Non-steroidal anti-inflammatory drugs for cancer prevention: promise, perils and pharmacogenetics

Molecular characterisation of canine nonsteroidal anti-inflammatory drug-activated gene (NAG-1)

Nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1), a divergent member of the transforming growth factor beta superfamily, was previously identified as a gene induced by several anti-tumorigenic compounds, including NSAIDs and peroxisome proliferator-activated receptor gamma (PPARgamma) ligands in humans. In this study, canine NAG-1 was characterised from a canine genomic database. Gene induction by some NSAIDs and PPARgamma ligands was demonstrated in canine osteosarcoma cell lines. Phylogenetic analysis indicates that canine NAG-1 is more homologous with the corresponding mouse and rat genes than with human NAG-1. Expression of canine NAG-1 was increased by treatment with piroxicam and SC-560 (NSAIDs) and the PPARgamma ligand rosiglitazone. This study demonstrates that canine NAG-1 is up-regulated by some anti-tumorigenic compounds in osteosarcoma cell lines and may provide an important target of chemotherapy in canine cancer.

Novel etodolac analog SDX-308 (CEP-18082) induces cytotoxicity in multiple myeloma cells associated with inhibition of beta-catenin/TCF pathway

We have reported previously that R-enantiomer of etodolac (R-etodolac), which is under investigation in phase 2 clinical trials in chronic lymphocytic leukemia, induces potent cytotoxicity at clinically relevant concentrations in multiple myeloma (MM) cells. In this study, we demonstrated that SDX-308 (CEP-18082), a novel analog of etodolac, has more potent cytotoxicity than R-etodolac against both MM cell lines and patient MM cells, including tumor cells resistant to conventional (dexamethasone, doxorubicine, melphalan) and novel (bortezomib) therapies. SDX-308-induced cytotoxicity is triggered by caspase-8/9/3 activation and poly (ADP-ribose) polymerase cleavage, followed by apoptosis. SDX-308 significantly inhibits beta-catenin/T-cell factor pathway by inhibiting nuclear translocation of beta-catenin, thereby downregulating transcription and expression of downstream target proteins including myc and survivin. Neither interleukin-6 nor insulin-like growth factor-1 protect against growth inhibition triggered by SDX-308. Importantly, growth of MM cells adherent to bone marrow (BM) stromal cells is also significantly inhibited by SDX-308. Our data therefore indicate that the novel etodolac analog SDX-308 can target MM cells in the BM milieu.

Tissue homeostasis and cancer

Epithelial cells are known to release an important amount of cytokines capable to modulate immune system functions. On the other hand, immune system cells can release cytokines, which play an important role in the control of the growth of epithelial cells. In this paper, we stand the hypothesis that a mutual (reciprocal) growth regulation exists between epithelial cells and immune system. We propose a model describing plausible cytokine circuits that may regulate (inhibit) both epithelial growth and epithelial inflammation. In addition, we describe how dysfunction of these circuits could lead to tumoral growth, excessive inflammation or both. A failure in the regulation of epithelial growth by the immune system could give rise to a neoplasm, and a failure in the regulation of the immune system by the epithelium could give rise to inflammatory or autoimmune diseases. This model may satisfactorily explain the link between inflammation and cancer.

Ovarian epithelial cancer: a role for PGE2-synthesis and signalling in malignant transformation and progression

Background

The involvement of the cyclooxygenases (COX), in particular COX-2, is well documented for many tumours, e.g. colon, breast and prostate cancer, by both experimental and clinical studies. There are epidemiological data from subjects using NSAIDs, and experimental evidence supporting the hypothesis of prostaglandins (PGs) as regulators of tumourigenesis in the ovary. One of the end products of PG-synthesis, PGE₂, regulates several key-processes, which are characteristic for tumour growth, e.g. angiogenesis, proliferation and apoptosisis. The present study investigated the pathway for PGE₂ – synthesis and signalling in ovarian tumourigenesis by analysing specimen from normal ovaries (n = 18), benign (B) (n = 8), borderline type (BL) (n = 6) and malignant tumours (AC) (n = 22). The expression and cell-specific localization of COX-1, COX-2, microsomal prostaglandin E synthase-1 (mPGES-1) and two of the receptors for PGE₂, EP₁ and EP₂, were examined by immunoblotting (IB) and immunohistochemistry (IHC).

Results

The results are in line with earlier studies demonstrating an increase of COX-2 in AC compared to the normal ovary, B and BL tumours. Increased expressions were also observed for COX-1, mPGES-1 and EP-1 which all were significantly (p < 0.05) augmented in less differentiated AC (grades: moderately-, poorly- and undifferentiated). The increase of COX-2 was also correlated to stage (FIGO classification) with significant elevations in stages II and III. EP₁ was increased in stage III while no significant alterations were demonstrated for COX-1, mPGES-1 or EP₂ for stage. IHC revealed staining of the tumour cells, but also increase of COX-1, COX-2, mPGES-1 and EP_1–2 in the stromal compartment of AC (grades: moderately-, poorly- and undifferentiated). This observation suggests interactions between tumour cells and stromal cells (fibroblasts, immune cells), e.g. paracrine signalling mediated by growth factors, cytokines and possibly PGs.

Conclusion

The increases of COX-1, COX-2, mPGES-1 and EP_1–2 in epithelial ovarian cancer, supports the hypothesis that PGE₂-synthesis and signalling are of importance for malignant transformation and progression. The observed augmentations of COX-1, COX-2 and mPGES-1 have implications for future therapeutic strategies.

Synthesis and biological activities of novel dexibuprofen tetraacetylriboflavin conjugates

A series of novel dexibuprofen derivatives covalently linked via alkylene spacers of variable length to tetraacetylated riboflavin have been developed. The target compounds became accessible by reaction of the chloromethyl ester of dexibuprofen with tetraacetylriboflavin (compound 7) or by synthesis of the appropriate N3-(omega-iodoalkyl)-2',3',4',5'-Tetraacetylriboflavin followed by treatment with dexibuprofen (derivatives 8-11), respectively. Biological screening revealed that the target compounds exhibit antiproliferative effects on MCF-7 breast cancer and HT-29 colon carcinoma cells with IC50 values in the range of 8-15 microM. Enzymatic studies on human platelets indicated significant COX-1 inhibitory activities of the target compounds.

Apigenin prevents UVB-induced cyclooxygenase 2 expression: coupled mRNA stabilization and translational inhibition

Cyclooxygenase 2 (COX-2) is a key enzyme in the conversion of arachidonic acid to prostaglandins, and COX-2 overexpression plays an important role in carcinogenesis. Exposure to UVB strongly increased COX-2 protein expression in mouse 308 keratinocytes, and this induction was inhibited by apigenin, a nonmutagenic bioflavonoid that has been shown to prevent mouse skin carcinogenesis induced by both chemical carcinogens and UV exposure. Our previous study suggested that one pathway by which apigenin inhibits UV-induced and basal COX-2 expression is through modulation of USF transcriptional activity in the 5' upstream region of the COX-2 gene. Here, we found that apigenin treatment also increased COX-2 mRNA stability, and the inhibitory effect of apigenin on UVB-induced luciferase reporter gene activity was dependent on the AU-rich element of the COX-2 3'-untranslated region. Furthermore, we identified two RNA-binding proteins, HuR and the T-cell-restricted intracellular antigen 1-related protein (TIAR), which were associated with endogenous COX-2 mRNA in 308 keratinocytes, and apigenin treatment increased their localization to cell cytoplasm. More importantly, reduction of HuR levels by small interfering RNA inhibited apigenin-mediated stabilization of COX-2 mRNA. Cells expressing reduced TIAR showed marked resistance to apigenin's ability to inhibit UVB-induced COX-2 expression. Taken together, these results indicate that in addition to transcriptional regulation, another mechanism by which apigenin prevents COX-2 expression is through mediating TIAR suppression of translation.

Leukocyte infiltration in cancer creates an unfavorable environment for antitumor immune responses: a novel target for therapeutic intervention

The interaction between tumor cells and the nearby environment is being actively investigated to explore how this interplay affects the initiation and progression of cancer. Host-tumor relationship results in the production of pro-inflammatory cytokines and chemokines that promote the recruitment of leukocytes within and around developing neoplasms. Cancer cells, together with newly recruited tumor-infiltrating cells, can also activate fibroblast and vascular responses, thus resulting in a chronic microenvironment perturbation. In this complex scenario, interactions between innate and adaptive immune cells can be disturbed, leading to a failure of immune-mediated tumor recognition and destruction. On the basis of the recent awareness about tumor promotion and immune deregulation by immune/inflammatory cells, novel anti-cancer strategies can be exploited.

Use of nonsteroidal anti-inflammatory drugs and risk of oral cancer: a cohort study

Epidemiologic data regarding the chemopreventive potential of nonsteroidal anti-inflammatory drugs (NSAIDs) against oral cancer are sparse. We found a relative risk for oral cancer of 1.2 (95% CI, 1.0–1.6) among 169 589 Danish NSAID users (≥2 prescriptions), with no apparent trends in subgroups. Our study provided no clear evidence that NSAIDs may protect against oral cancer.

Leukocytes, inflammation, and angiogenesis in cancer: fatal attractions

Leukocytes are cells of defense. Their main function is to protect our body against invading microorganisms. Some leukocytes, in particular, polymorphonuclear and monocytes, accumulate at sites of infection and neutralize pathogens through innate mechanisms. The blood and lymphatic vascular system are essential partners in this defensive reaction: Activated endothelial cells promote leukocyte recruitment at inflammatory sites; new blood vessel formation, a process called angiogenesis, sustains chronic inflammation, and lymphatic vessels transport antigens and antigen-presenting cells to lymph nodes, where they stimulate naive T and B lymphocytes to elicit an antigen-specific immune response. In contrast, leukocytes and lymphocytes are far less efficient in protecting us from cancer, the "enemy from within." Worse, cancer can exploit inflammation to its advantage. The role of angiogenesis, leukocytes, and inflammation in tumor progression was discussed at the second Monte Verità Conference, Tumor Host Interaction and Angiogenesis: Basic Mechanisms and Therapeutic Perspectives, held in Ascona, Switzerland, October 1-5, 2005. (Conference chairs were K. Alitalo, M. Aguet, C. Rüegg, and I. Stamenkovic.) Eight articles reporting about topics presented at the conference are featured in this issue of the Journal of Leukocyte Biology.

In vivo and in vitro cytotoxicity of R-etodolac with dexamethasone in glucocorticoid-resistant multiple myeloma cells

Glucocorticoids have been widely used in the treatment of multiple myeloma (MM) both as single agents and in combination with other drugs. However, primary or acquired glucocorticoid resistance occurs in most cases. It was recently reported that R-etodolac induced in vitro cytotoxicity in MM cell lines and in primary MM cells, as well as synergistically enhanced dexamethasone (Dex)-induced apoptosis in Dex-sensitive MM.1S cells. This study examined the in vitro and in vivo effects of combination treatment with R-etodolac and Dex on Dex-resistant OPM1 cells. Treatment with R-etodolac and Dex was found to enhance cytotoxicity, inhibit nuclear factor kappaB activity via upregulation of IkappaBalpha, as well as enhance Dex-induced caspase activation and poly (ADP)-ribose polymerase cleavage in OPM1 cells. R-etodolac also enhanced Dex cytotoxicity in patient MM cells that were resistant to glucocorticoids. The in vivo anti-tumour effect of this combination on MM cells was evaluated by using severe combined immunodeficient mice engrafted with OPM1. Treatment with R-etodolac or Dex alone did not induce a significant reduction of tumour volume; in contrast, combination treatment with R-etodolac and Dex induced significant synergistic inhibition of tumour growth. These data indicate that R-etodolac overcomes resistance to Dex in glucocorticoid-resistant MM cells, providing the framework for clinical trials of R-etodolac combined with Dex, to improve patient outcome in MM.

Inhibition of phorbol ester-induced mouse skin tumor promotion and COX-2 expression by celecoxib: C/EBP as a potential molecular target

PURPOSE

Inflammation acts as a driving force for the development of cancer. Multiple lines of evidence suggest that nonsteroidal anti-inflammatory drugs, especially those that specifically target cyclooxygenase-2 (COX-2), are effective in preventing certain cancers. The present study was aimed at investigating the antitumor promoting potential of celecoxib in chemically induced mouse skin tumorigenesis, as well as elucidating the underlying molecular mechanisms.

MATERIALS AND METHODS

To study the antitumor promoting effects of celecoxib, we used the classical two-stage mouse skin tumorigenesis model that involves initiation with a single application of 7,12-dimethylbenz [alpha]anthracene (DMBA) followed by promotion with repeated applications of 12-O-tetradecanoylphorbol-13-acetate (TPA). The effects of celecoxib on the expression of COX-2, vascular endothelial growth factor (VEGF), p65 and the different isoforms of CCAAT/enhancer binding protein (C/EBP) were examined by performing Western blot analysis. Electrophoretic mobility gel shift assay was used to examine the effects of celecoxib on the TPA-induced DNA binding activities of various transcription factors.

RESULTS

Our study revealed that topical application of celecoxib (10micromol) significantly reduced the multiplicity of papillomas in DMBA-initiated and TPA-promoted mouse skin. Pretreatment with celecoxib also diminished the expression of COX-2 and VEGF in the mouse skin papillomas. Pretreatment with celecoxib attenuated DNA binding of transcription factor (C/EBP) in the TPA-stimulated mouse skin. Moreover, celecoxib suppressed the TPA-induced nuclear expression of C/EBPdelta, but not C/EBPbeta, in mouse skin in vivo.

CONCLUSION

Our study demonstrates the inhibitory effects of celecoxib on mouse skin tumor promotion, which was associated with a decreased expression of COX-2 and VEGF, as well as inhibition of C/EBP activation.