Involvement of cancer-derived EMT cells in the accumulation of 18F-fluorodeoxyglucose in the hypoxic cancer microenvironment.

A high rate of glycolysis, one of the most common features of cancer, is used in positron emission tomography (PET) imaging to visualize tumor tissues using 18F-fluorodeoxyglucose (18F-FDG). Heterogeneous intratumoral distribution of 18F-FDG in tissues has been established in some types of cancer, and the maximum standardized uptake value (SUVmax) has been correlated with poor prognosis. However, the phenotype of cells that show high 18F-FDG accumulation in tumors remains unknown. Here, we combined quantitative micro-autoradiography with fluorescence immunohistochemistry to simultaneously visualize 18F-FDG distribution, the expression of multiple proteins, and hypoxic regions in the cancer microenvironment of a human A431 xenograft tumor in C.B-17/Icr-scid/scid mice. We found that the highest 18F-FDG accumulation was in cancer-derived cells undergoing epithelial-mesenchymal transition (EMT) in hypoxic regions, implicating these regions as a major contributor to increased glucose metabolism, as measured by 18F-FDG-PET.

A hypoxia-inducible factor (HIF)-3α splicing variant, HIF-3α4 impairs angiogenesis in hypervascular malignant meningiomas with epigenetically silenced HIF-3α4.

Hypoxia inducible factor is a dominant regulator of adaptive cellular responses to hypoxia and controls the expression of a large number of genes regulating angiogenesis as well as metabolism, cell survival, apoptosis, and other cellular functions in an oxygen level-dependent manner. When a neoplasm is able to induce angiogenesis, tumor progression occurs more rapidly because of the nutrients provided by the neovasculature. Meningioma is one of the most hypervascular brain tumors, making anti-angiogenic therapy an attractive novel therapy for these tumors. HIF-3α has been conventionally regarded as a dominant-negative regulator of HIF-1α, and although alternative HIF-3α splicing variants are extensively reported, their specific functions have not yet been determined. In this study, we found that the transcription of HIF-3α4 was silenced by the promoter DNA methylation in meningiomas, and inducible HIF-3α4 impaired angiogenesis, proliferation, and metabolism/oxidation in hypervascular meningiomas. Thus, HIF-3α4 could be a potential molecular target in meningiomas.

The effect of ciprofloxacin on CD14 and toll-like receptor-4 expression on human monocytes.

CD14/toll-like receptor (TLR)-4 complex on monocytes/macrophages can bind lipopolysaccharide (LPS) and transduce the signals intracellularly. An antibacterial drug, ciprofloxacin (CIP), has been reported to modulate the inflammatory and immune responses. In the present study, we examined the effects of CIP on the LPS-induced activation of monocytes isolated from human peripheral blood mononuclear cells (PBMC). CIP suppressed the expression of CD14, TLR-4, intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, and CD40 and the production of tumor necrosis factor (TNF)-alpha induced by LPS in monocytes. CIP induced the production of prostaglandin (PG)E2 and increased intracellular cyclic adenosine monophosphate (cAMP) levels. Cyclooxygenase (COX)-2 inhibitors, NS398 and indomethacin, reversed the effects of CIP on TNF-alpha production and reduced the levels of different surface antigens, whereas a protein kinase A (PKA) inhibitor, H89, did not. Therefore, CIP might regulate the TNF-alpha production induced by LPS by inhibiting the expression of LPS receptor complex, which seems to be mediated by COX-2 but not the cAMP/PKA pathway.

Effect of ciprofloxacin-induced prostaglandin E2 on interleukin-18-treated monocytes.

Ciprofloxacin, a fluorinated 4-quinolone, is useful for the clinical treatment of infections due to its antibacterial properties and also modulates the immune response of monocytes isolated from human peripheral blood mononuclear cells. In the present study, we found that ciprofloxacin induced the production of prostaglandin E(2) in monocytes in a concentration-dependent manner regardless of the presence of interleukin-18 by enhancing the expression of cyclooxygenase-2 protein and that this in turn led to the elevation of intercellular cyclic AMP in monocytes via the stimulation of prostaglandin receptors. The prostaglandin E(2) and cyclic AMP production increased by ciprofloxacin was inhibited by indomethacin, a nonselective cyclooxygenase-2 inhibitor, and NS398, a selective cyclooxygenase-2 inhibitor. In addition, ciprofloxacin suppressed the interleukin-18-induced production of tumor necrosis factor alpha, gamma interferon, and interleukin-12 in peripheral blood mononuclear cells by inhibiting the expression of intercellular adhesion molecule 1, B7.1, B7.2, and CD40 on monocytes, and this effect could be reversed by the addition of indomethacin or NS398. These results indicate that ciprofloxacin exerts immunomodulatory activity via the production of prostaglandin E(2) and imply therapeutic potential of ciprofloxacin for the treatment of systemic inflammatory responses initiated by interleukin-18.

Differential effect of prostaglandins E1 and E2 on lipopolysaccharide-induced adhesion molecule expression on human monocytes.

The effect of prostaglandins E1 and E2 on the 1 ng/ml lipopolysaccharide-induced expression of intercellular adhesion molecule (ICAM)-1, B7.1, B7.2, CD40 and CD40 ligand (CD40L) on monocytes was examined. Prostaglandin E1 suppressed B7.1 and CD40 expression, but prostaglandin E2 did not effect on any type of adhesion molecule expression. Both prostaglandins inhibited tumor necrosis factor (TNF)-alpha production and T-cell proliferation of lipopolysaccharide-treated human peripheral blood mononuclear cells (PBMC). Among prostaglandin E1 receptors (IP/EP1/EP2/EP3/EP4) agonists, ONO-1301, a prostanoid IP-receptor agonist, prevented B7.1 and CD40 expression. ONO-AE1-259-01 a prostanoid EP2-receptor agonist, ONO-AE1-329, a prostanoid EP4-receptor agonist, and ONO-1301 inhibited TNF-alpha production and T-cell proliferation. Moreover, anti-B7.1 and anti-CD40 Abs prevented lipopolysaccharide-induced TNF-alpha production and T-cell proliferation. Therefore, the effect of prostaglandin E1 on TNF-alpha production and T-cell proliferation might depend on the inhibition of B7.1 and CD40 expression, but that of prostaglandin E2 might be independent of adhesion molecules expression. In conclusion, the mechanism responsible for the effect of prostaglandin E1 on lipopolysaccharide-induced responses is distinct from that of prostaglandin E2.

alpha1-Adrenergic receptor antagonists induce production of IL-18 and expression of ICAM-1 and CD40 in human monocytes.

The activation of T cells plays a role in antitumor response. Monocytes activate T cells by inducing the cell-to-cell interaction that involves the engagement of adhesion molecules with their ligands, and the production of IL-18. The authors examined the effect of the quinazoline-based alpha1-adrenergic receptor antagonists bunazosin, doxazosin, prazosin, and terazosin on the expression of adhesion molecules such as ICAM-1, B7.1, B7.2, CD40, and CD40L on monocytes isolated from human peripheral blood mononuclear cells. Doxazosin, prazosin, and terazosin induced the expression of ICAM-1 and CD40 but had no effect on the expression of B7.1, B7.2, and CD40L. Moreover, IL-18 was detected in the medium of incubated monocytes treated with doxazosin, prazosin, and terazosin. Bunazosin did not affect adhesion molecule expression and IL-18 production, suggesting that the chemical structure of quinazoline might not be related to the effect of doxazosin, prazosin, and terazosin. Although caspase-1 inhibitor completely abolished the production of IL-18, anti-IL-18 mAb and caspase-1 inhibitor partially inhibited the increase in ICAM-1 and CD40 expression induced by doxazosin, prazosin, and terazosin. Doxazosin, prazosin, and terazosin can induce monocyte activation with a specific pattern of expression of adhesion molecules and IL-18 production, and this may lead to T-cell activation through the cell-to-cell interaction. The activation of T cells induced by the increase of the expression of ICAM-1 and CD40 and the production of IL-18 may be involved in the anti-cancer effects of doxazosin, prazosin, and terazosin.