Cyclooxygenase-2 (COX-2) inhibitors sensitize tumor cells specifically to death receptor-induced apoptosis independently of COX-2 inhibition

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Nimesulide, a COX-2 inhibitor, sensitizes pancreatic cancer cells to TRAIL-induced apoptosis by promoting DR5 clustering †

Nimesulide is a nonsteroidal anti-inflammatory drug and a COX-2 inhibitor with antitumor and antiproliferative activities that induces apoptosis in oral, esophagus, breast, and pancreatic cancer cells. Despite being removed from the market due to hepatotoxicity, nimesulide is still an important research tool being used to develop new anticancer drugs. Multiple studies have been done to modify the nimesulide skeleton to develop more potent anticancer agents and related compounds are promising scaffolds for future development. As such, establishing a mechanism of action for nimesulide remains an important part of realizing its potential. Here, we show that nimesulide enhances TRAIL-induced apoptosis in resistant pancreatic cancer cells by promoting clustering of DR5 in the plasma membrane. In this way, nimesulide acts like a related compound, DuP-697, which sensitizes TRAIL-resistant colon cancer cells in a similar manner. Our approach applies a time-resolved FRET-based biosensor that monitors DR5 clustering and conformational states in the plasma membrane. We show that this tool can be used for future high-throughput screens to identify novel, nontoxic small molecule scaffolds to overcome TRAIL resistance in cancer cells.

Effects of selective cyclooxygenase-2 inhibitor robenacoxib on primary cells derived from feline injection-site sarcoma

Feline injection-site sarcomas (FISSs) are highly invasive malignant mesenchymal neoplasms that arise from injection sites in cats. Although the tumorigenesis of FISSs is still uncertain, there is a consensus that FISS is associated with chronic inflammation caused by irritation of injection-related trauma and foreign chemical substances. Chronic inflammation can provide a proper microenvironment for tumour development, which has been known as one of the risk factors of tumorigenesis in many tumours. To investigate the tumorigenesis of FISS and screen for its potential therapeutic targets, cyclooxygenase-2 (COX-2), an inflammation-enhancing enzyme, was selected as a target for this study. In vitro experiments using FISS- and normal tissue-derived primary cells and robenacoxib, a highly selective COX-2 inhibitor, were performed. The results demonstrated that expression of COX-2 could be detected in formalin-fixed and paraffin-embedded FISS tissues and FISS-derived primary cells. Cell viability, migration and colony formation of FISS-derived primary cells were inhibited, and cell apoptosis was enhanced by robenacoxib in a dose-dependent manner. However, susceptibility to robenacoxib varied in different lines of FISS primary cells and was not completely correlated with COX-2 expression. Our results suggest that COX-2 inhibitors could be potential adjuvant therapeutics against FISSs.

Firocoxib as a Potential Neoadjuvant Treatment in Canine Patients with Triple-Negative Mammary Gland Tumors

This study aimed to investigate the pro-apoptotic effects of NSAID (Previcox®) in vitro and in vivo. Two CMT cell lines, one from the primary tumor and one from bone metastasis, were treated with firocoxib and MTT assay was performed to determine the half-maximal inhibitory concentration (IC50) value. The firocoxib IC50 for the cell lines UNESP-CM5 and UNESP-MM1 were 25.21 µM and 27.41 µM, respectively. The cell lines were then treated with the respective firocoxib IC50 concentrations and annexin V/propidium iodide (PI) assay was performed, to detect the induction of apoptosis in both cells (Annexin+/PI+). We conducted an in vivo study involving female dogs affected by CMT and divided them into control and treatment groups. For both groups, a biopsy was performed on day 0 (D0) and a mastectomy was performed on day 14 (D14). In the treatment group, after biopsy on D0, the patients received Previcox® 5 mg/kg PO once a day until mastectomy was performed on D14. COX-2/caspase-3 double immunostaining was performed on samples from D0 and D14, revealing no difference in the control group. In contrast, in the treatment group Previcox® increased the number of COX-2 positive apoptotic cells. Therefore, firocoxib can induce apoptosis in CMT cells in vitro and in vivo, and Previcox® can be a potential neoadjuvant treatment for patients with mammary cancer.

Methoxybenzamide derivative of nimesulide from anti-fever to anti-cancer: chemical characterization and cytotoxicity

The repurposing strategy of converting nimesulide from an anti-fever drug to an anti-cancer agent by modifying its main structure targeting HSP27 is gaining great attention these days. The goal of this study focuses on synthesizing a new nimesulide derivative with new ligands that have biological anti-cancer activities in different cancer models using the in-vitro assay. Nimesulide derivative L1 was synthesized, characterized by 1H NMR, 13C NMR, FTIR, melting point, mass spectra, and TGA analysis. A single crystal was diffracted and showed colorless block group P-1. The results revealed that L1 demonstrates potent anti-cancer activity with lung (H292), ovarian (SKOV3), and breast (SKBR3) cancer cell lines in-vitro models with IC₅₀ values below 8.8 µM.

Chemoprevention in Barrett's esophagus and esophageal adenocarcinoma

There has been a dramatic increase in the incidence of Barrett's esophagus and esophageal adenocarcinoma over the past several decades with a continued rise expected in the future. Several strategies have been developed for screening and surveillance of patients with Barrett's esophagus and endoscopic treatment of Barrett's associated dysplasia and early esophageal cancer; however, they have not made a substantial impact on the incidence of cancer. Herein, chemoprevention becomes an attractive idea for reducing the incidence of cancer in Barrett's patients. Several agents appear promising in preclinical and observational studies but very few have been evaluated in randomized controlled trials. Strongest evidence to date is available for proton-pump inhibitors and Aspirin that have been evaluated in a large randomized controlled trial. Other agents such as statins, metformin, ursodeoxycholic acid, and dietary supplements have insufficient evidence for chemoprevention in Barrett's patients.

Pharmacogenomics of 5-fluorouracil in colorectal cancer: review and update

BACKGROUND

Colorectal cancer (CRC) is a disease with high morbidity and mortality rates. 5-fluorouracil (5-FU) is the first-line recommended drug for chemotherapy in patients with CRC, and it has a good effect on a variety of other solid tumors as well. Unfortunately, however, due to the emergence of drug resistance the effectiveness of treatment may be greatly reduced. In the past decade, major progress has been made in the field of 5-FU drug resistance in terms of molecular mechanisms, pre-clinical (animal) models and clinical trials.

CONCLUSIONS

In this article we systematically review and update current knowledge on 5-FU pharmacogenomics related to drug uptake and activation, the expression and activity of target enzymes (DPD, TS and MTHFR) and key signaling pathways in CRC. Furthermore, a summary of drug combination strategies aimed at targeting specific genes and/or pathways to reverse 5-FU resistance is provided. Based on this, we suggest that causal relationships between genes, pathways and drug sensitivity should be systematically considered from a multidimensional perspective. In the design of research methods, emerging technologies such as CRISPR-Cas, TALENS and patient-derived xenograft models should be applied as far as possible to improve the accuracy of clinically relevant results.

Mechanistic insights of adipocyte metabolism in regulating breast cancer progression

Adipocyte account for the largest component in breast tissue. Dysfunctional adipocyte metabolism, such as metaflammation in metabolically abnormal obese patients, will cause hyperplasia and hypertrophy of its constituent adipocytes. Inflamed adipose tissue is one of the biggest risk factors causing breast cancer. Factors linking adipocyte metabolism to breast cancer include dysfunctional secretion of proinflammatory mediators, proangiogenic factors and estrogens. The accumulation of tumor supporting cells and systemic effects, such as insulin resistance, dyslipidemia and oxidative stress, which are caused by abnormal adipocyte metabolism, further contribute to a more aggressive tumor microenvironment and stimulate breast cancer stem cell to influence the development and progression of breast cancer. Here, in this review, we focus on the adipocyte metabolism in regulating breast cancer progression, and discuss the potential targets which can be used for breast cancer therapy.

α-bisabolol enhances radiotherapy-induced apoptosis in endometrial cancer cells by reducing the effect of XIAP on inhibiting caspase-3

Endometrial cancer (EC) is one of the most common cancers in females. Although the diagnosis and treatment in early stages can greatly improve the survival rate of patients, the advanced EC still is lethal. Radiotherapy is widely used against EC, and it is a great challenge to find an effective way to overcome the resistance of EC during radiotherapy. α-bisabolol is a promising drug, which has already exhibited its anti-tumor effect in some malignancies. Here we reported that α-bisabolol could inhibit the proliferation of EC cells. It is also shown that their abilities of migration and invasion were effectively reduced by α-bisabolol. Furthermore, our results also demonstrated that α-bisabolol could improve sensitivity of EC cells in radiotherapy and further inhibited the growth of EC cells. By Western blot, we found the expression of matrix metalloproteinases-9 (MMP-9) and cyclin E were significantly decreased, which indicated that EC cells can be further suppressed by using α-bisabolol and radiotherapy. It is also demonstrated in our study that the rate of apoptotic cells is markedly increased in EC by using these two treatments. The significant decrease in X-linked inhibitor of apoptosis protein (XIAP) and increase in caspase-3 detected in our study suggested that the enhancement of apoptosis is mediated by XIAP/caspase-3 pathway, which was further confirmed by examining the downstream effectors of caspase-3, COX-2, PARP and cleaved PARP. In the present study, we demonstrated that α-bisabolol could enhance the sensitivity of EC cells to radiotherapy, which provide a novel alternative for overcoming radioresistance of EC cells and achieving a better outcome in radiotherapy.

Aza-BODIPY probe for selective visualization of cyclooxygenase-2 in cancer cells

AZB-IMC₂ was developed as a COX-2 specific probe that exhibited a brighter fluorescence signal in cancer cells that overexpress COX-2 compared to normal cells. Oxidative stress agent-treated inflamed cell lines inducing high COX-2 levels revealed an enhanced fluorescence signal. Inhibitory studies showed a markedly reduced fluorescence intensity in cancer cells. The results suggested that AZB-IMC₂ could be developed as a promising molecular tool for imaging guiding during surgery.

A bivalent indomethacin/Aza-BODIPY conjugate can selectively visualize the COX-2 enzyme in cancer and inflamed cells confirming its potential as a COX-2-specific biomarker in clinical applications.

MDR1A deficiency restrains tumor growth in murine colitis-associated carcinogenesis

Patients with Ulcerative Colitis (UC) have an increased risk to develop colitis-associated colorectal cancer (CAC). Here, we found that protein expression of ABCB1 (ATP Binding Cassette Subfamily B Member 1) / MDR1 (multidrug resistance 1) was diminished in the intestinal mucosa of patients with active UC with or without CAC, but not in non-UC patients with sporadic colon cancer. We investigated the consequences of ABCB1/MDR1 loss-of-function in a common murine model for CAC (AOM/DSS). Mice deficient in MDR1A (MDR1A KO) showed enhanced intratumoral inflammation and cellular damage, which were associated with reduced colonic tumor size and decreased degree of dysplasia, when compared to wild-type (WT). Increased cell injury correlated with reduced capacity for growth of MDR1A KO tumor spheroids cultured ex-vivo. Gene expression analysis by microarray demonstrated that MDR1A deficiency shaped the inflammatory response towards an anti-tumorigenic microenvironment by downregulating genes known to be important mediators of cancer progression (PTGS2 (COX2), EREG, IL-11). MDR1A KO tumors showed increased gene expression of TNFSF10 (TRAIL), a known inducer of cancer cell death, and CCL12, a strong trigger of B cell chemotaxis. Abundant B220+ B lymphocyte infiltrates with interspersed CD138+ plasma cells were recruited to the MDR1A KO tumor microenvironment, concomitant with high levels of immunoglobulin light chain genes. In contrast, MDR1A deficiency in RAG2 KO mice that lack both B and T cells aggravated colonic tumor progression. MDR1A KO CD19+ B cells, but not WT CD19+ B cells, suppressed growth of colonic tumor-derived spheroids from AOM/DSS-WT mice in an ex-vivo co-culture system, implying that B-cell regulated immune responses contributed to delayed tumor development in MDR1A deficiency. In conclusion, we provide first evidence that loss of ABCB1/MDR1 function may represent an essential tumor-suppressive host defense mechanism in CAC.

Red Raspberry Phenols Inhibit Angiogenesis: A Morphological and Subcellular Analysis Upon Human Endothelial Cells

Polyphenols are a class of natural compounds whose potential as antioxidant, anti-inflammatory, and anti-angiogenesis has been reported in many pathological conditions. Red raspberry extract, rich in polyphenols, has been reported to exert anti-inflammatory effects and prevent cell proliferation in distinct animal models. However, the signaling pathways involved remain unknown. Herein, we used human microvascular endothelial cells (HMVECs) to determine the influence of red raspberry phenolic compound extract concentrations, ranging from 10 to 250 µg gallic acid equivalents (GAE)/mL, on endothelium viability (MTS assay), proliferation (BrdU incorporation), migration (injury assay), and capillary-like structures formation (Matrigel assay). Protein expression in cell lysates was determined by Western blot analysis. We showed that red raspberry extracts reduced cell viability (GI50  = 87,64 ± 6,59 μg GAE/mL) and proliferation in a dose-dependent manner. A significant abrogation of cells ability to migrate to injured areas, even at low concentrations, was observed by injury assay. Cell assembly into capillary-like structures on Matrigel also decreased in a dose dependent-manner for higher extract concentrations, as well as the number of branching points per unit of area. Protein expression analysis showed a dose-dependent decrease in Phospho-VEGFR2 expression, implying abrogation of VEGF signaling activity. We also showed for the first time that red raspberry phenolic compounds induce the rearrangement of filamentous actin cytoskeleton, with an isotropy increase found for higher testing concentrations. Taken together, our findings corroborate the anti-angiogenic potential of red raspberry phenolic compounds and provide new insights into their mode of action upon endothelium. J. Cell. Biochem. 117: 1604-1612, 2016. © 2015 Wiley Periodicals, Inc.

Therapeutic potential of cyclooxygenase-3 inhibitors in the management of glioblastoma

In this study we investigated the expression of COX-1, COX-2 and COX-3 mRNA in C6 glioblastoma and normal brain tissues and the effects of acetaminophen, indomethacin or metamizole treatments on the development of C6 glioblastoma in relation with COX inhibition. Glioblastoma cells were inoculated intracerebrally into frontal lobe of adult male Wistar albino rats. 10 days after inoculation, rats were treated with 150 mg/kg acetaminophen, 10 mg/kg indomethacin or 150 mg/kg metamizole. The tumor size was measured histologically and total RNA was isolated from tumor or normal brain tissue and mRNA levels of COX isoforms were determined by qRT-PCR. Our results showed the presence of COX-1, COX-2 and COX-3 expressions in both C6 glioblastoma and normal brain tissues. In tumor tissues COX-3 expression was significantly higher than normal brain tissue (p < 0.05) while there was no significant difference in COX-1 and COX-2 expressions. Acetaminophen and indomethacin decreased the tumor size by 71 and 43 % by inhibiting COX-3 mRNA expression around 87 and 91 % respectively. For the first time our study proposes a possible relationship between COX-3 mRNA expression and C6 glioblastoma development. We also suggested that the inhibition of COX-3 enzyme may be responsible for decrease in tumor size in part, the mechanism by which acetaminophen and indomethacin decreased rat C6 glioblastoma growth. However, the molecular events responsible for COX-3 effects on tumor development are still unresolved as these drugs exert their anti-cancer effect via both COX-3 dependent and independent mechanisms.

DNA-hypomethylating agent, 5'-azacytidine, induces cyclooxygenase-2 expression via the PI3-kinase/Akt and extracellular signal-regulated kinase-1/2 pathways in human HT1080 fibrosarcoma cells

The cytosine analogue 5'-azacytidine (5'-aza) induces DNA hypomethylation by inhibiting DNA methyltransferase. In clinical trials, 5'-aza is widely used in epigenetic anticancer treatments. Accumulated evidence shows that cyclooxygenase-2 (COX-2) is overexpressed in various cancers, indicating that it may play a critical role in carcinogenesis. However, few studies have been performed to explore the molecular mechanism underlying the increased COX-2 expression. Therefore, we tested the hypothesis that 5'-aza regulates COX-2 expression and prostaglandin E2 (PGE2) production. The human fibrosarcoma cell line HT1080, was treated with various concentrations of 5'-aza for different time periods. Protein expressions of COX-2, DNA (cytosine-5)-methyltransferase 1 (DNMT1), pAkt, Akt, extracellular signal-regulated kinase (ERK), and phosphorylated ERK (pERK) were determined using western blot analysis, and COX-2 mRNA expression was determined using RT-PCR. PGE2 production was evaluated using the PGE2 assay kit. The localization and expression of COX-2 were determined using immunofluorescence staining. Treatment with 5'-aza induces protein and mRNA expression of COX-2. We also observed that 5'-aza-induced COX-2 expression and PGE2 production were inhibited by S-adenosylmethionine (SAM), a methyl donor. Treatment with 5'-aza phosphorylates PI3-kinase/Akt and ERK-1/2; inhibition of these pathways by LY294002, an inhibitor of PI3-kinase/Akt, or PD98059, an inhibitor of ERK-1/2, respectively, prevents 5'-aza-induced COX-2 expression and PGE2 production. Overall, these observations indicate that the hypomethylating agent 5'-aza modulates COX-2 expression via the PI3-kinase/Akt and ERK-1/2 pathways in human HT1080 fibrosarcoma cells.

Potency of non-steroidal anti-inflammatory drugs in chemotherapy

Cancer cell resistance, particularly multidrug resistance (MDR), is the leading cause of chemotherapy failure. A number of mechanisms involved in the development of MDR have been described, including the overexpression of ATP-dependent membrane-bound transport proteins. The enhanced expression of these proteins, referred to as ATP-binding cassette (ABC) transporters, results in an increased cellular efflux of the cytotoxic drug, thereby reducing its intracellular concentration to an ineffective level. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently consumed drugs worldwide. NSAIDs are mainly used to treat pain, fever and inflammation. Numerous studies suggest that NSAIDs also show promise as anticancer drugs. NSAIDs have been shown to reduce cancer cell proliferation, motility, angiogenesis and invasiveness. In addition to these effects, NSAIDs have been shown to induce apoptosis in a wide variety of cancer types. Moreover, several studies have indicated that NSAIDs may sensitise cancer cells to the antiproliferative effects of cytotoxic drugs by modulating ABC transporter activity. Therefore, combining specific NSAIDs with chemotherapeutic drugs may have clinical applications. Such treatments may allow for the use of a lower dose of cytotoxic drugs and may also enhance the effectiveness of therapy. The objective of this review was to discuss the possible role of NSAIDs in the modulation of antitumour drug cytotoxicity. We particularly emphasised on the use of COX-2 inhibitors in combination with chemotherapy and the molecular and cellular mechanisms underlying the alterations in outcome that occur in response to this combination therapy.

TRAIL-mediated apoptosis in breast cancer cells cultured as 3D spheroids

TNF-alpha-related-apoptosis-inducing-ligand (TRAIL) has been explored as a therapeutic drug to kill cancer cells. Cancer cells in the circulation are subjected to apoptosis-inducing factors. Despite the presence of these factors, cells are able to extravasate and metastasize. The homotypic and heterotypic cell-cell interactions in a tumor are known to play a crucial role in bestowing important characteristics to cancer cells that leave the primary site. Spheroid cell culture has been extensively used to mimic these physiologically relevant interactions. In this work, we show that the breast cancer cell lines BT20 and MCF7, cultured as 3D tumor spheroids, are more resistant to TRAIL-mediated apoptosis by downregulating the expression of death receptors (DR4 and DR5) that initiate TRAIL-mediated apoptosis. For comparison, we also investigated the effect of TRAIL on cells cultured as a 2D monolayer. Our results indicate that tumor spheroids are enriched for CD44^hiCD24^loALDH1^hi cells, a phenotype that is predominantly known to be a marker for breast cancer stem cells. Furthermore, we attribute the TRAIL-resistance and cancer stem cell phenotype observed in tumor spheroids to the upregulation of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE₂) pathway. We show that inhibition of the COX-2/PGE₂ pathway by treating tumor spheroids with NS-398, a selective COX-2 inhibitor, reverses the TRAIL-resistance and decreases the incidence of a CD44^hiCD24^lo population. Additionally, we show that siRNA mediated knockdown of COX-2 expression in MCF7 cells render them sensitive to TRAIL by increasing the expression of DR4 and DR5. Collectively, our results show the effect of the third-dimension on the response of breast cancer cells to TRAIL and suggest a therapeutic target to overcome TRAIL-resistance.

Cyclooxygenase-2 and the inflammogenesis of breast cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that constitutive overexpression of cyclooxygenase-2 (COX-2) is a ubiquitous driver of mammary carcinogenesis, and reciprocally, that COX-2 blockade has strong potential for breast cancer prevention and therapy. Key findings include the following: (1) COX-2 is constitutively expressed throughout breast cancer development and expression intensifies with stage at detection, cancer progression and metastasis; (2) essential features of mammary carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis and immunosuppression) are linked to COX-2-driven prostaglandin E2 (PGE-2) biosynthesis; (3) upregulation of COX-2 and PGE-2 expression induces transcription of CYP-19 and aromatase-catalyzed estrogen biosynthesis which stimulates unbridled mitogenesis; (4) extrahepatic CYP-1B1 in mammary adipose tissue converts paracrine estrogen to carcinogenic quinones with mutagenic impact; and (5) agents that inhibit COX-2 reduce the risk of breast cancer in women without disease and reduce recurrence risk and mortality in women with breast cancer. Recent sharp increases in global breast cancer incidence and mortality are likely driven by chronic inflammation of mammary adipose and upregulation of COX-2 associated with the obesity pandemic. The totality of evidence clearly supports the supposition that mammary carcinogenesis often evolves as a progressive series of highly specific cellular and molecular changes in response to induction of constitutive over-expression of COX-2 and the prostaglandin cascade in the “inflammogenesis of breast cancer”.

Cyclooxygenase-1 and -2: molecular targets for cervical neoplasia

Cyclooxygenase (COX) is a key enzyme responsible for inflammation, converting arachidonic acid to prostaglandin and thromboxane. COX has at least two isoforms, COX-1 and COX-2. While COX-1 is constitutively expressed in most tissues for maintaining physiologic homeostasis, COX-2 is induced by inflammatory stimuli including cytokines and growth factors. Many studies have shown that COX-2 contributes to cancer development and progression in various types of malignancy including cervical cancer. Human papillomavirus, a necessary cause of cervical cancer, induces COX-2 expression via E5, E6 and E7 oncoproteins, which leads to prostaglandin E2 increase and the loss of E-cadherin, promotes cell proliferation and production of vascular endothelial growth factor. It is strongly suggested that COX-2 is associated with cancer development and progression such as lymph node metastasis. Many studies have suggested that non-selective COX-2 inhibitors such as non-steroidal anti-inflammatory drugs (NSAIDs), and selective COX-2 inhibitors might show anti-cancer activity in COX-2 -dependent and -independent manners. Two phase II trials for patients with locally advanced cervical cancer showed that celecoxib increased toxicities associated with radiotherapy. Contrary to these discouraging results, two phase II clinical trials, using rofecoxib and celecoxib, demonstrated the promising chemopreventive effect for patients with cervical intraepithelial neoplasia 2 or 3. However, these agents cause a rare, but serious, cardiovascular complication in spite of gastrointestinal protection in comparison with NSAIDs. Recent pharmacogenomic studies have showed that the new strategy for overcoming the limitation in clinical application of COX-2 inhibitors shed light on the use of them as a chemopreventive method.

Gallic acid: molecular rival of cancer

Gallic acid, a predominant polyphenol, has been shown to inhibit carcinogenesis in animal models and in vitro cancerous cell lines. The inhibitory effect of gallic acid on cancer cell growth is mediated via the modulation of genes which encodes for cell cycle, metastasis, angiogenesis and apoptosis. Gallic acid inhibits activation of NF-κB and Akt signaling pathways along with the activity of COX, ribonucleotide reductase and GSH. Moreover, gallic acid activates ATM kinase signaling pathways to prevent the processes of carcinogenesis. The data so far available, both from in vivo and in vitro studies, indicate that this dietary polyphenol could be promising agent in the field of cancer chemoprevention.

Radiosensitization in prostate cancer: mechanisms and targets

Prostate cancer is the second most commonly diagnosed cancer in American men over the age of 45 years and is the third most common cause of cancer related deaths in American men. In 2012 it is estimated that 241,740 men will be diagnosed with prostate cancer and 28,170 men will succumb to prostate cancer. Currently, radiation therapy is one of the most common definitive treatment options for localized prostate cancer. However, significant number of patients undergoing radiation therapy will develop locally persistent/recurrent tumours. The varying response rates to radiation may be due to 1) tumor microenvironment, 2) tumor stage/grade, 3) modality used to deliver radiation, and 4) dose of radiation. Higher doses of radiation has not always proved to be effective and have been associated with increased morbidity. Compounds designed to enhance the killing effects of radiation, radiosensitizers, have been extensively investigated over the past decade. The development of radiosensitizing agents could improve survival, improve quality of life and reduce costs, thus benefiting both patients and healthcare systems. Herin, we shall review the role and mechanisms of various agents that can sensitize tumours, specifically prostate cancer.

Epigenetic deregulation of the COX pathway in cancer

Inflammation is a major cause of cancer and may condition its progression. The deregulation of the cyclooxygenase (COX) pathway is implicated in several pathophysiological processes, including inflammation and cancer. Although, its targeting with nonsteroidal antiinflammatory drugs (NSAIDs) and COX-2 selective inhibitors has been investigated for years with promising results at both preventive and therapeutic levels, undesirable side effects and the limited understanding of the regulation and functionalities of the COX pathway compromise a more extensive application of these drugs. Epigenetics is bringing additional levels of complexity to the understanding of basic biological and pathological processes. The deregulation of signaling and biosynthetic pathways by epigenetic mechanisms may account for new molecular targets in cancer therapeutics. Genes of the COX pathway are seldom mutated in neoplastic cells, but a large proportion of them show aberrant expression in different types of cancer. A growing body of evidence indicates that epigenetic alterations play a critical role in the deregulation of the genes of the COX pathway. This review summarizes the current knowledge on the contribution of epigenetic processes to the deregulation of the COX pathway in cancer, getting insights into how these alterations may be relevant for the clinical management of patients.

Regulation of apoptosis in human melanoma and neuroblastoma cells by statins, sodium arsenite and TRAIL: a role of combined treatment versus monotherapy

Treatment of melanoma cells by sodium arsenite or statins (simvastatin and lovastatin) dramatically modified activities of the main cell signaling pathways resulting in the induction of heme oxygenase-1 (HO-1) and in a downregulation of cyclooxygenase-2 (COX-2) protein levels. Through heme degradation and the production of carbon monoxide and biliverdin, HO-1 plays a protective role in different scenario of oxidative stress followed by mitochondrial apoptosis. Both sodium arsenite and statins could be efficient inducers of apoptosis in some melanoma cell lines, but often exhibited only modest proapoptotic activity in others, due to numerous protective mechanisms. We demonstrated in the present study that treatment by sodium arsenite or statins with an additional inhibition of HO-1 expression (or activation) caused a substantial upregulation of apoptosis in melanoma cells. Sodium arsenite- or statin-induced apoptosis was independent of BRAF status (wild type versus V600E) in melanoma lines. Monotreatment required high doses of statins (20-40 μM) for effective induction of apoptosis. As an alternative approach, pretreatment of melanoma cells with statin at decreased doses (5-20 μM) dramatically enhanced TRAIL-induced apoptosis, due to suppression of the NF-κB and STAT3-transcriptional targets (including COX-2) and downregulation of cFLIP-L (a caspase-8 inhibitor) protein levels. Furthermore, combined treatment with sodium arsenite and TRAIL or simvastatin and TRAIL efficiently induced apoptotic commitment in human neuroblastoma cells. In summary, our findings on enhancing effects of combined treatment of cancer cells using statin and TRAIL provide the rationale for further preclinical evaluation.

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

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

Anti-angiogenic and anti-inflammatory properties of kahweol, a coffee diterpene

Background

Epidemiological studies have shown that unfiltered coffee consumption is associated with a low incidence of cancer. This study aims to identify the effects of kahweol, an antioxidant diterpene contained in unfiltered coffee, on angiogenesis and key inflammatory molecules.

Methodology/Principal Findings

The experimental procedures included in vivo angiogenesis assays (both the chicken and quail choriallantoic membrane assay and the angiogenesis assay with fluorescent zebrafish), the ex vivo mouse aortic ring assay and the in vitro analysis of the effects of treatment of human endothelial cells with kahweol in cell growth, cell viability, cell migration and zymographic assays, as well as the tube formation assay on Matrigel. Additionally, two inflammation markers were determined, namely, the expression levels of cyclooxygenase 2 and the levels of secreted monocyte chemoattractant protein-1. We show for the first time that kahweol is an anti-angiogenic compound with inhibitory effects in two in vivo and one ex vivo angiogenesis models, with effects on specific steps of the angiogenic process: endothelial cell proliferation, migration, invasion and tube formation on Matrigel. We also demonstrate the inhibitory effect of kahweol on the endothelial cell potential to remodel extracellular matrix by targeting two key molecules involved in the process, MMP-2 and uPA. Finally, the anti-inflammatory potential of this compound is demonstrated by its inhibition of both COX-2 expression and MCP-1 secretion in endothelial cells.

Conclusion/Significance

Taken together, our data indicate that, indeed, kahweol behaves as an anti-inflammatory and anti-angiogenic compound with potential use in antitumoral therapies. These data may contribute to the explanation of the reported antitumoral effects of kahweol, including the recent epidemiological meta-analysis showing that drinking coffee could decrease the risk of certain cancers.

COX-2 inhibitors block chemotherapeutic agent-induced apoptosis prior to commitment in hematopoietic cancer cells

Enzymatic inhibitors of pro-inflammatory cyclooxygenase-2 (COX-2) possess multiple anti-cancer effects, including chemosensitization. These effects are not always linked to the inhibition of the COX-2 enzyme. Here we analyze the effects of three COX-2 enzyme inhibitors (nimesulide, NS-398 and celecoxib) on apoptosis in different hematopoietic cancer models. Surprisingly, COX-2 inhibitors strongly prevent apoptosis induced by a panel of chemotherapeutic agents. We selected U937 cells as a model of sensitive cells for further studies. Here, we provide evidence that the protective effect is COX-independent. No suppression of the low basal prostaglandin (PG)E(2) production may be observed upon treatment by COX-2 inhibitors. Besides, the non-active celecoxib analog 2,5-dimethyl-celecoxib is able to protect from apoptosis as well. We demonstrate early prevention of the stress-induced apoptotic signaling, prior to Bax/Bak activation. This preventive effect fits with an impairment of the ability of chemotherapeutic agents to trigger apoptogenic stress. Accordingly, etoposide-induced DNA damage is strongly attenuated in the presence of COX-2 inhibitors. In contrast, COX-2 inhibitors do not exert any anti-apoptotic activity when cells are challenged with physiological stimuli (anti-Fas, TNFα or Trail) or with hydrogen peroxide, which do not require internalization and/or are not targeted by chemoresistance proteins. Altogether, our findings show a differential off-target anti-apoptotic effect of COX-2 inhibitors on intrinsic vs. extrinsic apoptosis at the very early steps of intracellular signaling, prior to commitment. The results imply that an exacerbation of the chemoresistance phenomena may be implicated.

Cyclooxygenase-2 in oncogenesis

Compelling experimental and clinical evidence supports the notion that cyclooxygenase-2, the inducible isoform of cyclooxygenase, plays a crucial role in oncogenesis. Clinical and epidemiological data indicate that aberrant regulation of cyclooxygenase-2 in certain solid tumors and hematological malignancies is associated with adverse clinical outcome. Moreover, findings extrapolated from experimental studies in cultured tumor cells and animal tumor models indicate that cyclooxygenase-2 critically influences all stages of tumor development from tumor initiation to tumor progression. Cyclooxygenase-2 elicits cell-autonomous effects on tumor cells resulting in stimulation of growth, increased cell survival, enhanced tumor cell invasiveness, stimulation of neovascularization, and tumor evasion from the host immune system. Additionally, the oncogenic effects of cyclooxygenase-2 stem from its unique ability to impact tumor cell surroundings and create a proinflammatory environment conducive for tumor development, growth and progression. The initial enthusiasm generated by the availability of cyclooxygenase-2 selective inhibitors for cancer prevention and therapy has been lessened by the severe cardiovascular adverse side effects associated with their long-term use, as well as by the mixed results of recent clinical trials evaluating the efficacy of cyclooxygenase-2 inhibitors in adjuvant chemotherapy. Therefore, our ability to efficiently target the oncogenic effects of cyclooxygenase-2 for therapeutic and preventive purposes strictly depends on a better understanding of the spatial and temporal aspects of its activation in tumor cells along with a clearer elucidation of the signaling networks whereby cyclooxygenase-2 affects tumor cells and their interactions with the tumor microenvironment. This knowledge has the potential of leading to the identification of novel cyclooxygenase-2-dependent molecular and signaling networks that can be exploited to improve cancer prevention and therapy.

Combined treatment with the Cox-2 inhibitor niflumic acid and PPARγ ligand ciglitazone induces ER stress/caspase-8-mediated apoptosis in human lung cancer cells

The present study was performed to investigate the possible combined use of the Cox-2 inhibitor niflumic acid and the PPARγ ligand ciglitazone and to elucidate the mechanisms underlying enhanced apoptosis by this combination treatment in human lung cancer cells. Combined niflumic acid-ciglitazone treatment synergistically induced apoptotic cell death, activated caspase-9, caspase-3, and induced caspase-3-mediated PARP cleavage. The combination treatment also triggered apoptosis through caspase-8/Bid/Bax activation, and the inhibition of caspase-8 suppressed caspase-8/Bid activation, caspase-3-mediated PARP cleavage, and concomitant apoptosis. In addition, combined niflumic acid-ciglitazone treatment significantly induced ER stress responses, and suppression of CHOP expression significantly attenuated the combined niflumic acid-ciglitazone treatment-induced activation of caspase-8 and caspase-3, and the subsequent apoptotic cell death, indicating a role of ER stress in caspase-8 activation and apoptosis. Interestingly, the pro-apoptotic effects of combined niflumic acid-ciglitazone treatment were realized through Cox-2- and PPARγ-independent mechanisms. Taken together, these results suggest that sequential ER stress and caspase-8 activation are critical in combined niflumic acid-ciglitazone treatment-induced apoptosis in human lung cancer cells.

The role of cyclooxygenase-2 in cell proliferation and cell death in human malignancies

It is well admitted that the link between chronic inflammation and cancer involves cytokines and mediators of inflammatory pathways, which act during the different steps of tumorigenesis. The cyclooxygenases (COXs) are a family of enzymes, which catalyze the rate-limiting step of prostaglandin biosynthesis. This family contains three members: ubiquitously expressed COX-1, which is involved in homeostasis; the inducible COX-2 isoform, which is upregulated during both inflammation and cancer; and COX-3, expressed in brain and spinal cord, whose functions remain to be elucidated. COX-2 was described to modulate cell proliferation and apoptosis mainly in solid tumors, that is, colorectal, breast, and prostate cancers, and, more recently, in hematological malignancies. These findings prompt us to analyze here the effects of a combination of COX-2 inhibitors together with different clinically used therapeutic strategies in order to further improve the efficiency of future anticancer treatments. COX-2 modulation is a promising field investigated by many research groups.

Enhancement of 5-fluorouracil efficacy on high COX-2 expressing HCA-7 cells by low dose indomethacin and NS-398 but not on low COX-2 expressing HT-29 cells

The antiproliferative effect of 5-fluorouracil (5-FU) in the presence of low dose non-steroidal anti-inflammatory drugs (NSAIDs) on high cyclooxygenase-2 (COX-2)-expressing HCA-7 and low COX-2-expressing HT-29 colon carcinoma cell lines was investigated. Pharmacogenetic parameters were studied to characterize the 5-FU sensitivity of the two cell lines. Thymidylate synthase (TS) and methylenetetrahydrofolate reductase (MTHFR) polymorphisms were determined by PCR analysis. Cell proliferation was measured by SRB assay, cell cycle distribution and apoptosis by FACS analysis. Cyclooxygenase expression was detected by Western blot and also by fluorescence microscopy. Prostaglandin E(2) (PGE(2)) levels were investigated with ELISA kit. The HT-29 cell line was found to be homozygous for TS 2R and 1494ins6 and T homozygous for MTHFR 677 polymorphisms predicting high 5-FU sensitivity (IC(50): 10 microM). TS 3R homozygosity, TS 1496del6 and MTHFR 677CT heterozygosity may explain the modest 5-FU sensitivity (IC(50): 1.1 mM) of the HCA-7 cell line. Indomethacin and NS-398 (10 microM and 1.77 microM, respectively) reduced the PGE(2) level in HCA-7 cells (>90%). Low concentrations of NSAIDs without antiproliferative potency increased the S-phase arrest and enhanced the cytotoxic action of 5-FU only in HCA-7 cells after 48-hours treatment. The presented data suggested that the enhancement of 5-FU cytotoxicity by indomethacin or NS-398 applied in low dose is related to the potency of NSAIDs to modulate the cell-cycle distribution and the apoptosis; however, it seems that this effect might be dependent on cell phenotype, namely on the COX-2 expression.

Enhanced 5-fluorouracil cytotoxicity in high cyclooxygenase-2 expressing colorectal cancer cells and xenografts induced by non-steroidal anti-inflammatory drugs via downregulation of dihydropyrimidine dehydrogenase

PURPOSE

To prove that 5-FU cytotoxicity could be increased by combination with low-dose non-steroidal anti-inflammatory drugs (NSAIDs) (indomethacin or NS-398) in high cyclooxygenase-2- (COX-2) expressing cells and xenografts through the modulation of dihydropyrimidine dehydrogenase (DPD) mRNA expression and/or enzyme activity.

METHODS

HT-29 cells were grown on collagen IV coated plates (HT-29-C). The antiproliferative effect of 5-fluorouracil (5-FU) +/- NSAIDs was examined on non-COX-2 expressing HT-29 and COX-2-expressing HT-29-C cells by sulphorhodamine B assay. The COX-2 and DPD expressions were visualized by immunofluorescent staining, and prostaglandin E(2) levels were measured by ELISA kit. The HT-29 xenograft was established in SCID mice and treated with 5-FU +/- NSAIDs for 5 days. The tumor volume, enzyme activity, and DPD mRNA expression were investigated by caliper, radioenzymatic method, and real-time RT-PCR, respectively. The drug interaction was calculated for both combinations (5-FU + indomethacin and 5-FU + NS-398).

RESULTS

Collagen IV up-regulated significantly the COX-2 and DPD mRNA, and protein expressions, and also their enzyme activities in HT-29 cells. NSAIDs enhanced in a synergistic manner the cytotoxic effect of 5-FU treatment both in vitro and in vivo. Downregulation of DPD was observed after 5-FU monotherapy, but the combined effect of NSAIDs and 5-FU on DPD mRNA expression, and enzyme activity was superior to the effect of 5-FU alone.

CONCLUSIONS

Since 5-FU + NSAID treatment can alter the DPD enzyme activity resulting in an enhanced cytotoxic effect, further studies in clinical practice are warranted.

Synthesis of hyaluronan in oesophageal cancer cells is uncoupled from the prostaglandin-cAMP pathway

BACKGROUND AND PURPOSE

Cyclooxygenase-2 (COX2) and hyaluronic acid (HA) are common in tumours and both independently promote tumour progression. Furthermore, COX2-dependent synthesis of prostaglandins (PGs) stimulates HA synthase-1 (HAS1) and HAS2 mRNA expression, together with HA synthesis via the cAMP/protein kinase A pathway in vascular smooth muscle cells. Therefore, the aim of the present study was to elucidate whether COX2-mediated PGs induce transcription of HAS isoforms in cancer cells as well.

EXPERIMENTAL APPROACH

Human oesophageal squamous cell (OSC) carcinoma specimens were characterized with respect to HA, COX2 and CD44 expression by immunohistochemistry. OSC cell lines (OSC1, OSC2) and HeLa cell lines (D98, H21) were exposed to exogenous PG analoques (100 nmol.L(-1)), etoricoxib (10 micromol.L(-1)) and forskolin (10 micromol.L(-1)). Subsequently, cAMP levels, HA secretion and HAS isoform expression were determined by elisa and real-time RT-PCR (reverse transcriptase polymerase chain reaction) respectively.

KEY RESULTS

COX2, HA and CD44 were detected immunohistochemically in >90% of human oesophageal tumour samples. Under basal conditions, OSC1 and OSC2 cells express HAS2 and HAS3, COX2 and Galpha(s)-coupled EP(2) and EP(4) PG receptors. Neither stimulation with the PGI(2) analogue, iloprost, addition of exogenous PGE(2) nor forskolin induced HAS1 or HAS2 mRNA expression in OSC1 and OSC2 cells. Furthermore, in HeLa cells after induction of COX2 by tumour necrosis factor alpha and subsequent PGE(2) release, inhibition of COX2 by etoricoxib did not affect HAS expression or HA secretion.

CONCLUSIONS AND IMPLICATIONS

We conclude that in oesophageal and HeLa cancer cells, HAS1/2 expression was not responsive to the PG/cAMP pathway.

Aspirin sensitizes cancer cells to TRAIL-induced apoptosis by reducing survivin levels

PURPOSE

Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and agonistic antibodies targeting its receptors are promising cancer therapies because of their tumor selectivity, many tumors are resistant to TRAIL-based therapies. We examined whether the nonsteroidal anti-inflammatory drug aspirin sensitized cancer cells to TRAIL agonists in vitro and in vivo and investigated the underlying mechanism.

EXPERIMENTAL DESIGN

The effects of aspirin on sensitivity to TRAIL agonists and expression of apoptosis regulators was determined in human breast cancer cell lines and xenograft tumors. The specific role of survivin depletion in the TRAIL-sensitizing effects of aspirin was determined by silencing survivin.

RESULTS

Aspirin sensitized human breast cancer cells, but not untransformed human mammary epithelial cells, to TRAIL-induced caspase activation and apoptosis by a cyclooxygenase-2-independent mechanism. Aspirin also sensitized breast cancer cells to apoptosis induced by a human agonistic TRAIL receptor-2 monoclonal antibody (lexatumumab). Aspirin treatment led to G1 cell cycle arrest and a robust reduction in the levels of the antiapoptotic protein survivin by inducing its proteasomal degradation, but did not affect the levels of many other apoptosis regulators. Silencing survivin with small interfering RNAs sensitized breast cancer cells to TRAIL-induced apoptosis, underscoring the functional role of survivin depletion in the TRAIL-sensitizing actions of aspirin. Moreover, aspirin acted synergistically with TRAIL to promote apoptosis and reduce tumor burden in an orthotopic breast cancer xenograft model.

CONCLUSIONS

Aspirin sensitizes transformed breast epithelial cells to TRAIL-based therapies in vitro and in vivo by a novel mechanism involving survivin depletion. These findings provide the first in vivo evidence for the therapeutic utility of this combination.

Regulation of Cox-2 by cyclic AMP response element binding protein in prostate cancer: potential role for nexrutine

We recently showed that Nexrutine, a Phellodendron amurense bark extract, suppresses proliferation of prostate cancer cell lines and tumor development in the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Our data also indicate that the anti-proliferative effects of Nexrutine are emediated in part by Akt and Cyclic AMP response element binding protein (CREB). Cyclooxygenase (Cox-2), a pro-inflammatory mediator, is a CREB target that induces prostaglandin E(2) (PGE(2)) and suppresses apoptosis. Treatment of LNCaP cells with Nexrutine reduced tumor necrosis factor alpha-induced enzymatic as well as promoter activities of Cox-2. Nexrutine also reduced the expression and promoter activity of Cox-2 in PC-3 cells that express high constitutive levels of Cox-2. Deletion analysis coupled with mutational analysis of the Cox-2 promoter identified CRE as being sufficient for mediating Nexrutine response. Immunohistochemical analysis of human prostate tumors show increased expression of CREB and DNA binding activity in high-grade tumors (three-fold higher in human prostate tumors compared to normal prostate; P = .01). We have identified CREB-mediated activation of Cox-2 as a potential signaling pathway in prostate cancer which can be blocked with a nontoxic, cost-effective dietary supplement like Nexrutine, demonstrating a prospective for development of Nexrutine for prostate cancer management.

Cyclooxygenase-2 (cox-2) and the inflammogenesis of cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that aberrant induction of COX-2 and up-regulation of the prostaglandin cascade play a significant role in carcinogenesis, and reciprocally, blockade of the process has strong potential for cancer prevention and therapy. Supporting evidence includes the following: [1] expression of constitutive COX-2-catalyzed prostaglandin biosynthesis is induced by most cancer-causing agents including tobacco smoke and its components (polycylic aromatic amines, heterocyclic amines, nitrosamines), essential polyunsaturated fatty acids (unconjugated linoleic acid), mitogens, growth factors, proinflammatory cytokines, microbial agents, tumor promoters, and other epigenetic factors, [2] COX-2 expression is a characteristic feature of all premalignant neoplasms, [3] COX-2 expression is a characteristic feature of all malignant neoplasms, and expression intensifies with stage at detection and cancer progression and metastasis, [4] all essential features of carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis, and immunosuppression) are linked to COX-2-driven prostaglandin (PGE-2) biosynthesis, [5] animal studies show that COX-2 up-regulation (in the absence of genetic mutations) is sufficient to stimulate the transformation of normal cells to invasive cancer and metastatic disease, [6] non-selective COX-2 inhibitors, such as aspirin and ibuprofen, reduce the risk of human cancer and precancerous lesions, and [7] selective COX-2 inhibitors, such as celecoxib, reduce the risk of human cancer and precancerous lesions at all anatomic sites thus far investigated. Results confirming that COX-2 blockade is effective for both cancer prevention and therapy have been tempered by observations that some COX2 inhibitors pose a risk to the cardiovascular system, and more studies are needed in order to determine if certain of these drugs can be taken at dosages that prevent cancer without increasing cardiovascular risk. It is emphasized that the "inflammogenesis model of cancer" is not mutually exclusive and may in fact be synergistic with the accumulation of somatic mutations in tumor suppressor genes and oncogenes or epigenetic factors in the development of cancer.

Apoptosis in the treatment of cancer: a promise kept?

A common feature of cancer cells is their ability to evade apoptosis as a result of alterations that block cell death signaling pathways. The extensive research efforts that elucidated these signaling pathways over the past decade have set the stage for the development of therapeutic agents that either kill cancer cells selectively or reset their apoptotic threshold. Over the past two years a number of these agents have been evaluated in preclinical and clinical trials. The results of these studies suggest that it might soon be possible to modulate apoptosis in cancer cells for therapeutic benefit.

TNF-alpha in cancer treatment: molecular insights, antitumor effects, and clinical utility

Tumor necrosis factor alpha (TNF-alpha), isolated 30 years ago, is a multifunctional cytokine playing a key role in apoptosis and cell survival as well as in inflammation and immunity. Although named for its antitumor properties, TNF has been implicated in a wide spectrum of other diseases. The current use of TNF in cancer is in the regional treatment of locally advanced soft tissue sarcomas and metastatic melanomas and other irresectable tumors of any histology to avoid amputation of the limb. It has been demonstrated in the isolated limb perfusion setting that TNF-alpha acts synergistically with cytostatic drugs. The interaction of TNF-alpha with TNF receptor 1 and receptor 2 (TNFR-1, TNFR-2) activates several signal transduction pathways, leading to the diverse functions of TNF-alpha. The signaling molecules of TNFR-1 have been elucidated quite well, but regulation of the signaling remains unclear. Besides these molecular insights, laboratory experiments in the past decade have shed light upon TNF-alpha action during tumor treatment. Besides extravasation of erythrocytes and lymphocytes, leading to hemorrhagic necrosis, TNF-alpha targets the tumor-associated vasculature (TAV) by inducing hyperpermeability and destruction of the vascular lining. This results in an immediate effect of selective accumulation of cytostatic drugs inside the tumor and a late effect of destruction of the tumor vasculature. In this review, covering TNF-alpha from the molecule to the clinic, we provide an overview of the use of TNF-alpha in cancer starting with molecular insights into TNFR-1 signaling and cellular mechanisms of the antitumor activities of TNF-alpha and ending with clinical response. In addition, possible factors modulating TNF-alpha actions are discussed.

Cyclooxygenase-independent effects of aspirin on HT-29 human colon cancer cells, revealed by oligonucleotide microarrays

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation of human colon cancer cells in vitro. Transmission electron microscope detected morphological features of apoptosis in the aspirin-treated (5 mM, 72 h) HT-29 cells in which cyclooxygenoase-2 is catalytically inactive. We investigated aspirin-induced genome-wide expression changes in HT-29 cells and further studied the time- and concentration-dependent expression changes in 374 apoptosis-related genes, which is the first to show stimulation of genome-wide expression of HT-29 cells by aspirin. The most marked effects of aspirin are on ribosome assembly and rRNA metabolism, which could explain why the quasi-apoptotic morphological changes are not accompanied by a classical DNA ladder. These findings demonstrate that aspirin induces apoptosis in HT-29 cells, bolstering the hypothesis that apoptosis may be a mechanism by which NSAIDs inhibit colon carcinogenesis.

A novel member of the IkappaB family, human IkappaB-zeta, inhibits transactivation of p65 and its DNA binding

A novel member of the IkappaB family, human IkappaB-zeta, was identified by a differential screening approach of apoptosis-sensitive and -resistant tumor cells. The protein consists of 6 ankyrin repeats at its COOH terminus and shares about 30% identity with other IkappaB members. IkappaB-zeta associates with both the p65 and p50 subunit of NF-kappaB and inhibits the transcriptional activity as well as the DNA binding of the transcription factor. Interestingly, IkappaB-zeta is localized in the nucleus where it aggregates in matrix-associated deacetylase bodies, indicating that IkappaB-zeta regulates nuclear NF-kappaB activity rather than its nuclear translocation from the cytoplasm. IkappaB-zeta expression itself was regulated by NF-kappaB, suggesting that its activity is controlled in a negative feedback loop. Unlike classical IkappaB proteins, IkappaB-zeta was not degraded upon cell stimulation. Treatment with tumor necrosis factor-alpha, interleukin-1beta, and lipopolysaccharide induced a strong induction of IkappaB-zeta transcripts. Expression of IkappaB-zeta was detected in different tissues including lung, liver, and in leukocytes but not in the brain. Suppression of endogenous IkappaB-zeta by RNA interference rendered cells more resistant to apoptosis, whereas overexpression of IkappaB-zeta was sufficient to induce cell death. Our results, therefore, suggest that IkappaB-zeta functions as an additional regulator of NF-kappaB activity and, hence, provides another control level for the activation of NF-kappaB-dependent target genes.

Cyclooxygenase-2 inhibition sensitizes human colon carcinoma cells to TRAIL-induced apoptosis through clustering of DR5 and concentrating death-inducing signaling complex components into ceramide-enriched caveolae

Cyclooxygenase-2 (COX-2) is up-regulated in human colon carcinomas, and its inhibition is associated with a reduction in tumorigenesis and a promotion of apoptosis. However, the mechanisms responsible for the antitumor effects of COX-2 inhibitors and how COX-2 modulates apoptotic signaling have not been clearly defined. We have shown that COX-2 inhibition sensitizes human colon carcinoma cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by inducing clustering of the TRAIL receptor DR5 at the cell surface and the redistribution of the death-inducing signaling complex components (DR5, FADD, and procaspase-8) into cholesterol-rich and ceramide-rich domains known as caveolae. This process requires the accumulation of arachidonic acid and sequential activation of acid sphingomyelinase for the generation of ceramide within the plasma membrane outer leaflet. The current study highlights a novel mechanism to circumvent colorectal carcinoma cell resistance to TRAIL-mediated apoptosis using COX-2 inhibitors to manipulate the lipid metabolism within the plasma membrane.

An overview of apoptosis and the prevention of colorectal cancer

Colorectal cancer arises as a result of the accumulation of genetic errors many of which affect the control of apoptosis. Effective chemoprevention strategies for colorectal cancer must rectify these genetic defects. Mutation of apc is often the initiating genetic lesion in colorectal cancers that develop along the chromosomal instability pathway. Depending on the cellular context, loss of apc activates the Wnt signalling pathway causing immediate widespread apoptosis of colorectal epithelial cells and defects in differentiation and cell migration. Only cells that are inherently resistant to apoptosis survive this initial wave of apoptosis. These surviving cells constitute the epithelial population that develop into adenomas. Two gene targets of the Wnt signalling pathway are of particular relevance to apoptosis. Although controversial, survivin may function to inhibit apoptosis. MYC has two outputs in normal cells, the induction of apoptosis and proliferation. These opposing functions work so that MYC can only induce cell proliferation in cells if apoptosis is disabled. p53 couples apoptosis to mitogenic signals and survival pathways. Under some circumstances, NF-kappaB can act as an inhibitor of apoptosis possibly through increased expression of bcl-x(L). Tumours that evolve by the microsatellite instability pathway often have mutations in the proapoptotic gene bax. Colonic adenomas express cyclo-oxygenase-2 (COX-2) and may be targets of chemoprevention before the development of malignancy. However, the recent discovery that coxibs increase the risk of serious cardiovascular events limits their use as chemopreventive agents. Nevertheless, aspirin remains a drug of great interest as it is already known to reduce the risk of colorectal cancer by up to 50%. The balance of evidence shows that high vegetable fibre diets can prevent colorectal cancer, probably via the fermentation of butyrate enhancing the apoptotic response to DNA damage.