EP1-4 subtype, COX and PPAR gamma receptor expression in colorectal cancer in prediction of disease-specific mortality

Expression of Peroxisome Proliferator-Activated Receptor γ in Human Colorectal Carcinoma and Its Correlation with Clinicopathological Characteristics

Peroxisome proliferator activator receptor γ (PPAR γ) activation may be responsible for inhibiting the growth of cancer cell lines, and drugs that activate PPAR γ may have therapeutic benefits. Therefore, a mutation in peroxisome proliferator activator receptor γ can produce carcinogenesis. This present study aims to assess the expression of PPAR γ by immunohistochemistry in colorectal carcinoma and its correlation with clinicopathological characteristics. Most of the cases were elderly males, and pelvic pain and bleeding were the predominant symptoms. Colon carcinoma was more common than rectal carcinoma. The adenocarcinoma NOS and mucinous carcinoma were the common histological types, and 40% cases showed lymph node metastasis. The PPAR γ expression was present in 61.8% of the patients, and it showed a significant correlation with lymph node metastasis and tumor location (p = 0.05 and p = 0.04). The overall survival was slightly higher but non-significant in patients with positive PPAR γ expression than negative ones (p = 0.7). The multivariate analysis revealed that nodal metastasis, lymphovascular invasion, and tumor-infiltrating lymphocytes were the independent prognostic factors for colorectal carcinoma. The PPAR γ expression showed a significant correlation with lymph node metastasis and tumor location. Thus, we hypothesized that the PPAR γ expression might affect the overall survival in colorectal cancer. However, more studies with larger sample size are required to understand the nature of colorectal cancer expressing PPAR γ which might benefit the patient therapeutically in future.

Prostaglandin E2 in the Tumor Microenvironment, a Convoluted Affair Mediated by EP Receptors 2 and 4

The involvement of the prostaglandin E2 (PGE2) system in cancer progression has long been recognized. PGE2 functions as an autocrine and paracrine signaling molecule with pleiotropic effects in the human body. High levels of intratumoral PGE2 and overexpression of the key metabolic enzymes of PGE2 have been observed and suggested to contribute to tumor progression. This has been claimed for different types of solid tumors, including, but not limited to, lung, breast, and colon cancer. PGE2 has direct effects on tumor cells and angiogenesis that are known to promote tumor development. However, one of the main mechanisms behind PGE2 driving cancerogenesis is currently thought to be anchored in suppressed antitumor immunity, thus providing possible therapeutic targets to be used in cancer immunotherapies. EP2 and EP4, two receptors for PGE2, are emerging as being the most relevant for this purpose. This review aims to summarize the known roles of PGE2 in the immune system and its functions within the tumor microenvironment. SIGNIFICANCE STATEMENT: Prostaglandin E2 (PGE2) has long been known to be a signaling molecule in cancer. Its presence in tumors has been repeatedly associated with disease progression. Elucidation of its effects on immunological components of the tumor microenvironment has highlighted the potential of PGE2 receptor antagonists in cancer treatment, particularly in combination with immune checkpoint inhibitor therapeutics. Adjuvant treatment could increase the response rates and the efficacy of immune-based therapies.

Leveraging Lymphatic System Targeting in Systemic Lupus Erythematosus for Improved Clinical Outcomes

The role of advanced drug delivery strategies in drug repositioning and minimizing drug attrition rates, when applied early in drug discovery, is poised to increase the translational impact of various therapeutic strategies in disease prevention and treatment. In this context, drug delivery to the lymphatic system is gaining prominence not only to improve the systemic bioavailability of various pharmaceutical drugs but also to target certain specific diseases associated with the lymphatic system. Although the role of the lymphatic system in lupus is known, very little is done to target drugs to yield improved clinical benefits. In this review, we discuss recent advances in drug delivery strategies to treat lupus, the various routes of drug administration leading to improved lymph node bioavailability, and the available technologies applied in other areas that can be adapted to lupus treatment. Moreover, this review also presents some recent findings that demonstrate the promise of lymphatic targeting in a preclinical setting, offering renewed hope for certain pharmaceutical drugs that are limited by efficacy in their conventional dosage forms. These findings underscore the potential and feasibility of such lymphatic drug-targeting approaches to enhance therapeutic efficacy in lupus and minimize off-target effects of the pharmaceutical drugs. SIGNIFICANCE STATEMENT: The World Health Organization estimates that there are currently 5 million humans living with some form of lupus. With limited success in lupus drug discovery, turning to effective delivery strategies with existing drug molecules, as well as those in the early stage of discovery, could lead to better clinical outcomes. After all, effective delivery strategies have been proven to improve treatment outcomes.

Prostaglandin E2 receptor EP1 expression in vulvar cancer

PURPOSE

In recent years, incidence of vulvar cancer has been on the rise, whereas therapeutic options are still restricted. Therefore, new prognosticators and therapeutic targets are essential. Chronic inflammation plays an important role in carcinogenesis and COX-2, and its product prostaglandin E2 and its receptors EP1-4 are known to be important mediators in cancer initiation and progression.

METHODS

EP1 expression in vulvar cancer specimens (n = 129) was investigated via immunohistochemistry and evaluated using the well-established immunoreactive score (IRS). Subsequently, the values were correlated with clinicopathological parameters.

RESULTS

Our analysis did not reveal EP1 expression as a negative prognostic factor in overall and disease-free survival. However, in the subgroup of patients with lymph-node metastasis, overall survival was significantly shorter in tumors with high EP1 expression. Moreover, EP1 expression correlated positively with good differentiation of the tumor, but not with p16 status or COX-2 expression.

CONCLUSIONS

This study shed first light on EP1 expression in vulvar carcinoma. EP1 expression correlated significantly with the grading of the tumor, suggesting that it influences cell differentiation. Further research on EP1 signaling may lead to a deeper understanding of the molecular mechanisms of carcinogenesis.

Reduced tumor growth in EP2 knockout mice is related to signaling pathways favoring an increased local anti‑tumor immunity in the tumor stroma

Inflammatory signaling through prostaglandin E2 receptor subtype 2 (EP2) is associated with malignant tumor growth in both experimental models and cancer patients. Thus, the absence of EP2 receptors in host tissues appears to reduce tumor growth and systemic inflammation by inducing major alterations in gene expression levels across tumor tissue compartments. However, it is not yet well‑established how signaling pathways in tumor tissue relate to simultaneous signaling alterations in the surrounding tumor‑stroma, at conditions of reduced disease progression due to decreased host inflammation. In the present study, wild‑type tumor cells, producing high levels of prostaglandin E2 (MCG 101 cells, EP2+/+), were inoculated into EP2 knockout (EP2‑/‑) and EP2 wild‑type (EP2+/+) mice. Solid tumors were dissected into tumor‑ and tumor‑stroma tissue compartments for RNA expression microarray screening, followed by metabolic pathway analyses. Immunohistochemistry was used to confirm adequate dissections of tissue compartments, and to assess cell proliferation (Ki‑67), prostaglandin enzymes (cyclooxygenase 2) and immunity biomarkers (CD4 and CD8) at the protein level. Microarray analyses revealed statistically significant alterations in gene expression in the tumor‑stroma compartment, while significantly less pathway alterations occurred in the tumor tissue compartment. The host knockout of EP2 receptors led to a significant downregulation of cell cycle regulatory factors in the tumor‑stroma compartment, while interferon γ‑related pathways, chemokine signaling pathways and anti‑tumor chemokines [chemokine (C‑X‑C motif) ligand 9 and 10] were upregulated in the tumor compartment. Thus, such gene alterations were likely related to reduced tumor growth in EP2‑deficient hosts. On the whole, pathway analyses of both tumor‑ and tumor‑stroma compartments suggested that absence of host EP2 receptor signaling reduces 'remodeling' of tumor microenvironments and increase local immunity, probably by decreased productions of stimulating growth factors, perhaps similar to well‑recognized physiological observations in wound healing.

Nanomolar EP4 receptor potency and expression of eicosanoid-related enzymes in normal appearing colonic mucosa from patients with colorectal neoplasia

Background

Aberrations in cyclooxygenase and lipoxygenase (LOX) pathways in non-neoplastic, normal appearing mucosa from patients with colorectal neoplasia (CRN), could hypothetically qualify as predisposing CRN-markers.

Methods

To test this hypothesis, biopsies were obtained during colonoscopy from macroscopically normal colonic mucosa from patients with and without CRN. Prostaglandin E2 (PGE₂) receptors, EP1-4, were examined in Ussing-chambers by exposing biopsies to selective EP receptor agonists, antagonists and PGE₂. Furthermore, mRNA expression of EP receptors, prostanoid synthases and LOX enzymes were evaluated with qPCR.

Results

Data suggest that PGE₂ binds to both high and low affinity EP receptors. In particular, PGE₂ demonstrated EP4 receptor potency in the low nanomolar range. Similar results were detected using EP2 and EP4 agonists. In CRN patients, mRNA-levels were higher for EP1 and EP2 receptors and for enzymes prostaglandin-I synthase, 5-LOX, 12-LOX and 15-LOX.

Conclusions

In conclusion, normal appearing colonic mucosa from CRN patients demonstrates deviating expression in eicosanoid pathways, which might indicate a likely predisposition for early CRN development and furthermore that PGE₂ potently activates high affinity EP4 receptor subtypes, supporting relevance of testing EP4 antagonists in colorectal neoplasia management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02311-z.

Inflammation Modulation by Vitamin D and Calcium in the Morphologically Normal Colorectal Mucosa of Patients with Colorectal Adenoma in a Clinical Trial

Increased COX-2 and decreased 15-hydroxyprostaglandin dehydrogenase (15-HPGD) expression promote prostaglandin-mediated inflammation and colorectal carcinogenesis. Experimental studies suggest that vitamin D and calcium may inhibit these pathways, but their effects on colorectal tissue COX-2 and 15-HPGD expression in humans are unknown. We tested the effects of supplemental vitamin D (1,000 IU/day) and/or calcium (1,200 mg/day) on COX-2 and 15-HPGD expression in the morphologically normal rectal mucosa from 62 paients with colorectal adenoma in a placebo-controlled chemoprevention trial. We measured biomarker expression using automated IHC and quantitative image analysis at baseline and 1-year follow-up, and assessed treatment effects using mixed linear models. The primary outcome was the COX-2/15-HPGD expression ratio, because these enzymes function as physiologic antagonists. After 1 year of treatment, the mean COX-2/15-HPGD expression ratio in full-length crypts proportionately decreased 47% in the vitamin D group (P = 0.001), 46% in the calcium group (P = 0.002), and 34% in the calcium + vitamin D group (P = 0.03), relative to the placebo group. Among individuals with the functional vitamin D-binding protein isoform DBP2 (GC rs4588*A), the COX-2/15-HPDG ratio decreased 70% (P = 0.0006), 75% (P = 0.0002), and 60% (P = 0.006) in the vitamin D, calcium, and combined supplementation groups, respectively, relative to placebo. These results show that vitamin D and calcium favorably modulate the balance of expression of COX-2 and 15-HPGD-biomarkers of inflammation that are strongly linked to colorectal carcinogenesis-in the normal-appearing colorectal mucosa of patients with colorectal adenoma (perhaps especially those with the DBP2 isoform). PREVENTION RELEVANCE: Supplemental calcium and vitamin D reduce indicators of cancer-promoting inflammation in normal colorectal tissue in humans, thus furthering our understanding of how they may help prevent colorectal cancer.

Prenatal testosterone exposure induces insulin resistance, uterine oxidative stress and pro-inflammatory status in rats

Prenatal androgen excess is considered one of the main causes of the development of polycystic ovary syndrome. In this study, we investigated the effect of prenatal hyperandrogenization (PH) on the physiology of the adult uterine tissue using a murine model of fetal programming caused by androgen excess in adult female rats. Pregnant rats were hyperandrogenized with testosterone and female offspring were studied when adult. Our results showed that PH leads to hyperglycemia and hyperinsulinemia. Consequently, PH developed insulin resistance and a systemic inflammatory state reflected by increased C-reactive protein. In the uterine tissue, levels of PPAR gamma-an important metabolic sensor in the endometrium-were found to be impaired. Moreover, PH induced a pro-inflammatory and an unbalanced oxidative state in the uterus reflected by increased COX-2, lipid peroxidation, and NF-κB. In summary, our results revealed that PH leads to a compromised metabolic state likely consequence of fetal reprogramming.

Common targets for a deadly duo of diabetes mellitus and colon cancer: Catching two fish with one worm

Colon cancer is a major health issue and number of cases are increasing every year. Diabetes mellitus is also a significant health issue that is growing day by day worldwide having negative influences on the survival of individuals. Research has shown a strong relationship between the two malignant diseases. The risk of colon cancer with patients who have type 2 diabetes mellitus has spiked by 30%. The scientific research suggests insulin has a major role in the spread of cancer and the condition unifying between the two diseases is hyperinsulinemia. Several anti-diabetic agents are used for the treatment of type 2 diabetesmellitus. However, their mechanism of action against cancer activity is a question and only a few agents have shown positive signs of action in colon cancer associated with type 2 diabetesmellitus. Hence, the identification of targets, which is common for both colon cancer, associated with type 2 diabetesmellitus has become an urgent requirement. Novel targets such as Liver X receptors, Histone deacetylase inhibitors (HDACi), Glucose Transporters (GLUTs), Peroxisome proliferator activator receptors (PPARs), Dipeptidyl peptidase-IV inhibitors (DPP4i), Cyclin-dependent kinase 4 inhibitors (CDK4i), Estrogen receptors,Mechanistic target of rapamycin (mTOR), Insulin-like growth factor receptors (IGF) are some of the targets which are common for both, type 2 diabetesmellitus and colon cancer. This current review gives an overview of the targets (using one worm) which are common for both viz. diabetes mellitus and colon cancer (two fish).

PPARG expression in colorectal cancer and its association with staging and clinical evolution

Purpose To evaluate the gene expression of peroxisome proliferator activated receptors gamma (PPARG) in colorectal tumors and to correlate this data with clinical variables of the patients. Methods We analyzed the gene expression of PPARG in 50 samples of colorectal tumors using real-time reverse transcription polymerase chain reaction, and 20 adjacent normal tissue samples as control. The results of these quantifications were correlated with the respective patients' medical records' clinical information. Results PPARG expression was not different in the tumor tissue compared to the control tissue. Patients older than 60 years, histological type with mucinous differentiation, more advanced staging at the time of diagnosis, and patients who evolved with recurrence of the disease or death did not present higher PPARG expression. Conclusion Expression of PPARGD was not associated with worse prognosis.

Telmisartan Influences the Antiproliferative Activity of Linoleic Acid in Human Colon Cancer Cells

Aim: Linoleic acid (LA) and telmisartan as PPARgamma agonists exhibit anticancer activity. The LA effect is observed for high non-achievable in vivo concentrations and in short treatment period, therefore we evaluate the effect of supplemental LA and pharmacological telmisartan plasma concentrations on human primary (SW480) and metastatic (SW620) colon cancer cells and immortal keratinocytes (HaCaT) cells in long-term treatment. Methods: Cell viability and proliferation were determined by TB and MTT and pro-apoptotic effect was measured by Annexin V binding assays, respectively.Results: LA decreased cancer cell viability and proliferation in a concentration-dependent manner, whereas no significant effect was found for HaCaT cells. Telmisartan (0.2 µM) suppresses antiproliferative effect of 60 µM LA on cancer cells in short-term treatment. Long-term administration of 60 µM LA reduced cancer cells viability after one week, while telmisartan delayed this effect by two weeks. Growth of all cell lines with 20 µM LA was unchanged during all treatment time. Telmisartan decreased late apoptosis of cancer and normal cells with 60 and 120 µM LA. Conclusion: The cytotoxic LA action depends not only on its concentration but also duration of treatment. Telmisartan exhibits biphasic but not synergistic effect on LA cytotoxicity in cancer cells.

PGE2 -induced migration of human brain endothelial cell is mediated though protein kinase A in cooperation of EP receptors

PGE₂ plays a critical role in angiogenesis, ischemic, and neuro-inflammatory disorders of the brain, which breakdown the blood-brain barrier (BBB). However, the effects of PGE₂ on human brain endothelial cell (HBECs) migration, a key process in the angiogenic response and BBB stability, are not well defined. In this study, we investigated the mechanism of PGE₂ in HBECs migration in vitro. Here we showed that PGE₂ stimulated migration of HBECs in a dose-time and matrix-dependent manner, evaluated by the Boyden chamber assay, but other prostanoids failed to do so. PGE₂ receptor (EP2; butaprost), EP3 (sulprostone), and EP4 (PGE₁ -OH) receptor agonists stimulated HBECs migration, but the silencing of EP significantly attenuated this effect. EP1 agonist (11-trinor PGE₁ ) had no effect on HBECs migration on silencing of the EP1 receptor. We further showed that PGE₂ stimulated cAMP production and activated protein kinase A (PKA), whereas pretreatment with the adenyl cyclase inhibitor (dideoxyadenosine; 1 μM) or PKA inhibitors, H89 (0.5 μM)/PKAI (1 μM), completely abrogated PGE₂ -induced migration. Furthermore, silencing of the EP2/EP4 receptors significantly inhibited PGE₂ -induced cAMP and PKA activation, whereas EP3 receptor silencing failed to do so. These results suggest that PGE₂ regulates HBEC migration via cooperation of EP2, EP3, and EP4 receptors. Coupling of PGE₂ to these receptors resulted in increased production of cAMP, which regulates HBEC migration via PKA pathway. The elucidation of molecular events involved is critical for the development of targeted strategies to treat cerebrovascular diseases associated with dysregulated angiogenesis.

Cellular density-dependent increases in HIF-1α compete with c-Myc to down-regulate human EP4 receptor promoter activity through Sp-1-binding region

The up-regulated expression of E-type prostanoid (EP) 4 receptors has been implicated in carcinogenesis; however, the expression of EP4 receptors has also been reported to be weaker in tumor tissues than in normal tissues. Indeed, EP4 receptors have been suggested to play a role in the maintenance of colorectal homeostasis. This study aimed to examine the underlying mechanisms/reasons for why inconsistent findings have been reported regarding EP4 receptor expression levels in homeostasis and carcinogenesis by focusing on cellular densities. Thus, the human colon cancer HCA-7 cells, which retain some functional features of normal epithelia, and luciferase reporter genes containing wild-type or mutated EP4 receptor promoters were used for elucidating the cellular density-dependent mechanisms about the regulation of EP4 receptor expression. In silico analysis was also utilized for confirming the relevance of the findings with respect to colon cancer development. We here demonstrated that the expression of EP4 receptors was up-regulated by c-Myc by binding to Sp-1 under low cellular density conditions, but was down-regulated under high cellular density conditions via the increase in the expression levels of HIF-1α protein, which may pull out c-Myc and Sp-1 from DNA-binding. The tightly regulated EP4 receptor expression mechanism may be a critical system for maintaining homeostasis in normal colorectal epithelial cells. Therefore, once the system is altered, possibly due to the transient overexpression of EP4 receptors, it may result in aberrant cellular proliferation and transformation to cancerous phenotypes. However, at the point, EP4 receptors themselves and their mediated homeostasis would be no longer required.

Chemoprevention with Cyclooxygenase and Epidermal Growth Factor Receptor Inhibitors in Familial Adenomatous Polyposis Patients: mRNA Signatures of Duodenal Neoplasia

To identify gene expression biomarkers and pathways targeted by sulindac and erlotinib given in a chemoprevention trial with a significant decrease in duodenal polyp burden at 6 months (P < 0.001) in familial adenomatous polyposis (FAP) patients, we biopsied normal and polyp duodenal tissues from patients on drug versus placebo and analyzed the RNA expression. RNA sequencing was performed on biopsies from the duodenum of FAP patients obtained at baseline and 6-month endpoint endoscopy. Ten FAP patients on placebo and 10 on sulindac and erlotinib were selected for analysis. Purity of biopsied polyp tissue was calculated from RNA expression data. RNAs differentially expressed between endpoint polyp and paired baseline normal were determined for each group and mapped to biological pathways. Key genes in candidate pathways were further validated by quantitative RT-PCR. RNA expression analyses of endpoint polyp compared with paired baseline normal for patients on placebo and drug show that pathways activated in polyp growth and proliferation are blocked by this drug combination. Directly comparing polyp gene expression between patients on drug and placebo also identified innate immune response genes (IL12 and IFNγ) preferentially expressed in patients on drug. Gene expression analyses from tissue obtained at endpoint of the trial demonstrated inhibition of the cancer pathways COX2/PGE2, EGFR, and WNT. These findings provide molecular evidence that the drug combination of sulindac and erlotinib reached the intended tissue and was on target for the predicted pathways. Furthermore, activation of innate immune pathways from patients on drug may have contributed to polyp regression. Cancer Prev Res; 11(1); 4-15. ©2017 AACRSee related editorial by Shureiqi, p. 1.

Prostaglandin receptors induce urothelial tumourigenesis as well as bladder cancer progression and cisplatin resistance presumably via modulating PTEN expression

BACKGROUND

We investigated the role of prostaglandin receptors (e.g. prostaglandin E2 receptor 2 (EP2), EP4) and the efficacy of celecoxib in urothelial tumourigenesis and cancer progression.

METHODS

We performed immunohistochemistry in bladder cancer (BC) tissue microarrays, in vitro transformation assay in a normal urothelial SVHUC line, and western blot/reverse transcription-polymerase chain reaction/cell growth assays in BC lines.

RESULTS

EP2/EP4 expression was elevated in BCs compared with non-neoplastic urothelial tissues and in BCs from those who were resistant to cisplatin-based neoadjuvant chemotherapy. Strong positivity of EP2/EP4 in non-muscle-invasive tumours or positivity of EP2/EP4 in muscle-invasive tumours strongly correlated with disease progression or disease-specific mortality, respectively. In SVHUC cells, exposure to a chemical carcinogen 3-methylcholanthrene considerably increased and decreased the expression of EP2/EP4 and phosphatase and tensin homologue (PTEN), respectively. Treatment with selective EP2/EP4 antagonist or celecoxib also resulted in prevention in 3-methylcholanthrene-induced neoplastic transformation of SVHUC cells. In BC lines, EP2/EP4 antagonists and celecoxib effectively inhibited cell viability and migration, as well as augmented PTEN expression. Furthermore, these drugs enhanced the cytotoxic activity of cisplatin in BC cells. EP2/EP4 and PTEN were also elevated and reduced, respectively, in cisplatin-resistant BC sublines.

CONCLUSIONS

EP2/EP4 activation correlates with induction of urothelial cancer initiation and outgrowth, as well as chemoresistance, presumably via downregulating PTEN expression.

DNA alterations in Cd133+ and Cd133- tumour cells enriched from intra-operative human colon tumour biopsies

Background

Tumour stem cells are considered important to promote disease progression, recurrence and treatment resistance following chemotherapy in colon cancer. However, genomic analyses of colorectal cancer have mainly been performed on integrated tumour tissue consisting of several different cell types in addition to differentiated tumour cells. The purpose of the present study was to compare genomic alterations in two cell fractions enriched of CD133+ and CD133−/EpCAM+ cells, respectively, obtained from fresh intraoperative human tumour biopsies.

Methods

The tumour biopsies were fractionated into CD133+ and CD133−/EpCAM+ cells by immunomagnetic separation, confirmed by immunocytochemistry and Q-PCR. DNA were extracted and used for array comparative genome hybridization (aCGH) after whole genome amplification. Frozen tumour tissue biopsies were used for DNA/RNA extraction and Q-PCR analyses to check for DNA alterations detected in the cell fractions.

Results

The number and size of DNA alterations were equally distributed across the cell fractions; however, large deletions were detected on chromosome 1, 7 and 19 in CD133−/EpCAM+ cells. Deletions were frequent in both cell fractions and a deletion on chromosome 19p was confirmed in 90% of the patients.

Conclusion

Isolation of enriched cells derived from tumour tissue revealed mainly genomic deletions, which were not observed in tumour tissue DNA analyses. CD133+ cells were genetically heterogeneous among patients without any defined profile compared to CD133−/EpCAM+ cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3206-8) contains supplementary material, which is available to authorized users.

Fatty acid-binding protein 1 is preferentially lost in microsatellite instable colorectal carcinomas and is immune modulated via the interferon γ pathway

Fatty acid-binding protein 1 (FABP1) is an intracellular protein responsible for the transportation of long chain fatty acids. Aside from its functions in lipid metabolism and cellular differentiation, FABP1 also plays a role in inflammation through its interaction with peroxisome proliferator-activated receptors (PPARs). Previously, we compared expression of colonic epithelium genes in a subset of microsatellite instable (MSI) colorectal carcinomas (medullary carcinomas) to normal colonic mucosa and found that FABP1 expression was markedly decreased in the tumors. Further analysis of RNA expression in the colorectal subtypes and The Cancer Genome Atlas data set found that FABP1 expression is decreased in the CMS1 subset of colorectal carcinomas, which is characterized by microsatellite instability. As MSI colorectal carcinomas are known for their robust immune response, we then aimed to link FABP1 to the immune microenvironment of MSI carcinomas. To confirm the gene expression results, we performed immunohistochemical analysis of a cohort of colorectal carcinomas. FABP1 was preferentially lost in MSI carcinomas (123/133, 93%) compared with microsatellite stable carcinomas (240/562, 43%, P<0.0001). In addition, higher numbers of tumor-infiltrating lymphocytes were present in tumors with loss of FABP1 (P<0.0001). Decreased expression of the fatty acid storage and glucose regulator, PPARγ, was associated with the loss of FABP1 (P<0.0001). Colorectal cancer cell lines treated with interferon γ exhibited decreased expression of FABP1. FABP1 expression was partially recovered with the treatment of the cell lines with rosiglitazone, a PPARγ agonist. This study demonstrated that the loss of FABP1 expression is associated with MSI carcinomas and that interferon γ stimulation plays a role in this process via its interaction with PPARγ.

Host knockout of E-prostanoid 2 receptors reduces tumor growth and causes major alterations of gene expression in prostaglandin E2-producing tumors

Prostaglandin E₂ (PGE₂) is elevated in a variety of malignant tumors and has been shown to affect several hallmarks of cancer. Accordingly, the PGE₂ receptor, E-prostanoid 2 (EP2), has been reported to be associated with patient survival and reduced tumor growth in EP2-knockout mice. Thus, the aim of the present study was to screen for major gene expression alterations in tumor tissue growing in EP2-knockout mice. EP2-knockout mice were bred and implanted with EP2 receptor-expressing and PGE₂-producing epithelial-like tumors. Tumor tissue and plasma were collected and used for analyses with gene expression microarrays and multiplex enzyme-linked immunosorbent assays. Tumor growth, acute phase reactions/systemic inflammation and the expression of interleukin-6 were reduced in EP2-knockout tumor-bearing mice. Several hundreds of genes displayed major changes of expression in the tumor tissue when grown in EP2-knockout mice. Such gene alterations involved several different cellular functions, including stemness, migration and cell signaling. Besides gene expression, several long non-coding RNAs were downregulated in the tumors from the EP2-knockout mice. Overall, PGE₂ signaling via host EP2 receptors affected a large number of different genes involved in tumor progression based on signaling between host stroma and tumor cells, which caused reduced tumor growth.

Prostaglandin E2-stimulated prostanoid EP4 receptors induce prolonged de novo prostaglandin E2 synthesis through biphasic phosphorylation of extracellular signal-regulated kinases mediated by activation of protein kinase A in HCA-7 human colon cancer cells

Approximately two decades have passed since E-type prostanoid 4 (EP4) receptors were cloned, and the signaling pathways mediated by these receptors have since been implicated in cancer development through the alliance of Gαi-protein/phosphatidylinositol 3-kinase (PI3K)/extracellular signal-regulated kinases (ERKs) activation. Although prostanoid EP4 receptors were initially identified as Gαs-coupled receptors, the specific/distinctive role(s) of prostanoid EP4 receptor-induced cAMP/protein kinase A (PKA) pathways in cancer development have not yet been elucidated in detail. We previously reported using HCA-7 human colon cancer cells that prostaglandin E2 (PGE2)-stimulated prostanoid EP4 receptors induced cyclooxygenase-2 (COX-2) as an initiating event in development of colon cancer. Moreover, this induction of COX-2 was mediated by transactivation of epidermal growth factor (EGF) receptors. However, direct activation of EGF receptors by EGF also induced similar amounts of COX-2 in this cell line. Thus, the emergence of unique role(s) for prostanoid EP4 receptors is expected by clarifying the different signaling mechanisms between PGE2-stimulated prostanoid EP4 receptors and EGF-stimulated EGF receptors to induce COX-2 and produce PGE2. We here demonstrated that prostanoid EP4 receptor activation by PGE2 in HCA-7 cells led to PKA-dependent re-activation of ERKs, which resulted in prolonged de novo synthesis of PGE2. Although EGF-stimulated EGF receptors in cells also induced COX-2 and the de novo synthesis of PGE2, the activation of this pathway was transient and not mediated by PKA. Therefore, the novel mechanism underlying prolonged de novo synthesis of PGE2 has provided an insight into the importance of prostanoid EP4 receptor-mediated Gαs-protein/cAMP/PKA pathway in development of colon cancer.

Prostaglandin E2 and the EP receptors in malignancy: possible therapeutic targets?

Elevated expression of COX-2 and increased levels of PGE2 are found in numerous cancers and are associated with tumour development and progression. Although epidemiological, clinical and preclinical studies have shown that the inhibition of PGE2 synthesis through the use of either non-steroidal anti-inflammatory drugs (NSAIDs) or specific COX-2 inhibitors (COXibs) has the potential to prevent and treat malignant disease, toxicities due to inhibition of COX-2 have limited their use. Thus, there is an urgent need for the development of strategies whereby COX-2 activity may be reduced without inducing any side effects. The biological effects of PGE2 are mediated by signalling through four distinct E-type prostanoid (EP) receptors - EP1 , EP2 , EP3 and EP4 . In recent years, extensive effort has gone into elucidating the function of PGE2 and the EP receptors in health and disease, with the goal of creating selective inhibitors as a means of therapy. In this review, we focus on PGE2 , and in particular on the role of the individual EP receptors and their signalling pathways in neoplastic disease. As knowledge concerning the role of the EP receptors in cancer grows, so does the potential for exploiting the EP receptors as therapeutic targets for the treatment of cancer and metastatic disease.

Clinical Significance of Peroxisome Proliferator-Activated Receptor γ and TRAP220 in Patients with Operable Colorectal Cancer

Purpose

The peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. Thyroid hormone receptor-associated proteins 220 (TRAP220) is an essential component of the TRAP/Mediator complex. The objective of this study was to clarify whether PPARγ or TRAP220 are significant prognostic markers in resectable colorectal cancer (CRC).

Materials and Methods

A total of 399 patients who underwent curative resection for CRC were enrolled. We investigated the presence of PPARγ and TARP220 in CRC tissues and adjacent normal tissues by immunohistochemistry. Correlation between the expression of these factors and clinicopathologic features and survival was investigated.

Results

Median age of the patients was 63 years (range, 22 to 87 years), and median follow-up duration 61.1 months (range, 2 to 114 months). PPARγ and TRAP220 expression showed significant correlation with depth of invasion (p=0.013 and p=0.001, respectively). Expression of TRAP220 also showed association with lymph node metastasis and TNM stage (p=0.001). Compared with patients with TRAP220 negative tumors, patients with TRAP220 positive tumors had longer 5-year disease-free survival (DFS) tendency (p=0.051). Patients who were PPARγ positive combined with TRAP220 positive had a better 5-year DFS (64.8% vs. 79.3%, p=0.013). In multivariate analysis expression of both PPARγ and TRAP220 significantly affected DFS (hazard ratio, 0.620; 95% confidence interval, 0.379 to 0.997; p=0.048).

Conclusion

TRAP220 may be a valuable marker for nodal metastasis and TNM stage. Tumor co-expression of PPARγ and TRAP220 represents a biomarker for good prognosis in CRC patients.

Chemotherapy and chemoprevention by thiazolidinediones

Thiazolidinediones (TZDs) are synthetic ligands of Peroxisome-Proliferator-Activated Receptor gamma (PPARγ). Troglitazone, rosiglitazone, and pioglitazone have been approved for treatment of diabetes mellitus type II. All three compounds, together with the first TZD ciglitazone, also showed an antitumor effect in preclinical studies and a beneficial effect in some clinical trials. This review summarizes hypotheses on the role of PPARγ in tumors, on cellular targets of TZDs, antitumor effects of monotherapy and of TZDs in combination with other compounds, with a focus on their role in the treatment of differentiated thyroid carcinoma. The results of chemopreventive effects of TZDs are also considered. Existing data suggest that the action of TZDs is highly complex and that actions do not correlate with cellular PPARγ expression status. Effects are cell-, species-, and compound-specific and concentration-dependent. Data from human trials suggest the efficacy of TZDs as monotherapy in prostate cancer and glioma and as chemopreventive agent in colon, lung, and breast cancer. TZDs in combination with other therapies might increase antitumor effects in thyroid cancer, soft tissue sarcoma, and melanoma.

Associations between single nucleotide polymorphisms of COX-2 and MMP-2 genes and colorectal cancer susceptibility in the Saudi population

BACKGROUND

It has been reported that COX-2 expression is associated with MMP-2 expression in thyroid and breast cancers, suggesting that MMPs are linked to COX-2-mediated carcinogenesis. Several polymorphisms within the MMP2 promoter region have been reported in cases with oncogenesis and tumor progression, especially in colorectal carcinogenesis.

MATERIALS AND METHODS

This research evaluated risk of association of the SNPs, including genes for COX-2 (A/G transition at +202) and MMP-2 (C/T transition at-1306), with colorectal cancer in 125 patients and 125 healthy controls.

RESULTS AND CONCLUSIONS

Our data confirmed that MMP2 C-1306 T mutations were significantly more common in colon cancer patients than in our control Saudi population; p=0.0121. On the other hand in our study, there was no significant association between genotype distribution of the COX2 polymorphism and colorectal cancer; p=0.847. An elevated frequency of the mutated genotype in the control group as compared to the patients subjects indeed suggested that this polymorphism could decrease risk in the Saudi population. Our study confirmed that the polymorphisms that could affect the expressions of MMP-2 and COX-2 the colon cancer patients were significantly higher than that in the COX-2 negative group. The frequency of individuals with MMP2 polymorphisms in colon cancer patients was higher than individuals with combination of COX2 and MMP2 polymorphisms. Our study confirmed that individuals who carried the polymorphisms that could affect the expressions of COX2 are more susceptible to colon cancer. MMP2 regulatory polymorphisms could be considered as protective; further studies need to confirm the results with more samples and healthy subjects.

Cellular density-dependent down-regulation of EP4 prostanoid receptors via the up-regulation of hypoxia-inducible factor-1α in HCA-7 human colon cancer cells

Increases in prostaglandin E₂ (PGE₂) and cyclooxygenase-2 (COX-2) levels are features of colon cancer. Among the different E-type prostanoid receptor subtypes, EP4 receptors are considered to play a crucial role in carcinogenesis by, for example, inducing COX-2 when stimulated with PGE₂. However, EP4 receptor levels and PGE₂-induced cellular responses are inconsistent among the cellular conditions. Therefore, the connections responsible for the expression of EP4 receptors were investigated in the present study by focusing on cell density-induced hypoxia-inducible factor-1α (HIF-1α). The expression of EP4 receptors was examined using immunoblot analysis, quantitative polymerase chain reaction, and reporter gene assays in HCA-7 human colon cancer cells with different cellular densities. The involvement of HIF-1α and its signaling pathways were also examined by immunoblot analysis, reporter gene assays, and with siRNA. We here demonstrated that EP4 receptors as well as EP4 receptor-mediated COX-2 expression levels decreased with an increase in cellular density. In contrast, HIF-1α levels increased in a cellular density-dependent manner. The knockdown of HIF-1α by siRNA restored the expression of EP4 receptors and EP4 receptor-mediated COX-2 in cells at a high density. Thus, the cellular density-dependent increase observed in HIF-1α expression levels reduced the expression of COX-2 by decreasing EP4 receptor levels. This novel regulation mechanism for the expression of EP4 receptors by HIF-1α may provide an explanation for the inconsistent actions of PGE₂. The expression levels of EP4 receptors may vary depending on cellular density, which may lead to the differential activation of their signaling pathways by PGE₂. Thus, cellular density-dependent PGE₂-mediated signaling may determine the fate/stage of cancer cells, i.e., the surrounding environments could define the fate/stage of malignancies associated with colon cancer.

Preoperative low dose NSAID treatment influences the genes for stemness, growth, invasion and metastasis in colorectal cancer

Preclinical data, and an increasing list of clinical investigations, show anti-inflammatory agents to favourably influence the biology of colorectal tumor. We have earlier reported on re-expression of activated immune cells after three days preoperative treatment of patients with colorectal carcinoma, randomized to receive oral NSAID (indomethacin or celebrex). Antisecretory prophylaxis (esomeprasol) was provided to all patients and served as sham treatment. Concomittant to MHC locus activation, Prominin1/CD133, a marker associated with stemness and poor prognosis in several solid tumors, was downregulated. The aim of the present study was to evaluate expression of additional regulators belonging to the stem cell niche, OCT4, SOX2 and BMP7, as well as some microRNAs, reported to act as tumor suppressors or oncomiRs. Peroperative tumor biopsies were analyzed by microarrays, quantitative real-time PCR and immunohistochemistry (IHC). The stem cell master regulator SOX2 was increased by NSAIDs (p<0.01), as well as the tumor suppressor miR-630 (p<0.01), while BMP7, a marker for poor prognosis in CRC, was downregulated by NSAID (indomethacin, p<0.02). The upregulation of SOX2, but not of its heterodimer binding partner OCT4, could imply a negative feed-back loop, with a switch‑off for stemness preservation of tumor cells. This is supported by the overall evaluation of gene expression profiles with subsequent events, indicating less aggressive tumors following NSAID treatment.

Over-expression of COX-2 mRNA in colorectal cancer

BACKGROUND

Cyclooxygenase-2 (COX-2, PTGS2) is an enzyme involved in the synthesis of prostaglandins and thromboxanes, which are regulators of biologic processes such as inflammation, cell proliferation and angiogenesis. COX-2 over-expression was reported in many (pre) malignant tissues, but data strongly vary and seem to depend on the methodology used.

METHODS

Normal colorectal mucosa and paired cancerous tissue from 60 patients with colorectal cancer was investigated for the levels of COX-2 mRNA by real-time quantitative Polymerase Chain Reaction (qPCR). COX-2 levels were expressed relative to either: tissue weight or levels of the housekeeping genes beta-2 microglobulin (B2M) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

RESULTS

COX-2 mRNA levels, normalized with respect to tissue weight or mRNA levels of the housekeeping genes B2M or GAPDH, were over-expressed in 80%, 70% and 40% of the colorectal tumor tissues, as compared to the paired adjacent normal colorectal mucosa samples, respectively. Highest mRNA COX-2 ratios tumor/normal were measured when expressed per mg tissue (mean ratio 21.6). When normalized with respect to the housekeeping genes B2M or GAPDH, mean tumor/normal ratios were 16.1 and 7.5, respectively.

CONCLUSION

Expression of COX-2 mRNA levels per mg tissue is most simple in comparison to normalization with respect to the housekeeping genes B2M or GAPDH. Levels of COX-2 mRNA are found over-expressed in almost 80% of the colorectal tumors, compared to paired adjacent normal colorectal mucosa, suggesting a role of COX-2 as a potential biomarker for cancer risk, whereas inhibitors of COX-2 could be of value in chemoprevention of colon cancer.

EGF receptor and COX-1/COX-2 enzyme proteins as related to corresponding mRNAs in human per-operative biopsies of colorectal cancer

Background

Cyclooxygenase (COX) and epidermal growth factor receptor (EGFR) activities promote progression of colorectal cancer. Combined treatment against these targets has not been more effective than single treatments alone. Therefore, our aim was to analyze relationships between COX and EGFR in peroperative colorectal tumor biopsies.

Method

Tumor and colon mucosa tissue were collected at primary intended curative operations in patients according to well-recognized statistical distributions of tumor stages in colorectal cancer. COX-1, COX-2 and EGFR content in tumor and colon mucosa tissue were quantified by western blot and Q-PCR.

Results

COX-2 protein appeared as two bands, one at 66 kDa in almost all tumor and mucosa samples and one at 74 kDa in 73% of the tumors and in 23% of the mucosa samples. Tumor COX-2 mRNA was not different from the content in mucosa samples, while COX-2 protein was increased in tumor tissue (p < 0.0003). A correlation between 74 kDa COX-2 protein and COX-2 mRNA occurred in tumor tissue, with significantly increasing COX-2 mRNA across tumor stages. EGFR mRNA content was lower in tumor tissue (p < 0.0001), while EGFR protein was similar in tumor and mucosa samples. COX-2 and EGFR proteins showed a positive correlation in mucosa, while a negative correlation occurred in tumor tissue. Tumor tissue with high COX-2 74 kDa protein lacked EGFR protein.

Conclusion

Our present results are compatible with the theory that COX-2 and EGFR signalling pathways are inversely related in colorectal cancer tissue. This may explain why combinatorial clinical treatments have been less rewarding.

Targeting the EP1 receptor reduces Fas ligand expression and increases the antitumor immune response in an in vivo model of colon cancer

Despite studies demonstrating that inhibition of cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2 ) has significant chemotherapeutic benefits in vitro and in vivo, inhibition of COX enzymes is associated with serious gastrointestinal and cardiovascular side effects, limiting the clinical utility of these drugs. PGE2 signals through four different receptors (EP1-EP4) and targeting individual receptor(s) may avoid these side effects, while retaining significant anticancer benefits. Here, we show that targeted inhibition of the EP1 receptor in the tumor cells and the tumor microenvironment resulted in the significant inhibition of tumor growth in vivo. Both dietary administration and direct injection of the EP1 receptor-specific antagonist, ONO-8713, effectively reduced the growth of established CT26 tumors in BALB/c mice, with suppression of the EP1 receptor in the tumor cells alone less effective in reducing tumor growth. This antitumor effect was associated with reduced Fas ligand expression and attenuated tumor-induced immune suppression. In particular, tumor infiltration by CD4(+) CD25(+) Foxp3(+) regulatory T cells was decreased, whereas the cytotoxic activity of isolated splenocytes against CT26 cells was increased. F4/80(+) macrophage infiltration was also decreased; however, there was no change in macrophage phenotype. These findings suggest that the EP1 receptor represents a potential target for the treatment of colon cancer.

MicroRNA-101 (miR-101) post-transcriptionally regulates the expression of EP4 receptor in colon cancers

PURPOSE

Expression of the PGE2 receptor, EP4, is up-regulated during colorectal carcinogenesis. However the mechanism leading to deregulation of the EP4 receptor is not known. The present study was conducted to investigate the regulation of EP4 receptor by miRNAs.

EXPERIMENTAL DESIGN

We analyzed 26 colon cancers (i.e. 15 adenocarcinomas and 9 adenomas) and 16 normal colon specimens for EP4 receptor expression by immunohistochemistry. A bioinformatics approached identified putative microRNA binding sites with the 3'-UTR of the EP4 receptor. Both colon cancer cell lines and tumor specimens were analyzed for miR-101 and EP4 expression by qRT-PCR and Western analysis respectively and simultaneously in situ hybridizations was used to confirm our results. In vitro and in vivo assays were used to confirm our clinical findings.

RESULTS

We observed an inverse correlation between the levels of miR-101 and EP4 receptor protein. Transfection of LS174T cells with miR-101 significantly suppressed a luciferase reporter containing the EP4 receptor-3'-UTR. In contrast, a mutant EP4 receptor-3'-UTR construct was unaffected. Ectopic expression of miR-101 markedly reduced cell proliferation and motility. Co-transfection of EP4 receptor could rescue colon cancer cells from the tumor suppressive effects of miR-101. Moreover, the pharmacologic inhibition of EP4 receptor signaling or silencing of EP4 receptor phenocopied the effect of miR-101. This is the first study to show that the EP4 receptor is negatively regulated by miR-101.

CONCLUSIONS

These data provide new insights in the modulation of EP-4 receptor expression at the post-transcriptional level by miR-101 and suggests therapeutic strategies against miR-101 targets may be warranted.

Cancer associated epigenetic transitions identified by genome-wide histone methylation binding profiles in human colorectal cancer samples and paired normal mucosa

BACKGROUND

Despite their well-established functional roles, histone modifications have received less attention than DNA methylation in the cancer field. In order to evaluate their importance in colorectal cancer (CRC), we generated the first genome-wide histone modification profiles in paired normal colon mucosa and tumor samples.

METHODS

Chromatin immunoprecipitation and microarray hybridization (ChIP-chip) was used to identify promoters enriched for histone H3 trimethylated on lysine 4 (H3K4me3) and lysine 27 (H3K27me3) in paired normal colon mucosa and tumor samples from two CRC patients and for the CRC cell line HT29.

RESULTS

By comparing histone modification patterns in normal mucosa and tumors, we found that alterations predicted to have major functional consequences were quite rare. Furthermore, when normal or tumor tissue samples were compared to HT29, high similarities were observed for H3K4me3. However, the differences found for H3K27me3, which is important in determining cellular identity, indicates that cell lines do not represent optimal tissue models. Finally, using public expression data, we uncovered previously unknown changes in CRC expression patterns. Genes positive for H3K4me3 in normal and/or tumor samples, which are typically already active in normal mucosa, became hyperactivated in tumors, while genes with H3K27me3 in normal and/or tumor samples and which are expressed at low levels in normal mucosa, became hypersilenced in tumors.

CONCLUSIONS

Genome wide histone modification profiles can be used to find epigenetic aberrations in genes associated with cancer. This strategy gives further insights into the epigenetic contribution to the oncogenic process and may identify new biomarkers.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

COX-2 gene expression in colon cancer tissue related to regulating factors and promoter methylation status

Background

Increased cyclooxygenase activity promotes progression of colorectal cancer, but the mechanisms behind COX-2 induction remain elusive. This study was therefore aimed to define external cell signaling and transcription factors relating to high COX-2 expression in colon cancer tissue.

Method

Tumor and normal colon tissue were collected at primary curative operation in 48 unselected patients. COX-2 expression in tumor and normal colon tissue was quantified including microarray analyses on tumor mRNA accounting for high and low tumor COX-2 expression. Cross hybridization was performed between tumor and normal colon tissue. Methylation status of up-stream COX-2 promoter region was evaluated.

Results

Tumors with high COX-2 expression displayed large differences in gene expression compared to normal colon. Numerous genes with altered expression appeared in tumors of high COX-2 expression compared to tumors of low COX-2. COX-2 expression in normal colon was increased in patients with tumors of high COX-2 compared to normal colon from patients with tumors of low COX-2. IL1β, IL6 and iNOS transcripts were up-regulated among external cell signaling factors; nine transcription factors (ATF3, C/EBP, c-Fos, Fos-B, JDP2, JunB, c-Maf, NF-κB, TCF4) showed increased expression and 5 (AP-2, CBP, Elk-1, p53, PEA3) were decreased in tumors with high COX-2. The promoter region of COX-2 gene did not show consistent methylation in tumor or normal colon tissue.

Conclusions

Transcription and external cell signaling factors are altered as covariates to COX-2 expression in colon cancer tissue, but DNA methylation of the COX-2 promoter region was not a significant factor behind COX-2 expression in tumor and normal colon tissue.

An agonist sensitive, quick and simple cell-based signaling assay for determination of ligands mimicking prostaglandin E2 or E1 activity through subtype EP1 receptor: Suitable for high throughput screening

BACKGROUND

Conventionally the active ingredients in herbal extracts are separated into individual components, by fractionation, desalting, and followed by high-performance liquid chromatography (HPLC). In this study we have tried to directly screen water-soluble fractions of herbs with potential active ingredients before purification or extraction. We propose that the herbal extracts mimicking prostaglandin E(1) (PGE(1)) and E(2) (PGE(2)) can be identified in the water-soluble non-purified fraction. PGE(1) is a potent anti-inflammatory molecule used for treating peripheral vascular diseases while PGE(2) is an inflammatory molecule.

METHODS

We used cell-based assays (CytoFluor multi-well plate reader and fluorescence microscopy) in which a calcium signal was generated by the recombinant EP(1) receptor stably expressed in HEK293 cells (human embryonic kidney). PGE(1) and PGE(2) were tested for their ability to generate a calcium signal. Ninety-six water soluble fractions of Treasures of the east (single Chinese herb dietary supplements) were screened.

RESULTS

After screening, the top ten stimulators were identified. The identified herbs were then desalted and the calcium fluorescent signal reconfirmed using fluorescence microscopy. Among these top ten agonists identified, seven stimulated the calcium signaling (1-40 μM concentration) using fluorescence microscopy.

CONCLUSIONS

Fluorescence microscopy and multi-well plate readers can be used as a target specific method for screening water soluble fractions with active ingredients at a very early stage, before purification. Our future work consists of purifying and separating the active ingredients and repeating fluorescence microscopy. Under ordinary circumstances we would have to purify the compounds first and then test all the extracts from 96 herbs. Conventionally, for screening natural product libraries, the procedure followed is the automated separation of all constituents into individual components using fractionation and high performance liquid chromatography. We, however, demonstrated that the active ingredients of the herbal extracts can be tested before purification using an agonist sensitive, quick and simple cell-based signaling assay for ligands mimicking the agonists, PGE(1) and PGE(2).

Cyclooxygenase-2 expression in animal cancers

Cyclooxygenase (COX; also known as prostaglandin endoperoxide synthase) is a key enzyme in the biochemical pathway leading to the synthesis of prostaglandins. A large amount of epidemiological and experimental evidence supports a role for COX-2, the inducible form of the enzyme, in human tumorigenesis, notably in colorectal cancer. COX-2 mediates this role through the production of PGE(2) that acts to inhibit apoptosis, promote cell proliferation, stimulate angiogenesis, and decrease immunity. Similarly, COX-2 is believed to be involved in the oncogenesis of some cancers in domestic animals. Here, the author reviews the current knowledge on COX-2 expression and role in cancers of dogs, cats, and horses. Data indicate that COX-2 upregulation is present in many animal cancers, but there is presently not enough information to clearly define the prognostic significance of COX-2 expression. To date, only few reports document an association between COX-2 expression and survival, notably in canine mammary cancers and osteosarcomas. Some evidence suggests that COX inhibitors could be useful in the prevention and/or treatment of certain cancers in domestic animals, the best example being urinary transitional cell carcinomas in dogs. However, determination of the levels of COX-2 in a tumor does not appear to be a good prognostic factor or a good indicator for the response to nonsteroidal anti-inflammatory drug therapy. Clearly, additional research, including the development of in vitro cell systems, is needed to determine if COX-2 expression can be used as a reliable prognostic factor and as a definite therapeutic target in animal cancers.

EP4 upregulation of Ras signaling and feedback regulation of Ras in human colon tissues and cancer cells

Previous studies indicate that COX-2 and prostaglandin E(2) (PGE(2)) receptor subtypes are involved in intestinal carcinogenesis and activation of downstream pathways. In this report, we try to understand the association of PGE(2) receptor and K-ras cellular mechanism during the development of colorectal cancer. We collected 21 colorectal cancer patients and compared the protein expression of tumor tissues and normal mucosa tissues by using immunoblot. Furthermore, we transferred empty vector and pcDNA-K-ras into Ras-HT29 colon cancer cells. Result showed that phosphorylation of Akt and EP(1)/EP(4) were over-expressed in the colorectal tumor tissue. K-ras induces HT29 cells proliferation through the expressions of COX-2, EP1/EP4, pAkt, GSK3beta and increases Tcf transcriptional factor activation. Additionally, Ras protein was suppressed when treated with EP(4) inhibitor in Ras-HT29 cell. In cell cycle assay, K-ras mutation causing cell cycle S phase was prolonged with an increase in the G2/M phase ratio. In conclusion, we suggested that Ras overexpression leads to cell proliferation through activating Ras/PI3K/GSK3beta/EP(4) PGE(2) receptor signals and caused a feedback regulation of Ras by EP4 in colorectal tumor progression.

The use of Cox-2 and PPARγ signaling in anti-cancer therapies

Increased production of the pro-inflammatory enzyme cyclooxygenase-2 (Cox-2) and altered expression and activity of peroxisome proliferator-activated receptor γ (PPARγ) have been observed in many malignancies. Both the PPARγ ligands and the Cox-2 inhibitors possess anti-inflammatory and anti-neoplastic effects in vitro and have been assessed for their therapeutic potential in several pre-clinical and clinical studies. Recently, multiple interactions between PPARγ and Cox-2 signaling pathways have been revealed. Understanding of the cross-talk between PPARγ and Cox-2 might provide important novel strategies for the effective treatment and/or prevention of cancer. This article summarizes recent achievements involving the functional interactions between the PPARγ and Cox-2 signaling pathways and discusses the implications of such interplay for clinical use.

PTGER2 overexpression in colorectal cancer is associated with microsatellite instability, independent of CpG island methylator phenotype

BACKGROUND

Prostaglandin-endoperoxide synthase 2 (PTGS2, the HUGO Gene Nomenclature Committee-approved official symbol for cycloxygenase-2, COX-2) and its enzymatic product prostaglandin E2 have critical roles in inflammation and carcinogenesis through the G protein-coupled receptor PTGER2 (EP2). The PTGS2 (COX-2) pathway is a promising target for cancer therapy and chemoprevention. PTGS2 (COX-2) expression in colon cancer has been inversely associated with survival as well as tumoral microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP). However, the prognostic significance of PTGER2 expression or its relationship with MSI, CIMP, LINE-1 hypomethylation, or PTGS2 (COX-2) remains uncertain.

METHODS

Using the database of 516 colorectal cancers in two prospective cohort studies with clinical outcome data, we detected PTGER2 overexpression in 169 (33%) tumors by immunohistochemistry. We analyzed MSI using 10 microsatellite markers; CIMP by MethyLight (real-time methylation-specific PCR) on an eight-marker panel [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1]; BRAF, KRAS, PIK3CA, and methylation in LINE-1 by Pyrosequencing; and CTNNB1 (beta-catenin) and TP53 (p53) by immunohistochemistry.

RESULTS

PTGER2 overexpression was positively associated with the mucinous component (P = 0.0016), signet ring cells (P = 0.0024), CIMP-high (P = 0.0023), and MSI-high (P < 0.0001). In multivariate analysis, the significant relationship between PTGER2 and MSI-high persisted (adjusted odds ratio, 2.82; 95% confidence interval, 1.69-4.72; P < 0.0001). PTGER2 was not significantly associated with PTGS2 (COX-2), TP53, or CTNNB1 expression, patient survival, or prognosis.

CONCLUSION

PTGER2 overexpression is associated with MSI-high in colorectal cancer.

IMPACT

Our data imply potential roles of inflammatory reaction by PTGER2 upregulation in carcinogenic process to MSI-high colorectal cancer.

Genetic variation in prostaglandin E2 synthesis and signaling, prostaglandin dehydrogenase, and the risk of colorectal adenoma

BACKGROUND

Prostaglandins are important inflammatory mediators; prostaglandin E2 (PGE2) is the predominant prostaglandin in colorectal neoplasia and affects colorectal carcinogenesis. Prostaglandins are metabolites of omega-6 and omega-3 polyunsaturated fatty acids; their biosynthesis is the primary target of nonsteroidal anti-inflammatory drugs (NSAID), which reduce colorectal neoplasia risk.

METHODS

We investigated candidate and tagSNPs in PGE2 synthase (PGES), PGE2 receptors (EP2 and EP4), and prostaglandin dehydrogenase (PGDH) in a case-control study of adenomas (n = 483) versus polyp-free controls (n = 582) and examined interactions with NSAID use or fish intake, a source of omega-3 fatty acids.

RESULTS

A 30% adenoma risk reduction was observed for EP2 4950G>A (intron 1; OR(GA/AA vs. GG), 0.71; 95% confidence interval, 0.52-0.99). For the candidate polymorphism EP4 Val294Ile, increasing fish intake was associated with increased adenoma risk among those with variant genotypes, but not among those with the Val/Val genotype (P(interaction) = 0.02). An interaction with fish intake was also observed for PGES -664A>T (5' untranslated region; P(interaction) = 0.01). Decreased risk with increasing fish intake was only seen among those with the AT or TT genotypes (OR(>2 t/wk vs. <1 t/wk), 0.56; 95% confidence interval, 0.28-1.13). We also detected interactions between NSAIDs and EP2 9814C>A (intron 1) and PGDH 343C>A (intron 1). However, none of the observed associations was statistically significant after adjustment for multiple testing. We investigated potential gene-gene interactions using the Chatterjee 1 degree of freedom Tukey test and logic regression; neither method detected significant interactions.

CONCLUSIONS

These data provide little support for associations between adenoma risk and genetic variability related to PGE(2), yet suggest gene-environment interactions with anti-inflammatory exposures.

Prostanoid receptor expression in colorectal cancer related to tumor stage, differentiation and progression

INTRODUCTION

Alterations in eicosanoid metabolism is well established in a variety of malignant tumors, particularly colorectal carcinoma. Recent studies in our laboratory have emphasized a role for EP subtype receptors in progression of colorectal cancer and disease specific mortality. Therefore, the aim of the present study was to extend our knowledge to include additional receptor expression (DP1, DP2, FP, IP, TP) for prostanoids (PGD2, TXA2, PGF2alpha, PGI2) in relationship to tumor stage, differentiation and progression of colorectal cancer.

MATERIAL AND METHODS

Total RNA from 62 tumors and adjacent normal colon tissue (n = 48) was extracted. Quantification of receptor expression was performed by realtime PCR and related to the expression of an appropriate housekeeping gene (GAPDH). Tumors were assessed according to Dukes A-D (stage I-IV).

RESULTS

DP1, DP2, FP and IP receptor subtypes displayed significantly reduced overall expression in tumor tissue compared to normal colon tissue, while the TP receptor subtype showed significantly higher expression in tumor tissue. Overall expression of the prostanoid receptors in tumor tissue was not related to clinical indexes as tumor stage and tumor cell differentiation evaluated by multivariate analyses. Cultured colorectal cancer cell lines with low (HT-29) and high (HCA-7) intrinsic PGE2 production at confluent state did not express DP1 and IP receptor subtypes, but displayed low expression of DP2, FP and TP receptor subtypes.

CONCLUSION

The results in the present study indicate imbalanced expression of prostanoid receptors in colorectal cancer compared to normal colon tissue without clear cut relationship to disease progression. Therefore, future studies should be performed on defined cells within the tumor tissue compartment determining whether any prostanoid receptor(s) is useful as a molecular target in treatment or prevention of colorectal cancer.

Proneoplastic effects of PGE2 mediated by EP4 receptor in colorectal cancer

Background

Prostaglandin E₂ (PGE₂) is the major product of Cyclooxygenase-2 (COX-2) in colorectal cancer (CRC). We aimed to assess PGE₂ cell surface receptors (EP 1–4) to examine the mechanisms by which PGE₂ regulates tumour progression.

Methods

Gene expression studies were performed by quantitative RT-PCR. Cell cycle was analysed by flow cytometry with cell proliferation quantified by BrdU incorporation measured by enzyme immunoassay. Immunohistochemistry was employed for expression studies on formalin fixed paraffin embedded tumour tissue.

Results

EP4 was the most abundant subtype of PGE₂ receptor in HT-29 and HCA7 cells (which show COX-2 dependent PGE₂ generation) and was consistently the most abundant transcript in human colorectal tumours (n = 8) by qRT-PCR (ANOVA, p = 0.01). G0/G1 cell cycle arrest was observed in HT-29 cells treated with SC-236 5 μM (selective COX-2 inhibitor) for 24 hours (p = 0.02), an effect abrogated by co-incubation with PGE₂ (1 μM). G0/G1 arrest was also seen with a specific EP4 receptor antagonist (EP4A, L-161982) (p = 0.01). Treatment of HT-29 cells with either SC-236 or EP4A caused reduction in intracellular cAMP (ANOVA, p = 0.01). Early induction in p21^WAF1/CIP1 expression (by qRT-PCR) was seen with EP4A treatment (mean fold increase 4.4, p = 0.04) while other genes remained unchanged. Similar induction in p21^WAF1/CIP1 was also seen with PD153025 (1 μM), an EGFR tyrosine kinase inhibitor, suggesting EGFR transactivation by EP4 as a potential mechanism. Additive inhibition of HCA7 proliferation was observed with the combination of SC-236 and neutralising antibody to amphiregulin (AR), a soluble EGFR ligand. Concordance in COX-2 and AR localisation in human colorectal tumours was noted.

Conclusion

COX-2 regulates cell cycle transition via EP4 receptor and altered p21^WAF1/CIP1 expression. EGFR pathways appear important. Specific targeting of the EP4 receptor or downstream targets may offer a safer alternative to COX-2 inhibition in the chemoprevention of CRC.

Colorectal cancer expression of peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is associated with good prognosis

BACKGROUND & AIMS

The peroxisome proliferator-activated receptor gamma (PPARG, PPARgamma) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. There is controversy over the pro-oncogenic or antioncogenic effects of PPARG, and little is known about its prognostic significance in colon cancer.

METHODS

Among 470 patients with colorectal cancer (stages I-IV) identified in 2 independent prospective cohorts, PPARG expression was detected in 102 tumors (22%) by immunohistochemistry. Cox proportional hazards models were used to compute hazard ratios (HRs) of colorectal cancer-specific and overall mortalities, adjusted for patient characteristics and molecular features including cyclooxygenase 2, fatty acid synthase, KRAS, BRAF, PIK3CA, p53, p21, beta-catenin, LINE-1 hypomethylation, microsatellite instability (MSI), and the CpG island methylation phenotype (CIMP).

RESULTS

Compared with patients with PPARG-negative tumors, patients with PPARG-positive tumors had significantly lower overall mortality, determined by Kaplan-Meier analysis (P=.0047), univariate Cox regression (HR, 0.55; 95% confidence interval [CI], 0.37-0.84; P=.0053), and multivariate analysis (adjusted HR, 0.43; 95% CI, 0.27-0.69; P=.0004). Patients with PPARG-positive tumors experienced lower colorectal cancer-specific mortality (adjusted HR, 0.44; 95% CI, 0.25-0.79; P=.0054). The relationship between PPARG and lower mortality did not appear to be significantly modified by MSI, CIMP, LINE-1, or the other clinical and molecular variables examined (all P(interaction)>.05).

CONCLUSIONS

Tumor expression of PPARG is independently associated with longer survival of patients. PPARG expression appears to mark an indolent subset of colorectal cancers.

Inhibition of arachidonic acid metabolism and its implication on cell proliferation and tumour-angiogenesis

Arachidonic acid (AA) and its metabolites have recently generated a heightened interest due to growing evidence of their significant role in cancer biology. Thus, inhibitors of the AA cascade, first and foremost COX inhibitors, which have originally been of interest in the treatment of inflammatory conditions and certain types of cardiovascular disease, are now attracting attention as an arsenal against cancer. An increasing number of investigations support their role in cancer chemoprevention, although the precise molecular mechanisms that link levels of AA, and its metabolites, with cancer progression have still to be elucidated. This article provides an overview of the AA cascade and focuses on the roles of its inhibitors and their implication in cancer treatment. In particular, emphasis is placed on the inhibition of cell proliferation and neo-angiogenesis through inhibition of the enzymes COX-2, 5-LOX and CYP450. Downstream effects of inhibition of AA metabolites are analysed and the molecular mechanisms of action of a selected number of inhibitors of catalytic pathways reviewed. Lastly, the benefits of dietary omega-3 fatty acids and their mechanisms of action leading to reduced cancer risk and impeded cancer cell growth are mentioned. Finally, a proposal is put forward, suggesting a novel and integrated approach in viewing the molecular mechanisms and complex interactions responsible for the involvement of AA metabolites in carcinogenesis and the protective effects of omega-3 fatty acids in inflammation and tumour prevention.

Friend or foe? Role of peroxisome proliferator-activated receptor-gamma in human bladder cancer

The peroxisome proliferator-activated receptor (PPAR) family is an important group of transcription factors that regulates immune surveillance, cell proliferation, fatty acid regulation, and angiogenesis--functions which have all been implicated in the pathogenesis of bladder cancer. One particular subtype, PPARgamma, is expressed at higher levels in bladder cancer specimens than in benign urothelium, and is an attractive molecular target for the development of novel treatment strategies for bladder cancer. In this review, we summarize the data available regarding relevance of PPARgamma in bladder cancer and discuss the potential value of PPAR-targeted treatment of bladder cancer.

Cyclooxygenase-2 expression is an independent predictor of poor prognosis in colon cancer

PURPOSE

Cyclooxygenase-2 (COX-2; PTGS2) is considered to play an important role in colorectal carcinogenesis and is often up-regulated in colon cancers. However, previous data on the influence of COX-2 expression on patient outcome have been conflicting.

EXPERIMENTAL DESIGN

Using 662 colon cancers (stage I-IV) in two independent prospective cohorts (the Nurses' Health Study and the Health Professionals Follow-up Study), we detected COX-2 overexpression in 548 (83%) tumors by immunohistochemistry. Cox proportional hazards models were used to compute hazard ratios (HR) of colon cancer-specific and overall mortalities, adjusted for patient characteristics and related molecular events, including the CpG island methylation phenotype, microsatellite instability, and p53, CIMP, KRAS, and BRAF mutations.

RESULTS

During follow-up of the 662 cases, there were 283 deaths, including 163 colon cancer-specific deaths. Patients with COX-2-positive tumors showed a trend towards an inferior colon cancer-specific mortality [HR, 1.37; 95% confidence interval (95% CI), 0.87-2.14], which became significant after adjusting for tumor stage and other predictors of clinical outcome (multivariate HR, 1.70; 95% CI, 1.06-2.74; P = 0.029). Notably, the prognostic effect of COX-2 expression might differ according to p53 status (Pinteraction = 0.04). Compared with tumors with both COX-2 and p53 negative, COX-2-positive tumors were significantly associated with an increased cancer-specific mortality (multivariate HR, 2.12; 95% CI, 1.23-3.65) regardless of p53 status. A similar trend was observed when overall mortality was used as an outcome.

CONCLUSION

COX-2 overexpression is associated with worse survival among colon cancer patients. The effect of COX-2 on clinical outcome may be modified by p53 status.

Antagonism of the prostaglandin E receptor EP4 inhibits metastasis and enhances NK function

Cyclooxygenase-2 (COX-2) is associated with aggressive breast cancers. The COX-2 product prostaglandin E(2) (PGE(2)) acts through four G-protein-coupled receptors designated EP1-4. Malignant and immortalized normal mammary epithelial cell lines express all four EP. The EP4 antagonist AH23848 reduced the ability of tumor cells to colonize the lungs or to spontaneously metastasize from the mammary gland. EP4 gene silencing by shRNA also reduced the ability of mammary tumor cells to metastasize. Metastasis inhibition was lost in mice lacking either functional Natural Killer (NK) cells or interferon-gamma. EP4 antagonism inhibited MHC class I expression resulting in enhanced ability of NK cells to lyse mammary tumor target cells. These studies support the hypothesis that EP4 receptor antagonists reduce metastatic potential by facilitating NK-mediated tumor cell killing and that therapeutic targeting of EP4 may be an alternative approach to the use of COX inhibitors to limit metastatic disease.

Distinct expression pattern of the full set of secreted phospholipases A2 in human colorectal adenocarcinomas: sPLA2-III as a biomarker candidate

Recent studies suggest that secreted phospholipases A₂ (sPLA₂s) represent attractive potential tumour biomarkers and therapeutic targets for various cancers. As a first step to address this issue in human colorectal cancer, we examined the expression of the full set of sPLA₂s in sporadic adenocarcinomas and normal matched mucosa from 21 patients by quantitative PCR and immunohistochemistry. In normal colon, PLA2G2A and PLA2G12A were expressed at high levels, PLA2G2D, PLA2G5, PLA2G10 and PLA2G12B at moderate levels, and PLA2G1B, PLA2G2F and PLA2G3 at low levels. In adenocarcinomas from left and right colon, the expression of PLA2G3 was increased by up to 40-fold, while that of PLA2G2D and PLA2G5 was decreased by up to 23- and 14-fold. The variations of expression for sPLA₂-IID, sPLA₂-III and sPLA₂-V were confirmed at the protein level. The expression pattern of these sPLA₂s appeared to be linked respectively to the overexpression of interleukin-8, defensin α6, survivin and matrilysin, and downregulation of SFRP-1 and RLPA-1, all these genes being associated to colon cancer. This original sPLA₂ profile observed in adenocarcinomas highlights the potential role of certain sPLA₂s in colon cancer and suggests that sPLA₂-III might be a good candidate as a novel biomarker for both left and right colon cancers.