Plasminogen activator inhibitor-1 (Pai-1) blockers suppress intestinal polyp formation in Min mice.

Obesity and hyperlipidemia are known to increase colorectal tumor risk. We noticed that Min mice, featuring a defect in the adenomatous polyposis coli (Apc) gene, develop intestinal polyps along with high serum triglyceride (TG) levels up to 10-fold those observed in wild-type mice. In these mice, messenger RNA (mRNA) expression of lipoprotein lipase, which catalyzes hydrolysis of TG, is downregulated. In the present study, we focused on adipocytokines, especially plasminogen activator inhibitor-1 (Pai-1), which is involved in hyperlipidemic status and may promote intestinal polyp formation in Min mice. Serum Pai-1 levels in the 15-week-old male Min mice were eight times higher than in wild-type mice and hepatic Pai-1 mRNA levels were 11-fold increased. In addition, Pai-1 immunostaining was strong in small intestinal epithelial cells of Min mice. Administration of a PAI-1 inhibitor, SK-216, at 25, 50 and 100 p.p.m. doses in the diet for 9 weeks reduced serum Pai-1 levels and hepatic Pai-1 mRNA levels of Min mice to the wild-type levels. Moreover, SK-216 at 50 and 100 p.p.m. significantly reduced total numbers of intestinal polyps to 64 and 56% of the untreated group value, respectively. Serum TG levels were also decreased by 43% at the dose of 100 p.p.m. Administration of 50 p.p.m. SK-116, another PAI-1 inhibitor, for 9 weeks similarly reduced serum Pai-1 levels and total numbers of intestinal polyps to 70% of the untreated group value. These results indicate that Pai-1 induction associated with hypertriglyceridemia may contribute to intestinal polyp formation with Apc deficiency, and PAI-1 could thus be a novel target for colorectal chemopreventive agents.

Improvement of hyperlipidemia by indomethacin in Min mice.

Apc gene-deficient Min and Apc(1309) mice feature a hyperlipidemic state with a markedly low expression level of lipoprotein lipase (LPL) compared to their wild-type counterparts. We previously showed that induction of LPL mRNA by peroxisome proliferator-activated receptor (PPAR) alpha and gamma agonists or an LPL selective inducer suppresses both high serum lipid levels and intestinal polyp formation in these model animals. Since the general cyclooxygenase inhibitor, indomethacin, is known to suppress intestinal tumor development, but not to affect serum lipids, its influence in Min mice was here investigated. Treatment with 2.5, 5 and 10 ppm indomethacin in the diet for 14 weeks from 6 weeks of age caused significant dose-dependent reduction in serum triglycerides, along with a reduction in the numbers of intestinal polyps to 25% of the untreated control value. LPL mRNA levels in the liver were slightly increased by indomethacin treatment. We further performed oligonucleotide microarray analysis and quantitative PCR analysis and found 8 lipid metabolism-related genes, regulated by sterol regulatory element binding protein-1c, to be modulated by indomethacin-treatment in the Min mouse liver. Furthermore, TNFalpha was downregulated. These results indicate that indomethacin might suppress intestinal tumor formation together with a hyperlipidemic state by regulating LPL and other lipid metabolic factors.

Enhanced thyroid carcinogenicity of N-nitrosobis(2-oxopropyl)amine in Otsuka Long-Evans Tokushima Fatty rats, a model of type II diabetes mellitus.

Epidemiologic data suggest that diabetes mellitus type II is a risk factor for several types of cancer, including pancreatic, liver, colon and thyroid cancers. In the present study, effects of diabetes/hyperlipidemia on N-nitrosobis(2-oxopropyl)amine (BOP)-induced cancer development were examined in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, model animals for non-insulin-dependent diabetes mellitus and Long-Evans Tokushima Otsuka (LETO) rats, appropriate controls. Males of both strains were given four subcutaneous injections of BOP (10 mg/kg body wt) or saline on alternative days, starting at 5 weeks of age. BOP induced tumors in a variety of tissues, including the thyroid gland, colon, kidney, liver and lung. The highest yields were noted for thyroid tumors, the incidence (P = 0.0182) and multiplicity (P < 0.001) of BOP-induced thyroid cancers with marked fibrosis being significantly higher in OLETF than in LETO rats. Interestingly, anaplastic thyroid carcinomas were observed limited to the BOP-treated OLETF rats. Additionally, a greater incidence and frequency of aberrant crypt foci, putative precursor lesions for colon tumors, was observed in the BOP-treated OLETF group. However, BOP was ineffective at inducing pancreatic ductal tumors. No thyroid, liver, lung or colon tumors were found in the OLETF and LETO rats receiving the vehicle. Significant increases in serum levels of insulin, glucose, phospholipids, triglycerides and total cholesterol were detected in the OLETF rats compared with the LETO rats, regardless of the treatment. Our results indicate that diabetic/hyperlipidemic state can enhance BOP-induced carcinogenesis of the thyroid gland and to a lesser extent the colon in OLETF rats.

Suppression of N-nitrosobis(2-oxopropyl)amine-induced pancreatic carcinogenesis in hamsters by pioglitazone, a ligand of peroxisome proliferator-activated receptor gamma.

Fat intake and obesity are positively correlated with pancreatic cancer in humans. N-nitrosobis(2-oxopropyl)amine (BOP) induces pancreatic ductal adenocarcinomas limited to Syrian golden hamsters, other rodents not being susceptible. In the present study, we found markedly high levels of serum triglycerides (TGs) and total cholesterol (TC) in Syrian golden hamsters, but not C57BL/6 mice, ICR mice, F344 rats and Wistar rats. Consistent with this, lipoprotein lipase (LPL) activities in the liver were lower in hamsters compared with mice and rats. To examine effects of pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, on LPL expression, serum lipid levels and pancreatic cancer development, 6-week-old female Syrian golden hamsters were subcutaneously injected with BOP (10 mg/kg body wt) four times in a week and thereafter fed a diet containing 800 p.p.m. pioglitazone for 22 weeks. The treatment elevated LPL mRNA expression in the liver and significantly improved hyperlipidemia with serum levels of TG and TC being decreased to 62 and 71%, respectively, of the control values. Concurrently, the incidence and multiplicity of pancreatic ductal adenocarcinomas were significantly decreased by pioglitazone in comparison with the controls (38 versus 80%, P < 0.01 and 0.55 +/- 0.15 versus 1.37 +/- 0.22, P < 0.01, respectively). The suppression rates were greater in invasive adenocarcinomas than non-invasive ones. The incidence of cholangiocellular carcinomas was also reduced. Thus, suppression of pancreatic adenocarcinoma development by pioglitazone is possibly associated with improvement in the serum lipid profile, and hyperlipidemia could be an enhancing factor for development of pancreatic cancer in hamsters.

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.

Concomitant suppression of hyperlipidemia and intestinal polyp formation by increasing lipoprotein lipase activity in Apc-deficient mice.

Epidemiologically, a high-fat diet is associated with the risk of colon cancer. In addition, serum levels of triglycerides (TGs) and cholesterol have been demonstrated to be positively associated with colon carcinogenesis. We recently found that an age-dependent hyperlipidemic state (high serum TG levels) exists in Apc-deficient mice, an animal model for human familial adenomatous polyposis. The mRNA levels of lipoprotein lipase (LPL), which catalyzes TG hydrolysis, were shown to be downregulated in the liver and intestines of mice. Moreover, treatment with a peroxisome proliferator-activated receptor (PPAR) alpha agonist, bezafibrate, or a PPARgamma agonist, pioglitazone, suppressed both hyperlipidemia and intestinal polyp formation in the mice, with induction of LPL mRNA. PPARalpha and PPARgamma agonists are reported to exert anti-proliferative and pro-apoptotic effects in cancer cells. One compound that also increases LPL expression levels but does not possess PPAR agnostic activity is NO-1886. When given at 400 or 800 ppm in the diet, it suppresses both hyperlipidemia and intestinal polyp formation in Apc-deficient mice, with elevation of LPL mRNA. In conclusion, a decrease in serum lipid levels by increasing LPL activity may contribute to a reduction in intestinal polyp formation with Apc deficiency. PPARalpha and PPARgamma agonists, as well as NO-1886, could be useful as chemopreventive agents for colon cancer.

Inhibition of intestinal carcinogenesis by a new flavone derivative, chafuroside, in oolong tea.

A new flavone derivative, chafuroside, has been isolated as a strong anti-inflammatory compound from oolong tea leaves, and its structure determined to be (2R,3S,4S,4aS,11bS)-3,4,11-trihydroxy-2-(hydroxymethyl)-8-(4-hydroxyphenyl)-3,4,4a,11b-tetrahydro-2H,10H-pyrano[2',3':4,5]furo[3,2-g]chromen-10-one. To assess its potential to inhibit intestinal carcinogenesis, 2.5, 5 and 10 p.p.m. chafuroside was given in the diet to Apc-deficient Min mice for 14 weeks from 6 weeks of age. Total numbers of polyps were reduced to 83, 73 and 56% of the control value, respectively. Moreover, dietary administration at 10 and 20 p.p.m. reduced azoxymethane (AOM)-induced colon aberrant crypt foci (ACF) development in rats to 69% of the AOM-treated control value with the higher dose. Chafuroside-associated toxicity was not observed at 2.5-10 p.p.m. in Min mice and 10-20 p.p.m. in AOM-treated rats. These results suggest that chafuroside might be a good chemopreventive agent for colon cancer.

Possible involvement of hyperlipidemia in increasing risk of colorectal tumor development in human familial adenomatous polyposis.

BACKGROUND: Familial adenomatous polyposis (FAP) results from germline adenomatous polyposis coli (APC) gene mutations and many affected patients die from colorectal cancers which arise from colorectal polyps. We previously reported that two strains of Apc gene-deficient mice developing multiple intestinal polyps exhibit a hyperlipidemic state. The triglyceride (TG) levels were approximately 10-fold higher than the levels observed in wild-type mice. METHODS: To examine whether a positive relationship might exist between hyperlipidemia and colorectal tumor development in FAP patients, as with Apc gene-deficient mice, a pilot experiment was performed using readily available clinical data such as ages, serum lipid levels, number of colorectal polyps and cancer development in 28 FAP patients from the National Cancer Center Hospital, Japan. RESULTS: The overall prevalence of hyperlipidemia in FAP cases was 58%. Average TG levels in the 40-60 year age groups of FAP patients were > or =150 mg/dl (the defined threshold level of hyperlipidemia). Moreover, there was a tendency for higher serum TG levels in patients who developed colorectal cancer, as compared with those without colorectal cancer. CONCLUSIONS: These results show that a hyperlipidemic state occurs in FAP patients. Although it is weaker than that in Apc gene-deficient mice, it may be linked to colon tumor development. These data warrant further studies for wider populations of FAP patients.

Dextran sodium sulfate strongly promotes colorectal carcinogenesis in Apc(Min/+) mice: inflammatory stimuli by dextran sodium sulfate results in development of multiple colonic neoplasms.

The mouse model for familial adenomatous polyposis, Apc(Min/+) mouse, contains a truncating mutation in the Apc gene and spontaneously develops numerous adenomas in the small intestine but few in the large bowel. Our study investigated whether dextran sodium sulfate (DSS) treatment promotes the development of colonic neoplasms in Apc(Min/+) mice. Apc(Min/+) and Apc+/+ mice of both sexes were exposed to 2% dextran sodium sulfate in drinking water for 7 days, followed by no further treatment for 4 weeks. Immunohistochemistry for cyclooxygenase-2, inducible nitric oxide synthase, beta-catenin, p53, and nitrotyrosine, and mutations of beta-catenin and K-ras and loss of wild-type allele of the Apc gene in the colonic lesions were examined. Sequential observation of female Apc(Min/+) mice that received DSS was also performed up to week 5. At week 5, numerous colonic neoplasms developed in male and female Apc(Min/+) mice but did not develop in Apc+/+ mice. Adenocarcinomas developed in Apc(Min/+) mice that received DSS showed loss of heterozygosity of Apc and no mutations in the beta-catenin and K-ras genes. The treatment also significantly increased the number of small intestinal polyps. Sequential observation revealed increase in the incidences of colonic neoplasms and dysplastic crypts in female Apc(Min/+) mice given DSS. DSS treatment increased inflammation scores, associated with high intensity staining of beta-catenin, cyclooxygenase-2, inducible nitric oxide synthase and nitrotyrosine. Interestingly, strong nuclear staining of p53 was specifically observed in colonic lesions of Apc(Min/+) mice treated with DSS. Our results suggest a strong promotion effect of DSS in the intestinal carcinogenesis of Apc(Min/+) mice. The findings also suggest that strong oxidative/nitrosative stress caused by DSS-induced inflammation may contribute to the colonic neoplasms development.

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.

Concurrent suppression of hyperlipidemia and intestinal polyp formation by NO-1886, increasing lipoprotein lipase activity in Min mice.

We have previously reported a hyperlipidemic state in two strains of Apc-deficient mice, Min and Apc(1309), associated with low expression levels of lipoprotein lipase (LPL) in the liver and small intestine, and enforced induction of LPL mRNA by peroxisome proliferator-activated receptor (PPAR)alpha and PPARgamma agonists clearly suppressed hyperlipidemia and intestinal polyp formation in these mice. Meanwhile, a compound, NO-1886, has been shown to increase LPL mRNA and protein levels but not to possess PPARalpha and PPARgamma agonistic activity. In this study, therefore, the effects of NO-1886 on hyperlipidemia and intestinal polyp formation were investigated in Min mice. Administration of 400 and 800 ppm NO-1886 in the diet for 13 weeks from 7 weeks of age caused a reduction of serum triglycerides to 39% and 31% of the untreated value, respectively, and the values for very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were improved almost to the wild-type level with a corresponding elevation of the LPL mRNA. Moreover, total numbers of intestinal polyps in the groups receiving NO-1886 at 400 and 800 ppm were decreased to 48% and 42% of the control value, respectively. We also found that NO-1886 suppressed cyclooxygenase-2 transcriptional promoter activity in a reporter gene assay and reduced cyclooxygenase-2 mRNA levels in the small intestine of Min mice. These results indicate that suppression of serum lipid levels by increasing LPL activity may contribute to a reduction of intestinal polyp formation with Apc-deficiency, and NO-1886 and its derivatives could be useful as chemopreventive agents for colon cancer.

Dose-dependent suppression of hyperlipidemia and intestinal polyp formation in Min mice by pioglitazone, a PPAR gamma ligand.

In our previous study, a peroxisome proliferator-activated receptor gamma (PPAR gamma) agonist, pioglitazone, suppressed both hyperlipidemia and intestinal polyp formation in Apc(1309) mice at doses of 100 and 200 ppm in the diet. In contrast, it has been reported that doses of 1500 or 2000 ppm of another PPAR gamma agonist, troglitazone, enhanced colon polyp development in Min mice. In the present study, we therefore investigated the effects of a wide range of pioglitazone doses on both hyperlipidemia and intestinal polyp formation in Min mice. Serum triglycerides and very low density lipoprotein (VLDL) cholesterol in the basal diet group were elevated to levels 13-15 times higher than those in the wild-type counterparts at 20 weeks of age. They were reduced dose-dependently by treatment with 100, 200, 400 and 1600 ppm pioglitazone from 6-20 weeks of age with suppression to almost the wild-type level at the highest dose. Moreover, up-regulation of the liver mRNA levels for lipoprotein lipase (LPL) was evident in the pioglitazone-treated animals. Dose-dependent reduction of intestinal polyps was observed in Min mice given 100-1600 ppm for 14 weeks, total numbers being decreased to 63-9% of the control value. A suppressive effect of pioglitazone on colon polyp formation was also found. The PPAR gamma agonist, pioglitazone, may thus be a promising candidate chemopreventive agent for colon cancer.

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.

Lack of significant effects of genistein on the progression of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in ovariectomized Sprague-Dawley rats.

Genistein is thought to be one of the possible factors for decreasing the incidence of breast cancer in Asian peoples who take soy-rich diets. However, some experimental data suggest that genistein can stimulate breast cancer development via its estrogenic activities. To clarify the influence of genistein on the promotion/progression stage of mammary carcinogenesis, female Sprague-Dawley rats received a single intragastric administration of 7,12-dimethylbenz(a)anthracene (DMBA). When the incidence of palpable mammary tumors reached about 50%, all animals were then subjected to ovariectomy and divided into tumor-bearing [DMBA-tumor (+)] and no-tumor-bearing [DMBA-tumor (-)] groups, with subgroups of each treated with genistein at concentrations of 0, 25, or 250 ppm in soybean-free diet for 36 wk. At terminal sacrifice, the 25-ppm subgroup of DMBA-tumor(+) had a higher tumor incidence and volume, whereas the 250-ppm subgroup showed lower incidence, number, and volume than the 0-ppm subgroup, although differences were not statistically significant. In the DMBA-tumor(-) groups, eventual tumor volumes in the genistein-treated groups were dose dependently smaller than in the 0-ppm subgroup, although again without statistical significance. The present study indicates that genistein does not exert clear inhibitory effects on mammary carcinogenesis in the promotion/progression stage in female rats under ovarian hormone-free conditions.

Priming effects of novel nonsteroidal progesterone receptor modulators CP8816 and CP8863 on the development of adenomyosis in the mouse uterus.

The possibility of therapeutic application of novel nonsteroidal progesterone receptor modulators CP8816 and CP8863 for preventing the development of uterine adenomyosis was investigated in mice. First priming effects of CP8816 on 17beta-estradiol (E2)-induced cell division in uterine tissues were examined. As a result, pretreatment with CP8816 or progesterone significantly suppressed the elevation of the mitotic activity in the luminal epithelial cells of mice treated with E2 later. Priming with CP8816 had little effect on the stromal cells, but progesterone priming caused an increase of stromal mitotic activity in mice treated with E2 later. To evaluate the inhibitory effect of these compounds on the development of adenomyosis induced experimentally by pituitary grafting, 7-week-old female mice were isografted with a single anterior pituitary in the uterus and divided into four groups. Two groups of mice were given daily subcutaneous injections of 1 mg of CP8816 or the vehicle alone for 6 weeks from the day after the grafting. Remaining two groups of mice were given oral administration of 1 mg of CP8863 or the vehicle only for 5 weeks starting one week after the grafting. The incidence of adenomyosis was significantly lower in the groups of mice treated with CP8816 and CP8863 than in the respective control groups. The mechanism by which CP compounds inhibited the development of adenomyosis might be related to their priming effects, i.e., their inhibitory effect on epithelial cell division and lack of effect on stromal cell division after subsequent exposure to E2.