Evidence for colorectal cancer cell specificity of aspirin effects on NF kappa B signalling and apoptosis

Targeting NF-κB and HIF-1 pathways for the treatment of cancer: part I

The process of chronic inflammation is a common link which connects different kinds of environmental pollutants and infections with tumorigenesis. Transcription factor NF-κB is a common final target for many inflammatory and cell proliferation pathways, independent of the source of stimuli (e.g., cytokines, growth factors, environmental carcinogens, radiation, hypoxia, bacteria, and viruses). Over-activation of NF-κB has been confirmed in many tumors, resulting in worse prognosis for patient survival. Therefore, inhibition of cellular pathways for NF-κB activation is nowadays considered as a promising anti-cancer therapy and is extensively studied in clinical trials, or even has been adopted as an approved therapy in some kinds of cancer.

c-Src dependency of NSAID-induced effects on NF-κB-mediated apoptosis in colorectal cancer cells

Long-term aspirin or related non-steroidal anti-inflammatory drugs (NSAIDs) ingestion can protect against colorectal cancer (CRC). NSAIDs have a pro-apoptotic activity and we have shown that stimulation of the nuclear factor-kappaB (NF-κB) pathway is a key component of this pro-apoptotic effect. However, the upstream pathways have yet to be fully elucidated. Here, we demonstrate that aspirin activates the c-Src tyrosine kinase pathway in CRC cells. We show that c-Src activation occurs in a time- and dose-dependent manner, preceding aspirin-mediated degradation of IκBα, nuclear/nucleolar translocation of NF-κB/RelA and induction of apoptosis. Furthermore, inhibition of c-Src activity, by chemical inhibition or expression of a kinase dead form of the protein abrogates aspirin-mediated degradation of IκBα, nuclear translocation of RelA and apoptosis, suggesting a causal link. Expression of constitutively active c-Src mimics aspirin-induced stimulation of the NF-κB pathway. The NSAIDs sulindac, sulindac sulphone and indomethacin all similarly activate a c-Src-dependent NF-κB and apoptotic response. These data provide compelling evidence that c-Src is an upstream mediator of aspirin/NSAID effects on NF-κB signalling and apoptosis in CRC cells and have relevance to the development of future chemotherapeutic/chemopreventative agents.

Ibuprofen inhibits activation of nuclear {beta}-catenin in human colon adenomas and induces the phosphorylation of GSK-3{beta}

Nonselective cyclooxygenase (COX) inhibitors target many of the same cancer-associated molecular pathways as COX-2-specific inhibitors. Although these nonsteroidal anti-inflammatory drugs (NSAIDs) are often associated with gastrointestinal toxicity, there is renewed interest in their use as colorectal cancer (CRC) chemopreventive agents due to the adverse side effects associated with long-term use of selective COX-2 inhibitors. In this study, we investigated the effects of long-term use (up to 25 years) of NSAIDs (ibuprofen or aspirin) on adenoma pathology and β-catenin-mediated signaling in sporadic human colon adenomas. Although NSAID use did not impact overall adenoma size or degree of dysplasia, it did cause a significant inhibition of nuclear β-catenin localization, which correlated with suppression of cyclin D1 expression. To further elucidate the effect of these agents in regulating β-catenin, we treated SW480 colon cancer cells with a panel of NSAIDs and determined their effects on β-catenin levels and cellular localization. In agreement with our in vivo results, both S-ibuprofen and aspirin were found to decrease total levels of β-catenin while increasing its phosphorylation. In addition, S-ibuprofen induced both degradation of IκBα and nuclear localization of NF-κB. Despite its nuclear localization, however, the activation of the NF-κB target genes, Bcl-2, survivin, and cyclin D1, was suppressed. This reduction in NF-κB transcriptional activity may be due to increased phosphorylation of GSK-3β following S-ibuprofen treatment. These data suggest that ibuprofen can effectively target both the Wnt/β-catenin and NF-κB pathways, and potentially uncovers a novel mechanism through which NSAIDS may exert their chemopreventive efficacy.

Polymorphisms in NFkB, PXR, LXR and risk of colorectal cancer in a prospective study of Danes

Background

Transcription factors and nuclear receptors constitute a link between exposure to heterocyclic amines and polycyclic aromatic hydrocarbons from meat and tobacco smoke and colorectal cancer (CRC) risk. The aim of this study was to investigate if polymorphisms in nuclear factor kappa-B, pregnane X receptor, and liver X receptor were associated with risk of CRC, and to investigate possible interactions with lifestyle factors such as smoking, meat consumption, and NSAID use.

Methods

The polymorphisms nuclear factor kappa-B (NFkB, NFKB1) -94 insertion/deletion ATTG (rs28362491), pregnane X receptor (PXR, NR1I2) A-24381C (rs1523127), C8055T (rs2276707), A7635G (rs6785049), liver X receptor (LXR-β, NR1H3) C-rs1405655T, T-rs2695121C were assessed together with lifestyle factors in a nested case-cohort study of 378 CRC cases and 756 random participants from the Danish prospective Diet, Cancer and Health study of 57,053 persons.

Results

Carriers of NFkB -94deletion were at 1.45-fold higher risk of CRC than homozygous carriers of the insertion allele (incidence rate ratio (IRR) = 1.45, 95% confidence interval (95% CI): 1.10-1.92). There was interaction between this polymorphism and intake of red and processed meat in relation to CRC risk. Carriers of NFkB -94deletion were at 3% increased risk pr 25 gram meat per day (95% CI: 0.98-1.09) whereas homozygous carriers of the insertion were not at increased risk (p for interaction = 0.03). PXR and LXR polymorphisms were not associated with CRC risk. There was no interaction between use of nonsteroid antiinflammatory drugs (NSAID) or smoking status and NFkB, PXR or LXR polymorphisms.

Conclusions

A polymorphism in NFkB was associated with CRC risk and there was interaction between this polymorphism and meat intake in relation to CRC risk. This study suggests a role for NFkB in CRC aetiology.

Inflexinol inhibits colon cancer cell growth through inhibition of nuclear factor-kappaB activity via direct interaction with p50

Kaurane diterpene compounds have been known to be cytotoxic against several cancer cells through inhibition of nuclear factor-kappaB (NF-kappaB) activity. Here, we showed that inflexinol, a novel kaurane diterpene compound, inhibited the activity of NF-kappaB and its target gene expression as well as cancer cell growth through induction of apoptotic cell death in vitro and in vivo. These inhibitory effects on NF-kappaB activity and on cancer cell growth were suppressed by the reducing agents DTT and glutathione and were abrogated in the cells transfected with mutant p50 (C62S). Sol-gel biochip and surface plasmon resonance analysis showed that inflexinol binds to the p50 subunit of NF-kappaB. These results suggest that inflexinol inhibits colon cancer cell growth via induction of apoptotic cell death through inactivation of NF-kappaB by a direct modification of cysteine residue in the p50 subunit of NF-kappaB.

Aspirin, salicylates, and cancer

Evidence from a wide range of sources suggests that individuals taking aspirin and related non-steroidal anti-inflammatory drugs have reduced risk of large bowel cancer. Work in animals supports cancer reduction with aspirin, but no long-term randomised clinical trials exist in human beings, and randomisation would be ethically unacceptable because vascular protection would have to be denied to a proportion of the participants. However, opportunistic trials of aspirin, designed to test vascular protection, provide some evidence of a reduction in cancer, but only after at least 10 years. We summarise evidence for the potential benefit of aspirin and natural salicylates in cancer prevention. Possible mechanisms of action and directions for further work are discussed, and implications for clinical practice are considered.

Anti-tumor effect of non-steroidal anti-inflammatory drugs on human ovarian cancers

Many reports have demonstrated that non-steroidal anti-inflammatory drugs (NSAIDs) suppress malignant transformation and tumor growth, and some NSAIDs are expected to be new anti-cancer agents. In this study, we examined the anti-tumor effects of the non-specific cyclooxygenase (COX) inhibitors aspirin and piroxicam, and the selective COX-2 inhibitor meloxicam on xenotransplanted ovarian cancer. Tumor growth and survival were compared in female nu/nu mice, xenografted with subcutaneous OVCAR-3 tumors or with intraperitoneal DISS tumors and treated with aspirin (200 ppm in diet, everyday), piroxicam (150 ppm in diet, everyday) or meloxicam (162 ppm in diet, everyday). Al, of the agents tested significantly suppressed the growth of OVCAR-3 tumors xenotransplanted subcutaneously as compared to the control. There was a significant difference in inhibition of OVCAR-3 tumor growth between meloxicam and aspirin treatment. Meloxicam and piroxicam treatment significantly prolonged survival of mice with malignant ascites derived from DISS cells as compared to control and aspirin treatment. Mice treated with meloxicam survived significantly longer than those treated with piroxicam. There was no significant difference in survival between control and aspirin treatment. Necropsy revealed that one of the 6 cancer-bearing mice treated with piroxicam suffered from stomach perforation. These results indicate that a selective COX-2 inhibitor produces greater anti-tumor effect against ovarian cancer than a nonselective COX inhibitor and that meloxicam may have a potential of leading to a novel therapeutic strategy against ovarian cancer.

The proapoptotic effects of sulindac, sulindac sulfone and indomethacin are mediated by nucleolar translocation of the RelA(p65) subunit of NF-kappaB

Understanding the mechanisms that underlie the antitumour activity of non-steroidal anti-inflammatory drugs (NSAIDs) against colorectal cancer will allow the development of more effective and specific chemopreventative agents. Modulation of the NF-kappaB pathway has been implicated as a key effector of the antitumour effect of aspirin, but the effects of non-aspirin NSAIDs on this pathway have yet to be fully defined. Here, we demonstrate that sulindac, sulindac sulfone and indomethacin activate the NF-kappaB pathway in colorectal cancer cells, as determined by western blot analysis of cytoplasmic levels of IkappaBalpha and immunocytochemical analysis of nuclear NF-kappaB/RelA. Furthermore, we show that all of these NSAIDs induce nucleolar translocation of the RelA subunit of NF-kappaB. Using RelA deleted for the previously described nucleolar localization signal, we demonstrate that this response is causally involved in the apoptotic effects of these agents. Finally, we demonstrate that NSAID-mediated nucleolar translocation of RelA is associated with downregulation of NF-kappaB-driven transcription and of the NF-kappaB target gene, ICAM-1. These data identify nucleolar translocation of RelA and the associated repression of the NF-kappaB-driven transcription as a central molecular mechanism of NSAID-mediated growth inhibition and apoptosis. As well as providing new understanding of the molecular determinants of RelA function, these findings also have relevance to the development of novel chemotherapeutic and chemopreventative agents.

Crocin from Crocus sativus possesses significant anti-proliferation effects on human colorectal cancer cells

AIM

To investigate the anti-proliferative effects of Crocus sativus extract and its major constituent, crocin, on three colorectal cancer cell lines (HCT-116, SW-480, and HT-29). The cell growth inhibition effect was compared to that of non-small cell lung cancer (NSCLC) cells. In addition, Crocus sativus' effect on non-cancer cells was evaluated.

METHODS

Using high performance liquid chromatography (HPLC), the purity of crocin and the content of crocin extract were determined. Anti-proliferative effects of Crocus sativus extract and crocin on test cells was evaluated by MTS assay.

RESULTS

The purity of crocin was found to be 95.9% and the content of crocin in the extract was 22.9%. Significant concentration-related inhibition effects of the extract on all three colorectal cancer cell lines were observed (P<0.01). The proliferation was reduced most significantly in HCT-116 cells, to 45.5% at 1.0 mg/ml and to 6.8% at 3.0 mg/ml. Crocin at 1.0 mM, significantly reduced HCT-116, SW-480, and HT-29 cell proliferation to 2.8%, 52%, and 16.8%, respectively (P<0.01). Since 3.0 mg/ml Crocus sativus extract contained approximately 0.6 mM crocin, the observed effects suggest that crocin is a major responsible constituent in the extract. Significant anti-proliferative effects were also observed in non-small cell lung cancer cells. However, Crocus sativus extract did not significantly affect the growth of non-cancer young adult mouse colon cells.

CONCLUSION

Data from this study demonstrated that Crocus sativus extract and its major constituent, crocin, significantly inhibited the growth of colorectal cancer cells while not affecting normal cells. Crocus sativus extract should be investigated further as a viable option in the treatment of colorectal cancer.

Exploring the potential chemopreventative effect of aspirin and rofecoxib on hereditary nonpolyposis colorectal cancer-like endometrial cancer cells in vitro through mechanisms involving apoptosis, the cell cycle, and mismatch repair gene expression

Women in hereditary nonpolyposis colorectal cancer (HNPCC) families have up to a 71% lifetime risk for developing endometrial cancer (EC). This compares to the female lifetime risk for colorectal cancer (CRC) in HNPCC of 60%. The basis of HNPCC is an inherited mutation in a mismatch repair gene (MMR). Aspirin and COX2 inhibitors seem to have a chemoprotective effect on CRC in the general population and are the subject of prospective clinical studies in patients at high risk for CRC including HNPCC. There is no evidence that these agents have any protective effect against EC in the general population. This study investigated the effect of aspirin and a COX2 inhibitor (rofecoxib) on an HNPCC EC cell line model (Ishikawa) by assessing the effect on proliferation, apoptosis, the cell cycle, and MMR gene expression. Aspirin inhibits EC cell proliferation by inducing apoptosis and changes in the cell cycle. This effect is not mediated by changes in MMR gene (hMSH2) expression as assessed by quantitative reverse transcription-polymerase chain reaction. Rofecoxib inhibits EC cell proliferation; this did not appear to be mediated by induction of apoptosis, by alterations of the cell cycle, or by changes in MMR gene expression.

NF-kappaB/PPAR gamma and/or AP-1/PPAR gamma 'on/off' switches and induction of CBP in colon adenocarcinomas: correlation with COX-2 expression

BACKGROUND AND AIMS

Several studies indicate that peroxisome proliferator-activated receptor gamma (PPAR gamma) represses activator protein-1 (AP-1) and nuclear factor kappa B (NF-kappaB) transcriptional activity and this negative cross-talk occupies an important role in carcinogenesis. The present study evaluated the differential expression profile of AP-1 constituents (c-FOS and phosphorylated-active pc-JUN), p-I kappaB-alpha (phosphorylated I kappaB-alpha, a signaling intermediate of NF-kappaB pathway), PPAR gamma, cyclic AMP-response element binding-binding protein (CBP, a known AP-1, NF-kappaB, and PPAR gamma transcriptional coactivator), epidermal growth factor receptor (EGF-R), p53, and COX-2 in normal colonic epithelial cells and colon adenocarcinoma cells.

MATERIALS AND METHODS

Immunohistochemical methodology was performed on formalin-fixed, paraffin-embedded sections from 60 patients with colon adenocarcinomas. A molecular profile was created for each patient and the induction or down-regulation of each pathway from normal to cancer cells was documented. Relationships between transcription factors and downstream molecular targets were evaluated by Spearman's rho correlation coefficient and validated by nonparametric Kruskal-Wallis test.

RESULTS/FINDINGS

P-I kappaB-alpha (P<0.001), CBP (P<0.001), c-FOS (P=0.047), pc-JUN (P=0.047), and EGF-R (P<0.001) were up-regulated in colon adenocarcinomas while PPAR gamma (P<0.001) was concomitantly down-regulated. p-I kappaB-alpha, CBP, pc-JUN, EGF-R, and p53 expression all correlated positively with COX-2 while PPAR gamma expression correlated inversely with COX-2.

INTERPRETATION/CONCLUSION

NF-kappaB/PPAR gamma and/or AP-1/PPAR gamma expressional 'on/off' switches are common molecular events during colorectal carcinogenesis. Down-regulation of PPAR gamma and induction of the CBP transcriptional coactivator can augment NF-kappaB and AP-1 transcriptional activities leading to up-regulation of COX-2 expression in colon adenocarcinoma cells. p-I kappaB-alpha, pc-JUN, and CBP could potentially provide the basis for future molecular-targeted anticancer therapies.

Prevention and early detection of colorectal cancer--new horizons

Colorectal cancer is potentially one of the most preventable malignancies. Nutritional awareness (low fat, low red meat, high fruits and vegetables) and regular physical activity have major potential for primary prevention of this malignancy, while early detection technologies have the potential of both influencing mortality from colorectal cancer as well as enhancing primary prevention through detection and removal of lesions that could potentially develop into cancer. While the potential for prevention is large, its materialization is far from being optimal. The large-scale lifestyle changes in the population necessary to reduce colorectal cancer rates are hard to achieve, and most of the early detection technologies are either invasive or otherwise nonappealing to the population. Thus, without abandoning the proven prevention methods, new avenues need to be investigated to deal with this malignancy, which carries both high morbidity and high mortality. Such new avenues can now be followed, both in prevention and detection. Chemoprevention, or the use of medications to prevent disease, has now been extensively explored in colorectal cancer. Some of these interventions, such as supplemental fibers, have failed to demonstrate the anticipated effect, while others such as calcium supplementation have been shown to reduce formation of premalignant lesions, polyps, or adenomas. Data accumulating in recent years have suggested that aspirin, nonsteroidal anti-inflammatory drugs, and selective COX-II inhibitors all have a potential to reduce both colorectal cancer and colorectal adenomas. Issues of safety and therapeutic indexes have recently come up as barriers to the use of COX-II inhibitors, and have again drawn attention to aspirin as a potential drug of choice. Association studies have also shown a major potential role for statins in colorectal cancer prevention. New methodologies in cancer detection involve the introduction of colonography or virtual colonoscopy, and the development of methods of detection of genetic somatic mutations in feces or peripheral blood. While radiological techniques currently avoid the need for premedication and are less invasive, they currently still require similar gut cleansing to colonoscopy, can also lead to perforation, are costly, and carry a non-negligible exposure to radiation. Genetic analysis of the stool for mutations in tumor cells is evolving as a promising technique, struggling to achieve both high sensitivity and high specificity with the right combination of mutations sought. With all of these developments taking place, the near future will undoubtedly bring about the expected reduction in colorectal cancer mortality.

Preadministration of high-dose salicylates, suppressors of NF-kappaB activation, may increase the chemosensitivity of many cancers: an example of proapoptotic signal modulation therapy

NF-kappaB activity is elevated in a high proportion of cancers, particularly advanced cancers that have been treated previously. Cytotoxic treatment selects for such up-regulation inasmuch as NF-kappaB promotes transcription of a large number of proteins that inhibit both the intrinsic and extrinsic pathways of apoptosis; NF-kappaB also boosts expression of mdr1, which expels many drugs from cells. Indeed, high NF-kappaB activity appears to be largely responsible for the chemo- and radioresistance of many cancers. Thus, agents that suppress NF-kappaB activity should be useful as adjuvants to cytotoxic cancer therapy. Of the compounds that are known to be NF-kappaB antagonists, the most practical for current use may be the nonsteroidal anti-inflammatory drugs aspirin, salicylic acid, and sulindac, each of which binds to and inhibits Ikappa kinase- beta, a central mediator of NF-kappa activation; the low millimolar plasma concentrations of salicylate required for effective inhibition of this kinase in vivo can be achieved with high-dose regimens traditionally used to manage rheumatic disorders. The gastrointestinal toxicity of such regimens could be minimized by using salsalate or enteric-coated sodium salicy-late or by administering misoprostol in conjunction with aspirin therapy. Presumably, best results would be seen if these agents were administered for several days prior to a course of chemo- or radiotherapy, continuing throughout the course. This concept should first be tested in nude mice bearing xenografts of chemoresistant human tumors known to have elevated NF-kappa activity. Ultimately, more complex adjuvant regimens can be envisioned in which salicylates are used in conjunction with other NF-kappa antagonists and/or agents that target other mediators of down-regulated apoptosis in cancer, such as Stat3; coadministration of salicylate and organic selenium may have intriguing potential in this regard. These strategies may also have potential as adjuvants to metronomic chemotherapy, which seeks to suppress angio-genesis by targeting cycling endothelial cells in tumors.

The Established and Emerging Uses of Aspirin

In this paper, summary narratives on the established and emerging uses of aspirin are presented. On the former, aspirin is used to treat conditions such as headache and also reduce the risks associated with cardiovascular disease and also with pre-eclampsia. On the latter, aspirin might be taken more widely by individuals over 50 years, used as a dietary supplement to possibly reduce cancer risk and used post-transplant to improve organ survival. Aspirin will continue to be an important therapeutic agent and to generate considerable interest among the research community for the foreseeable future.

Aspirin reduces the outcome of anticancer therapy in Meth A-bearing mice through activation of AKT-glycogen synthase kinase signaling

Aspirin displays, at millimolar concentrations, several mechanisms independent from its ability to inhibit cyclooxygenases. Occasionally, the mechanisms displayed in vitro have been clearly related to an effect of clinical relevance in vivo. An expanding literature has been focusing on the cytoprotective effect of aspirin in neurodegenerative disorders and the activation of AKT pathway in neuroprotection and induction of resistance to anticancer drugs. In this work, we tested the ability of aspirin to activate the AKT survival pathway in methylcholanthrene-induced fibrosarcoma cells (Meth A) transplanted into BALB/c nude mice and the clinical effect of aspirin cotreatment during etoposide (VP-16)-based anticancer therapy. We found that cotreatment with aspirin reduced VP-16-induced apoptosis and activated AKT in vitro and in vivo. In Meth A-bearing mice, aspirin administration also activated glycogen synthase kinase-3 and reduced the activity and the efficacy of anticancer therapy in VP-16 cotreated animals. Our data suggest that the antiapoptotic effect of aspirin operates in vivo through the activation of AKT-glycogen synthase kinase pathway causing a decrease in the outcome of VP-16-based therapy. These findings could have clinical relevance in treatment of human malignancies.

Epidermal growth factor receptor signaling is up-regulated in human colonic aberrant crypt foci

Aberrant crypt foci (ACF) are collections of abnormal colonic crypts with heterogeneous molecular and pathologic characteristics. Large and dysplastic ACF are putative precursors of colon cancer with neoplastic risk related to increased proliferation. In this study, we examined the role of epidermal growth factor receptor (EGFR) signaling in regulating ACF proliferation. Using magnification chromoendoscopy, we collected large ACF with endoscopic features of dysplasia and separately biopsied adjacent mucosa. Transcript levels were measured by real-time PCR, proteins were assessed by Western blotting, and levels were expressed as fold changes of adjacent mucosa. K-ras and B-Raf mutations were assessed by PCR and Ras activation by the ratio Ras-GTP / (Ras-GTP + Ras-GDP). At the RNA level, 38% of ACF were hyperproliferative, with proliferating cell nuclear antigen (PCNA) mRNA >/=2-fold of adjacent mucosa. Hyperproliferative ACF had significantly increased mRNA levels of EGFR (6.0 +/- 1.7-fold), transforming growth factor-alpha (14.4 +/- 5.0-fold), heparin-binding EGF-like growth factor (4.5 +/- 1.4-fold), cyclin D1 (4.6 +/- 0.7-fold), and cyclooxygenase-2 (COX-2; 9.3 +/- 4.2-fold; P < 0.05). At the protein level, 46% of ACF were hyperproliferative (PCNA, 3.2 +/- 1.2-fold). In hyperproliferative ACF, 44% possessed significant increases in four EGFR signaling components: EGFR (9.5 +/- 1.3-fold), phosphoactive ErbB2 (2.6 +/- 0.4-fold), phosphoactive extracellular signal-regulated kinase (3.7 +/- 1.1-fold), and cyclin D1 (3.4 +/- 0.8-fold; P < 0.05). Ras was activated in 46% of ACF (3.2 +/- 0.4-fold; P < 0.05), but K-ras mutations were present in only 7% of ACF. In contrast to COX-2 mRNA, the protein was not increased in hyperproliferative ACF. In summary, we have shown that ACF with up-regulated PCNA possess increased EGFR signaling components that likely contribute to the enhanced proliferative state of dysplastic-appearing ACF.

Can targeting apoptosis resolve the cancer saga?

A defect in apoptosis is almost always linked to many pathologies, including cancer. Carcinogenesis has been linked to abnormalities in the apoptotic pathway, and many drugs that are targeted at different parts of this pathway are being developed. There have been many promising drugs that target the extrinsic death receptor pathway as well as the intrinsic mitochondrial apoptotic pathway. There have also been developments in targeting initiator and effector caspases, as well as the death domains that are involved in transducing the apoptotic signals. In this review, the authors will briefly explain how apoptosis deregulation can lead to cancer and discuss drugs that promise success in targeting this anomaly. This article shall also explain how co-treatments with chemotherapy can increase survival of cancer patients. There is a problem of acquired resistance in some of these therapies but there may be ways to overcome this.

Cytokines, NF-kappaB, microenvironment, intestinal inflammation and cancer

Inflammation and cancer have been viewed as closely linked for many years. This link is not merely a loose association but causative. In colorectal cancer (CRC), chronic inflammation as observed in inflammatory bowel (IBD) disease is a key predisposing factor and IBD-associated CRC comprises five percent of all CRCs. Although the molecular mechanisms linking IBD with CRC are not well understood, recent results obtained in preclinical models point to the transcription factor NF-kappaB as a central player. On the one hand, NF-kappaB regulates the expression of various cytokines and modulates the inflammatory processes in IBD. On the other, NF-kappaB stimulates the proliferation of tumor cells and enhances their survival through the regulation of anti-apoptotic genes. Furthermore, it has been clearly established that most carcinogens and tumor promoters activate NF-kappaB, while chemopreventive agents generally suppress this transcription factor. Actually, several lines of evidence suggest that activation of NF-kappaB may cause cancer. These include the finding that NF-kappaB genes can be oncogenes, and that this transcription factor controls apoptosis, cell-cycle progression and proliferation, and possibly also cell differentiation.

The historical analysis of aspirin discovery, its relation to the willow tree and antiproliferative and anticancer potential

For several millennia, the willow tree and salicin have been associated with salicylic acid, the key precursor molecule that has contributed to the discovery of acetylsalicylic acid, traded as aspirin. These molecules have been shown to possess phyto- and chemotherapeutic activities as analgesic drugs. In recent decades, aspirin has become the focus of extensive investigation into antiproliferative and anticancer activities. The historical steps that led to the discovery of aspirin, and its antiproliferative and anticancer potential are highlighted in this review.

Induction of HSP70 is dispensable for anti-inflammatory action of heat shock or NSAIDs in mast cells

OBJECTIVE

It is well known that nonsteroidal anti-inflammatory drugs (NSAIDs), such as acetylsalicylic acid, ibuprofen, and indomethacin, induce anti-inflammatory effects through inhibition of cyclooxygenase enzyme activity. However, it has also been established that a variety of their anti-inflammatory effects are independent of cyclooxygenase. In the search for alternative modes of action, it was found that NSAIDs share some cellular effects with heat shock treatment. This prompted us to investigate whether NSAIDs modulate production of proinflammatory cytokines by mast cells through the heat shock response.

MATERIALS AND METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-) mice, responsiveness to heat shock and NSAIDs was monitored by measuring tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) production and signaling pathways.

RESULTS

In bone marrow-derived mast cells (BMMC), we found that heat shock and a number of NSAIDs induced heat shock protein 70 (HSP70), which was closely paralleled with inhibition of IL-6 and TNF-alpha production. Surprisingly, in BMMC from HSF-1(-/-)mice, heat shock and selected NSAIDs were still able to suppress cytokine production in the absence of HSP70 induction.

CONCLUSION

In this article, we provide evidence that inhibition of release of proinflammatory cytokines by NSAIDs and heat shock may be attributed to inhibition of the inhibitory nuclear factor kappaB (NF-kappaB) kinase activity, extracellular signal-regulated kinases 1/2, and p38 pathways, resulting in decreased transcriptional activity of the NF-kappaB pathway.

Inhibition of human telomerase reverse transcriptase by nonsteroidal antiinflammatory drugs in colon carcinoma

BACKGROUND

Telomerase activation, which is observed in most human cancers, plays an important role in carcinogenesis. Human telomerase reverse transcriptase (hTERT) is a subunit of telomerase that is essential for telomerase activity. The aim of the study was to investigate whether nonsteroidal antiinflammatory drugs (NSAIDs) inhibit telomerase activity and hTERT.

METHODS

Four colon carcinoma cell lines, HT-29, COLO205, CRL-2134, and SW1116, were used in the experiments. Polymerase chain reaction-based telomeric repeat amplification (TRAP) enzyme-linked immunosorbent assay (ELISA) was used to measure telomerase activity in the cells after treatment with aspirin, indomethacin, or SC-236 (a specific cyclooxygenase-2 [COX-2] inhibitor). Expression of hTERT mRNA and protein was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The dual luciferase reporter assay was performed to identify the potential cis-response elements to NSAIDs in the promoter region of hTERT.

RESULTS

Aspirin, indomethacin, and SC-236 inhibited telomerase activity in HT-29, COLO205, and CRL-2134 cell lines, but not in the SW1116 cell line. NSAIDs inhibited hTERT mRNA and protein expression through suppression of hTERT transcriptional activity. The hTERT promoter fragment -145 to -330 basepairs (bp) upstream of the ATG starting site was sufficient to respond to the NSAID-induced inhibitory effect and the inhibition was COX-2-independent.

CONCLUSION

NSAIDs inhibit telomerase activity at hTERT transcriptional, mRNA, and protein levels in colon carcinoma cells. The hTERT promoter fragment -145 to -330 bp may be the cis-response element to NSAIDs.

Cytokines, NF-kappaB, microenvironment, intestinal inflammation and cancer

Inflammation and cancer have been viewed as closely linked for many years. This link is not merely a loose association but causative. In colorectal cancer (CRC), chronic inflammation as observed in inflammatory bowel (IBD) disease is a key predisposing factor and IBD-associated CRC comprises five percent of all CRCs. Although the molecular mechanisms linking IBD with CRC are not well understood, recent results obtained in preclinical models point to the transcription factor NF-kappaB as a central player. On the one hand, NF-kappaB regulates the expression of various cytokines and modulates the inflammatory processes in IBD. On the other, NF-kappaB stimulates the proliferation of tumor cells and enhances their survival through the regulation of anti-apoptotic genes. Furthermore, it has been clearly established that most carcinogens and tumor promoters activate NF-kappaB, while chemopreventive agents generally suppress this transcription factor. Actually, several lines of evidence suggest that activation of NF-kappaB may cause cancer. These include the finding that NF-kappaB genes can be oncogenes, and that this transcription factor controls apoptosis, cell-cycle progression and proliferation, and possibly also cell differentiation.

Induction of apoptotic cell death by 2'-hydroxycinnamaldehyde is involved with ERK-dependent inactivation of NF-kappaB in TNF-alpha-treated SW620 colon cancer cells

2'-Hydroxycinnamaldehyde (HCA) inhibits cell growth of several human cancer cells with unknown mechanisms. We investigated the inhibitory effect of HCA on TNF-alpha-induced cell growth and possible signal pathway in SW620 colon cancer cells. HCA inhibited TNF-alpha-induced SW620 colon cell growth in time- and dose-dependent manner through induction of apoptotic cell death. Parallel with inhibitory effect on cell growth, HCA dose dependency inhibited TNF-alpha-induced activation of NF-kappaB accompanied with inhibition of the translocation of p50. HCA also induced expression of caspase-3 and Bax, but decreased Bcl-2. HCA furthermore activated ERK pathway, and ERK inhibitor reversed inhibitory effect of HCA on cell growth and transcriptional activation of NF-kappaB. These results demonstrate that HCA inhibits cell growth through induction of apoptotic cell death by ERK pathway-dependent NF-kappaB inactivation.

Diclofenac attenuates Wnt/beta-catenin signaling in colon cancer cells by activation of NF-kappaB

The dysregulation of Wnt/beta-catenin signaling and subsequent upregulation of beta-catenin response transcription (CRT) occur frequently in colon cancer cells. Non-steroidal anti-inflammatory drugs (NSAIDs) can repress CRT in colorectal cancer, but little is known about the mechanism of action. We show that the NSAID diclofenac inhibits Wnt/beta-catenin signaling without altering the level of beta-catenin protein and reduces the expression of beta-catenin/TCF-dependent genes. Diclofenac induced the degradation of IkappaBalpha, which increased free nuclear factor kappaB (NF-kappaB) in cells. Also, the ectopic expression of p65, which is a component of NF-kappaB, suppressed CRT. Our findings suggest that diclofenac inhibits Wnt/beta-catenin signaling via the activation of NF-kappaB in colon cancer cells.

Nucleolar sequestration of RelA (p65) regulates NF-kappaB-driven transcription and apoptosis

The molecular mechanisms that regulate nuclear NF-kappaB to determine whether the stimulation of this pathway has a pro- or anti-apoptotic effect on cells have yet to be fully defined. Nuclear compartmentalization is increasingly recognized as an important mechanism for regulating the activity of transcription-related proteins and modulating cell growth and death. We have investigated whether such compartmentalization serves as a mechanism for regulating NF-kappaB transcriptional activity. We demonstrate that the RelA component of NF-kappaB is sequestered in the nucleolus in response to the proapoptotic NF-kappaB stimuli aspirin, serum withdrawal, and UV-C radiation. In contrast, RelA is excluded from the nucleolus in response to the cytokines tumor necrosis factor and TRAIL. We identify an N-terminal motif of RelA that is essential for the nucleolar localization of the protein and show that deleting this motif inhibits the translocation of RelA from the nucleoplasm to the nucleolus. We demonstrate that the nucleolar accumulation of RelA is paralleled by a decrease in basal levels of NF-kappaB transcriptional activity and by apoptosis. Furthermore, we show that the retention of RelA in the nucleoplasm inhibits this decrease in NF-kappaB-driven transcription and blocks apoptosis induced by aspirin and UV-C radiation. This work identifies a novel cellular mechanism for regulating NF-kappaB-driven transcription and apoptosis, involving the nucleolar sequestration of a key NF-kappaB subunit. These data contribute to the understanding of the complexities of NF-kappaB function and have considerable relevance to cancer prevention and therapy.

14-3-3sigma expression is an independent prognostic parameter for poor survival in colorectal carcinoma patients

PURPOSE

14-3-3sigma is an intracellular, dimeric, phosphoserine binding protein that is expressed in epithelial cells and involved in cancer development. In this study, we examined the expression of 14-3-3sigma and evaluated its clinical significance in colorectal carcinoma.

EXPERIMENTAL DESIGN

Expression of 14-3-3sigma was analyzed by Western blot in nine colorectal carcinoma cell lines, eight paired colorectal carcinoma tissues, and normal mucosas. Immunohistochemistry was used to evaluate expression of 14-3-3sigma in tissues of 121 colorectal carcinoma patients and to correlate it with clinical parameters.

RESULTS

Western blot analysis of colorectal carcinoma cell lines and tissues revealed strong 14-3-3sigma expression in four of eight cell lines and 14-3-3sigma overexpression in carcinomas compared with normal mucosa in six of eight colorectal carcinoma tissue pairs. Immunohistochemical analysis revealed 14-3-3sigma overexpression in 38.8% of colorectal carcinoma samples. Furthermore, highly positive immunoreactivity was significantly correlated with tumor differentiation (P < 0.001) and pT stage (P < 0.003). In Kaplan-Meier analysis, 14-3-3sigma overexpression was associated with a significantly decreased survival time compared with negatively stained or low stained cases (P < 0.0096). In multivariate regression analysis, 14-3-3sigma expression emerged as a significant independent parameter (P < 0.037).

CONCLUSIONS

These results provide evidence that 14-3-3sigma expression increases during carcinoma progression in a subset of colorectal carcinoma. The overexpression of this antigen identifies patients at high risk. It is tempting to suggest that 14-3-3sigma overexpression either promotes tumor proliferation and/or prevents apoptotic signal transduction in colorectal carcinoma. Thus, targeting 14-3-3sigma might be a new therapeutic strategy in colorectal carcinoma.

Olive oil and modulation of cell signaling in disease prevention

Epidemiological studies show that populations consuming a predominantly plant-based Mediterranean-style diet exhibit lower incidences of chronic diseases than those eating a northern European or North American diet. This observation has been attributed to the greater consumption of fruits and vegetables and the lower consumption of animal products, particularly fat. Although total fat intake in Mediterranean populations can be higher than in other regions (ca. 40% of calories), the greater proportion is derived from olive oil and not animals. Increased olive oil consumption is implicated in a reduction in cardiovascular disease, rheumatoid arthritis, and, to a lesser extent, a variety of cancers. Olive oil intake also has been shown to modulate immune function, particularly the inflammatory processes associated with the immune system. Olive oil is a nonoxidative dietary component, and the attenuation of the inflammatory process it elicits could explain its beneficial effects on disease risk since oxidative and inflammatory stresses appear to be underlying factors in the etiology of these diseases in man. The antioxidant effects of olive oil are probably due to a combination of its high oleic acid content (low oxidation potential compared with linoleic acid) and its content of a variety of plant antioxidants, particularly oleuropein, hydroxytyrosol, and tyrosol. It is also possible that the high oleic acid content and a proportionate reduction in linoleic acid intake would allow a greater conversion of alpha-linolenic acid (18:3n-3) to longer-chain n-3 PUFA, which have characteristic health benefits. Adoption of a Mediterranean diet could confer health benefits in high-risk populations.

Aspirin-induced nuclear translocation of NFkappaB and apoptosis in colorectal cancer is independent of p53 status and DNA mismatch repair proficiency

Substantial evidence indicates nonsteroidal anti-inflammatory drugs (NSAIDs) protect against colorectal cancer (CRC). However, the molecular basis for this anti-tumour activity has not been fully elucidated. We previously reported that aspirin induces signal-specific IκBα degradation followed by NFκB nuclear translocation in CRC cells, and that this mechanism contributes substantially to aspirin-induced apoptosis. We have also reported the relative specificity of this aspirin-induced NFκB-dependent apoptotic effect for CRC cells, in comparison to other cancer cell types. It is now important to establish whether there is heterogeneity within CRC, with respect to the effects of aspirin on the NFκB pathway and apoptosis. p53 signalling and DNA mismatch repair (MMR) are known to be deranged in CRC and have been reported as potential molecular targets for the anti-tumour activity of NSAIDs. Furthermore, both p53 and MMR dysfunction have been shown to confer resistance to chemotherapeutic agents. Here, we set out to determine the p53 and hMLH1 dependency of the effects of aspirin on NFκB signalling and apoptosis in CRC. We specifically compared the effects of aspirin treatment on cell viability, apoptosis and NFκB signalling in an HCT-116 CRC cell line with the p53 gene homozygously disrupted (HCT-116^p53−/−) and an HCT-116 cell line rendered MMR proficient by chromosomal transfer (HCT-116^+ch3), to the parental HCT-116 CRC cell line. We found that aspirin treatment induced apoptosis following IκBα degradation, NFκB nuclear translocation and repression of NFκB-driven transcription, irrespective of p53 and DNA MMR status. These findings are relevant for design of both novel chemopreventative agents and chemoprevention trials in CRC.

Sulindac corrects defective apoptosis and suppresses azoxymethane-induced colonic oncogenesis inp53 knockout mice

The acute apoptotic response to genotoxic carcinogens (AARGC) might be important for controlling the subsequent colonic mutational load and progression through oncogenesis. We have found previously that AARGC is p53-dependent with a gene-dosage effect, and that decreased AARGC in p53(+/-) and p53(-/-) mice is associated with increased susceptibility to carcinogen-induced oncogenesis. We tested the ability of sulindac to reverse these defects. The effect of sulindac on azoxymethane (AOM)-induced apoptosis was measured in colonic epithelium in wild-type, p53(+/-) and p53(-/-) mice, 8 hr after a single AOM injection. Sulindac supplementation (0.5 +/- 0.1 mg/day) restored defective AARGC in p53(+/-) but not in p53(-/-) mice. For effect on colon tumor development, sulindac treatment was started at age 4 weeks in wild-type, p53(+/-) and p53(-/-) mice; three weekly AOM injections were commenced at 6 weeks of age to induce tumors. Sulindac reduced significantly tumor incidence and multiplicity in wild-type mice (17% and 0.3 tumors/mouse compared to 36% and 0.8 respectively without drug), in p53(+/-)mice (38% and 0.8 compared to 64% and 1.63) and in p53(-/-) mice (63% and 1.0 compared to 90% and 1.74). Although loss of p53 function impairs the apoptotic response to AOM-induced DNA damage, sulindac is capable of partly restoring this defect. As sulindac also reverses the increased risk of oncogenesis due to p53 dysfunction, its enhancement of the apoptotic response to initiating mutations might act to reduce mutational load driving oncogenesis. Sulindac is an effective chemopreventive agent in the presence of p53 dysfunction.