The cyclo-oxygenase and lipoxygenase pathways in human oral cancer tissue

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

Analysis of human serum metabolome for potential biomarkers identification of erosive oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is a chronic auto-inflammatory mucositis and potentially oral premalignant lesion. Erosive OLP patients display the higher canceration rate as compared to the patients with non-erosive OLP. Identification of the potential biomarkers associated with erosive OLP may help to investigate the disease pathogenesis and to improve clinical treatment.

METHODS

Ultra-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UPLC-QTOF-MS) combined with pattern recognition approaches were integrated to acquire differentially expressed metabolites for the pathways analysis and elucidate mechanisms of disease.

RESULTS

Totally, 10 modulated metabolites were characterized as the potential biomarkers of erosive OLP, whose dysregulations could affect multiple metabolic pathways and pathological processes in the disease.

CONCLUSION

These findings indicated that the analysis of human serum metabolome might be conducive to the achievement of the objectives of this study.

5-lipoxygenase expression and tepoxalin-induced cell death in squamous cell carcinomas in cats

OBJECTIVE

To assess expression pattern and subcellular compartmentalization of 5-lipoxygenase in cutaneous, UV radiation-induced, and oral squamous cell carcinomas (SCCs) in cats and determine the effects of cyclooxygenase or 5-lipoxygenase inhibition on proliferation or apoptosis in a feline oral squamous cell carcinoma (SCCF1) cell line.

SAMPLE

60 archived paraffin-embedded samples of SCCs from 60 cats and SCCF1 cells.

PROCEDURES

Retrospective immunohistochemical analysis of the archived samples of SCCs (20 cutaneous, 20 UV radiation-induced, and 20 oral tumors) was performed. Cell culture proliferation assays involving SCCF1 cells were performed, and tepoxalin-induced apoptosis and signaling were examined via western blotting and annexin V staining.

RESULTS

Immunohistochemically, staining for 5-lipoxygenase was most frequently of greatest intensity in oral SCCs, whereas staining of cutaneous and UV radiation-induced lesions had less consistent 5-lipoxygenase expression. Exposure of SCCF1 cells to the 5-lipoxygenase inhibitor tepoxalin resulted in apoptosis; the effect appeared to be mediated via alteration of cell signaling rather than via suppression of lipid mediators that are typically produced as a result of 5-lipoxygenase activity.

CONCLUSIONS AND CLINICAL RELEVANCE

In cats, expression of 5-lipoxygenase in SCCs appeared to differ depending on tumor location. The influence of tepoxalin-induced 5-lipoxygenase inhibition on a 5-lipoxygenase-expressing cell line coupled with the notable expression of 5-lipoxygenase in oral SCCs suggested that 5-lipoxygenase inhibition may have therapeutic benefits in affected cats. Although the safety of tepoxalin in cats has yet to be investigated, 5-lipoxygenase inhibitors should be evaluated for use as a potential treatment for SCCs in that species.

Arachidonic acid metabolism: a primer for head and neck surgeons

The arachidonic acid metabolites, or eicosanoids, are a large series of lipid-derived mediators capable of producing a multitude of physiologic effects in the local environment. They play important roles in a variety of signaling pathways in endocrinology, immunology, and oncology. A significant body of work in this area has occurred in squamous cell carcinomas of the head and neck over the past 15 years. This review will attempt to familiarize the head and neck surgical oncologist with the basic biochemical steps in the formation of these compounds, newer developments in the field of eicosanoid biochemistry, and related experimental evidence of the roles of these substances in head and neck cancer.

Evidence that cyclosporine inhibits periodontal prostaglandin I2 synthesis

Cyclosporine (CsA) is a selective immunosuppressant widely used in clinical therapy. Like phenytoin and nifedipine, the drug is associated with gingival overgrowth. This study considers the interaction of CsA and prostaglandin I2 (PGI2), in particular the action of the drug on gingival tissue in vitro and in vivo. The PGI2-synthesis of rat, rabbit and human gingival tissue was examined by bioassay. In vivo CsA-therapy reduces gingival PGI2-synthesis. The results furthermore show a dose-dependent inhibition of PGI2-synthesis by CsA (1-100 micrograms/ml) in vitro. PGI2-synthesis from in vivo CsA-pretreated probes was further dose-dependently diminished by in vitro addition of CsA. As PGI2 exerts an antiproliferative activity via cAMP-elevation, the drug-induced inhibition of PGI2 production is claimed to be responsible for gingival hyperplasia in CsA-treated patients.

Acetylsalicylic acid (ASA) protects the prostaglandin-cAMP-system of human hypernephroma cells against irradiation-induced alterations

There is abundant evidence that inhibitors of prostaglandin (PG) biosynthesis might increase the radioresponse of certain tumour cells. This study investigated specific PG binding sites, eicosanoid production as well as intracellular cAMP levels in cultured human hypernephroma cells derived from 11 patients upon nephrectomy. Scatchard analyses of the binding data revealed specific PGE1-, PGE2- as well as PGI2-binding sites (PGE1: Bmax = 755 +/- 206 fmol mg-1 protein, Kd = 3.7 +/- 2.7 nM PGE2: Bmax = 494 +/- 221 fmol mg-1 protein, Kd = 4.2 +/- 2.5 nM; PGI2: Bmax = 693 +/- 164 fmol mg-1 protein, Kd = 6.0 +/- 4.5 nM). Significant (P < 0.01) increase in PG binding sites expressed on human hypernephroma cells (PGE1: Bmax = 1084 +/- 303 fmol mg-1 protein, Kd = 2.8 +/- 1.3 nM; PGE2: Bmax = 663 +/- 309 fmol mg-1 protein, Kd = 2.2 +/- 1.5 nM; PGI2: Bmax = 1021 +/- 391 fmol/protein, Kd = 4.2 +/- 3.6 nM) and inhibition of PG biosynthesis (TXB2: -82.5%, PGE2: -87.5%. PGD2: -80.6%, PGF2: -81.3%) were found after acetylsalicylic acid (ASA)-treatment (0.5 mg 10(-6) cells for 24 h). Following irradiation (60Co, 1.0 Gy/min-1 over 10(min), PG binding sites (PGE1: Bmax = 266 +/- 153 fmol mg-1 protein, Kd = 5.0 +/- 5.0 nM; PGE2: Bmax = 148 +/- 66 fmol mg-1 protein, Kd = 4.7 +/- 3.6 nM; PGI2: Bmax = 325 +/- 194 fmol mg-1 protein, Kd = 6.8 +/- 7.1 nM) were significantly (P < 0.01) diminished. However, irradiation had no significant effect on PG binding sites in ASA-pretreated cells (PGE1: Bmax = 699 +/- 240 fmol mg-1 protein, Kd = 3.5 +/- 1.8 nM; iloprost: Bmax = 766 +/- 452 fmol mg-1 protein, Kd = 3.2 +/- 2.2 nM). Although there was no significant difference in the basal values for cAMP between control and ASA-treated group cells, the PG-induced cAMP-production was less pronounced in the control group. Taken together, the findings suggest that ASA may modify the radioresponse of cultured human hypernephroma cells by preventing the decrease of PG binding sites induced by irradiation.

Tissue markers of potentially malignant human oral epithelial lesions

Tissue markers of potential malignancy have been sought for many years. Cell surface markers, particularly blood group and histocompatibility antigens, have shown great promise and several squamous carcinoma antigens have been identified--but not fully studied in potentially malignant lesions. Growth factors and receptors also need further study. Cytoplasmic markers of potential malignancy have been examined and, of these, keratins, filaggrin, and some carcinoma antigens show most promise. Nuclear analyses have promise but are time-consuming and expensive. Image cytometric analyses appear to be sensitive and predictive: oncogene and tumour suppressor analyses remain to be fully evaluated. New investigative techniques at the cellular and molecular level show increasing promise at defining potentially malignant oral epithelial lesions but more prospective studies are required.

Effects of leukotrienes on osteoblastic cell proliferation

Leukotriene B4 (LTB4) is an arachidonic acid lipoxygenase metabolite with well-characterized effects on leukocytes. LTB4 has been implicated in acute inflammatory reactions and in bone resorption. In the present study, the effect of LTB4 on osteoblastic cells was examined. LTB4 inhibited cell proliferation in normal osteoblastic rat calvaria cells in a dose-dependent manner and had biphasic effects in the human osteoblast-like osteosarcoma cell lines Saos-2 and G292. Indomethacin did not modulate the nature of these LTB4 effects in any of the cells. However, it potentiated the high LTB4 dose effects in normal cells and G292 cells. AA861, an inhibitor of lipoxygenase, did not modulate the LTB4 effects in these two cell lines. These results suggest that LTB4 is involved in the regulation of osteoblastic cell proliferation and may interact with prostaglandins to modulate these effects.

Leukotriene B4 and oral cancer

The quantitation of leukotriene B4 (LTB4) in induced squamous cell carcinoma (SCC) of the Syrian hamster cheek pouch and histologically proven human oral SCC was investigated by a combination of reverse phase-high performance liquid chromatography (RP-HPLC) and radioimmunoassay (RIA). Healthy tissue obtained from these same patients and animals treated with vehicle alone were used as controls. From both animal and human studies our results show a 10 to 30 fold increase in the levels of LTB4 found in tumour compared to control tissue. Furthermore, this dihydroxy acid was not detected in the mucosal tissue of normal subjects undergoing routine surgery. Since LTB4 is a potent inflammatory mediator and modulator of immune responses, its presence at biologically active concentrations in human squamous cell carcinoma suggests a possible role in the pathogenesis of head and neck cancer.

The optimal processing of plasma samples for the determination of bicyclo-PGE in patients with malignant maxillofacial tumors

Prostaglandins (PGs) have been shown to be increased in several tumor tissues. PGE2 and PGF1-alpha Radioimmunoassays (RIAs) have been widely used for quantitative PG-measurements in cancer patients. Our results indicate that optimal processing of plasma samples for the determination of bicyclo-PGE2 is of the highest importance in order to get reproducible results. Therefore it is necessary to fulfill the following requirements: 1. 30 minutes rest before sampling; 2. Avoid venous occlusion; 3. Use constant needle diameter; 4. Precooled anticoagulant; 5. Addition of a cyclooxygenase inhibitor is necessary; 6. Control of processing temperature; 7. Storage at -70 degrees C less than -20 degrees C; 8. Control of storage time; 9. The samples have to be examined after thawing once; 10. Only blood samples processed under the above discovered optimal conditions are of clinical relevance; 11. An international standardization for the processing of plasma samples seems to be necessary considering all these requirements; 12. In 41 patients with maxillo-facial carcinomas the PG-value was significantly higher than in the controls; 13. A RIA-evaluation methodologically properly done may be used as an additional aid for clinical monitoring of the patients.

Stimulation of bone resorption by lipoxygenase metabolites of arachidonic acid

We have studied the effect of leukotrienes, (LT): B4, C4, D4 and E4 and the hydroxyeicosatetraenoic acids (HETEs) 5-HETE and 12-HETE on bone resorption in vitro. Resorption was measured by colorimetric assay of calcium released from neonatal mouse calvaria maintained in organ culture for 72h. All the LTs and HETEs stimulated bone resorption, with optimum responses at picomolar or nanomolar concentrations. The responses were biphasic, with a decreasing effect at higher concentrations. In contrast, prostaglandin E2 (PGE2) stimulated resorption only at 10nM and above. Indomethacin partially inhibited resorption by LTB4, LTC4 and LTD4, but did not affect resorption stimulated by LTE4, 5-HETE and 12-HETE. These results indicate that lipoxygenase products of arachidonic acid are highly potent bone resorbing factors and may play an important role in the localised bone loss associated with inflammatory lesions.

Macromolecular osteolytic factor synthesised by squamous carcinoma cell lines from the head and neck in vitro is interleukin 1

Three human cell lines derived from oro-pharyngeal squamous cell carcinomas of the head were investigated for bone-resorbing activity in vitro. Culture media from all three spontaneously produced a non-dialysable osteolytic factor with activity in three in vitro assays for interleukin 1 (IL1), viz. the lymphocyte activating factor (LAF) assay, stimulation of collagenase synthesis by articular chondrocytes, and stimulation of prostaglandin E2 synthesis by fibroblasts. Addition of anti-human IL1 antibody to the culture media abolished all the bone-resorbing activity. Fractionation of the cell culture media by high performance liquid chromatography (HPLC) showed a single peak of activity in the chondrocyte assay with an apparent mol.wt of 15-17,000. This co-eluted with activity in a preparation of IL1 from rat peritoneal macrophage cultures. These results indicate that IL1 is responsible for the prostaglandin-independent bone resorbing activity synthesised by these cells in vitro, and may contribute to the bone destruction associated with the tumour.

Plasma thromboxane A2 and prostacyclin concentrations in squamous cell carcinoma of the head and neck

Circulating prostaglandins, including thromboxane A2 and prostacyclin, have been implicated as possible facilitative agents in the growth and dissemination of squamous cell carcinomas of the head and neck. The purpose of this study was to evaluate the relationship of plasma concentrations of these compounds to tumor stage and the effect of surgical resection on plasma prostaglandin levels. Blood samples were obtained from 40 patients with head and neck cancer. Ten treated patients were clinically disease-free (NED), and 30 patients with active disease were previously untreated at the time of this study. Plasma concentrations of thromboxane A2 and prostacyclin were measured by radioimmunoassay of their stable metabolites thromboxane B2 (TxB) and prostaglandin 6-keto-F1 (PGI). Platelet aggregation was performed with normal donor platelets (PRP) and normal control or patient plasma (PPP). TxB and TxB/PGI ratios were increased in T1N0M0 patients, compared with NED and with T4N0M0 primary lesions versus all other groups. With lymphatic and hematogenous metastases, TxB and TxB/PGI ratios fell to NED levels. ADP-induced platelet aggregation was significantly increased in head and neck cancer patients, compared with normal controls, and with T4N0M0 lesions, compared with NED. There were no significant differences in PGI levels. TxB, PGI, TxB/PGI, and platelet aggregometry did not change significantly with curative surgery. TxB and TxB/PGI interactions are involved in head and neck cancer. Changes in TxB and TxB/PGI may be related to increased platelet aggregation.

The effect of indomethacin on tumor regression in DMBA-induced epithelial neoplasia of hamster cheek pouch mucosa

Tumors were allowed to develop in the cheek pouches in two groups of hamsters following topical application three times per week of a 0.5% solution of 7, 12-dimethylbenz(alpha)anthracene (DMBA) in liquid paraffin administered for 10 weeks. Two control groups received no DMBA treatment. After carcinogen application, the animals in one DMBA-treated group and those in one of the control groups were given indomethacin daily; this was administered through the oral route for an additional 10 weeks. At this time, all of the animals were killed and their cheek pouches, the draining cervical lymph nodes, and other organs were removed for examination. The number and size of tumors in each pouch were recorded, and each pouch was weighed. Indomethacin, in the dosage administered, was not found to cause regression of established tumors. The effects of prostaglandins, indomethacin, and other prostaglandin-synthesis inhibitors in tumor tissue are discussed. It is suggested that more knowledge is needed about the role of prostaglandins, and the related products of AA metabolism, in squamous cell cancer before indomethacin is used therapeutically.

Biosynthesis of prostaglandins and hydroxy fatty acids in primary squamous carcinomas of head and neck in humans

The metabolism of [14C]arachidonic acid into cyclooxygenase and lipoxygenase products by homogenates of primary squamous carcinomas of head and neck in 12 patients was studied in vitro. The lipoxygenase pathway was predominant in all samples. The major metabolites were 12-hydroxy-5,8,11-14-eicosatetraenoic acid, (12-HETE) and 15-HETE. 5-HETE, 5,12-diHETE, 8-HETE and 9-HETE were also detected. The cyclooxygenase products detected were in the following order: PGE2 greater than PGF2 alpha greater than TxB2 greater than 15-keto-PGE2 greater than 6-keto-PGF1 alpha greater than PGD2. Literature review of the biological activities of these oxygenated metabolites of arachidonic acid suggest important modulatory roles in the pathophysiology of head and neck cancer.