Effects of ibuprofen on arylamine N-acetyltransferase activity in human colon tumor cells

Epigallocatechin gallate sensitizes CAL-27 human oral squamous cell carcinoma cells to the anti-metastatic effects of gefitinib (Iressa) via synergistic suppression of epidermal growth factor receptor and matrix metalloproteinase-2

Human head and neck squamous cell carcinoma (HNSCC) is a major cause of cancer-related death during the last decade due to its related metastasis and poor treatment outcomes. Gefitinib (Iressa), a tyrosine kinase inhibitor has been reported to reduce the metastatic abilities of oral cancer. Previous studies have shown that epigallocatechin gallate (EGCG), a green tea polyphenol, possesses cancer chemopreventive and anticancer activity. However, the mechanisms involved in the suppression of invasion and metastasis of human oral cancer cells following co-incubation with gefitinib and EGCG remain poorly understood. In the present study, we attempted to investigate the synergistic effects of a combined treatment of gefitinib and EGCG in CAL-27 cells in vitro and to elucidate the underlying molecular mechanisms associated with the supression of cell migration and invasion. In the present study, we found that the individual treatments or the combined treatment of gefitinib and EGCG synergistically inhibited the invasion and migration of CAL-27 cells using Transwell invasion and wound-healing scratch assays, respectively. Similarly, gefitinib in combination with EGCG synergistically attenuated enzymatic activity and the protein expression of MMP-2 in CAL-27 cells. Furthermore, individual or combined treatment with EGCG and gefitinib suppressed the protein expression of p-EGFR and the phosphorylated protein levels of ERK, JNK, p38 and AKT and displayed inhibitory effects on metastatic ability of CAL-27 cells. Combined effects of EGCG and gefitinib-altered anti-metastatic actions for related gene expression were observed using DNA microarray analysis. Importantly, EGCG sensitizes CAL-27 cells to gefitinib-suppressed phosphorylation of epidermal growth factor receptor (EGFR in vitro. Taken together, our results suggest that the synergistic suppression of the metastatic ability of CAL-27 cells after EGCG and gefitinib individual or combined treatment are mediated through mitogen-activated protein kinase (MAPK) signaling. Our novel findings provide potential insights into the mechanism involved with synergistic responses of gefitinib and EGCG against the progression of oral cancer.

Evidence of COX-2 independent induction of apoptosis and cell cycle block in human colon carcinoma cells after S- or R-ibuprofen treatment

Ibuprofen belongs to the 2-aryl propionic-acid derivatives and consists of two enantiomers, of which S-ibuprofen is a potent cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) inhibitor whereas the R-enantiomer is two to three orders of magnitude less potent to inhibit cyclooxygenases. Beside its positive effects on inflammation and pain several animal studies have shown that ibuprofen also inhibits tumor initiation and proliferation but the molecular mechanisms are not fully understood. To investigate to which extent the antiproliferative effect of ibuprofen depends on COX-inhibition we tested both enantiomers in different human colon carcinoma cell lines (HCA-7 express COX-1, COX-2 and produce high prostaglandin E2 level; HCT-15 express only COX-1 and produce nearly no prostaglandin E2). S- and R-ibuprofen reduced concentration dependently cell survival in both cell lines to a similar extent and caused a G0/G1 phase block as well as apoptosis. The cell cycle block was accompanied by a down regulation of cyclin A and B and an increase of the cell cycle inhibitory protein p27Kip-1. HCA-7 cells were less sensitive against the antiproliferative effects of ibuprofen enantiomers which was probably due to lower ibuprofen concentrations in this cell type. Also in the nude mice model both enantiomers inhibited tumor growth of HCA-7 and HCT-15 xenografts to a similar extent. However, in mice about 54% of R-ibuprofen was unidirectionally inverted to S-ibuprofen, thus the observed antitumorigenic effect of R-ibuprofen in vivo cannot solely be assigned to this enantiomer. In conclusion our data indicate that S- and R-ibuprofen show similar antiproliferative effects in human colon carcinoma cell lines irrespective of its COX-inhibiting potencies.

Interaction of ibuprofen and probenecid with drug metabolizing enzyme phenotyping procedures using caffeine as the probe drug

AIMS

To examine the suspected inhibitory potential of the over-the-counter (OTC) drug ibuprofen on N-acetyltransferase 2 (NAT2) in vitro and in vivo and the possible implications for phenotyping procedures using caffeine as probe drug.

METHODS

We first studied the inhibitory effect of ibuprofen on NAT2 in vitro, using human liver cytosol and sulfamethazine as substrate. In vivo 15 fast and 15 slow acetylating healthy volunteers were treated with a single dose of ibuprofen (800 mg) orally and phenotyped for NAT2, CYP1A2, and xanthine oxidase (XO) with caffeine as probe drug before and during drug treatment. Because of unexpected in vivo results with ibuprofen this study was repeated in 20 healthy volunteers with probenecid, a model substrate of renal organic anion transport (OAT). For phenotyping tests a urine sample was collected 6 h after caffeine (200 mg) intake. The caffeine metabolites acetyl-6-formylamino-3-methyluracil (AFMU), 1-methylxanthine (1MX), 1-methyluric acid (1MU), and 1,7-dimethyluric acid (17MU) were quantified by HPLC, and the corresponding metabolic ratios for CYP1A2, NAT2, and XO were then calculated. Genotyping for NAT2 was performed with standard PCR-RFLP methods.

RESULTS

In vitro, with human liver cytosol an inhibition by ibuprofen of the acetylation of sulfamethazine with Ki values between 2.2 and 3.1 mm was observed. Surprisingly, in vivo a significant (P < 0.001) increase of the acetyl-6-formylamino-3-methyluracil/1-methylxanthine (AFMU/1MX) urinary ratio from 0.97 +/- 0.16 to 1.08 +/- 0.18 (95% CI on the difference 0.049, 0.170) was found, indicating an apparent elevation of NAT2 activity. In contrast, no change was observed for the ratios used for XO and CYP1A2. Because an induction of NAT2 could be excluded, an interaction of ibuprofen with the tubular secretion of some of the caffeine metabolites was assumed. To prove this assumption, the in vivo study was repeated with probenecid, a model substrate of the renal OAT system. Again, a prominent elevation of the AFMU/1MX ratio from 0.97 +/- 0.21 to 1.53 +/- 0.35 was found (P < 0.002; 95% CI on the difference 0.237, 0.876), but also the XO ratio 1MU/1MX was significantly (P < 0.0001) increased from 1.34 +/- 0.09 to 2.24 +/- 0.14 (95% CI on difference 0.735, 1.059) due to a reduction of 1MX excretion.

CONCLUSIONS

Substrates of OAT interact with renal excretion of caffeine metabolites and may falsify NAT2 and XO phenotyping results. Other phenotyping procedures, which are based on urinary metabolic ratios, should also be validated in this respect, especially in patients under polymedication.

Leukemia inhibitory factor decreases the arylamine N-acetyltransferase activity in human cumulus granulosa cells

PURPOSE

To evaluate the activities of acetyl coenzyme A (AcCoA):arylamine N-acetyltransferase (NAT) of intact cumulus granulosa cells and the role of leukemia inhibitory factor (LIF) upon their NAT activities.

METHODS

Thirty women accepted controlled ovarian hyperstimulation (COH) and oocyte retrievals. Human cumulus granulosa cells were obtained during oocyte retrievals. Using 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA) as substrates, NAT activity of all samples was determined by high pressure liquid chromatography. After the incubation with different time and concentrations of 2-AF, PABA, and LIF, 2-acetyl-aminofluorene (2-AAF) and N-acetyl-PABA (N-Ac-PABA) were measured.

RESULTS

After incubation with 2.812, 5.625, 11.25, and 22.5 microM of 2-AF/PABA, their product concentrations (2-AAF/N-Ac-PABA) were 0.42/0.32, 0.76/0.58, 1.29/1.04, and 1.94/1.26 nmol/10(6) cells, respectively. After 6, 12, 18, and 24 h incubation with 11.25 microM of 2-AF/PABA, their product concentrations were 0.19/0.12, 0.56/0.4, 0.98/0.79, and 1.3/1.0 nmol/10(6) cells, respectively. After incubation with 0, 5, and 50 microM of LIF, the 2-AAF/N-Ac-PABA concentrations were 0.98/0.80, 0.70/0.52, and 0.49/0.30 nmol/10(6) cells, respectively.

CONCLUSION

Intact human cumulus granulosa cells could acetylate arylamine carcinogen (2-AF) and noncarcinogens drug (PABA). LIF decreased the NAT activities. It provides a model for monitoring the effects of COH and LIF upon the oocytes.

Kinetics of acetyl coenzyme A: arylamine N-acetyltransferase from human cumulus cells

PURPOSE

N-acetyltransferase (NAT) activity is involved in the detoxification of exogenous amines. We aimed to evaluate the kinetics of acetyl coenzyme A (AcCoA): arylamine NAT for human cumulus cells.

METHODS

Thirty infertile women who were undergoing controlled ovarian hyperstimulation (COH) and oocyte retrievals were recruited. Human cumulus cells were obtained during oocyte retrievals. Using 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA) as substrates, NAT activity and Michaelis-Menten kinetics constants of all samples were determined by using high-pressure liquid chromatography.

RESULTS

There were 6 rapid, 10 intermediate, and 14 slow acetylators. 2-AF-NAT and PABA-NAT activities were 0.97 +/- 0.74 and 0.89 +/- 0.77 nmol/min/mg protein, respectively. Km/Vmax of rapid and slow acetylators for 2-AF were (161 +/- 55)/(15.6 +/- 2.9) and (27.8 +/- 11.4)/(2.6 +/- 0.9), respectively. Km/Vmax of rapid and slow acetylators for PABA were (104 +/- 36)/(13.2 +/- 2.8) versus (20.0 +/- 10)/(2.0 +/- 0.7), respectively. Compared to slow acetylators, the rapid acetylators exhibited higher Km/Vmax values for 2-AF (5.8-/6-fold) and PABA (6-/6.6-fold), respectively.

CONCLUSION

Human cumulus could acetylate arylamine carcinogen (2-AF) and noncarcinogen drug (PABA). Higher percentage of rapid acetylators established in the cumulus during COH. It provides a model for monitoring the effects of pollution or carcinogenesis upon the oocyte during COH and oocyte retrievals.