The prognosis for patients with high-grade brain tumors remains poor despite extensive treatment, including surgery, radiotherapy and chemotherapy. 1,2 Treatment failure is mainly ascribed to the infiltrative capacity of the tumor cells, which form tumor microsatellites deep in the normal brain parenchyma. Immunotherapy represents a novel approach that could target these residual tumor cells and has been shown to be safe and induce prolonged survival in clinical trials. [3][4][5] However, the therapeutic effect of immunotherapy is often down-regulated because of immunosuppression.Prostaglandin E 2 (PGE 2 ) constitutes a key suppressive mediator and is synthesized from arachidonic acid by cyclooxygenases (COX) and prostaglandin synthases. The inducible COX-2 and the downstream microsomal prostaglandin E synthase-1 (mPGES-1) are overexpressed in a wide range of tumors, including high-grade brain tumors, and most reports show correlations with poor prognosis, although adverse results are reported. 6-8 PGE 2 has been alleged to exert immunosuppression by either direct effects on T cells by stimulating T h 2 cytokines as interleukin-10 (IL-10) and simultaneously inhibiting T h 1 cytokines as interferon-g (IFN-g) or by indirect effects via promotion of myeloid-derived suppressor cells (MDSCs) and regulatory T (T reg ) cells, which in turn induce T cell tolerance. [9][10][11][12] We and others have shown that peripheral immunotherapy using granulocyte macrophage-colony stimu...

Establishment and characterization of an orthotopic patient-derived Group 3 medulloblastoma model for preclinical drug evaluation

“…The primary tumour displayed the same staining patterns, although COX-2 was also seen on subsets of tumour cells. We have repeatedly observed distinct cellular origin of mPGES-1 and COX-2 in neuroblastoma44, experimental glioma49 and here in medulloblastoma, and demonstrated that inhibition of COX-2 has a therapeutic effect in vivo even though COX-2 and mPGES-1 are expressed in different cell types49. These data suggests that intermediate metabolites are transferred between cell types, as previously described50, and the MB-LU-181 model will be useful to study such interactions.…”

“…Immunofluorescent labeling of cryosections was performed as previously described49. The following primary antibodies were used: mouse anti-CD133/2 (5 μg/ml, Milteney Biotec GmbH, Bergisch Gladbach, Germany); FITC-mouse anti-GFAP (5 μg/ml), PE-mouse anti-human CD8 (diluted 1:10), PE-mouse anti-human CD15 (diluted 1:10), PE-mouse anti-human CD44 (diluted 1:10), FITC-mouse anti-human CD45 (diluted 1:10), FITC-mouse anti-human CD163 (diluted 1:10), rat anti-mouse NK-1.1.…”

Intratumorally implanted mesenchymal stromal cells potentiate peripheral immunotherapy against malignant rat gliomas

“…Immunotherapy per se induces an immune response associated with elevated plasma IFNγ levels and CD4 + and CD8 + T cells systemically and intratumorally (Visse et al, 2000;Eberstal et al, 2012;Fritzell et al, 2013a, b;Eberstal et al, 2014). IFNγ is predominately produced by activated T cells and thus, intratumorally implanted MSCs are most likely exposed to significant levels of IFNγ.…”

COX-2 Inhibitors, a Potential Synergistic Effect with Antineoplastic Drugs in Lung Cancer

“…Examination of genetic and epigenetic background and exploration of biomarkers defining a subset of lung cancer patients that would benefit by these combinations combined with better understanding of COX-2 biology would shed more light on how to achieve clinical improvement. Cox-2 inhibitors have been used with immunotherapeutic agents with effectiveness [73,74], however; more trials are necessary for non-small cell lung cancer.…”