Urinary prostaglandin D2 metabolite excretion during the first six months of life was significantly lower in breast-fed than formula-fed infants.

AIM: The metabolic changes that occur during the postnatal weaning period appear to be particularly important for future health, and breast milk is considered to provide the optimal source of infant nutrition. This pilot study from September 2013 to May 2015 examined the effect of breastfeeding on prostaglandin metabolism in healthy term infants. METHODS: Urine samples were collected from 19 infants at one month of age in the Juntendo University Hospital, Tokyo, Japan. The 13 infants in the breast-fed group received less than 540 mL/week of their intake from formula, and the other six were exclusively fed on formula. At six months, we sampled 14 infants: nine breast-fed and five receiving formula. The infants were from normal single pregnancies and free from perinatal complications. We analysed urinary prostaglandin metabolites-tetranor prostaglandin E2 metabolite (t-PGEM) and tetranor prostaglandin D2 metabolite (t-PGDM)-using liquid chromatography tandem-mass spectrometry. RESULTS: Urinary t-PGDM excretion at one and six months was significantly lower in breast-fed infants than formula-fed infants. However, urinary t-PGEM excretion at one and six months was not significantly different between the groups. CONCLUSION: Our study showed that the type of feeding in early infancy affected prostaglandin metabolism in healthy term infants.

A pilot study of the effect of human breast milk on urinary metabolome analysis in infants.

BACKGROUND: This study aimed to examine the nutritional effect of breast feeding on healthy term infants by using urinary metabolome analysis. METHODS: Urine samples were collected from 19 and 14 infants at 1 and 6 months, respectively. Infants were separated into two groups: the breast-fed group receiving <540 mL/week of their intake from formula (n=13 at 1 month; n=9 at 6 months); and the formula-fed group receiving no breast milk (BM) (n=6 at 1 month; n=5 at 6 months). Urinary metabolome analysis was performed using capillary electrophoresis-time-of-flight mass spectrometry (CE-TOF/MS). RESULTS: A total of 29 metabolites were detected by CE-TOF/MS metabolome analysis in all samples. Urinary excretion of choline metabolites (choline base solution, N,N-dimethylglycine, sarcosine, and betaine) at 1 month were significantly (p<0.05) higher in breast-fed infants than in formula-fed infants. However, choline metabolites were not significantly different between the groups at 6 months. Urinary excretion of lactic acid in breast-fed infants at 1 and 6 months was significantly lower than that in formula-fed infants. Urinary l(-)-threonine and l-carnosine excretion at 1 month was significantly lower in breast-fed infants than in formula-fed infants, but it was not significantly different between the groups at 6 months. CONCLUSIONS: The type of feeding in early infancy affects choline metabolism, as well as lactate, threonine, and carnosine levels, in healthy term infants. Urinary metabolome analysis by the CE-TOF/MS method is useful for assessing nutritional metabolism in infants.

Association of zinc and copper with clinical parameters in the preterm newborn.

BACKGROUND: Given that preterm infants are born at a time of rapid fetal growth, they are at risk of deficiency of essential nutrients for brain development, including zinc (Zn) and copper (Cu). This study evaluate the relationship between serum Cu or Zn, gestational age (GA) and anthropometric parameters at birth in preterm infants. METHODS: This was a retrospective study of infants <35 weeks' GA from January 2010 to August 2012. We collected the data from medical records of 59 preterm infants at birth with regard to GA, anthropometric parameters, and serum Cu and Zn levels. Correlation of Cu, Zn, and GA with anthropometric parameters at birth was then done. RESULTS: Zn was inversely correlated with GA, bodyweight (BW), body length (BL), and head circumference (HC), and Cu was inversely correlated with the standard deviation (SD) score for BW, BL, and HC. On stepwise multiple regression analysis, GA was a significant independent predictor of Zn level, and HC SD score was a significant independent predictor of Cu level. CONCLUSIONS: Prematurity influences Zn, and intrauterine head growth restriction influences Cu at birth in preterm infants. Further research is needed to evaluate the relationship between intrauterine growth restriction and brain Cu metabolism.

The Ratio of Docosahexaenoic Acid and Arachidonic Acid in Infant Formula Influences the Fatty Acid Composition of the Erythrocyte Membrane in Low-Birth-Weight Infants.

OBJECTIVE: The arachidonic acid (ARA) and docosahexaenoic acid (DHA) contents in the infant formula influence on the growth and development of low-birth-weight infants (LBWI). In Japan, many infant formulas are fortified only with DHA. We investigated the safety and efficacy of an infant formula (H2025A) fortified with DHA and ARA (DHA/ARA ratio of 2:1, the same as that in Japanese breast milk). METHODS: In this randomized double-blind trial, 35 LBWI were randomly allocated to 2 groups fed with H2025A or an infant formula fortified only with DHA (control formula) after discharge from the NICU. The duration of this study was one month, and the growth and fatty acid composition of the erythrocyte membrane were compared between the 2 groups. RESULTS: No difference was found in the body weight gain, height gain and head circumstance gain development between the 2 groups, and no adverse event occurred in both groups. The ARA content of the erythrocyte membrane after feeding for 1 month was significantly higher in the H2025A group than in the control group. On analysis adjusted with the breast-fed ratio, the ARA and DHA contents were significantly higher in the H2025A group. CONCLUSION: It was suggested that H2025A significantly increased the ARA and DHA contents of the erythrocyte membrane of LBWI compared to the contents of the control formula.

Amplitude-integrated electroencephalography in patients with acute encephalopathy with refractory, repetitive partial seizures.

We report amplitude-integrated EEG findings in two children with acute encephalopathy with refractory, repetitive partial seizures. Both patients had a febrile illness one week before the onset of seizure. They had reduction of consciousness and repetitive seizures refractory to first-line antiepileptic drugs. Seizure frequency rapidly increased and evolved into status epilepticus. Continuous seizure monitoring with amplitude-integrated EEG revealed frequent subclinical seizures which were missed by direct observation. In addition, the site of origin of seizures was multifocal, and seizure foci shifted from one hemisphere to the other. Their seizures were controlled after an administration of high-dose phenobarbital. Continuous seizure monitoring with amplitude-integrated EEG will contribute to correct estimation of seizure burden and efficacy of antiepileptic drugs in children with acute encephalopathy with refractory, repetitive partial seizures.

Clustered subclinical seizures in a patient with acute encephalopathy with biphasic seizures and late reduced diffusion.

Using single-channel amplitude-integrated electroencephalography (aEEG), we monitored clustered seizures in a 12-month-old boy suffering from acute encephalopathy with biphasic seizures and late reduced diffusion (AESD). He was admitted to our hospital after losing consciousness and experiencing repeated seizures in association with fever. Although the patient's state of consciousness improved the next day, it declined on the fifth day of illness, and clinical seizures were observed. Diffusion-weighted images revealed abnormal high intensities in the frontal area bilaterally. On the same day, aEEG monitoring revealed an unexpected cluster of subclinical seizures. Attending pediatricians, nurses, and other caregivers did not recognize the presence of these frequent subclinical seizures. The efficacy of antiepileptic drugs could also be objectively assessed from aEEG findings. aEEG is useful for continuous monitoring in children with acute encephalopathy, may disclose subclinical seizures, and can contribute to an objective evaluation of the efficacy of antiepileptic drugs.

Effects of ghrelin on growth and cardiac function in infants with congenital heart disease.

BACKGROUND: Ghrelin has effects on appetite and growth. Recent reports suggest effects on cardiac function, but no study has evaluated the ghrelin levels of congenital heart disease (CHD) infants with heart failure. The purpose of the present study was therefore to investigate the relationship between ghrelin level and growth and cardiac function in CHD infants. METHODS: Twenty-eight infants with CHD were eligible for the study. Blood samples were obtained at the time of insertion of intracardiac catheter and correlation was examined between ghrelin plasma level and anthropometric parameters, including z score of height and weight, body mass index (BMI), and %bodyweight gain rate, severity of heart failure, and the levels of leptin and insulin-like growth factor-1. RESULTS: In the CHD group, active ghrelin (A-Ghr) had a significant negative correlation with z score of bodyweight, and a significant positive correlation with cardiac function. There were no correlations, however, with height and BMI. A-Ghr levels were significantly higher in the high heart failure index score group. Significant correlation between A-Ghr and desacyl-ghrelin in the CHD group was observed. CONCLUSIONS: A-Ghr is involved in cardiac function and has little effect on their physique in infants with CHD.

Usefulness of single-channel amplitude-integrated electroencephalography for continuous seizure monitoring in infancy: a case report.

We continuously monitored clustered seizures using single-channel amplitude-integrated electroencephalography (aEEG) in a 6-month-old girl with probable benign partial epilepsy in infancy (BPEI). The patient was admitted with clustered seizures, and aEEG using three disposable electrodes was started by a non-expert pediatrician. During the recording, seven seizures were detected. The last seizure was nearly overlooked on clinical observation, but was later confirmed on the basis of aEEG findings. The efficacy of antiepileptic drugs could also be objectively assessed from aEEG findings. Our results show that aEEG is useful for the continuous monitoring of seizures even in older children.

Effects of alpha-linolenic acid on colonic secretion in rats with experimental colitis.

BACKGROUND: Few studies have specifically examined the effects of n-3 polyunsaturated fatty acids (PUFAs) on intestinal water and ion secretion in ulcerative colitis (UC). The aim of this study was to examine the contribution of prostaglandins (PGs) and leukotrienes (LTs) to mucosal secretion in intestines with UC and to evaluate the effect of dietary n-3 PUFAs on diarrhea in UC. METHODS: We measured the short-circuit current (Isc), using the Ussing chamber method, and fatty acid composition in the colonic mucosa of rats with dextran sulfate sodium (DSS)-induced experimental colitis. The DSS-treated rats were fed either a perilla oil-enriched diet (perilla group) or a soybean oil-enriched diet (soybean group); a control group did not undergo DSS administration. RESULTS: The bradykinin-stimulated DeltaIsc in the soybean and perilla groups was significantly higher than that in the control group. The mucosal level of arachidonic acid in the perilla group was significantly lower than that in the soybean group. The mucosal levels of alpha-linolenic acid and EPA in the perilla group were significantly higher than those in the soybean group. The bradykinin-stimulated DeltaIsc was significantly suppressed after pretreatment with indomethacin in both the soybean and perilla groups, and was also significantly reduced in both groups after pretreatment with AA861. The suppression of bradykinin-stimulated DeltaIsc by the addition of AA861 was significantly higher in the perilla group than in the soybean group. CONCLUSIONS: Our results suggest that supplementation with alpha-linolenic acid, in combination with a lipoxygenase inhibitor, could suppress the increase in Cl- secretion in patients with UC.

Suppression of azoxymethane-induced colon cancer development in rats by a cyclooxygenase-1 selective inhibitor, mofezolac.

We demonstrated recently that mofezolac, a cyclooxygenase-1 (COX-1) selective inhibitor, suppresses the development of azoxymethane (AOM)-induced colonic aberrant crypt foci in F344 rats and intestinal polyps in APC1309 mice. In the present study, we therefore investigated the effects of mofezolac on colon cancer development. Male F344 rats were injected subcutaneously with 15 mg/kg body weight of AOM in the back twice at 7-day intervals from 5 weeks of age, and fed a diet containing 600 or 1200 ppm mofezolac for 32 weeks, starting 1 day before the first dosing of AOM. Treatment with 1200 ppm mofezolac significantly reduced the incidence, multiplicity and volume of colon carcinomas to 79%, 2.15 +/- 1.65 and 7.5 +/- 11.8 mm3, respectively, compared with 94%, 3.19 +/- 1.87 and 23.7 +/- 31.2 mm3 in the AOM treatment alone. Administration of 600 ppm mofezolac showed only a slight reduction. No side effects were observed in any of the groups. These results confirm that COX-1, as well as COX-2, contributes to colon carcinogenesis and that mofezolac may be a good chemopreventive agent for human colon cancer.

Prostaglandin E receptor EP3 deficiency modifies tumor outcome in mouse two-stage skin carcinogenesis.

We have recently shown that the prostaglandin E(2) (PGE(2)) receptor EP(3) plays an important role in suppression of colon cancer cell proliferation and that its deficiency enhances late stage colon carcinogenesis. Here we examined the effects of EP(3)-deficiency on two-stage skin carcinogenesis. 7,12-Dimethylbenz[a]anthracene (50 microg/200 microl of acetone) was thus applied to the back skin of female EP(3)-knockout and wild-type mice at 8 weeks of age, followed by treatment with 12-O-tetradecanoylphorbol-13-acetate (5 microg/200 microl of acetone) twice a week for 25 weeks. First tumor appearance was observed in EP(3)-knockout mice at week 10, which was 3 weeks later than in EP(3) wild-type mice, and multiplicity observed at week 11 was significantly lower in the EP(3)-knockout case. However, histological examination showed that the tumor incidence and multiplicity at week 25 were not significantly changed in knockout mice and wild-type mice (incidence, 19/19 versus 23/24; multiplicity, 3.58 +/- 0.51 versus 3.17 +/- 0.63, respectively). Interestingly, there were no squamous cell carcinomas (SCCs) in the EP(3)-knockout mice, while SCCs were observed in 3 out of 24 wild-type mice. Furthermore, benign keratoacanthomas only developed in EP(3)-knockout mice (6/19 versus 0/24, P < 0.01). The results suggest that PGE(2) receptor EP(3) signaling might contribute to development of SCCs in the skin.

Suppression of azoxymethane-induced colon cancer development in rats by a prostaglandin E receptor EP1-selective antagonist.

Prostaglandin E(2) is involved in colon carcinogenesis through its binding to the PGE(2) receptor subtypes EP(1), EP(2), EP(3) and EP(4). We have demonstrated that administration of ONO-8711, an EP(1)-selective antagonist, suppresses development of AOM-induced ACF in C57BL/6 mice and F344 rats. ONO-8711 also reduced the numbers of intestinal polyps in Min mice. In the present study, we investigated the long-term effects of ONO-8711 on colon cancer development in rats treated with AOM. Male F344 rats were injected subcutaneously with AOM (15 mg/kg body weight) once a week for the first 2 weeks to develop colon cancer. Administration of 400 or 800 p.p.m. ONO-8711 in their diets for 32 weeks reduced the incidence, multiplicity and volume of colon carcinomas. The incidence of colon adenocarcinomas in AOM-treated rats was 97, 83 and 76% (P < 0.05) in the 0, 400 and 800 p.p.m. of ONO-8711 groups, respectively. The multiplicity of adenocarcinomas was also decreased significantly, being 3.31 +/- 0.33, 2.34 +/- 0.27 (P < 0.05) and 2.06 +/- 0.34 (P < 0.01) with 0, 400 and 800 p.p.m. of ONO-8711, respectively. Moreover, treatment with 800 p.p.m. ONO-8711 reduced the mean volume of adenocarcinomas to 49% (P < 0.05) of the value for the AOM treatment alone. Furthermore, the BrdU labeling index was decreased significantly in colon cancer cells by 800 p.p.m. ONO-8711. These results confirm that EP(1) is involved in colon carcinogenesis and that EP(1)-selective antagonists might be promising candidates for colon cancer chemopreventive agents.

Prostaglandin E receptor subtype EP(1) deficiency inhibits colon cancer development.

Prostaglandin E(2) exerts its biological activity through binding to its membrane receptors, E-prostanoid (EP) receptors. Our previous finding that lack of EP(1) receptor inhibits the early stages of colon carcinogenesis led us to investigate whether EP(1) receptor deficiency reduces colon cancer development induced by azoxymethane (AOM) using EP(1) receptor knockout mice. At 6 weeks of age 33 homozygous EP(1)-deficient (EP(1)(-/-)) mice and 28 wild-type (EP(1)(+/+)) mice were given i.p. AOM (10 mg/kg body wt) once a week for 6 weeks. At 56 weeks of age all animals were killed and intestinal tumors were examined. The results clearly indicated that lack of EP(1) receptor significantly reduced colon cancer incidence (27 versus 57%, P < 0.05) and multiplicity (0.30 versus 0.76, P < 0.05) as well as tumor volume (12.2 versus 75.6 mm(3), P < 0.05). In EP(1)(-/-) mice, silver stained nucleolar organization region protein count as cell proliferation marker was significantly reduced (1.35 versus 2.17, P < 0.001) and apoptosis was significantly increased (0.685 versus 0.077, P < 0.001) in colon tumors induced by AOM compared with those in EP(1)(+/+) mice. We confirmed that EP(1) receptor mRNA was overexpressed in colon cancers of EP(1)(+/+) mice using reverse transcription-polymerase chain reaction. These results provide strong evidence that the EP(1) receptor is of major importance for colon cancer development and it could be a new target for a mechanism-based chemoprevention strategy against colon cancer development.

Carcinogenicity of aminophenylnorharman, a possible novel endogenous mutagen, formed from norharman and aniline, in F344 rats.

A novel mutagenic compound, 9-(4'-aminophenyl)-9H- pyrido[3,4-b]indole (aminophenylnorharman, APNH), is shown to be formed by the in vitro enzymatic reaction of 9H-pyrido[3,4-b]indole (norharman) and aniline. APNH generates DNA adducts (dG-C8-APNH), and is potently genotoxic to bacteria and mammalian cells. APNH has also been demonstrated to be formed in vivo from norharman and aniline, and suggested to be a new type of endogenous mutagenic compound. To determine its carcinogenic activity, long-term administration of APNH was investigated in 93 male and 90 female F344 rats. Rats were fed diets containing 0, 20 or 40 p.p.m. from 7 weeks of age. All animals were killed after 85 weeks treatment and necropsy was performed. Hepatocellular carcinomas (HCCs) were induced at incidences of 10 and 79% in male rats fed 20 and 40 p.p.m. APNH, and 34% in female rats fed 40 p.p.m. of APNH, respectively. In addition, colon adenocarcinomas were found at incidences of 3 and 9% in male rats, and 4 and 13% in female rats fed 20 and 40 p.p.m. of APNH, respectively. Other tumors, including thyroid carcinomas and mononuclear cell leukemia, were also seen in rats fed APNH. Polymerase chain reaction-single strand conformation polymorphism analysis revealed beta-catenin gene mutations in 24% of HCCs and K-ras, beta-catenin and Apc gene mutations were found in 22, 44 and 33% of colon cancers induced by APNH, respectively. Most mutations occurred at G:C base pairs. beta-Catenin protein accumulations in the nucleus and cytoplasm were also revealed in both liver and colon tumors. Thus, APNH induced liver and colon cancers with K-ras, beta-catenin and Apc gene mutations in F344 rats.

Combined effects of cyclooxygenase-1 and cyclooxygenase-2 selective inhibitors on intestinal tumorigenesis in adenomatous polyposis coli gene knockout mice.

As with cyclooxygenase (COX)-2, genetic disruption of COX-1 gene or pharmacologic inhibition of its activity has been shown to decrease the number of intestinal polyps in Apc gene-deficient mice. The present study was designed to investigate the combined effects of COX-1 and COX-2 selective inhibitors on spontaneous polyp formation in APC1309 female mice. The animals were treated with 300 or 600 ppm mofezolac (a COX-1 selective inhibitor) alone, 200 or 400 ppm nimesulide (a COX-2 selective inhibitor) alone, 300 ppm mofezolac plus 200 ppm nimesulide, 600 ppm mofezolac plus 400 ppm nimesulide, or 10 ppm indomethacin (a dual-COX inhibitor) in the diet from 7 weeks of age for 4 weeks. Percentage inhibition of polyp area in the intestine was 17% with 600 ppm mofezolac alone and 25% with 400 ppm nimesulide alone, their sum of 42% being almost equal to the 37% observed for the combination treatment. Administration of 300 ppm mofezolac plus 200 ppm nimesulide also significantly decreased polyp area in the intestine by 30%. Moreover, the numbers of polyps more than 2.5 mm in diameter were markedly decreased by combined treatment of both COX inhibitors. With 10 ppm indomethacin, the dual inhibitor, polyp area was also clearly reduced by 46%. Our results indicate that COX-1 and COX-2 may to some extent contribute to polyp formation independently and inhibitor combination treatment thus has particular potential for chemoprevention of colon carcinogenesis.

Concomitant suppression of hyperlipidemia and intestinal polyp formation in Apc-deficient mice by peroxisome proliferator-activated receptor ligands.

Epidemiological studies have shown a positive association of colon cancer with hyperlipidemia. Furthermore, signaling generated by peroxisome proliferator-activated receptor (PPAR) alpha and gamma ligands, suggested to be candidate tumor preventive agents, has been shown to lower serum triglyceride levels. In the present study, we assessed hyperlipidemia in Apc-deficient mice, model animals for human familial adenomatous polyposis, and examined the effects of pioglitazone and bezafibrate, respectively, PPARgamma and PPARalpha agonists, on both hyperlipidemia and intestinal polyposis. Serum lipid levels in Apc(1309) mice and Min mice from 6 to 15 weeks of age were measured. Although serum levels of triglyceride and cholesterol were low in both Apc(1309) and wild-type mice at 6 weeks, triglycerides were elevated 10-fold in Apc(1309) mice by the age of 12 weeks but not in their wild-type counterparts. Cholesterol was also increased significantly, and marked centrilobular-restricted steatosis was observed in the livers of aged Apc(1309) mice. Similar findings were observed for Min mice at 15 weeks of age. Moreover, lipoprotein lipase mRNA levels in the liver and small intestine of Apc(1309) and Min mice were demonstrated to be lower than those in wild-type mice. Treatment of Apc(1309) mice with 100 and 200 ppm pioglitazone or bezafibrate for 6 weeks from 6 weeks of age caused dose-dependent reduction in serum triglycerides and cholesterol, along with reduction in the numbers of intestinal polyps to 67% of the control value. The present study clearly demonstrated a hyperlipidemic state in Apc gene-deficient mice and a potential of PPARalpha and PPARgamma ligands to suppress both hyperlipidemia and polyp formation. Hyperlipidemia in these mice may thus be associated with their intestinal lesion development.

Combined effects of prostaglandin E receptor subtype EP1 and subtype EP4 antagonists on intestinal tumorigenesis in adenomatous polyposis coli gene knockout mice.

Previous studies have shown that prostaglandin E(2) (PGE(2)) is involved in intestinal carcinogenesis through its binding to the PGE(2) receptor subtypes EP(1) and EP(4) and activation of downstream pathways. ONO-8711 and ONO-AE2-227, prostaglandin E receptor subtype EP(1)- and EP(4)-selective antagonists, respectively, are known to suppress formation of intestinal polyps in adenomatous polyposis coli gene-deficient mice. The present study was designed to investigate the combined effects of EP(1) and EP(4) antagonists on spontaneous polyp formation in APC1309 mice in order to determine the contribution of each receptor to intestinal tumorigenesis. APC1309 mice were treated with 400 ppm of ONO-8711 alone, 400 ppm of ONO-AE2-227 alone or both in combination in the diet for 6 weeks. The mean area of polyps found in the intestine, calculated as the longer diameter x the shorter diameter x pi, was reduced by 12%, 43% (P < 0.01) and 56% (P < 0.01) of the mean control value (8.8 mm(2)) in the ONO-8711 alone, ONO-AE2-227 alone and combination treatment groups, respectively, suggesting clear additive effects of the combination. The same additive tendency for suppression was also observed with respect to the numbers of polyps in the intestine. Polyp size reduction was more remarkable with the EP(4) antagonist, while the number reduction was more pronounced with the EP(1) antagonist. Our results indicate that EP(1) and EP(4) may have separate intrinsic roles and, to some extent, contribute to polyp formation independently. Thus, combination treatment has potential for the chemoprevention of colon carcinogenesis.

Inhibitory effects of mofezolac, a cyclooxygenase-1 selective inhibitor, on intestinal carcinogenesis.

Cyclooxygenase (COX)-2, one enzyme isoform responsible for producing prostanoids from arachidonic acid, contributes to colon carcinogenesis. Recently, genetic disruption of COX-1, the other isoform, was shown to decrease the number of intestinal polyps and prostaglandin E(2) levels in intestinal mucosa, like the case with COX-2 gene disruption, in Min mice. We therefore investigated whether a COX-1 selective inhibitor, mofezolac, suppresses intestinal carcinogenesis in rodents. F344 male rats, receiving azoxymethane (AOM, 15 mg/kg body wt) s.c. injections at 5 and 6 weeks of age, were fed a diet containing 600 or 1200 p.p.m. mofezolac for 4 weeks. The number of aberrant crypt foci (ACFs) per rat and the bromodeoxyuridine labeling index of the crypt epithelium were dose-dependently decreased by administration of mofezolac, the value for the former at 1200 p.p.m. being 60% of control value. When Apc gene knockout mice (APC1309 mice) were given 600 or 1200 p.p.m. mofezolac in their diet for 8 weeks, the numbers of intestinal polyps were also dose-dependently decreased, with reduction to 59% of that in the control diet group at the higher dose. Nimesulide, a COX-2 selective inhibitor used as positive control, showed similar suppressive effects on the development of ACFs in AOM-treated rats and polyps in Apc gene knockout mice. The data indicate that both COX-1 and COX-2 can contribute to intestinal tumorigenesis.

Involvement of prostaglandin E receptor subtype EP(4) in colon carcinogenesis.

Accumulating evidence indicates that overproduction of prostanoids attributable to overexpression of cyclooxygenase-2 (COX-2) plays an important role in colon carcinogenesis. We have shown recently that the prostaglandin (PG) E receptor, EP(1), but not EP(3), is involved in mouse colon carcinogenesis. In line with our previous study, here we examined the role of prostanoid receptors in colon carcinogenesis using six additional lines of knockout mice deficient in prostanoid receptors EP(2), EP(4), DP, FP, IP, or TP. The animals were treated with the colon carcinogen, azoxymethane (AOM), and examined for the development of aberrant crypt foci (ACFs), putative preneoplastic lesions in the colon. Formation of ACFs was decreased only in the EP(4)-knockout mice, to 56% of the wild-type level. To confirm these results, we also examined the inhibitory effects of an EP(4)-selective antagonist, ONO-AE2-227, in the diet on the formation of AOM-induced colon ACFs in C57BL/6Cr mice and on the development of intestinal polyps in Min mice. ONO-AE2-227 at a dose of 400 ppm reduced the formation of ACFs to 67% of the control level, and intestinal polyp numbers in Min mice receiving 300 ppm were decreased to 69% of the control level. Plating efficiency assays showed that addition of 1.0 microM ONO-AE1-329, an EP(4)-selective agonist, resulted in a 1.8-fold increase in the colony number of the human colon cancer cell line, HCA-7, similar to the effect of PGE(2). Moreover, EP(4) mRNA expression was clearly observed in normal colon mucosa and colon tumors in mice. Our previous and present results indicate that PGE(2) contributes to colon carcinogenesis through its actions mediated through EP(1) and EP(4) receptors; therefore, antagonists for these two receptors may be good candidates as chemopreventive agents against colon cancer.