Cyclooxygenase-2 inhibition decreases primary and metastatic tumor burden in a murine model of orthotopic lung adenocarcinoma

Discovery of small molecule acting as multitarget inhibitor of colorectal cancer by simultaneous blocking of the key COX-2, 5-LOX and PIM-1 kinase enzymes

Colorectal cancer (CRC) is the second cause of cancer death worldwide. Inhibitors of COX-2, 5-LOX and PIM-1 kinase were very effective in the treatment and prevention of CRC in mouse models in vivo. Furthermore, thymol was confirmed to inhibit CRC cell proliferation in cancer cell lines and inhibitory activity against COX-2 and 5-LOX. On the other hand, 4-thiazolidinone pharmacophore was incorporated in the structures of various reported COX-2, 5-LOX and PIM kinase inhibitors. Consequently, the aim of the present investigation was to combat CRC by synthesis and biological evaluation of new thymol - 4-thiazolidinone hybrids as multitarget anticancer agents that could inhibit the key COX-2, 5-LOX and PIM-1 kinase enzymes simultaneously. Compounds 5a-d and 5g displayed inhibitory activity against COX-2 nearly equal to Celecoxib with high selectivity index (SI). Moreover, compounds 5b-e showed 5-LOX inhibitory activity nearly equal to the reference Quercetin while compounds 5a, 5f and 5g elicited inhibitory activity slightly lower than Quercetin. Furthermore, in vivo formalin-induced paw edema test revealed that, compounds 5a, 5c, 5f and 5g showed higher % inhibition than Celecoxib and compounds 5a, 5f and 5g showed higher % inhibition than Diclofenac sodium. In addition, compounds 5a-c, 5e-g showed in vivo superior gastrointestinal safety profile as Celecoxib in fasted rats. Besides, compounds 5d, 5e and 5g exhibited the highest activity against human CRC cell lines (Caco-2 and HCT-116) at doses less than their EC₁₀₀ on normal human cells. Furthermore, compounds 5e and 5g induced apoptosis-dependent death by above 50% in the treated CRC cell lines. Moreover, compounds 5e and 5g induced caspase activation by >50% in human CRC. Also, compounds 5d, 5e and 5g showed in vitro inhibitory activity against both PIM-1\2 kinases comparable to the reference Staurosporine. In silico docking studies were concordant with the biological results. In conclusion, compound 5g, of simple chemical structure, achieved the target goal of inhibiting three targets leading to inhibition of human CRC cell proliferation. It inhibited the target key enzymes COX-2, 5-LOX and PIM-1\2 kinase in vitro. Besides, it revealed in vitro inhibition of cell proliferation in cancer cell lines via activation of caspase 3\7 dependent-apoptosis in human CRC cell lines. In addition, it elicited in vivo anti-inflammatory activity in formalin-induced paw edema test and in vivo oral safety in gastric ulcerogenic activity test.

HER2 induces cell proliferation and invasion of non-small-cell lung cancer by upregulating COX-2 expression via MEK/ERK signaling pathway

HER2 positivity has been well studied in various cancers, but its importance in non-small-cell lung cancer (NSCLC) is still being explored. In this study, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to detect HER2 and COX-2 expression in NSCLC tissues. Then, pcDNA3.1-HER2 was used to overexpress HER2, while HER2 siRNA and COX-2 siRNA were used to silence HER2 and COX-2 expression. MTT assay and invasion assay were used to detect the effects of HER2 on cell proliferation and invasion. Our study revealed that HER2 and COX-2 expression were upregulated in NSCLC tissues and HER2 exhibited a significant positive correlation with the levels of COX-2 expression. Overexpression of HER2 evidently elevated COX-2 expression, while silencing of HER2 evidently decreased COX-2 expression. Furthermore, overexpressed HER2 induced the ERK phosphorylation, and this was abolished by the treatment with U0126, a pharmacological inhibitor of MEK, an upstream kinase of ERK. HER2-induced expression and promoter activity of COX-2 were also suppressed by U0126, suggesting that the MEK/ERK signaling pathway regulates COX-2 expression. In addition, HER2 induced activation of AKT signaling pathway, which was reversed by pretreatment with U0126 and COX-2 siRNA. MTT and invasion assays revealed that HER2 induced cell proliferation and invasion that were reversed by pretreatment with U0126 and COX-2 siRNA. In this study, our results demonstrated for the first time that HER2 elevated COX-2 expression through the activation of MEK/ERK pathway, which subsequently induced cell proliferation and invasion via AKT pathway in NSCLC tissues.

Cyclooxygenase-2 up-regulates vascular endothelial growth factor via a protein kinase C pathway in non-small cell lung cancer

Background

Vascular endothelial growth factor (VEGF) expression is up-regulated via a cyclooxygenase-2 (COX-2)-dependent mechanism in non-small cell lung cancer (NSCLC), but the specific signaling pathway involved is unclear. Our aim was to investigate the signaling pathway that links COX-2 with VEGF up-regulation in NSCLC.

Material and methods

COX-2 expression in NSCLC samples was detected immunohistochemically, and its association with VEGF, microvessel density (MVD), and other clinicopathological characteristics was determined. The effect of COX-2 treatment on the proliferation of NSCLC cells (A549, H460 and A431 cell lines) was assessed using the tetrazolium-based MTT method, and VEGF expression in tumor cells was evaluated by flow cytometry. COX-2-induced VEGF expression in tumor cells was monitored after treatment with inhibitors of protein kinase C (PKC), PKA, prostaglandin E2 (PGE₂), and an activator of PKC.

Results

COX-2 over-expression correlated with MVD (P = 0.036) and VEGF expression (P = 0.001) in NSCLC samples, and multivariate analysis demonstrated an association of VEGF with COX-2 expression (P = 0.001). Exogenously applied COX-2 stimulated the growth of NSCLCs, exhibiting EC₅₀ values of 8.95 × 10^-3, 11.20 × 10^-3, and 11.20 × 10^-3 μM in A549, H460, and A431 cells, respectively; COX-2 treatment also enhanced tumor-associated VEGF expression with similar potency. Inhibitors of PKC and PGE₂ attenuated COX-2-induced VEGF expression in NLCSCs, whereas a PKC activator exerted a potentiating effect.

Conclusion

COX-2 may contribute to VEGF expression in NSCLC. PKC and downstream signaling through prostaglandin may be involved in these COX-2 actions.

Preclinical evaluation of a gene therapy treatment for transitional cell carcinoma

Three drugs were compared for their efficacy in treating murine transitional cell carcinoma (TCC) of the bladder. Intravesical gene therapy treatments utilizing expression-targeted plasmids, where the murine cyclooxygenase-2 (Cox-2) promoter was used to drive the expression of exogenously inducible forms of caspases 3 and 9, were compared with treatment modalities employing Bacille Calmette-Guérin (BCG) and celecoxib. When administered via lavage, only the gene therapy regimen was found to be effective at restricting tumor progression following a 7-day incubation of tumor tissues. Celecoxib was also administered via the diet to allow for systemic delivery of the drug. The most efficacious celecoxib use tested yielded tumors with masses of (18.3±8.4 mg) versus the gene delivery method, which yielded tumors with masses of (3.6±7.7 mg). The difference was significant (t-test, n≥4, P<0.025). The results showed that the Cox-2 expression-targeted gene therapy system could efficiently bypass the bladder permeability barrier and more effectively inhibit tumor growth and development than either BCG or celecoxib treatments. Long-term data further demonstrated that the gene therapy system could effectively inhibit tumor growth and elongate life expectancy.

Selective COX-2 inhibitor celecoxib combined with EGFR-TKI ZD1839 on non-small cell lung cancer cell lines: in vitro toxicity and mechanism study

Constitutive expression of cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) occurs frequently in non-small cell lung cancer (NSCLC). Anticancer research targeting EGFR has got an extensive attention especially in NSCLC and COX-2 inhibitor also shown a certain anticancer activity in recent years. Simultaneously targeting COX-2 and EGFR may be a promising therapeutic way. We carried out the in vitro study using selective COX-2 inhibitor celecoxib combined with EGFR-tyrosine kinase inhibitor (EGFR-TKI) ZD1839 on NSCLC cell lines to investigate the anti proliferation effect and the cell molecular mechanism. MTT growth assay showed the synergistic therapeutic effect of certain concentration of celecoxib combined with ZD1839 and synergistic apoptosis effect was detected by Hoechest33258 fluorescence staining and flow cytometric analysis. In western blot analysis, ZD1839 single agent inhibited the activation of EGFR and downstream cell signal transduction AKT and extrocellular signal-regulated kinase (ERK) pathways, the transcription activity of nuclear factor-kappa B (NF-kappaB), and the expression of COX-2. Celecoxib single agent could also inhibit AKT and ERK pathway in NSCLC, even the EGFR expression under high concentration treatment. Celecoxib combined with ZD1839 led to stronger inhibition of related cell signal transduction pathways in NSCLC.

Involvement of mitochondrial and Akt signaling pathways in augmented apoptosis induced by a combination of low doses of celecoxib and N-(4-hydroxyphenyl) retinamide in premalignant human bronchial epithelial cells

Celecoxib is being evaluated as a chemopreventive agent. However, its mechanism of action is not clear because high doses were used for in vitro studies to obtain antitumor effects. We found that celecoxib inhibited the growth of premalignant and malignant human bronchial epithelial cells with IC(50) values between 8.9 and 32.7 micromol/L, irrespective of cyclooxygenase-2 (COX-2) expression. Normal human bronchial epithelial cells were less sensitive to celecoxib. Because these concentrations were higher than those attainable in vivo (<or=5.6 micromol/L), we surmised that combining celecoxib with the synthetic retinoid N-(4-hydroxyphenyl) retinamide (4HPR) might improve its efficacy. Treatment of premalignant lung cell lines with combinations of clinically relevant concentrations of celecoxib (<or=5 micromol/L) and 4HPR (<or=0.25 micromol/L) resulted in greater growth inhibition, apoptosis induction, and suppression of colony formation than did either agent alone. This combination also decreased the levels of Bcl-2, induced the release of mitochondrial cytochrome c, activated caspase-9 and caspase-3, and induced cleavage of poly(ADP-ribose)polymerase at concentrations at which each agent alone showed no or minimal effects. Furthermore, combinations of celecoxib and 4HPR suppressed the phosphorylation levels of serine/threonine kinase Akt and its substrate glycogen synthase kinase-3beta more effectively than the single agents did. Accordingly, overexpression of constitutively active Akt protected bronchial epithelial cells from undergoing apoptosis after incubation with both celecoxib and 4HPR. These findings indicate that activation of the mitochondrial apoptosis pathway and suppression of the Akt survival pathway mediate the augmented apoptosis and suggest that this combination may be useful for lung cancer chemoprevention.

Effect of celecoxib and novel agent LC-1 in a hamster model of lung cancer

BACKGROUND

Lung cancer is the leading cause of cancer deaths in the United States. Inflammatory molecules, cyclooxygenase-2 (COX-2) and nuclear factor kappa B (NF-kappaB) have been implicated in lung carcinogenesis. The therapeutic potential of celecoxib, a COX-2 selective inhibitor, and LC-1, a pro-apoptotic drug with accompanying inhibition of NF-kappaB, were investigated.

MATERIALS AND METHODS

Syrian golden hamsters (n = 140) underwent N-nitroso-bis(2-oxopropyl)amine (BOP) injection weekly for 6 wk. Hamsters were randomized into seven groups: placebo and low/high doses of LC-1, celecoxib, and LC-1/celecoxib. Treatments were given via orogastric lavage for 32 wk. Immunohistochemistry was used to determine COX-2 expression and NF-kappaB activity. Ki-67 labeling was used as an index of proliferation. COX activity was measured by prostaglandin E(2) enzyme-linked immunosorbent assay.

RESULTS

BOP successfully induced lung adenocarcinoma in 63% of placebo animals. Lung tumors strongly expressed COX-2 and NF-kappaB. Prostaglandin E(2) levels were decreased in celecoxib compared with placebo groups (P < 0.05) reflecting suppression of COX activity, but no decrease in NF-kappaB was seen as measured by immunohistochemistry in the tumors. There was no significant difference in tumor size, tumor incidence, or tumor proliferation index between placebo and treatment groups.

CONCLUSIONS

Carcinogen exposure results in increased COX-2 and NF-kappaB expression and suggests a role in carcinogenesis. Celecoxib and LC-1 did not have any effect in preventing lung cancer development when co-administered with and continued after the carcinogen BOP. Higher doses that can result in suppression of NF-kappaB activity will need to be explored to determine the viability of this approach to prevent lung cancer development.

A comparison of the effectiveness of selected non-steroidal anti-inflammatory drugs and their derivatives against cancer cells in vitro

PURPOSE

Previously, we reported in vitro observations suggesting that ibuprofen is an effective non-prescription non-steroidal anti-inflammatory drug (NSAID) to reduce the survival of human prostate cancer cells (Andrews et al. in Cancer Chemother Pharmacol 502:77-284, 2002), and that this observed effectiveness is mediated by an up-regulation of the p75 NTR tumor suppressor (Khwaja et al. in Cancer Res 646:207-6213, 2004). However, other NSAIDs and their derivatives have received significant attention with regard to their anti-cancer effectiveness and have been selected for clinical trials to treat a variety of human cancers. In this investigation, we compared celecoxib, sulindac sulfone, nitric oxide linked NSAIDs, and R-flurbiprofen with ibuprofen in their ability to inhibit the growth of a variety of human cancer cells lines including cells lines with multi-drug resistance. We also evaluated whether, like ibuprofen, an up-regulation of p75 NTR is a molecular mechanism that mediates the anti-growth effectiveness of these drugs.

MATERIALS AND METHODS

Selected dosages for each drug were evaluated for their ability to reduce the growth (MTT analysis) and induce apoptosis (Hoechst staining) of a variety of different cancer cell lines, including an ovarian cell line expressing multidrug resistance-1 glycoprotein (MDR-1). The drugs were then analyzed using immunoblot, RT-PCR and siRNA to study the role of p75 NTR in their anti-growth effectiveness.

RESULTS

Our study revealed consistency in the drug dosages that inhibit the survival of different human cancer cell lines. While NO-linked aspirin and celecoxib were most effective in decreasing cell growth and inducing apoptosis at the lowest dosages, R-flurbiprofen and ibuprofen were most effective at clinically relevant dosages. A multidrug resistant ovarian cell line is more resistant to growth inhibition by the drugs tested than its non-drug resistant parental counterpart. There was no correlation between the expression of cyclooxygenase-2 (COX-2) and the ability of the drugs to reduce cancer cell survival. All the drugs tested induced an up-regulation in p75 NTR tumor suppressor gene expression in concert with their observed growth inhibiting ability. Inhibition of p75 NTR expression with siRNA reduced the cell growth inhibiting effects of all the drugs tested.

CONCLUSIONS

The method of chemotherapy (i.e., intravascular, intrathecal, oral) might dictate the choice of NSAID/NSAID derivative used to treat/prevent a given type of cancer. Also, the p75 NTR tumor suppressor appears to be a common molecular mechanism that mediates the growth inhibiting effectiveness of these drugs.

Calcium-activated endoplasmic reticulum stress as a major component of tumor cell death induced by 2,5-dimethyl-celecoxib, a non-coxib analogue of celecoxib

A drawback of extensive coxib use for antitumor purposes is the risk of life-threatening side effects that are thought to be a class effect and probably due to the resulting imbalance of eicosanoid levels. 2,5-Dimethyl-celecoxib (DMC) is a close structural analogue of the selective cyclooxygenase-2 inhibitor celecoxib that lacks cyclooxygenase-2-inhibitory function but that nonetheless is able to potently mimic the antitumor effects of celecoxib in vitro and in vivo. To further establish the potential usefulness of DMC as an anticancer agent, we compared DMC and various coxibs and nonsteroidal anti-inflammatory drugs with regard to their ability to stimulate the endoplasmic reticulum (ER) stress response (ESR) and subsequent apoptotic cell death. We show that DMC increases intracellular free calcium levels and potently triggers the ESR in various tumor cell lines, as indicated by transient inhibition of protein synthesis, activation of ER stress-associated proteins GRP78/BiP, CHOP/GADD153, and caspase-4, and subsequent tumor cell death. Small interfering RNA-mediated knockdown of the protective chaperone GRP78 further sensitizes tumor cells to killing by DMC, whereas inhibition of caspase-4 prevents drug-induced apoptosis. In comparison, celecoxib less potently replicates these effects of DMC, whereas none of the other tested coxibs (rofecoxib and valdecoxib) or traditional nonsteroidal anti-inflammatory drugs (flurbiprofen, indomethacin, and sulindac) trigger the ESR or cause apoptosis at comparable concentrations. The effects of DMC are not restricted to in vitro conditions, as this drug also generates ER stress in xenografted tumor cells in vivo, concomitant with increased apoptosis and reduced tumor growth. We propose that it might be worthwhile to further evaluate the potential of DMC as a non-coxib alternative to celecoxib for anticancer purposes.

Preclinical models of regional lymph node tumor metastasis

Animal models have produced vital information regarding the mechanisms of RLN metastasis. Modern imaging and molecular techniques have made it clear that growing tumors secrete cytokines that induce invasion, angiogenesis, lymphangiogenesis, increased intratumoral IFV and IFP, increased fluid flow from the tumor to the surrounding tissues, increased lymphatic flow, an increase in the rate of entry of tumor cells into lymphatic capillaries, and an increased number of tumor cells reaching the RLN(s). This is important knowledge that will help direct translational research in human patients. We can look forward to continued improvement in the management of human tumors that metastasize to the RLNs.

Molecular mechanisms of metastasis

A major topic covered at the First International Symposium on Cancer Metastasis and the Lymphovascular System was the molecular mechanisms of metastasis. This has become of major interest in recent years as we have discovered new metastasis-related genes and gained understanding of the molecular events of lymphatic metastasis. The symposium covered new aspects and important questions related to the events of metastasis in both humans and animals. The basic and clinical related research covered in this topic represented many disciplines. The presentations showed novel findings and at the same time, raised many new unanswered questions, indicating the limited knowledge we still have regarding the molecular events of metastasis. The hope is that further unraveling of the direct and indirect molecular events of lymphatic metastasis will lead to new approaches in developing effective therapeutics.

Perioperative cyclooxygenase 2 inhibition to reduce tumor cell adhesion and metastatic potential of circulating tumor cells in non-small cell lung cancer

OBJECTIVE

Surgical manipulation of lung cancers may increase circulating tumor cells and contribute to metastatic recurrence after resection. Cyclooxygenase 2 is overexpressed in most non-small cell lung cancer and upregulates the cell adhesion receptor CD44. Our goal was to examine the effects of perioperative cyclooxygenase blockade on the metastatic potential of circulating tumor cells, CD44 expression, and adhesion of cancer cells to extracellular matrix.

METHODS

Human non-small cell lung cancer cells (A549) were injected through the lateral tail vein in an in vivo murine model of tumor metastasis with three random treatment groups: no treatment, perioperative selective cyclooxygenase 2 inhibition (celecoxib) only, and continuous celecoxib. Lung metastases were assessed at 6 weeks by a blinded observer. For in vitro experiments, cells were treated with celecoxib, and expression of CD44 was determined by Western blotting. Extracellular matrix adhesion was assessed by Matrigel (BD Labware, Bedford, Mass) assay.

RESULTS

In vivo lung metastases were significantly decreased relative to control by both perioperative and continuous celecoxib (P = .0135). There was no significant difference in number of metastases between continuous and perioperative treatment groups. In vitro adhesion to the extracellular matrix was significantly inhibited by celecoxib in a dose-dependent manner (P < .01). A549 cells expressed high levels of CD44, upregulated by interleukin 1beta and downregulated by celecoxib.

CONCLUSION

Celecoxib significantly reduced establishment of metastases by circulating tumor cells in a murine model. It also inhibited CD44 expression and extracellular matrix adhesion in vitro. Perioperative modulation of cyclooxygenase 2 may be a novel strategy to minimize metastases from circulating tumor cells during this high-risk period.

Downregulation of survivin expression and concomitant induction of apoptosis by celecoxib and its non-cyclooxygenase-2-inhibitory analog, dimethyl-celecoxib (DMC), in tumor cells in vitro and in vivo

Background

2,5-Dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib (Celebrex^®) that lacks COX-2-inhibitory function. However, despite its inability to block COX-2 activity, DMC is able to potently mimic the anti-tumor effects of celecoxib in vitro and in vivo, indicating that both of these drugs are able to involve targets other than COX-2 to exert their recognized cytotoxic effects. However, the molecular components that are involved in mediating these drugs' apoptosis-stimulatory consequences are incompletely understood.

Results

We present evidence that celecoxib and DMC are able to down-regulate the expression of survivin, an anti-apoptotic protein that is highly expressed in tumor cells and known to confer resistance of such cells to anti-cancer treatments. Suppression of survivin is specific to these two drugs, as other coxibs (valdecoxib, rofecoxib) or traditional NSAIDs (flurbiprofen, indomethacin, sulindac) do not affect survivin expression at similar concentrations. The extent of survivin down-regulation by celecoxib and DMC in different tumor cell lines is somewhat variable, but closely correlates with the degree of drug-induced growth inhibition and apoptosis. When combined with irinotecan, a widely used anticancer drug, celecoxib and DMC greatly enhance the cytotoxic effects of this drug, in keeping with a model that suppression of survivin may be beneficial to sensitize cancer cells to chemotherapy. Remarkably, these effects are not restricted to in vitro conditions, but also take place in tumors from drug-treated animals, where both drugs similarly repress survivin, induce apoptosis, and inhibit tumor growth in vivo.

Conclusion

In consideration of survivin's recognized role as a custodian of tumor cell survival, our results suggest that celecoxib and DMC might exert their cytotoxic anti-tumor effects at least in part via the down-regulation of survivin – in a manner that does not require the inhibition of cyclooxygenase-2. Because inhibition of COX-2 appears to be negligible, it might be worthwhile to further evaluate DMC's potential as a non-coxib alternative to celecoxib for anti-cancer purposes.

Dimethyl celecoxib as a novel non-cyclooxygenase 2 therapy in the treatment of non-small cell lung cancer

OBJECTIVES

The cyclooxygenase 2 enzyme has become a therapeutic target in cancer treatment. Cyclooxygenase 2 blockade with selective inhibitors increases apoptosis and decreases the metastatic potential of lung cancer cells. Some of the antitumor effects of these inhibitors may occur through both cyclooxygenase 2-dependent and independent pathways. Our goal was to investigate these pathways using celecoxib (selective cyclooxygenase 2 inhibitor) and 2,5-dimethyl celecoxib, a structural analog modified to eliminate cyclooxygenase 2 inhibitory activity, while potentially maintaining antineoplastic properties.

METHODS

2,5-dimethyl celecoxib was synthesized in the Department of Chemistry at the University of Southern California. With the use of non-small cell lung cancer cells (A549), prostaglandin E2 production was quantified by enzyme-linked immunosorbent assay to assess cyclooxygenase 2 activity. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay. Cell migration was performed using transwell inserts that were matrigel coated for invasion experiments. Gelatin zymography was used to assess matrix-metalloproteinase activity.

RESULTS

2,5-dimethyl celecoxib did not inhibit interleukin-1beta-stimulated prostaglandin E2 production, whereas celecoxib did even at low doses. Both celecoxib and 2,5-dimethyl celecoxib decreased tumor cell viability and proliferation with IC50 for celecoxib and 2,5-dimethyl celecoxib of 73 and 53 micromol/L, respectively. Both drugs were also potent inducers of apoptosis, and both inhibited tumor cell migration and invasion. This was associated with down-regulation of matrix metalloproteinase activity.

CONCLUSIONS

2,5-dimethyl celecoxib is a structural analog of celecoxib that lacks cyclooxygenase 2 inhibitory activity but exhibits significant antineoplastic properties comparable to celecoxib. This suggests that the antineoplastic activities of celecoxib are, at least in part, cyclooxygenase independent and that therapeutic strategies can be developed without the side effects of global cyclooxygenase 2 blockade.

Effects of celecoxib in human retinoblastoma cell lines and in a transgenic murine model of retinoblastoma

BACKGROUND/AIM

Celecoxib, a cyclooxygenase-2 inhibitor and antiangiogenic agent, has demonstrated potent anticancer effects in preclinical studies and in human clinical trials. To evaluate the potential utility of this agent in the treatment of retinoblastoma, the authors investigated the effects of celecoxib in retinoblastoma cell lines and in a murine model of this disease.

METHODS

Growth inhibitory effects of celecoxib were evaluated in Y79 and Weri-RB1 human retinoblastoma cell lines by WST-1 cell proliferation assay. For animal study, two groups of 24, 8 week old LHbeta-TAg transgenic mice were treated with celecoxib (250 mg/kg, orally once a day) or vehicle control, 5 days/week for 6 weeks. Mice were sacrificed on day 43. Enucleated eyes were serially sectioned and ocular tumour burden was quantified by histopathological analysis.

RESULTS

Celecoxib did not inhibit proliferation of Y79 or Weri-RB1 cells, even at concentrations far exceeding clinically achievable levels. No significant difference in ocular tumour burden between celecoxib treated and control mice (p=0.73) was found.

CONCLUSION

Celecoxib was ineffective at inhibiting proliferation of retinoblastoma cells in vitro and was ineffective at controlling retinoblastoma tumour growth in a murine model of this disease. On the basis of these findings, oral celecoxib therapy is unlikely to have clinical utility in the treatment of retinoblastoma.

Surgical management of T3 and T4 lung cancer

Locally advanced lung cancer (T(3) or T(4)) has a significantly worse prognosis than lower stage disease. However, this diagnosis is usually made radiologically, and experienced thoracic surgeons are familiar with the low radiologic to pathologic correlation in tumors that abut the great vessels, mediastinum, or chest wall. Commonly these tumors do not directly invade adjacent structures and are, in fact, T(1) or T(2) tumors that are resectable through standard techniques. Where there is no clearly evident invasion of unresectable structures, the patient should be given the benefit of the doubt and considered at a lower (resectable) stage until proven otherwise. The curability of T(3) tumors varies according to the involved site. A T(3)N(0) tumor involving the chest wall provides the most favorable prognosis among the resected T(3) lesions, with a 5-year survival of >50% in lymph node-negative patients if resection is complete. Palliative incomplete resections of T(4) disease, in which tumor has invaded mediastinal structures, have not shown any survival benefit and are associated with very high morbidity and mortality. However, patients with limited invasion of the carina, left atrium, superior vena cava, or pulmonary artery may be able to be completely resected despite their T(4) classification. Surgical resection remains an important part of the therapy for patients with locally advanced lung cancer. Modern techniques of chest wall resection and reconstruction and bronchoplastic procedures allow complete resection of locally advanced tumors with favorable 5-year survival rates and low morbidity and mortality.

Albumin microspheres as carriers for the antiarthritic drug celecoxib

The present study investigates the preparation of celecoxib-loaded albumin microspheres and the biodistribution of technetium-99m ((99m)Tc)-labeled celecoxib as well as its microspheres after intravenous administration. Microspheres were prepared using a natural polymer BSA using emulsification chemical cross-linking method. The prepared microspheres were characterized for entrapment efficiency, particle size, and in vitro drug release. Surface morphology was studied by scanning electron microscopy. Biodistribution studies were performed by radiolabeling celecoxib (CS) and its microspheres (CMS) using (99m)Tc and injecting arthritic rats intravenously. The geometric mean diameter of the microspheres was found to be 5.46 microm. In vitro release studies indicated that the microspheres sustained the release of the drug for 6 days. Radioactivity measured in different organs after intravenous administration of celecoxib solution showed a significant amount of radioactivity in the liver and spleen. In case of celecoxib-loaded microspheres, a significant amount of radioactivity accumulated in the lungs. No significant difference (P > .1) in the radioactivity was observed between the inflamed joint and the noninflamed joint following intravenous injection of (99m)Tc-CS. However, in case of the microspheres (CMS), the radioactivity present in the inflamed joint was 2.5-fold higher than in the noninflamed joint. The blood kinetic studies revealed that celecoxib-loaded albumin microspheres exhibited prolonged circulation than the celecoxib solution.

Evaluation of cyclooxygenase-2 inhibition in an orthotopic murine model of lung cancer for dose-dependent effect

OBJECTIVES

Cyclooxygenase-2 plays a role in growth, apoptosis, angiogenesis, and metastasis in lung cancer. Inhibition of cyclooxygenase-2 with celecoxib has been shown to inhibit tumor growth. We evaluated the effect of increasing doses of celecoxib in a murine model of human lung cancer.

METHODS

Human lung adenocarcinoma cells (A549) were implanted in the left lung upper lobe of mice with severe combined immunodeficiency syndrome. Mice were randomly assigned to 4 groups at implantation (n = 10 per group): control, 125 mg/kg chow, 500 mg/kg chow, 1000 mg/kg chow. After 3 weeks, mice were killed, and a blinded observer measured total tumor volume. The dose effect of celecoxib was examined in vitro by studying cell proliferation, expression of cyclooxygenase-2 (mRNA and protein), and production of prostaglandin E 2 in unstimulated and interleukin 1beta-stimulated cells.

RESULTS

All 40 mice survived for 3 weeks with no observed toxicities. Total tumor volume was inhibited in each celecoxib group ( P = .0038, Welch analysis of variance): 206.7 +/- 119.5 mm 3 (control group), 41.4 +/- 54.0 mm 3 (low-dose group), 34.5 +/- 39.3 mm 3 (medium-dose group), and 27.3 +/- 53.6 mm 3 (high-dose group). In vitro celecoxib was effective at inhibiting production of prostaglandin E 2 , even in stimulated cells, although little effect was seen on cyclooxygenase-2 protein levels. Inhibition of proliferation was evident only at doses that exceeded those used in the animal model.

CONCLUSION

Inhibition of cyclooxygenase-2 with low-dose celecoxib restricted the growth of lung cancer in this model. This might be mediated by prostaglandin E 2 . Higher doses of celecoxib afforded no additional benefit. Chronic therapy with low-dose cyclooxygenase-2 inhibition has the potential to influence tumor progression in non-small cell lung cancer.

Integrin alpha v beta 3-targeted imaging of lung cancer

A series of radiolabeled cyclic arginine-glycine-aspartic acid (RGD) peptide ligands for cell adhesion molecule integrin alpha v beta 3-targeted tumor angiogenesis targeting are being developed in our laboratory. In this study, this effort continues by applying a positron emitter 64Cu-labeled PEGylated dimeric RGD peptide radiotracer 64Cu-DOTA-PEG-E[c(RGDyK)]2 for lung cancer imaging. The PEGylated RGD peptide indicated integrin alpha v beta 3 avidity, but the PEGylation reduced the receptor binding affinity of this ligand compared to the unmodified RGD dimer. The radiotracer revealed rapid blood clearance and predominant renal clearance route. The minimum nonspecific activity accumulation in normal lung tissue and heart rendered high-quality orthotopic lung cancer tumor images, enabling clear demarcation of both the primary tumor at the upper lobe of the left lung, as well as metastases in the mediastinum, contralateral lung, and diaphragm. As a comparison, fluorodeoxyglucose (FDG) scans on the same mice were only able to identify the primary tumor, with the metastatic lesions masked by intense cardiac uptake and high lung background. 64Cu-DOTA-PEG-E[c(RGDyK)]2 is an excellent position emission tomography (PET) tracer for integrin-positive tumor imaging. Further studies to improve the receptor binding affinity of the tracer and subsequently to increase the magnitude of tumor uptake without comprising the favorable in vivo kinetics are currently in progress.

Signal transduction pathways regulating cyclooxygenase-2 expression: potential molecular targets for chemoprevention

Expression of cyclooxygenase-2 (COX-2) has been reported to be elevated in human colorectal adenocarcinoma and other tumors, including those of breast, cervical, prostate, and lung. Genetic knock-out or pharmacological inhibition of COX-2 has been shown to protect against experimentally-induced carcinogenesis. Results from epidemiological and laboratory studies indicate that regular intake of selective COX-2 inhibitors reduces the risk of several forms of human malignancies. Thus, it is conceivable that targeted inhibition of abnormally or improperly elevated COX-2 provides one of the most effective and promising strategies for cancer chemoprevention. The COX-2 promoter contains a TATA box and binding sites for several transcription factors including nuclear factor-kappaB (NF-kappaB), nuclear factor for interleukin-6/CCAAT enhancer-binding protein (NF-IL6/C/EBP) and cyclic AMP response element (CRE) binding protein. Upregulation of COX-2 is mediated by a variety of stimuli including tumor promoters, oncogenes, and growth factors. Stimulation of either protein kinase C (PKC) or Ras signaling enhances mitogen-activated protein kinase (MAPK) activity, which, in turn, activates transcription of cox-2. Celecoxib, the first US FDA approved selective COX-2 inhibitor, initially developed for the treatment of adult rheumatoid arthritis and osteoarthritis, has been reported to reduce the formation of polyps in patients with familial adenomatous polyposis. This COX-2 specific inhibitor also protects against experimentally-induced carcinogenesis, but the underlying molecular mechanisms are poorly understood. The present review covers the signal transduction pathways responsible for regulating COX-2 expression as novel molecular targets of chemopreventive agents with celecoxib as a specific example.

Celecoxib: a potent cyclooxygenase-2 inhibitor in cancer prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used therapeutic agents in the treatment of pain, inflammation and fever. They may also have a role in the management of cancer prevention, Alzheimer's disease and prophylaxis against cardiovascular disease. These drugs act primarily by inhibiting cyclooxygenase enzyme, which has two isoforms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Selective COX-2 inhibitors provide potent anti-inflammatory and analgesic effects without the side effects of gastric and renal toxicity and inhibition of platelet function. Celecoxib is a potent COX-2 inhibitor being developed for the treatment of rheumatoid arthritis and osteoarthritis. Chemoprevention is the use of pharmacological or natural agents to prevent, suppress, interrupt or reverse the process of carcinogenesis. For this purpose, celecoxib is being used for different cancer types. The effects of NSAIDs on tumor growth remain unclear, but are most likely to be multifocal. In this article, we reviewed COX-2 selectivity, the pharmacological properties of celecoxib, the use of celecoxib for cancer prevention and the mechanisms of chemoprevention.