Inhibitory effects of selective cyclooxygenase-2 inhibitors, nimesulide and etodolac, on the development of squamous cell dysplasias and carcinomas of the tongue in rats initiated with 4-nitroquinoline 1-oxide

The efficacy of photodynamic therapy in rat tongue dysplasia

Background

Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) has previously shown promising results in cancerous cell destruction. The present study was conducted to evaluate the efficacy of this treatment option on oral epithelial dysplasia in Wistar rats. Furthermore, microscopic effects of systemic versus topical administration of ALA before laser illumination was assessed.

Material and Methods

Thirty male Wistar rats (200- 250 grams) were used in the present study. Tongue dysplasia was induced by a daily delivery of a 20 ppm solution of 4-nitroquinoline -1- oxide (4NQO) for 3 months. Then, rats were divided into 3 groups of 10 including, group 1 that was received systemic ALA-based PDT (30 mg/kg ALA), group 2 that was received topical ALA-based PDT (20% ALA solution) and group 3 (control) which was left untreated. Tongue specimens were fixed for histopathological evaluation and dysplasia was graded at microscopic level. Data was compared between various treatment groups using Mann Whitney test (p<0.05).

Results

The rate of atypical dysplastic cells was decreased significantly in both topical (p= 0.006) and systemic (p= 0.001) treatment groups compared to control group. Furthermore, systemic use of ALA resulted in a remarkable destruction of dysplastic cells compared to its topical application (p=0.045). Nevertheless, some evidence of muscle destruction was documented in systemic ALA group.

Conclusions

It seems that ALA mediated PDT is an effective treatment option for the destruction of dysplastic cells. However, the extent of this effect depends on the mode of ALA administration before light illumination.

Key words:Photodynamic therapy, 5-aminolevulinic acid, Dysplasia, Potentially malignant disorders.

Altered mRNA Expression of Genes Involved in Endocannabinoid Signalling in Squamous Cell Carcinoma of the Oral Tongue

Little is known about the endocannabinoid (eCB) system in squamous cell carcinoma of the oral tongue (SCCOT). Here we have investigated, at the mRNA level, expression of genes coding for the components of the eCB system in tumour and non-malignant samples from SCCOT patients. Expression of NAPEPLD and PLA2G4E, coding for eCB anabolic enzymes, was higher in the tumour tissue than in non-malignant tissue. Among genes coding for eCB catabolic enzymes, expression of MGLL was lower in tumour tissue while PTGS2 was increased. It is concluded that the eCB system may be dysfunctional in SCCOT.

Advanced glycation end products (AGE) induce the receptor for AGE in the colonic mucosa of azoxymethane-injected Fischer 344 rats fed with a high-linoleic acid and high-glucose diet

BACKGROUND

Advanced glycation end products (AGE) and the receptor for advanced glycation end products (RAGE) are closely associated with colorectal cancer progression. The association between RAGE and AGE in colon carcinogenesis needs to be clarified.

METHODS

Levels of RAGE and AGE were examined in azoxymethane (AOM)-injected Fischer 344 rats fed a control diet (Group C), a 15 % linoleic acid (LA) diet (Group L), a control diet with 10 % glucose drink (Group G), and a 15 % LA diet with 10 % glucose drink (Group L + G). Group L + G showed the most pronounced increase of body weight, blood sugar, and serum insulin.

RESULTS

The rats in Group L + G showed the most pronounced multiplicity of aberrant crypt foci (ACF) and carcinomas with increased mucosal RAGE and AGE. IEC6 rat intestinal epithelial cells treated with AGE showed increased RAGE expression, which was inhibited by treatment with metformin or losartan. In the AOM-injected rat colon cancer model, the levels of RAGE and AGE, and the multiplicity of ACF and carcinomas, in Group L + G rats were suppressed by treatment with metformin or losartan.

CONCLUSIONS

These results suggest that AGE-RAGE induced by high-LA and high-glucose diets substantially enhances colon cancer development; thus, suppression of AGE-RAGE could be a potential target for colon cancer chemoprevention.

From COX-2 inhibitor nimesulide to potent anti-cancer agent: synthesis, in vitro, in vivo and pharmacokinetic evaluation

Cyclooxygenase-2 (COX-2) inhibitor nimesulide inhibits the proliferation of various types of cancer cells mainly via COX-2 independent mechanisms, which makes it a good lead compound for anti-cancer drug development. In the presented study, a series of new nimesulide analogs were synthesized based on the structure-function analysis generated previously. Some of them displayed very potent anti-cancer activity with IC(50)s around 100 nM-200 nM to inhibit SKBR-3 breast cancer cell growth. CSUOH0901 (NSC751382) from the compound library also inhibits the growth of the 60 cancer cell lines used at National Cancer Institute Developmental therapeutics Program (NCIDTP) with IC(50)s around 100 nM-500 nM. Intraperitoneal injection with a dosage of 5  mg/kg/d of CSUOH0901 to nude mice suppresses HT29 colorectal xenograft growth. Pharmacokinetic studies demonstrate the good bioavailability of the compound.

Prevention of upper aerodigestive tract cancer in zinc-deficient rodents: inefficacy of genetic or pharmacological disruption of COX-2

Zinc deficiency in humans is associated with an increased risk of upper aerodigestive tract (UADT) cancer. In rodents, zinc deficiency predisposes to carcinogenesis by causing proliferation and alterations in gene expression. We examined whether in zinc-deficient rodents, targeted disruption of the cyclooxygenase (COX)-2 pathway by the COX-2 selective inhibitor celecoxib or by genetic deletion prevent UADT carcinogenesis. Tongue cancer prevention studies were conducted in zinc-deficient rats previously exposed to a tongue carcinogen by celecoxib treatment with or without zinc replenishment, or by zinc replenishment alone. The ability of genetic COX-2 deletion to protect against chemically-induced forestomach tumorigenesis was examined in mice on zinc-deficient versus zinc-sufficient diet. The expression of 3 predictive biomarkers COX-2, nuclear factor (NF)-kappa B p65 and leukotriene A(4) hydrolase (LTA(4)H) was examined by immunohistochemistry. In zinc-deficient rats, celecoxib without zinc replenishment reduced lingual tumor multiplicity but not progression to malignancy. Celecoxib with zinc replenishment or zinc replenishment alone significantly lowered lingual squamous cell carcinoma incidence, as well as tumor multiplicity. Celecoxib alone reduced overexpression of the 3 biomarkers in tumors slightly, compared with intervention with zinc replenishment. Instead of being protected, zinc-deficient COX-2 null mice developed significantly greater tumor multiplicity and forestomach carcinoma incidence than wild-type controls. Additionally, zinc-deficient COX-2-/- forestomachs displayed strong LTA(4)H immunostaining, indicating activation of an alternative pathway under zinc deficiency when the COX-2 pathway is blocked. Thus, targeting only the COX-2 pathway in zinc-deficient animals did not prevent UADT carcinogenesis. Our data suggest zinc supplementation should be more thoroughly explored in human prevention clinical trials for UADT cancer.

Effects of a selective cyclooxygenase-2 inhibitor, nimesulide, on the growth of ovarian carcinoma in vivo

New therapies against cancer are based on targeting cyclooxygenase-2 (COX-2). Whether COX-2 inhibitor therapy would be beneficial in the prevention and/or treatment of ovarian cancer still remains unclear. This study was designed to investigate whether nimesulide, a COX-2 selective inhibitor, could suppress tumor growth in implanted ovarian carcinoma mice and to explore the molecular mechanisms. Human ovarian SKOV-3 carcinoma cells xenograft-bearing mice were treated with nimesulide 62.5 mg/kg or 250 mg/kg alone i.g., daily for 21 days. Microvessel density (MVD) of ovarian carcinoma was determined with anti-CD(34) as the label. Prostaglandin E2 (PGE2) levels were also determined by ELISA. In addition, the expression of COX-2 and COX-1 at protein and mRNA levels in the control groups was also detected by immunohistochemistry and reverse-transcription polymerase chain reaction (RT-PCR). Nimesulide treatment showed a dose-dependent growth-inhibitory effect of human ovarian SKOV-3 tumors. The inhibitory rates in nimesulide 62.5 mg/kg group and 250 mg/kg group were 20.40% and 50.55% respectively, however, which is not significant statistically compared with that of control group (P > 0.05). In treatment groups, nimesulide significantly reduced intratumor PGE2 levels (all, P < 0.01). Microvessel densities in treatment groups were 61.20 +/- 1.67 (62.5 mg/kg) and 66.27 +/- 1.20 (250 mg/kg), which are significant statistically compared with that of control group (79.97 +/- 1.07) (all, P < 0.01). However, COX-1, not COX-2, mRNA, and protein levels are elevated in tumor tissues. Nimesulide decreased microvessel density is associated with the reduction of PGE2 levels but without affecting growth inhibition and the expression of COX-2. Importantly, tumor growth implanted in SKOV-3 mice was not significantly attenuated suggesting that COX-1 in ovarian carcinoma tissue also has an important role in tumor growth. These findings may implicate COX-1 as a suitable target for the treatment of ovarian cancer.

Expression of receptor for advanced glycation end products during rat tongue carcinogenesis by 4-nitroquinoline 1-oxide and effect of a selective cyclooxygenase-2 inhibitor, etodolac

OBJECTIVES

The expression of a receptor for advanced glycation end products (RAGE) in lesions developed during rat tongue carcinogenesis by 4-nitroquinoline 1-oxide (4-NQO) and the effect of a selective cyclooxygenase-2 inhibitor, etodolac, were investigated.

METHODS

The tongue lesions were induced in Fischer 344 rats given 20-30 ppm 4-NQO in their drinking water for 12 weeks and then fed the basal diet containing 150 and 300 ppm of etodolac for 16 weeks, respectively.

RESULTS

The incidence of carcinomas in the 4-NQO-alone group was 100%. Etodolac significantly reduced the incidences of carcinomas to 66.7% (p < 0.05) and 50% (p < 0.01) at doses of 150 and 300 ppm, respectively. RAGE protein was immunohistochemically expressed in dysplastic cells and cancer cells of dysplasias and carcinomas. Etodolac significantly decreased the stainability of RAGE protein in dysplasias (p < 0.02) and carcinomas (p < 0.01). The expression of RAGE mRNA analyzed by RT-PCR was clearly detected in carcinomas developing in the 4-NQO-alone group. In carcinomas developing in the etodolac-treated group, RAGE mRNA expression significantly decreased (p < 0.03).

CONCLUSIONS

These results indicate that RAGE is involved in rat tongue carcinogenesis by 4-NQO and suggest that the chemopreventive effect exerted by etodolac is partly related to the inhibition of RAGE expression.

Significance of COX-2 expression in human esophageal squamous cell carcinoma

Cyclooxygenase-2 (COX-2) is well established to play an important role in the tumorigenesis of a variety of human cancers; however, the function of COX-2 in the development of esophageal squamous cell carcinoma (ESCC) remains less clear. Here, we determined, first, the pattern of COX-2 expression in normal esophageal mucosa, dysplasia, carcinoma in situ (CIS) and invasive SCC. Immunohistochemical analysis showed that, while COX-2 was weakly expressed, if at all, in normal squamous epithelium, strong COX-2 expression was detected as early as the stage of dysplasia and frequently in 20 of 26 (77%) CIS and 86 of 111 (77%) invasive SCC. Upregulation of COX-2 in ESCC was found to be significantly associated with tumor progression (R = 0.493, P < 0.01). Further, treatment of human ESCC cell lines (KYSE450 and KYSE510) with NS-398, a COX-2 specific chemical inhibitor, suppressed the production of prostaglandin E2 (PGE2) and induced cell growth inhibition, cell cycle arrest at the G1-S checkpoint, and the expression of cyclin-dependent kinase inhibitors p21waf1/cip1 and p27kip1. Finally, knockdown expression of COX-2 in KYSE450 cells by a specific COX-2 siRNA dramatically inhibited PGE2 production, cell growth and, more importantly, colony formation and tumorigenesis in nude mice. Together, this study suggested that COX-2 may be involved in an early stage of squamous cell carcinogenesis of the esophagus and has a non-redundant role in the regulation of cellular proliferation and tumorigenesis of esophageal epithelial cells.

Cyclooxygenase-2: how good is it as a target for cancer chemoprevention?

There is now substantial evidence for a role for cyclooxygenase-2 (COX-2)-mediated prostaglandin (PG) signalling during carcinogenesis in a number of tissues and selective COX-2 inhibitors (coxibs) were considered attractive candidate chemoprevention agents. However, recent concerns over the toxicity of systemic selective COX-2 inhibition and the realisation that COX-1 may also contribute to carcinogenesis have cast some doubt on COX-2 inhibition as a safe and effective chemoprevention strategy. This review will describe the available evidence relating to the known benefits (preventive efficacy in rodent tumorigenesis models and limited human data from small randomised, controlled trials and epidemiological studies) and risks (cardiovascular and renal toxicity) of coxib therapy for cancer chemoprevention. Potential, alternative strategies for inhibition of COX-PG signalling that minimise or avoid systemic selective COX-2 inhibition will also be discussed.

Selection of topically applied non-steroidal anti-inflammatory drugs for oral cancer chemoprevention

Topical delivery of non-steroidal anti-inflammatory drugs through the oral mucosa has been used for oral cancer chemoprevention. Local permeation of these agents has been one of the major concerns. Here we propose an approach to predict the permeability of topically applied agents for oral cancer chemoprevention. In theory, the total flux through the oral mucosa (Jmax) can be estimated by adding the transcellular flux (JTC) and the paracellular flux (JPC). To target the Cox-2 enzyme in oral epithelial cells, it is desirable to maximize the theoretical activity index, the ratio of JTC and IC50 of a Cox-2 inhibitor (JTC/IC50-Cox-2). Among the 12 commonly used NSAIDs, celecoxib, nimesulide and ibuprofen had the highest values and may be the agents of choice to target Cox-2 in oral epithelial cells through topical application. Based on these calculations, a long-term chemopreventive experiment using celecoxib (3% or 6%) through topical application was performed in a DMBA induced hamster oral cancer model. Both 3% and 6% reduced the incidence of squamous cell carcinoma at the post-initiation stage.

Suppressive effects of a selective cyclooxygenase-2 inhibitor, etodolac, on 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis

The present study was conducted to examine effects of a clinically available selective cyclooxygenase (COX)-2 inhibitor, etodolac, on the development of rat tongue squamous cell carcinomas (SCCs) induced by 4-nitroquinoline 1-oxide (4-NQO), and on the immunohistochemically demonstrable expression of COX-2. Fischer 344 rats, 6 weeks old at the commencement, were administered 4-NQO at the doses of 20-30 ppm in their drinking water for 12 weeks. Then, etodolac was supplemented into the diet at doses of 150 and 300ppm for 16 weeks. Rats were sacrificed at 28 weeks and tongue lesions were histologically examined. The incidence and the multiplicity of SCCs induced by 4-NQO were dose-dependently reduced by etodolac, with significance at the highest dose of 300 ppm. Etodolac did not significantly affect the immunohistochemical expression of COX-2 in the lesions which did develop. These results indicate that etodolac can inhibit the development of rat tongue SCCs, probably by inhibiting COX-2 activity rather than its expression. Thus, etodolac may be a promising candidate chemopreventive agent for individuals at high risk of oral cancer.

Cyclo-oxygenase-1 and -2 expression in human oral mucosa, dysplasias and squamous cell carcinomas and their pathological significance

Cyclo-oxygenase (COX) is a key enzyme in the conversion of arachidonic acid to prostanoids. The expression of its isoforms, COX-1 and -2 is found in many human malignancies. This study analyzed the correlation between COX expression and the pathobiological nature of human oral mucosa, dysplasias and squamous cell carcinomas (SCCs). We examined 9 specimens of normal oral epithelia, 65 lesions with dysplasias and 50 SCCs. Labeling indices (LIs) for COX-1, COX-2, Ki-67 and P53, microvessel density (MVD) and apoptotic index (AI) were evaluated using immunohistochemistry and TUNEL methods. Western blot analysis of COX-1 and -2 was performed on four human oral SCC cell lines, all of which showed expression. The LIs for COX-1 and -2 were higher for the dysplasias than the SCCs. LIs of COX-2 but not COX-1 correlated with the histological grade of dysplasia, being highest for the severe dysplasias (p < 0.05). In contrast, the COX-2 LIs as well as COX-1 were significantly (p < 0.05) inversely correlated with the histological differentiation of the SCCs. COX-2 expression was significantly correlated with LIs of COX-1 for dysplasia (p < 0.05), but not for the SCCs. In addition no significant relationship was noted between COX-2 expression and the Lis of Ki-67, P53, AI as well as MVD for the dysplasias and SCCs. The expression of COX-1 and -2 is correlated with early stage tumorigenesis and cellular differentiation of SCCs in the oral dysplasia-carcinoma sequence.