Prostaglandin synthesis by squamous carcinoma cells of head and neck, and its inhibition by non-steroidal anti-inflammatory drugs

Ginseng saponin metabolite induces apoptosis in MCF-7 breast cancer cells through the modulation of AMP-activated protein kinase

Previous studies have shown that the ginseng saponin metabolite, Compound K (20-O-d-glucopyranosyl-20(S)-protopanaxadiol, IH901), suppresses proliferation of various cancers and induces apoptosis. AMP-activated protein kinase (AMPK) is a sensor of cellular energy states and is involved in apoptosis of cancer cells. We hypothesized that Compound K may exert cytotoxicity in MCF-7 human breast cancer cells through modulation of AMPK, followed by a decrease in cyclooxygenase-2 (COX-2) expression. Compound K inhibited cell growth, induced apoptosis via generation of reactive oxygen species (ROS), as well as decreasing COX-2 expression and prostaglandin E(2) (PGE(2)) levels. These effects of Compound K were induced via an AMPK-dependent pathway and were abrogated by a specific AMPK inhibitor. These results suggest that Compound K induced apoptosis by modulating AMPK-COX-2 signaling in MCF-7 human breast cancer cells.

Apoptotic effect of EGCG in HT-29 colon cancer cells via AMPK signal pathway

EGCG [(-)epigallocatechin-3-gallate], a green tea-derived polyphenol, has been shown to suppress cancer cell proliferation, and interfere with the several signaling pathways and induce apoptosis. Practically, there is emerging evidence that EGCG has a potential to increase the efficacy of chemotherapy in patients. We hypothesized that EGCG may exert cell cytotoxicity through modulating AMPK (AMP-activated protein kinase) followed by the decrease in COX-2 expression. EGCG treatment to colon cancer cells resulted in a strong activation of AMPK and an inhibition of COX-2 expression. The decreased COX-2 expression as well as prostaglandin E(2) secretion by EGCG was completely abolished by inhibiting AMPK by an AMPK inhibitor, Compound C. Also, the activation of AMPK was accompanied with the reduction of VEGF (vascular endothelial growth factor) and glucose transporter, Glut-1 in EGCG-treated cancer cells. These findings support the regulatory role of AMPK in COX-2 expression in EGCG-treated cancer cells. Furthermore, we have found that reactive oxygen species (ROS) is an upstream signal of AMPK, and the combined treatment of EGCG and chemotherapeutic agents, 5-FU or Etoposide, exert a novel therapeutic effect on chemo-resistant colon cancer cells. AMPK, a molecule of newly defined cancer target, was shown to control COX-2 in EGCG-treated colon cancer cells.

Combination of 5-fluorouracil and genistein induces apoptosis synergistically in chemo-resistant cancer cells through the modulation of AMPK and COX-2 signaling pathways

5-Fluorouracil (5-FU) is one of the widely used chemotherapeutic drugs targeting various cancers, but its chemo-resistance remains as a major obstacle in clinical settings. In the present study, HT-29 colon cancer cells were markedly sensitized to apoptosis by both 5-FU and genistein compared to the 5-FU treatment alone. There is an emerging evidence that genistein, soy-derived phytoestrogen, may have potential as a chemotherapeutic agent capable of inducing apoptosis or suppressing tumor promoting proteins such as cyclooxygenase-2 (COX-2). However, the precise mechanism of cellular cytotoxicity of genistein is not known. The present study focused on the correlation of AMPK and COX-2 in combined cytotoxicity of 5-FU and genistein, since AMPK is known as a primary cellular homeostasis regulator and a possible target molecule of cancer treatment, and COX-2 as cell proliferation and anti-apoptotic molecule. Our results demonstrated that the combination of 5-FU and genistein abolished the up-regulated state of COX-2 and prostaglandin secretion caused by 5-FU treatment in HT-29 colon cancer cells. These appear to be followed by the specific activation of AMPK and the up-regulation of p53, p21, and Bax by genistein. Under same conditions, the induction of Glut-1 by 5-FU was diminished by the combination treatment with 5-FU and genistein. Furthermore, the reactive oxygen species (ROS) was found as an upstream signal for AMPK activation by genistein. These results suggested that the combination of 5-FU and genistein exert a novel chemotherapeutic effect in colon cancers, and AMPK may be a novel regulatory molecule of COX-2 expression, further implying its involvement in cytotoxicity caused by genistein.

Inhibition of cyclooxygenase-2 activity in head and neck cancer cells by genistein

Genistein, rich in soybean, has been reported to have anti-cancer activity on several cancers. However, the molecular mechanism of its anti-cancer activity still remains unclear. We investigated the effect of genistein on a human oral squamous carcinoma line (SCC-25), and demonstrated that genistein inhibited SCC-25 cell growth via G2/M phase arrest. We observed a significant decrease of proliferating cell nuclear antigen expression in these cells after treatment, but no significant change in the number of apoptotic cells, indicating that the major action of genistein is inhibition of cancer cell proliferation. We also observed a high level of prostaglandin E2 (PGE2) in these cells and PGE2 synthesis in SCC-25 cells was significantly suppressed by genistein. We demonstrated that genistein directly inhibited cycloxygenase-2 (COX-2) activity, an inducible enzyme that converts arachidonic acid to prostaglandins, similar to the action of celecoxib, a selective COX-2 inhibitor. However, the anticancer activity of genistein was much weaker than that of indomethacin (non-selective COX inhibitor), celecoxib and baicalein (flavonoid isolated from Scutellaria baicalensis). These results suggested that genistein might be useful as a chemopreventive agent rather than a chemotherapeutic agent.

Protective association of aspirin/NSAIDs and esophageal cancer: a systematic review and meta-analysis

BACKGROUND & AIMS

Esophageal carcinomas have high fatality rates, making chemoprevention agents desirable. We performed a systematic review with meta-analysis of observational studies evaluating the association of aspirin/nonsteroidal anti-inflammatory drug (NSAID) use and esophageal cancer.

METHODS

We evaluated the MEDLINE, BIOSIS, and Web of Science electronic databases (1980-2001); manually reviewed the literature; and consulted with experts. Studies were included if they: (1) evaluated exposure to NSAIDs, aspirin, or both; (2) evaluated esophageal cancer; and (3) reported relative risks or odds ratios or provided data for their calculation. Data were independently abstracted by 2 investigators. The primary and sensitivity analyses used both fixed and random-effects models.

RESULTS

Nine studies (2 cohort, 7 case control) containing 1813 cancer cases were identified. All primary summary estimates were homogeneous. Statistical pooling showed a protective association between any use of aspirin/NSAID and esophageal cancer (odds ratio [OR] = 0.57; 95% confidence interval [CI], 0.47-0.71). Both intermittent (OR = 0.82; CI, 0.67-0.99) and frequent medication use were protective (OR = 0.54; CI, 0.43-0.67), with greater protection with more frequent use. Stratified by medication type, aspirin use was protective (OR = 0.5; CI, 0.38-0.66), and NSAIDs had a borderline protective association (OR = 0.75; CI, 0.54-1.0). Any use was protective against both esophageal adenocarcinoma (OR = 0.67; CI, 0.51-0.87) and squamous cell carcinoma (OR = 0.58; CI, 0.43-0.78).

CONCLUSIONS

Pooled results support a protective association between aspirin and NSAIDs and esophageal cancer (of both histological types) and provide evidence for a dose effect. These findings support evaluating these agents in clinical trials of high-risk patients.

Arachidonic acid metabolism: a primer for head and neck surgeons

The arachidonic acid metabolites, or eicosanoids, are a large series of lipid-derived mediators capable of producing a multitude of physiologic effects in the local environment. They play important roles in a variety of signaling pathways in endocrinology, immunology, and oncology. A significant body of work in this area has occurred in squamous cell carcinomas of the head and neck over the past 15 years. This review will attempt to familiarize the head and neck surgical oncologist with the basic biochemical steps in the formation of these compounds, newer developments in the field of eicosanoid biochemistry, and related experimental evidence of the roles of these substances in head and neck cancer.

Synergistic effects of 13-cis retinoic acid and arachidonic acid cascade inhibitors on growth of head and neck squamous cell carcinoma in vitro

Products of arachidonic acid metabolism can influence normal and malignant cell growth. In vivo, inhibitors of arachidonic acid metabolism have been associated with inhibition of tumor growth, including head and neck squamous cell carcinoma (HNSCC). This has not been evaluated extensively in vitro in an HNSCC model. Therefore we investigated the effects of several arachidonic acid cascade inhibitors (AACIs) (indomethacin, curcumin, phenidone, nordihydroguaiaretic acid, 5,8,11,14-eicosatetraynoic acid, and 13-cisretinoic acid) on the growth of two HNSCC cell lines (MDA 886Ln and 1483). We found that AACIs caused dose-dependent growth inhibition of both cell lines. In an effort to inhibit HNSCC cell growth at lower concentrations of these drugs, we evaluated the effects of a variety of AACIs in combination with 13-cis retinoic acid. We observed synergistic growth inhibition when the drugs were used in all combinations, with the exception of indomethacin. These results suggest that AACIs may have some utility in the direct treatment of HNSCC, and a strategy combining 13-cis retinoic acid with other AACIs may prove to be even more effective.

Vitamin E succinate potentiates the inhibitory effect of prostaglandins on oral squamous carcinoma cell proliferation

Previous studies have shown that prostaglandin E2 (PGE2) and vitamin E succinate can act in an additive manner to inhibit the proliferation of human oral squamous carcinoma cells (SCC-25). The initial studies on the additive anticancer activity of PGE2 and vitamin E succinate have been extended to include antineoplastic PGs, delta 12-PGJ2 and PGJ2. Treatment of oral squamous carcinoma cells (SCC-15) with delta 12-PGJ2, PGJ2, and vitamin E succinate, individually, caused significant concentration-dependent inhibition of cell proliferation to various degrees. PGJ2 was most potent and caused an inhibition that corresponded to 85.55% at 10(-5) M. Addition of 1 microM of vitamin E succinate to delta 12-PGJ2 or PGJ2 resulted in a significant increase in the inhibitory potency of the lower concentrations of the two PGs. These results suggest a novel role for a mixture of PGs and vitamin E as potent antitumor proliferative agents.

Treatment with a non-steroidal anti-inflammatory agent delays the growth of spontaneous pulmonary metastases of a mammary adenocarcinoma of non-detected immunogenicity

Previous reports showed that treatment with non-steroidal anti-inflammatory agents (NSAIA) can alter the growth profile of a variety of tumours. In this study, the effect of NSAIA treatment on the growth of the primary tumour and the appearance of spontaneous pulmonary metastases, was investigated. A mammary adenocarcinoma of non-detected immunogenicity, C7HI, was grafted subcutaneously in the lateral flank of Balb/c mice. Oral treatment with approximately 1 mg kg-1 day-1 piroxicam delayed both tumour growth and the growth of pulmonary metastases. Survival of mice bearing the primary tumour was significantly lengthened by anti-inflammatory treatment. Similarly, in separate experiments, after surgical removal of the primary tumour by day 34 after grafting, the group of mice treated orally with piroxicam also exhibited a higher survival rate than the control group. Upon surgical removal of the primary tumour 34 days after grafting, piroxicam treatment significantly decreased both the number and size of pulmonary metastases. The results of this study lends support to the hypothesis that inhibition or modulation of inflammation may delay tumour organisation and growth. It is suggested that piroxicam treatment may be an appropriate adjunct therapy to delay the appearance of pulmonary metastases and to increase life-expectancy in a host whose primary tumour has to be surgically removed.

A role for prostaglandins in the suppression of cutaneous cellular immunity and tumour development in benzo(a)pyrene- but not dimethylbenz(a)anthracene-treated mice

Prostaglandins have been implicated in the immune suppression associated with the development of some tumours. Application of the prostaglandin synthetase inhibitor indomethacin, to murine skin prior to treatment with the chemical carcinogens benzo(a)pyrene (BP) or 7,12 dimethylbenz(a)anthracene (DMBA), restored contact sensitivity responses to 2,4-dinitrofluorobenzene in BP- but not DMBA-treated mice. However, indomethacin failed to restore antibody responses in either group of mice. Prolonged treatment with BP or DMBA led to cutaneous tumour formation. Indomethacin was found to delay the onset and reduce the size of tumours in BP- but not DMBA-treated mice. It is proposed that prostaglandin-induced suppression of cellular cutaneous immunity may play a role in BP- but not DMBA-induced cutaneous carcinogenesis.

Suppression of x-ray induced transformation by Valium and aspirin in mouse C3H10T1/2 cells

Two commonly used drugs, Valium (diazepam) and Aspirin (acetylsalicyclic acid), were shown to suppress X-ray induced transformation in mouse C3H/10T1/2 cells. Valium was studied in an ethanol solution. Aspirin, which is soluble in both water and ethanol, was active only in the ethanol solution. Both drugs were effective only when present throughout the entire assay period.

Comparison of the inhibitory effect of polyunsaturated fatty acids on prostaglandin synthesis. II. Fibroblasts

In a previous publication we reported that PUFAs of the n-6 and n-3 series caused significant inhibition of synthesis of both PGE2 (28.4-92.8%) and PGF2 alpha (24.4-84.0%) in the oral squamous carcinoma cell line SCC-25. In this report we describe the inhibitory effect of the same acids on PG synthesis in normal human gingival fibroblasts under the same experimental conditions. It was found that a combination of EPA + DCHA (6:4), DCHA and ALA caused significant reduction in synthesis of PGE2 (10.1-87.8%) and PGF2 alpha (14.0-54.6%) at the four dose levels studied. The rank order of potency of acids in reduction of PG synthesis was: EPA + DCHA greater than DCHA greater than EPA greater than ALA greater than LA greater than DGLA greater than GLA. The data suggest that although PUFAs are effective inhibitors of PG synthesis by gingival fibroblasts and SCC-25, the fibroblast is less susceptible to the inhibitory effect of fatty acids.

Comparison of the inhibitory effect of polyunsaturated fatty acids on prostaglandin synthesis I oral squamous carcinoma cells

Polyunsaturated fatty acids (PUFAs) have been shown to suppress the growth rate of human osteogenic sarcoma cells and to have selective cytotoxic activity against human cancer cells. The purpose of this study was to investigate the efficacy of various PUFAs on inhibition of prostaglandin (PG) synthesis by oral squamous carcinoma cells (SCC-25). A significant inhibition of PGE2 and PGF2 alpha synthesis in SCC-25 was observed by all PUFAs tested except in the case of linoleic acid (LA) at 10 microM level. At 10 microM level the rank order of inhibition of PG synthesis by PUFAs was docosahexaenoic (DHA) greater than eicosapentaenoic (EPA) + DHA greater than dihomogamma-linolenic (DGLA) greater than EPA greater than alpha-linolenic (ALA) greater than linoleic (LA). At 50, 75, 100 microM the rank order of inhibition was DGLA greater than EPA greater than EPA + DHA greater than DHA greater than ALA greater than LA.