A selective cyclooxygenase-2 inhibitor suppresses tumor growth in nude mouse xenografted with human head and neck squamous carcinoma cells

Molecular pathways modulated by phytochemicals in head and neck cancer

In the last few years, natural dietary phytochemicals have shown immense potential in the suppression and incidence of Head and Neck Cancer (HNC). From various in-vitro, animal, and epidemiological studies it is now clear that intake of foods rich in dietary phytochemicals lower the risk of HNC. These phytochemicals have been reported to target different stages of Head and Neck cancer (initiation to promotion) by modulating many cellular signaling pathways. A single phytochemical may target different pathways simultaneously or a single pathway may be targeted by a diversity of phytochemicals. This review highlights the molecular pathways modulated by a large number of phytochemicals relevant to HNC with an intent to identify specific signaling pathways that could be therapeutically targeted. Therefore, relevant literature was screened and scrutinized for molecular details. We have focused on the complexity of the molecular mechanisms that are modulated by various phytochemicals and the role they can play in better clinical efficacy and management of head and neck cancer. In-depth knowledge of these molecular mechanisms can lead to innovative therapeutic strategies using phytochemicals alone or along with available treatments for various cancers including HNC. Molecular pathways modulated by Phytochemicals.

In Vitro Cytotoxic Effects of Celecoxib, Mefenamic Acid, Aspirin and Indometacin on Several Cells Lines

STATEMENT OF THE PROBLEM

Use of cyclooxygenase inhibitors as chemotherapy agents has attracted the attention of a large number of investigators in recent years. Given the importance of cancer therapy, only a limited number of studies have been carried out to investigate the effects of cyclooxygenase inhibitors on specific cell lines.

PURPOSE

This research aimed to determine the in vitro cytotoxic effects of cyclooxygenase inhibitors (COX-1 and COX-2 inhibitors) on KB, Saos-2, 1321N, U-87MG, SFBF-PI 39 cell lines.

MATERIALS AND METHOD

Powders of celecoxib, mefenamic acid, aspirin and indometacin were dissolved in the appropriate solvent. The viability of cell lines was carried out by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay technique. Data gathered from four separate experiments were expressed as mean±SD. Statistical significance was defined at p< 0.05 by using analysis of variance. Significant treatment mean values were subjected to post-hoc Tukey's test.

RESULTS

Celecoxib showed marked cytotoxic effects on KB, Saos-2, and 1321N cells, which was significant in comparison with the control group. Celecoxib was not effective in killing U-87MG cell line. Mefenamic acid exerted cytotoxic effects on KB, Saos-2, and 1321N cells, where the viability was approximately 75%. U-87MG cells were resistant to mefenamic acid. Indometacin had the highest rate of activity on U-87MG cells, which was significant in comparison with the control group. Aspirin did not exhibit any activity on these cell lines and was not effective in killing U-87MG, KB, Saos-2, and 1321N cells.

CONCLUSION

This research showed that celecoxib, indometacin, and mefenamic acid have the cytotoxic effects on KB, Saos-2, 1321N and U-87MG cell lines. Therefore, it appears that these drugs can be considered as anti-neoplastic agents in the experimental phase.

Non-steroidal anti-inflammatory drugs and the risk of head and neck cancer: A case-control analysis

Non-steroidal anti-inflammatory drugs (NSAIDs) and acetylsalicylic acid (aspirin) have been associated with a reduced risk for certain cancers. We explored the association between use of NSAIDs and the risk of head and neck cancer (HNC). We conducted a case-control analysis in the UK-based Clinical Practice Research Datalink (CPRD) among people below the age of 90 years with incident HNC between 1995 and 2013. Six controls per case were matched on age, sex, calendar time, general practice, and number of years of active history in the CPRD prior to the HNC diagnosis. Other potential confounders including comorbidities and comedication were also evaluated, and we adjusted our final analyses for BMI, smoking and alcohol consumption. Our analyses included 2,745 HNC cases and 16,470 controls. Aspirin or NSAID use overall did not significantly change the HNC risk. However, patients with six or more prescriptions for ibuprofen were at a statistically significantly reduced risk for HNC (adjusted OR 0.59, 95% CI 0.37-0.94). The HNC risk tended to decrease with increasing cumulative exposure to ibuprofen, and to be more pronounced for cancer of the larynx. To conclude, in this large population-based observational study we found a decreased risk for HNC associated with regular use of ibuprofen.

Reducing tumor growth and angiogenesis using a triple therapy measured with Contrast-enhanced ultrasound (CEUS)

Background

To evaluate the in vivo response by detecting the anti-angiogenic and invasion-inhibiting effects of a triple-combination-therapy in an experimental-small-animal-squamous-cell-carcinoma-model using the “flash-replenishment” (FR) method to assess tissue hemodynamics via contrast-enhanced-ultrasound (CEUS).

Methods

Human hypopharynx-carcinoma-cells were subcutaneously injected into the left flank of 22-female-athymic-nude-rats. After seven days of subcutaneous tumor growth, FR-measurements were performed on each rat. Treatment-group and control-group were treated every day for a period of one week, with the treatment-group receiving solvents containing a triple therapy of Upamostat®, Celecoxib® and Ilomastat® and the control-group solvents only. On day seven, follow-up measurements were performed using the same measurement protocol to assess the effects of the triple therapy. VueBox® was used to quantify the kinetic parameters and additional immunohistochemistry analyses were performed for comparison with and validation of the CEUS results against established methods (Proliferation/Ki-67, vascularization/CD31, apoptosis/caspase3).

Results

Compared to the control-group, the treatment-group that received the triple-therapy resulted in a reduction of tumor growth by 48.6% in size. Likewise, the immunohistochemistry results showed significant decreases in tumor proliferation and vascularization in the treatment-group in comparison to the control-group of 26%(p≤0.05) and 32.2%(p≤0.05) respectively. Correspondingly, between the baseline and follow-up measurements, the therapy-group was associated with a significant(p ≤ 0.01) decrease in the relative-Blood-Volume(rBV) in both the whole tumor(wt) and hypervascular tumor(ht) areas (p≤0.01), while the control-group was associated with a significant (p≤0.01) increase of the rBV in the wt area and a non-significant increase (p≤0.16) in the ht area. The mean-transit-time (mTT) of the wt and the ht areas showed a significant increase (p≤0.01) in the follow-up measurements in the therapy group.

Conclusion

The triple-therapy is feasible and effective in reducing both tumor growth and vascularization. In particular, compared with the placebo-group, the triple-therapy-group resulted in a reduction in tumor growth of 48.6% in size when assessed by CEUS and a significant reduction in the number of vessels in the tumor of 32% as assessed by immunohistochemistry. As the immunohistochemistry supports the CEUS findings, CEUS using the “flash replenishment”(FR) method appears to provide a useful assessment of the anti-angiogenic and invasion-inhibiting effects of a triple combination therapy.

Chemoprevention of head and neck squamous cell carcinoma through inhibition of NF-κB signaling

Nuclear factor-kappa B (NF-κB) transcription factors regulate cellular processes such as inflammation and cell survival. The NF-κB pathway is often activated with development and progression of head and neck squamous cell carcinoma (HNSCC). As such, NF-κB represents an attractive target for chemoprevention. HNSCC involves progression of lesions from premalignant to malignant, providing a window of opportunity for intervention with chemopreventive agents. Appropriate chemopreventive agents should be inexpensive, nontoxic, and target important pathways involved in the development of HNSCC. Several such agents that inhibit the NF-κB pathway have been investigated in HNSCC. Retinoids have been studied most extensively but have shown limited potential in human trials. Epidermal growth factor receptor inhibitors and PI3K-mTOR inhibitors may benefit a subset of patients. Other agents such as green tea extract and curcumin are appealing because they are generally regarded as safe. In contrast, there is evidence that Vitamin E supplementation may actually increase mortality of cancer patients. Repurposed drugs such as cyclooxygenase (COX) inhibitors and antidiabetic drugs are an emerging area of interest. Future research to develop agents with lower toxicity and higher specificity for the NF-κB pathway, and to target these therapies to individual patient genetic signatures should help to increase the utility of chemoprevention in HSNCC.

In vitro characterization of chitosan gels for buccal delivery of celecoxib: influence of a penetration enhancer

Celecoxib (Cx) shows high efficacy in the treatment of osteoarthritis and rheumatoid arthritis as a result of its high specificity for COX-2, without gastrolesivity or interference with platelet function at therapeutic concentrations. Besides of anti-inflammatory effects, Cx also has a potential role for oral cancer chemoprevention. For these conditions, oral administration in long-term treatment is a concern due to its systemic side effects. However, local application at the site of injury (e.g., buccal inflammation conditions or chemoprevention of oral cancer) is a promising way to reduce its toxicity. In this study, the in vitro characterization of mucoadhesive chitosan (CHT) gels associated to Azone® was assessed to explore the potential buccal mucosal administration of Cx in this tissue. Rheological properties of gels were analyzed by a rheometer with cone-plate geometry. In vitro Cx release and permeability studies used artificial membranes and pig cheek mucosa, respectively. Mucoadhesion were measured with a universal test machine. CHT gels (3.0%) containing 2.0% or 3.0% Az showed more appropriate characteristics compared to the others: pH values, rheology, higher amount of Cx retained in the mucosa, and minimal permeation through mucosa, besides the highest mucoadhesion values, ideal for buccal application. Moreover, the flux (J) and amounts of drug released decreased with increased CHT and Az concentrations. CHT gels (3.0%) associated with 2.0% or 3.0% Az may be considered potential delivery systems for buccal administration of Cx.

Chemopreventive potential of natural compounds in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is one of the most fatal cancers worldwide. Despite advances in the management of HNSCC, the overall survival for patients has not improved significantly due to advanced stages at diagnosis, high recurrence rate after surgical removal, and second primary tumor development, which underscore the importance of novel strategies for cancer prevention. Cancer chemoprevention, the use of natural or synthetic compounds to prevent, arrest, or reverse the process of carcinogenesis at its earliest stages, aims to reverse premalignancies and prevent second primary tumors. Genomics and proteomics information including initial mutation, cancer promotion, progression, and susceptibility has brought molecularly targeted therapies for drug development. The development of preventive approaches using specific natural or synthetic compounds, or both, requires a depth of understanding of the cross-talk between cancer signaling pathways and networks to retain or enhance chemopreventive activity while reducing known toxic effects. Many natural dietary compounds have been identified with multiple molecular targets, effective in the prevention and treatment of cancer. This review describes recent advances in the understanding of the complex signaling networks driving cancer progression and of molecularly targeted natural compounds under preclinical and clinical investigation.

Multimodal therapy for synergic inhibition of tumour cell invasion and tumour-induced angiogenesis

Background

Squamous cell carcinoma of the head and neck (SCCHN) are highly invasive tumours with frequent local and distant recurrence. Metastasis formation requires degradation of the extracellular matrix, which is fulfilled by membrane-associated proteases such as the urokinase plasminogen activator (uPA). WX-UK1 is a competitive active site inhibitor of the protease function of uPA that impairs on the capacity of tumour cells to invade in vitro.

Methods

In the present study, effects of combinations of WX-UK1 with matrix metalloprotease inhibitors (MMP, galardin^®) and cyclooxygenase-2 (COX-2, celecoxib^®) inhibitors on tumour cell proliferation, invasion, and angiogenesis induction were evaluated. Matrigel invasion chambers and a spheroid co-cultivation model with human fibroblast served to determine the invasive potential of both FaDu (SCCHN) and HeLa (cervical carcinoma) cells, each treated with combinations of Celecoxib^®, Galardin^®, and WX-UK1.

Results

Blocking of single protease systems resulted in a significant 50% reduction of tumour cell invasion using WX-UK1, while the triple combination was even more effective with 80% reduction of invasion. Additionally, a sprouting assay with HUVEC was used to test the anti-angiogenetic potential of the triple combination, resulting in a 40% decrease in the sprouting rate.

Conclusions

A combined approach targeting different families of proteases and cyclooxygenases represents a promising adjuvant therapy.

No association of the NF-kappaB1 -94ins/delATTG promoter polymorphism with relapse-free and overall survival in patients with squamous cell carcinomas of the head and neck region

The transcription factor, nuclear factor-kappaB (NF-kappaB) is known to play a major role in immune response, inflammation and, via apoptosis and proliferation, also in oncogenesis. Transcription of NFKB1, which encodes the subunit p50/p105 of NF-kappaB, seems to be influenced by an insertion/deletion polymorphism in its promoter region. Accordingly, the goal of this study is to investigate whether this polymorphism can serve as a putative prognostic marker in patients with Squamous Cell Carcinomas of the Head and Neck region (HNSCC). The prognostic value of the -94ins/delATTG NFKB1 promoter polymorphism was analyzed in an unselected series of patients treated with curative intent for HNSCC, including all tumor stages with different therapeutical regimens. Genotyping was performed by means of pyrosequencing, using DNA from paraffin-embedded tissue samples from 364 patients with a median follow-up of 61 (2-143) months. The various genotypes were correlated with relapse-free and overall survival, as well as risk, compared to healthy volunteers. The NFKB1 polymorphism was not related to risk of HNSCC. Kaplan-Meier curves revealed no significant association between the -94ins/delATTG alleles and survival or disease progression of patients with HNSCC. In conclusion, the results suggest that the investigated NFKB1 promoter polymorphism has no prognostic impact on risk or clinical course in HNSCC.

The expression of COX-2, hTERT, MDM2, LATS2 and S100A2 in different types of non-small cell lung cancer (NSCLC)

Several studies have reported different expression levels of certain genes in NSCLC, mostly related to the stage and advancement of the tumours. We investigated 65 stage I-III NSCLC tumours: 32 adenocarcinomas (ADC), 26 squamous cell carcinomas (SCC) and 7 large cell carcinomas (LCC). Using the real-time reverse transcription polymerase chain reaction (RT-PCR), we analysed the expression of the COX-2, hTERT, MDM2, LATS2 and S100A2 genes and researched the relationships between the NSCLC types and the differences in expression levels. The differences in the expression levels of the LATS2, S100A2 and hTERT genes in different types of NSCLC are significant. hTERT and COX-2 were over-expressed and LATS2 under-expressed in all NSCLC. We also detected significant relative differences in the expression of LATS2 and MDM2, hTERT and MDM2 in different types of NSCLC. There was a significant difference in the average expression levels in S100A2 for ADC and SCC. Our study shows differences in the expression patterns within the NSCLC group, which may mimic the expression of the individual NSCLC type, and also new relationships in the expression levels for different NSCLC types.

Nasopharyngeal carcinoma--review of the molecular mechanisms of tumorigenesis

Nasopharyngeal carcinoma (NPC) is a head and neck cancer rare throughout most of the world but common in certain geographic areas, such as southern Asia. While environmental factors and genetic susceptibility play important roles in NPC pathogenesis, the Epstein-Barr virus in particular has been implicated in the molecular abnormalities leading to NPC. There is upregulation of cellular proliferation pathways such as the Akt pathway, mitogen-activated protein kinases, and the Wnt pathway. Cell adhesion is compromised due to abnormal E-cadherin and beta-catenin function. Aberrations in cell cycle are due to dysregulation of factors such as p16, cyclin D1, and cyclin E. Anti-apoptotic mechanisms are also upregulated. There are multiple abnormalities unique to NPC that are potential targets for novel treatments.

Cyclooxygenase 2 expression in cervical intraepithelial neoplasia and vulvar cancer

OBJECTIVE

The purpose of this study is to describe the expression of cyclooxygenase (COX) 2 cervical intraepithelial neoplasia (CIN) and vulvar cancer specimens.

MATERIALS AND METHODS

Archived tissues from 21 cases including 6 cases negative for CIN (no CIN), 71 low-grade (CIN 1) diseases, 8 high-grade (CIN 2, 3) diseases, and 14 vulvar cancer cases were examined. Immunohistochemistry was evaluated in COX-2 expression in tissue using an isoform-specific COX-2 polyclonal antibody. Specimens were assigned an immunohistochemical score for intensity of staining and the percent of cells stained. The slides were scored by 2 independent pathologists and compared across histological categories.

RESULTS

A greater proportion of cells were stained in specimens with high-grade CIN (p = 0.01). Staining intensity was not statistically different among the 3 groups. Higher scores were found for vulvar cancer as compared with normal vulva (p = 0.01).

CONCLUSIONS

The increase in COX-2 in cervical cancer precursors may provide a potential target for prevention studies.

Selective cyclooxygenase-2 inhibitor downregulates the paracrine epithelial-mesenchymal interactions of growth in scirrhous gastric carcinoma

The importance of cancer-mesenchymal interactions in the aggressive behavior of scirrhous gastric cancer is supported by experimental and clinical evidences. We have previously reported that gastric fibroblasts secretion of keratinocyte growth factor (KGF) underline the remarkable proliferation of scirrhous gastric cancer cells. Cyclooxygenase-2 (COX-2) is not only expressed in cancer cells, but also in interstitial fibroblasts in gastric carcinoma. To clarify the mechanisms responsible for the antiproliferation effect of COX-2 inhibitors, effect of COX-2 inhibitor on the paracrine epithelial-mesenchymal interactions of growth was examined. Scirrhous gastric cancer cell line, OCUM-2M, gastric fibroblasts, NF-21, and COX-2 inhibitor, JTE-522, were used. Growth-interaction was examined by calculating the number of cancer cells or by measuring [(3)H] thymidine incorporation of cancer cells. Effect of JTE-522 on KGF expression from NF-21 cells and OCUM-2M cells was analyzed by ELISA and RT-PCR. The conditioned medium from gastric fibroblasts significantly stimulated the growth of scirrhous gastric cancer cells. JTE-522 at the concentrations of 10(-5) and 10(-6) M significantly decreased the growth-stimulating activity of gastric fibroblasts. JTE-522 reduced the expression of KGF mRNA and the production of KGF from gastric fibroblasts. Oral administration of JTE-522 significantly decreased the size of xenografted tumor coinoculated with OCUM-2M cells and NF-21 cells in nude mice. JTE-522 decreased COX-2 expression and Ki67 labeling index within the coinoculated tumor. These findings suggested that a selective COX-2 inhibitor, JTE-522, downregulates KGF production from gastric fibroblasts, resulting in the inhibition of paracrine epithelial-mesenchymal interactions of proliferation between scirrhous gastric cancer cells and gastric fibroblasts.

Coordinated upregulation of COX-2 and NF-kappaB is a steady feature of laryngeal carcinogenesis

BACKGROUND/AIMS

Laryngeal cancer is the endpoint of a multistage process involving hyperplastic and dysplastic lesions, not adequately defined in their molecular aspect. Our objective was to evaluate the expression of the prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2) and the chief transcription factor nuclear factor-kappaB (NF-kappaB) in laryngeal carcinomas and their precursors, as well as to explore any association between the two molecules.

METHODS

We performed paraffin section immunohistochemistry for COX-2 and the p65 subunit of NF-kappaB, in tissues from 129 patients with tumors or premalignancies. p65 cytoplasmic and nuclear immunostaining were listed individually.

RESULTS

COX-2 was positively correlated with histopathological grading from normal mucosa to carcinomas (Spearman's coefficient r(s) = 0.286, p < 0.001). No association was revealed between COX-2 expression and tumor grade. p65 immunoreactivity, both of cytoplasmic and nuclear origin, increased along the carcinogenesis course, manifesting highest expression in invasive cancer (r(s) = 0.419, p < 0.001 and r(s) = 0.241, p < 0.001, respectively). Again, tumor grade had no influence on expression. COX-2 and p65 cytoplasmic, but no nuclear, expression showed a positive correlation (r(s) = 0.352, p < 0.001).

CONCLUSIONS

This study demonstrates that lesional advance in the larynx towards cancer is marked by ongoing upregulation of COX-2 and NF-kappaB. Synchronism between individual expressions may denote a regulatory role of the latter in COX-2 transactivation.

Celecoxib Inhibits Prostate Cancer Growth: Evidence of a Cyclooxygenase-2-Independent Mechanism

PURPOSE

Selective cyclooxygenase-2 (COX-2) inhibitors may suppress carcinogenesis by both COX-2-dependent and COX-2-independent mechanisms. The primary purpose of this study was to evaluate whether celecoxib or rofecoxib, two widely used selective COX-2 inhibitors, possess COX-2-independent antitumor activity.

EXPERIMENTAL DESIGN

PC3 and LNCaP human prostate cancer cell lines were used to investigate the growth inhibitory effects of selective COX-2 inhibitors in vitro. To complement these studies, we evaluated the effect of celecoxib on the growth of PC3 xenografts.

RESULTS

COX-1 but not COX-2 was detected in PC3 and LNCaP cells. Clinically achievable concentrations (2.5-5.0 micromol/L) of celecoxib inhibited the growth of both cell lines in vitro, whereas rofecoxib had no effect over the same concentration range. Celecoxib inhibited cell growth by inducing a G(1) cell cycle block and reducing DNA synthesis. Treatment with celecoxib also led to dose-dependent inhibition of PC3 xenograft growth without causing a reduction in intratumor prostaglandin E(2). Inhibition of tumor growth occurred at concentrations (2.37-5.70 micromol/L) of celecoxib in plasma that were comparable with the concentrations required to inhibit cell growth in vitro. The highest dose of celecoxib led to a 52% reduction in tumor volume and an approximately 50% decrease in both cell proliferation and microvessel density. Treatment with celecoxib caused a marked decrease in amounts of cyclin D1 both in vitro and in vivo.

CONCLUSIONS

Two clinically available selective COX-2 inhibitors possess different COX-2-independent anticancer properties. The anticancer activity of celecoxib may reflect COX-2-independent in addition to COX-2-dependent effects.

Effects of p53 or p27 overexpression on cyclooxygenase-2 gene expression in head and neck squamous cell carcinoma cell lines

BACKGROUND

Although cyclooxygenase-2 (COX-2) has been suggested to play an important role in carcinogenesis, the effects of tumor suppressors on COX-2 gene expression and the combined antitumor effects of tumor suppressors and COX-2 inhibitors have rarely been investigated.

METHODS

The effects of p53 or p27 gene transfer on COX-2 expression by adenoviral vector and the combined effects of p53 or p27 gene transfer and COX-2 inhibitor exposure on the proliferation of cancer cells were investigated in head and neck squamous cell carcinoma (HNSCC) cell lines.

RESULTS

Overexpression of p53 markedly downregulated the transcription of COX-2, but the overexpression of p27 did not affect COX-2 levels in HNSCC cell lines. The combined antitumor effects of p53 or p27 gene transfer and of a COX-2 inhibitor (NS 398) were mainly at least additive in terms of the inhibition of cell proliferation and cell cycle arrest and additive in terms of apoptotic induction.

CONCLUSIONS

These results suggest that the overexpression of p53 could exert antitumor effects, at least in part, through the suppression of COX-2 gene expression, whereas growth suppression by the overexpression of p27 probably occurs by mechanisms other than the downregulation of COX-2 expression. In addition, the administration of COX-2 inhibitors, as an adjunct to p53 or p27 gene therapy, could offer a new strategy of cancer treatment and prevention.

Different cell kinetic changes in rat stomach cancer after treatment with celecoxib or indomethacin: Implications on chemoprevention

AIM: Mechanisms underlying the chemopreventive effects of cyclooxygenase (COX) inhibitors remain elusive. We have previously shown that celecoxib but not indomethacin could prevent carcinogen-induced gastric cancer development in Wistar rats. This chemopreventive effect appeared to be independent of COX-2 and prostaglandin (PG) E2 suppression since the lowest PGE₂ was obtained in indomethacin group. This study compared the cell kinetic changes in stomachs of rats after treatment with celecoxib (5, 10, 20 mg/(kg·d)) or indomethacin (3 mg/(kg·d)) to gain more insights into the chemopreventive mechanism.

METHODS: The apoptosis and proliferation indexes in gastric tumor, adjacent non-cancer tissues and normal gastric tissues were determined. Apoptosis was quantified by apoptotic nuclei counting and TUNEL, whereas proliferation was determined by Ki67 immunostaining.

RESULTS: Treatment with either celecoxib or indomethacin inhibited gastric tumor proliferation by more than 65% (P<0.02). However, celecoxib caused a dose-dependent increase in apoptosis (P<0.05) which was not seen in indomethacin-treated tumors (P = 0.54). The highest apoptosis to proliferation ratio was seen in tumors treated with celecoxib at 10 mg/(kg·d). Treatment with this dose of celecoxib was associated with the lowest incidence of gastric cancer development.

CONCLUSION: Our findings suggest that the difference in chemopreventive effects of indomethacin and celecoxib in this animal model of gastric carcinogenesis is largely due to the differential cell kinetic changes, which does not correlate with the degree of COX-2 and PG suppression.

Novel therapeutic targets in squamous cell carcinoma of the head and neck

The treatment of squamous cell carcinoma of the head and neck (SCCHN) has recently witnessed the introduction of molecularly targeted agents based on disease biology, target discovery, and validation. One class of agents, the epidermal growth factor receptor (EGFR) inhibitors, is currently in phase III trials. There are multiple processes, however, that appear to be suitable for targeted therapy beyond EGFR. These include signal transduction, cell cycle control, prostaglandin synthesis, protein degradation, hypoxia, and angiogenesis. These systems and specific protein targets will be reviewed in detail with emphasis on promising preclinical and early clinical evidence of activity.

Prognostic Factors in Resected Stage I Non–Small-Cell Lung Cancer: A Multivariate Analysis of Six Molecular Markers

Purpose

To analyze the prognostic significance of six molecular biomarkers (death-associated protein kinase [DAPK] promoter methylation, interleukin-10 [IL-10] protein expression, cyclooxygenase-2 [COX-2] mRNA expression, human telomerase reverse transcriptase catalytic subunit [hTERT] mRNA expression, retinoic acid receptor-beta [RAR-β] mRNA expression, and K-ras mutational status) in stage I non–small-cell lung cancer (NSCLC) patients.

Patients and Methods

Biomarker analyses were performed on tumors from 94 patients with stage I NSCLC who underwent surgical resection at our institution. A minimum follow-up period of 5 years was required. DAPK methylation was assessed by methylation-specific polymerase chain reaction (PCR). RAR-β, COX-2, and hTERT mRNA levels were determined by in situ hybridization with digoxigenin-labeled antisense riboprobes. K-ras mutation status was determined by the PCR–primer introduced restriction with enrichment for mutant alleles method. IL-10 protein expression was analyzed by immunohistochemistry using a polyclonal antihuman IL-10 antibody. Cancer-specific survival was analyzed with a Cox proportional hazards model. To identify independent prognostic factors, a stepwise selection method was used.

Results

DAPK methylation, IL-10 lack of expression, COX-2 expression, hTERT expression, RAR-β expression, and K-ras mutations were observed in 46.8%, 29.8%, 59.6%, 34.0%, 23.4%, and 34.0% of patients, respectively. In the final model, DAPK methylation and IL-10 lack of expression were significant negative prognostic factors for cancer-specific survival, whereas COX-2 expression was of borderline significance.

Conclusion

In this cohort of resected stage I NSCLC patients, molecular markers that independently predict cancer-specific survival have been identified. The prognostic roles of DAPK methylation, IL-10, and other biomarkers in NSCLC merit further investigation.

Sequence-dependent effect of a cyclooxygenase-2 inhibitor on topoisomerase I inhibitor and 5-fluorouracil-induced cytotoxicity of colon cancer cells

Selective cyclooxygenase-2 (COX-2) inhibitors have been found to induce anti-proliferative and apoptotic activity in many cancer cells. However, interaction between COX-2 inhibitors and other chemotherapeutic agents remains to be determined. We investigated the interactive effects of a selective COX-2 inhibitor, etodolac, in combination with 5-fluorouracil (5-FU) or SN-38 (active metabolite of irinotecan) on colon cancer cell lines, HT29 and SW620, in simultaneous and sequential administration schedules. Isobologram analysis demonstrated that etodolac in combination with 5-FU or SN-38 according to a simultaneous schedule resulted in only an additive effect; however, synergism was achieved in a sequential schedule. Apoptosis induction in both cell lines was also significantly increased after sequential treatment with etodolac followed by either 5-FU or SN-38 compared to that after simultaneous treatment with etodolac and either 5-FU or SN-38. Our study suggests apoptosis-inducing synergism resulted from administration of etodolac and either 5-FU or SN-38 sequentially, but not simultaneously.

Cyclooxygenase-2 inhibitor nimesulide suppresses telomerase activity by blocking Akt/PKB activation in gastric cancer cell line

Nonsteroidal antiinflammatory drugs (NSAIDs) have been reported to have antiproliferative effects in neoplastic cells of different origin during the past few decades. We aimed to study the effects of the selective COX-2 inhibitor, nimesulide, on cell viability and telomerase and Akt/PKB activity in the human gastric cancer cell line MKN-45 and to explore the molecular mechanism for the antitumor activity of the selective COX-2 inhibitor. We tested the influence of nimesulide on the gastric cancer cell line MKN-45 in vitro. Trypan blue exclusion was used to determine the cell viability after incubation for 0, 12, 24, and 48 hr in different concentrations of nimesulide 0, 25, 50, 100, 200 microM). After treatment or no treatment with 100 microM nimesulide for 0, 12, 24, or 48 hr in the presence or absence of 300 nM okadaic acid for 2 hr, telomerase and Akt/PKB activity was measured using TRAP PCR-ELISA and nonradioactive IP kinase assays, respectively. In the gastric cancer cell line MKN-45 nimesulide caused a time- and dose-dependent reduction in cell numbers and significantly inhibited telomerase and Akt/PKB activity; the inhibition of telomerase activity was partly associated with the attenuation of Akt/PKB activity. These results demonstrate that the selective COX-2 inhibitor suppresses the telomerase activity of gastric cancer cells, in part by blocking the activation of protein kinase B, which provides a new signaling mechanism responsible for the anticancer effects of the selective COX-2 inhibitor.

Cyclooxygenase-2 inhibitor nimesulide suppresses telomerase activity by blocking Akt/PKB activation in gastric cancer cell line

Nonsteroidal antiinflammatory drugs (NSAIDs) have been reported to have antiproliferative effects in neoplastic cells of different origin during the past few decades. We aimed to study the effects of the selective COX-2 inhibitor, nimesulide, on cell viability and telomerase and Akt/PKB activity in the human gastric cancer cell line MKN-45 and to explore the molecular mechanism for the antitumor activity of the selective COX-2 inhibitor. We tested the influence of nimesulide on the gastric cancer cell line MKN-45 in vitro. Trypan blue exclusion was used to determine the cell viability after incubation for 0, 12, 24, and 48 hr in different concentrations of nimesulide 0, 25, 50, 100, 200 microM). After treatment or no treatment with 100 microM nimesulide for 0, 12, 24, or 48 hr in the presence or absence of 300 nM okadaic acid for 2 hr, telomerase and Akt/PKB activity was measured using TRAP PCR-ELISA and nonradioactive IP kinase assays, respectively. In the gastric cancer cell line MKN-45 nimesulide caused a time- and dose-dependent reduction in cell numbers and significantly inhibited telomerase and Akt/PKB activity; the inhibition of telomerase activity was partly associated with the attenuation of Akt/PKB activity. These results demonstrate that the selective COX-2 inhibitor suppresses the telomerase activity of gastric cancer cells, in part by blocking the activation of protein kinase B, which provides a new signaling mechanism responsible for the anticancer effects of the selective COX-2 inhibitor.

Overexpression of cyclooxygenase-2 is associated with radioresistance in oral squamous cell carcinoma

Cyclooxygenase-2 (COX-2), an inducible isoform of cyclooxygenase, is overexpressed in many types of malignant tumors, which in turn may stimulate tumor growth and protect against damage by irradiation or cytotoxic agents. The purpose of this study is to investigate the relationship between the radiation sensitivity and elevated level of COX-2. Radiation sensitivity of the eight oral SCC cell lines differed greatly in their response to radiation. Further, the level of the COX-2 expression correlated inversely with increased tumor radiation sensitivity. The similar significant association between the response to preoperative radiation therapy and COX-2 overexpression was observed in the oral SCC patients. In addition, treatment with a COX-2 selective inhibitor enhanced the radioresponse of HSC-2 cell, which constitutively expressed COX-2. These results suggested that COX-2 expression level correlates to radiation tolerance and the COX-2 selective inhibitor may be a potent enhancer for tumor radioresponse in oral SCC.

Anti-angiogenic therapy in breast cancer

Breast cancer is a worldwide epidemic among women, and one of the most rapidly increasing cancers. Not only the incidence rate but also the death rate is increasing. Despite enthusiastic efforts in early diagnosis, aggressive surgical treatment and application of additional non-operative modalities, its prognosis is still dismal. This emphasizes the necessity to develop new measures and strategies for its prevention. The understanding of the biology of angiogenesis is improving rapidly, offering the hope for more specific vascular targeting of tumor neovasculature. Anti-angiogenic therapy is a promising, relatively new form of cancer treatment using drugs called angiogenesis inhibitors that specifically inhibit new blood vessel growth. Extensive studies conducted over the past few years have recognized that overexpression of COX-2, VEGF in the cancer might be the leading factors, can induce angiogenesis via induction of multiple pro-angiogenic regulators. Breast tumor growth and metastasization are both hormone-sensitive and angiogenesis-dependent. A single angiogenic inhibitor is not capable to inhibit angiogenesis. Therefore, we should select a combination of angiogenesis inhibitors targeting COX-2, VEGF, and bFGF pathway. This article reviews the background and implementation of the current use of angiogenesis inhibitors and discusses the likely therapeutic roles in the early and advanced breast cancer together with its potential for chemoprevention.

COX-2 inhibition in upper aerodigestive tract tumors

Evidence continues to accumulate that cyclooxygenase-2 (COX-2), an inducible COX isoform, represents a potential pharmacological target for the prevention and treatment of cancer, including tumors affecting the entire upper aerodigestive tract. Studies in experimental models of these malignancies show that selective COX-1 inhibitors reduce tumor formation and growth. Clinical studies have been initiated to determine the chemoprotective effects of selective COX-2 inhibitors in patients with oral leukoplakia and Barrett's esophagus, and other studies are assessing the feasibility of incorporating these agents into existing treatment modalities for patients with locally advanced or metastatic cancer.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

The effect of nitric oxide on cyclooxygenase-2 (COX-2) overexpression in head and neck cancer cell lines

The overexpression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) has been previously reported in head and neck squamous cell carcinoma (HNSCC), as well as in many cancers. We hypothesized that endogenous nitric oxide (NO) might increase the expression of COX-2 in cancer cells. Therefore, we investigated the cross-talk between NO and the prostaglandin (PG) pathways in HNSCC cell lines. We found that COX-2 and iNOS expressions were elevated simultaneously. On adding the NO donor, SNAP, the PGE2 level was increased 2-20 times due to increased COX-2 expression. This increase of COX-2 expression by SNAP or PMA (potent inducer of both iNOS and COX-2) was blocked to various degrees by NO scavengers and NOS inhibitors (L-NAME and 1400W). Also, the expression of COX-2 in resting cells was inhibited by NOS inhibitors. Moreover, COX-2 expression, induced by SNAP, was inhibited by ODQ, a soluble guanylate cyclase (sGC) inhibitor. The effect of dibutyryl-cGMP on COX-2 expression was similar to that of SNAP. These results imply that endogenous or exogenous NO activates sGC and that the resulting increase of cGMP induces a signaling that upregulates the expression of COX-2 in HNSCC cell lines. We also observed that NO increased COX-2 expression in different cancer cell lines, including cervic and gastric cancer cell lines. These findings further support the notion that NO can be associated with carcinogenesis through the upregulation of COX-2, and that NOS inhibitor may be also useful for cancer prevention.

Chemopreventive effect of JTE-522, a selective cyclooxygenase-2 inhibitor, on 1, 2-dimethylhydrazine-induced rat colon carcinogenesis

Selective COX-2 inhibitors have been suggested to be an effective strategy in the prevention of colon cancer without the adverse side effects of non-selective, nonsteroid anti-inflammatory drugs. The present experiment was designed to assess the potential chemopreventive properties of JTE-522, a new selective cyclooxygenase-2 inhibitor, on the induction of 1,2-dimethylhydrazine (DMH)-induced colonic aberrant crypt foci (ACF), a marker of rat colon carcinogenesis. A total of 80 male F344 rats were treated with 3 or 10 mg/kg of body weight JTE-522 or vehicle by oral gavage five times weekly from the start of the experiment. One week later, rats received s.c. injections of saline or 20 mg/kg of body weight DMH once weekly for four successive weeks. At the end of 12 weeks after the start of experiment, all rats were sacrificed and colons were evaluated for ACF. 10 mg/kg JTE522 significantly suppressed the total ACF/colon. No inhibitory effect was observed in the 3 mg/kg JTE-522 treatment group. This result suggests that JTE-522 possesses chemopreventive activity against colon carcinogenesis.

Genetic deficiency or pharmacological inhibition of cyclooxygenase‐1 or ‐2 induces mouse keratinocyte differentiation in vitro and in vivo

Previously we demonstrated that genetic deficiency of the cyclooxygenases (COX-1 or COX-2) altered keratinocyte differentiation in mouse skin [Tiano et. al. (2002) Cancer Res. 62, 3395-3401]. In this study, we show that topical application of SC-560 (a COX-1 selective inhibitor) or celecoxib (COX-2 selective) to TPA-treated wild-type skin caused fivefold increases in the number of basal keratinocytes expressing the early differentiation marker keratin 1 (K1). In contrast to skin, COX-2 not COX-1 was the major isoform expressed in cultured primary keratinocytes. COX-1 was predominantly expressed in detached, differentiated cells, whereas COX-2 was found in the attached, proliferating cells. High Ca++ medium induced K1 and COX-1 in wild-type keratinocytes but did not change COX-2 expression. As observed in skin, COX-1-/- and COX-2-/- primary keratinocytes expressed fivefold more K1 than wild-type cells. K1 levels in cultured wild-type keratinocytes were also increased by treatment with celecoxib and indomethacin. However, unlike its in vivo effect, SC-560, possibly due to low COX-1 expression in cultured mouse keratinocytes, did not increase K1 levels. Furthermore, no increases in apoptotic cell numbers were observed in COX-deficient keratinocytes or COX-inhibitor treated wild-type cells. Thus, a major effect of COX inhibitors and COX-deficiency is the induction of keratinocyte differentiation.

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 present study was conducted to examine the effects of selective cyclooxygenase (COX)-2 inhibitors, nimesulide and etodolac, on early stages of tongue carcinogenesis due to 4-nitroquinoline 1-oxide(4-NQO). Fischer 344 rats, 6 weeks old, were given 15 ppm of 4-NQO in their drinking water for 8 weeks followed by diet containing either nimesulide or etodolac at the doses of 150 and 300 ppm for 16 weeks. Rats were sacrificed at 24 weeks and tongue lesions were histologically examined. Nimesulide dose-dependently reduced the incidence and multiplicity of squamous cell dysplasias and carcinomas (SCCs), with significance at the 300 ppm dose. This suppression was associated with an increased incidence and multiplicity of hyperplasias. Etodolac exhibited similar but less extensive suppressive effects. The results suggest that COX-2 is involved in the progression of hyperplasia to dysplasia and from dysplasia to SCCs.

Carcinogenesis and cyclooxygenase: the potential role of COX-2 inhibition in upper aerodigestive tract cancer

Cyclooxygenase-2 (COX-2) is upregulated in a number of epithelial cancers, including in upper aerodigestive tract (UADT) premalignant and malignant lesions. The purpose of this review is to provide a comprehensive examination of the potential of COX-2 inhibition in prevention of UADT premalignant and malignant disease. A Medline and Cancerlit literature search was conducted for the period 1993-2002, and identified literature was reviewed. There is evidence from in vitro studies, as well as animal models, that inhibition of COX-2 may suppress carcinogenesis by affecting a number of pathways of carcinogenesis, promoting apoptosis and inhibiting angiogenesis. Preliminary studies of gastro-intestinal (GI) carcinogenesis suggest that COX-2 inhibitors may represent an approach to the chemoprevention of epithelial cancers. COX-2 inhibitors may have a potential role in chemoprevention of UADT cancer, and clinical trials appear warranted.

Development of COX inhibitors in cancer prevention and therapy

On the strength of in vitro, in vivo, observational, and clinical data, nonsteroidal antiinflammatory drugs (NSAIDs)-also referred to as COX inhibitors-have emerged as lead compounds for cancer prevention, and possible adjuncts to cancer therapy. Thus far, the routine use of NSAIDs for these indications is limited, largely owing to toxicity concerns, the paucity of efficacy data for any specific target organ, and uncertainties with regard to the most appropriate regimen (i.e., the best agent, formulation, dose, route of administration, and duration). Strategies to address these concerns primarily aim to improve the therapeutic index (i.e., benefit:risk ratio) of COX inhibitors by 1) minimizing systemic exposures whenever feasible, 2) achieving greater mechanistic specificity, 3) coadministering agents that provide prophylaxis against common toxicities, and 4) coadministering other effective anticancer agents. Clinical trials testing most of these strategies have been completed or are under way. The National Cancer Institute has a substantial research portfolio dedicated to the identification, testing, and development of NSAIDs as preventive and therapeutic anticancer agents. Discovering how to apply NSAIDs in persons with-or at risk for-cancer, although challenging, has the potential for considerable clinical and public health benefits.

Topical inhibition of oral carcinoma cell with polymer delivered celecoxib

Celecoxib has a potential role for oral cancer chemoprevention but its systemic side effects are a concern. Topical chemoprevention is a promising way to reduce the toxicity. This study was designed to determine whether topical application of polymer delivered celecoxib would have an inhibitory effect on human oral carcinoma cells. Seventeen nude mice were intradermally inoculated with the carcinoma cells, and then were divided into control and treatment groups. Tumor growth was measured for 15 days, at which significant difference was found between two groups (P<0.001). This study indicates a potential role of polymer film delivered celecoxib for topical inhibition of oral cancer.

Celecoxib, a selective cyclo-oxygenase-2 inhibitor, enhances the response to preoperative paclitaxel and carboplatin in early-stage non-small-cell lung cancer

PURPOSE

Preclinical studies suggest that treatment with a selective cyclo-oxygenase-2 (COX-2) inhibitor may augment the antitumor effects of chemotherapy. In this study, patients with non-small-cell lung cancer (NSCLC) were preoperatively treated with celecoxib in combination with chemotherapy. End points were toxicity, response rates, and measurement of intratumoral levels of prostaglandin E2 (PGE2).

METHODS

In this phase II trial, 29 patients with stages IB to IIIA NSCLC were treated with two preoperative cycles of paclitaxel and carboplatin, as well as daily celecoxib, followed by surgical resection. Levels of PGE2 in the primary tumors and adjacent normal lung tissue were compared in 17 study patients versus 13 controls, who received preoperative paclitaxel/carboplatin without celecoxib.

RESULTS

All patients completed preoperative chemotherapy, and 26 completed preoperative celecoxib. The overall clinical response rate was 65% (48% with partial response; 17% with complete response). Grade 3 or 4 neutropenia was observed in 18 patients (62%). Twenty-eight patients were explored and underwent complete resection of their tumors. There were no complete pathologic responses, but seven patients (24%) had minimal residual microscopic disease. The addition of celecoxib to a regimen of paclitaxel and carboplatin abrogated the marked increase in levels of PGE2 detected in primary tumors after treatment with paclitaxel and carboplatin alone.

CONCLUSION

In comparison with historically reported response rates, these data suggest that the addition of a selective COX-2 inhibitor may enhance the response to preoperative paclitaxel and carboplatin in patients with NSCLC. Moreover, treatment with celecoxib 400 mg twice daily was sufficient to normalize the increase in PGE2 levels found in NSCLC patients after treatment with paclitaxel and carboplatin. Confirmatory trials are planned.

A wholly nutritional 'multifocal angiostatic therapy' for control of disseminated cancer

A great deal of effort is now being devoted to the development of new drugs that hopefully will control the spread of inoperable cancer by safely inhibiting tumor-evoked angiogenesis. However, there is growing evidence that certain practical nutritional measures have the potential to slow tumor angiogenesis, and it is reasonable to anticipate that, by combining several measures that work in distinct but complementary ways to impede the angiogenic process, a clinically useful 'multifocal angiostatic therapy' (MAT) might be devised. Several measures which might reasonably be included in such a protocol are discussed below, and include: a low-fat, low-glycemic index vegan diet, which may down-regulate the systemic IGF-I activity that supports angiogenesis; supplemental omega-3-rich fish oil, which has been shown to inhibit endothelial expression of Flk-1, a functionally crucial receptor for VEGF, and also can suppress tumor production of pro-angiogenic eicosanoids; high-dose selenium, which has recently been shown to inhibit tumor production of VEGF; green tea polyphenols, which can suppress endothelial responsiveness to both VEGF and fibroblast growth factor; and high-dose glycine, whose recently reported angiostatic activity may reflect inhibition of endothelial cell mitosis, possibly mediated by activation of glycine-gated chloride channels. In light of evidence that tumor-evoked angiogenesis has a high requirement for copper, copper depletion may have exceptional potential as an angiostatic measure, and is most efficiently achieved with the copper-chelating drug tetrathiomolybdate. If logistical difficulties make it difficult to acquire this experimental drug, high-dose zinc supplementation can achieve a slower depletion of the body's copper pool, and in any case can be used as maintenance therapy to maintain an adequate level of copper depletion. A provisional protocol is offered for a nutritionally based MAT entailing a vegan diet and supplemental intakes of fish oil, selenium, green tea polyphenols, glycine, and zinc. Inasmuch as cox-2 is overexpressed in many cancers, and cAMP can boost tumor production of various angiogenic factors as well as autogenous growth factors, adjunctive use of cox-2-specific NSAIDS may be warranted in some cases.

Cancer "photo-chemoprevention" with pulsed dye laser and celecoxib

BACKGROUND AND OBJECTIVES

Our previous study demonstrated the efficacy of pulsed dye laser (PDL) in inhibiting cancer growth. This study is to determine the synergic effect of PDL and Celecoxib, when they are combined for treatment of oral cancer.

STUDY DESIGN/MATERIALS AND METHODS

Fifteen mice were inoculated with oral cell carcinoma and divided into three groups of five each (30 seeding sites/group): (1) control (no treatment), (2) PDL only, and (3) treatment with combined PDL and Celecoxib (1,500 ppm). The number and volume of tumors were counted and measured for 21 days.

RESULTS

The combined treatment developed tumor at the slowest rate. On day 21, the average tumor volumes were (1) 483.6 mm(3) (control), (2) 312.1 mm(3) (PDL only), and (3) 151.4 mm(3) (combined treatment).

CONCLUSIONS

A synergic effect was found in the combined treatment group. This study provides the first evidence of the efficacy of a new strategy for the treatment of oral cancer, namely, cancer "photo-chemoprevention."

Management of transitional cell carcinoma

Canine TCC of the bladder is a disease for which early detection and multimodality therapy are likely to produce the most favorable results. Urine screening tests are being investigated as tools to permit earlier detection. The possibility of tumor seeding must be considered when obtaining urine for analysis and when performing surgery. Because these tumors tend to be very locally invasive at the time of diagnosis and are likely to metastasize, cures are unlikely. Currently, combination protocols using chemotherapy and the nonsteroidal anti-inflammatory agent piroxicam show the most promise in producing tumor responses. Surgery and radiation therapy are useful treatment modalities in select cases. Despite advances in treatment of canine TCC, median survival times reported for prospective clinical trials have never exceeded 1 year, regardless of the treatment modality. Development of accurate tests for early tumor detection could have a significant impact on the success of treatment of this tumor in canine patients.

Colon cancer cells with high invasive potential are susceptible to induction of apoptosis by a selective COX-2 inhibitor

Cyclooxygenase-2 (COX-2) expression has been shown to correlate with the invasiveness of colon cancer cells. To further investigate this positive correlation and its possible therapeutic implications, a selective COX-2 inhibitor, etodolac, was tested on three variants of HT-29 colon cancer cell lines, HT-29/Inv1, HT-29/Inv2 and HT-29/Inv3, with graded increases of in vitro Matrigel invasive potential and COX-2 expression levels. HT-29 variants with higher invasive potential were found to be more sensitive to etodolac by in vitro growth inhibition assays, the estimated LD(50) being 0.5 mM for highly invasive HT-29/Inv2 and HT-29/Inv3 cells, 0.6 mM for slightly less invasive HT-29/Inv1, and 1.8 mM for the parental HT-29. Treatment of the highly invasive HT-29/Inv2 and Inv3 variants with as little as 0.1 mM etodolac in the growth medium produced signs of apoptosis, as detected by DNA fragmentation and TUNEL (terminal deoxynucleotidyl transferase dUTP-biotin nick end labeling) assay. In vivo experiments in SCID mice showed that etolodac inhibited the growth of subcutaneous tumors induced by HT-29/Inv3 cells significantly more than those by the parental HT-29 cells. These results suggest that COX-2 inhibitors have a potential role in prevention of tumor invasion in colon cancer patients.

Cyclooxygenase 2: a molecular target for cancer prevention and treatment

Cyclooxygenase2 (COX-2), an inducible prostaglandin G/H synthase, is overexpressed in several human cancers. Here, the potential utility of selective COX-2 inhibitors in the prevention and treatment of cancer is considered. The mechanisms by which COX-2 levels increase in cancers, key data that indicate a causal link between increased COX-2 activity and tumorigenesis, and possible mechanisms of action of COX-2 are discussed. In a proof-of-principle clinical trial, treatment with the selective COX-2 inhibitor celecoxib reduced the number of colorectal polyps in patients with familial adenomatous polyposis. Selective COX-2 inhibitors appear to be sufficiently safe to permit large-scale clinical testing and numerous clinical trials are currently under way to determine whether selective inhibitors of COX-2 are effective in the prevention and treatment of cancer.

Mouse skin as a model for cancer chemoprevention by nonsteroidal anti-inflammatory drugs

The mouse skin model of multistage carcinogenesis has demonstrated that cancer results from a synergism between genotoxic and nongenotoxic factors. The former induce irreversible genetic alterations, whereas the latter promote tumor development by favoring the clonal outgrowth of the genetically altered cells. While therapeutic gene repair is a still unrealized dream, tumor promotion provides an attractive target for cancer prevention. A key event in epithelial tumor development is an aberrant constitutive overexpression of cyclooxygenase-2 (COX-2), being detectable already in premalignant lesions and leading to an overproduction of prostaglandins. In the mouse skin model, prostaglandin F2alpha has been identified as an endogenous tumor promoter. The well-established chemopreventive effect of nonsteroidal anti-inflammatory drugs seems to be mainly due to COX-2 inhibition. Targeted transgenic overexpression of COX-2 in mouse epidermis induces a preneoplastic phenotype and renders the tissue extremely sensitive to genotoxic carcinogens; i.e., for the induction of skin tumor development, tumor promoter treatment can be omitted in those animals. It is concluded that COX-2 acts as an endogenous tumor promoter and that its overexpression represents a first order risk factor for cancer development. Conversely, specific COX-2 inhibitors rank among the most promising agents for cancer chemoprevention.

Selective cyclooxygenase-2 inhibition: a target in cancer prevention and treatment

A major goal in the area of cancer prevention and treatment is to make rational use of defined molecular targets in order to block carcinogenesis. Studies conducted in experimental animal models for many human cancers, including those of lung, skin, mammary gland, urinary bladder, colon, and pancreas, have demonstrated that carcinogenesis often may be inhibited by the administration of a highly diverse group of biologic and chemical agents. One very promising and well-studied target is cyclooxygenase (COX)-2. Interestingly, a number of cancers appear to overexpress the COX-2 enzyme, which may play several roles in carcinogenesis. Recent clinical studies have demonstrated the effect of COX-2 inhibitors in the treatment of familial adenomatous polyposis, a genetic disorder that increases the risk for developing colorectal cancer. Ongoing clinical trials with COX-2 inhibitors will increase our understanding and may give us profound insights into the general applicability of this new targeted approach for cancer control.