Peroxisome Proliferator-Activated Receptor δ Suppresses the Cytotoxicity of CD8+ T Cells by Inhibiting RelA DNA-Binding Activity.

The molecular mechanisms regulating CD8+ cytotoxic T lymphocytes (CTL) are not fully understood. Here, we show that the peroxisome proliferator-activated receptor δ (PPARδ) suppresses CTL cytotoxicity by inhibiting RelA DNA binding. Treatment of ApcMin/+ mice with the PPARδ agonist GW501516 reduced the activation of normal and tumor-associated intestinal CD8+ T cells and increased intestinal adenoma burden.

Dual Blockade of EP2 and EP4 Signaling is Required for Optimal Immune Activation and Antitumor Activity Against Prostaglandin-Expressing Tumors.

Unlabelled: While the role of prostaglandin E2 (PGE2) in promoting malignant progression is well established, how to optimally block the activity of PGE2 signaling remains to be demonstrated. Clinical trials with prostaglandin pathway targeted agents have shown activity but without sufficient significance or dose-limiting toxicities that have prevented approval. PGE2 signals through four receptors (EP1-4) to modulate tumor progression.

The COX-2-PGE2 Pathway Promotes Tumor Evasion in Colorectal Adenomas.

Unlabelled: The mechanisms underlying the regulation of a checkpoint receptor, PD-1, in tumor-infiltrating immune cells during the development of colorectal cancer are not fully understood. Here we demonstrate that COX-2-derived PGE2, an inflammatory mediator and tumor promoter, induces PD-1 expression by enhancing NFκB's binding to the PD-1 promoter via an EP4-PI3K-Akt signaling pathway in both CD8+ T cells and macrophages. Moreover, PGE2 suppresses CD8+ T-cell proliferation and cytotoxicity against tumor cells and impairs macrophage phagocytosis of cancer cells via an EP4-PI3K-Akt-NFκB-PD-1 signaling pathway.

Cyclooxygenases and Prostaglandins in Tumor Immunology and Microenvironment of Gastrointestinal Cancer.

Chronic inflammation is a known risk factor for gastrointestinal cancer. The evidence that nonsteroidal anti-inflammatory drugs suppress the incidence, growth, and metastasis of gastrointestinal cancer supports the concept that a nonsteroidal anti-inflammatory drug target, cyclooxygenase, and its downstream bioactive lipid products may provide one of the links between inflammation and cancer. Preclinical studies have demonstrated that the cyclooxygenase-2-prostaglandin E pathway can promote gastrointestinal cancer development.

Mutant APC promotes tumor immune evasion via PD-L1 in colorectal cancer.

PD-L1 expression is elevated in various human cancers, including colorectal cancer. High levels of PD-L1 expressed on tumor epithelial cells are one of the potential mechanisms by which tumor cells become resistant to immune attack. However, PD-L1 regulation in tumor cells is not fully understood.

Prostaglandin E Induces miR675-5p to Promote Colorectal Tumor Metastasis via Modulation of p53 Expression.

Background & Aims: Prostaglandin E (PGE) promotes colorectal tumor formation and progression by unknown mechanisms. We sought to identify microRNAs (miRNAs) that might mediate the effects of PGE on colorectal cancer (CRC) development.

Methods: We incubated LS174T colorectal cancer cells with PGE or without (control) and used miRNA-sequencing technology to compare expression patterns of miRNAs.

PPARδ Mediates the Effect of Dietary Fat in Promoting Colorectal Cancer Metastasis.

The nuclear hormone receptor peroxisome proliferator-activated receptor delta (PPARδ) is a ligand-dependent transcription factor involved in fatty acid metabolism, obesity, wound healing, inflammation, and cancer. Although PPARδ has been shown to promote intestinal adenoma formation and growth, the molecular mechanisms underlying the contribution of PPARδ to colorectal cancer remain unclear. Here, we demonstrate that activation of PPARδ induces expansion of colonic cancer stem cells (CSC) and promotes colorectal cancer liver metastasis by binding to the Nanog promoter and enhancing Nanog expression.

Role of prostanoids in gastrointestinal cancer.

Chronic inflammation is a risk factor for gastrointestinal cancer and other diseases. Most studies have focused on cytokines and chemokines as mediators connecting chronic inflammation to cancer, whereas the involvement of lipid mediators, including prostanoids, has not been extensively investigated. Prostanoids are among the earliest signaling molecules released in response to inflammation.

CXCL1 Is Critical for Premetastatic Niche Formation and Metastasis in Colorectal Cancer.

Emerging evidence suggests that the primary tumor influences the development of supportive metastatic microenvironments, referred to as premetastatic niches, in certain distant organs before arrival of metastatic cells. However, the mechanisms underlying the contributions of the primary tumor to premetastatic niche formation are not fully understood. Here, we demonstrate that colorectal carcinoma cells secrete VEGFA, which stimulates tumor-associated macrophages to produce CXCL1 in the primary tumor.

Krüppel-Like Factor 12 Promotes Colorectal Cancer Growth through Early Growth Response Protein 1.

Krüppel-like factor 12 (KLF12) is a transcription factor that plays a role in normal kidney development and repression of decidualization. KLF12 is frequently elevated in esophageal adenocarcinoma and has been reported to promote gastric cancer progression. Here, we examined the role of KLF12 in colorectal cancer (CRC).

The Role of Prostaglandin E(2) in Tumor-Associated Immunosuppression.

Tumor-associated inflammation can create an immunosuppressive microenvironment allowing tumor cells to escape immunosurveillance. Inhibiting immunosuppression remains one of the major challenges in cancer immunotherapy via checkpoint inhibitors. Recent preclinical data from the Reis e Sousa group may provide a strong rationale for developing new therapeutics to subvert tumor-induced immunosuppression via prostaglandin inhibition.

Immunosuppression associated with chronic inflammation in the tumor microenvironment.

Chronic inflammation contributes to cancer development via multiple mechanisms. One potential mechanism is that chronic inflammation can generate an immunosuppressive microenvironment that allows advantages for tumor formation and progression. The immunosuppressive environment in certain chronic inflammatory diseases and solid cancers is characterized by accumulation of proinflammatory mediators, infiltration of immune suppressor cells and activation of immune checkpoint pathways in effector T cells.

PPARδ and PGE signaling pathways communicate and connect inflammation to colorectal cancer.

The nuclear hormone receptor peroxisome proliferator-activated receptor δ (PPARδ) is a ligand-dependent transcription factor that is involved in fatty acid metabolism, obesity, wound healing, inflammation, and cancer. Despite decades of research, the role of PPARδ in inflammation and colorectal cancer remains unclear and somewhat controversial. Our recent work presented the first genetic evidence demonstrating that PPARδ is required for chronic colonic inflammation and colitis-associated carcinogenesis.

Prostaglandin E2 Promotes Colorectal Cancer Stem Cell Expansion and Metastasis in Mice.

Background & Aims: Inflammation may contribute to the formation, maintenance, and expansion of cancer stem cells (CSCs), which have the capacity for self-renewal, differentiation, and resistance to cytotoxic agents. We investigated the effects of the inflammatory mediator prostaglandin E2 (PGE2) on colorectal CSC development and metastasis in mice and the correlation between levels of PGE2 and CSC markers in human colorectal cancer (CRC) specimens.

Methods: Colorectal carcinoma specimens and matched normal tissues were collected from patients at the Mayo Clinic (Scottsdale, AZ) and analyzed by mass spectrometry and quantitative polymerase chain reaction.

CG100649, a novel COX-2 inhibitor, inhibits colorectal adenoma and carcinoma growth in mouse models.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase-2 (COX-2) inhibitors (COXIBs) can reduce the risk of developing colorectal cancer (CRC) and are being considered for use as adjuvant therapy for treatment of CRC patients. However, long-term use of most NSAIDs, except aspirin, increases cardiovascular risk, hampering use of these drugs in CRC prevention and possibly for treatment. CG100649 is a new member of the COXIB family, which is proposed to inhibit both COX-2 and carbonic anhydrase-I/-II (CA-I/-II) activity.

Myeloid-derived suppressor cells link inflammation to cancer.

Our recent work has provided the first evidence that MDSCs promote chronic colonic inflammation and colitis-associated carcinogenesis. Our findings not only reveal a novel function of MDSCs in connecting inflammation to cancer, but also provide a rationale for developing effective therapeutic strategies to subvert inflammation- and tumor-induced immunosuppression.

Peroxisome proliferator-activated receptor δ promotes colonic inflammation and tumor growth.

Although epidemiologic and experimental evidence strongly implicates chronic inflammation and dietary fats as risk factors for cancer, the mechanisms underlying their contribution to carcinogenesis are poorly understood. Here we present genetic evidence demonstrating that deletion of peroxisome proliferator-activated receptor δ (PPARδ) attenuates colonic inflammation and colitis-associated adenoma formation/growth. Importantly, PPARδ is required for dextran sodium sulfate induction of proinflammatory mediators, including chemokines, cytokines, COX-2, and prostaglandin E2 (PGE2), in vivo.

An inflammatory mediator, prostaglandin E2, in colorectal cancer.

It is widely accepted that intake of dietary fats and chronic inflammation are risk factors for developing colorectal cancer. Arachidonic acid is a major component of animal fats, and the bioactive lipids produced from this substrate play critical roles in a variety of biologic processes, including cancer. Cyclooxygenase-derived prostaglandin E2 is a known proinflammatory lipid mediator that promotes tumor progression.

CXCR2-expressing myeloid-derived suppressor cells are essential to promote colitis-associated tumorigenesis.

A large body of evidence indicates that chronic inflammation is one of several key risk factors for cancer initiation, progression, and metastasis. However, the underlying mechanisms responsible for the contribution of inflammation and inflammatory mediators to cancer remain elusive. Here, we present genetic evidence that loss of CXCR2 dramatically suppresses chronic colonic inflammation and colitis-associated tumorigenesis through inhibiting infiltration of myeloid-derived suppressor cells (MDSCs) into colonic mucosa and tumors in a mouse model of colitis-associated cancer.

HIG2 promotes colorectal cancer progression via hypoxia-dependent and independent pathways.

HIG2 (hypoxia-inducible gene 2) is a biomarker of hypoxia and elevated in several cancers. Here, we show that HIG2 also upregulated HIF-1α expression under hypoxic conditions and enhanced AP-1 expression under normoxic conditions, which affects colorectal cancer cell survival. Importantly, over-expression of HIG2 promoted tumor growth by suppressing apoptosis in a mouse orthotopic model.

Urinary PGE-M: a promising cancer biomarker.

Cancer prevention, early diagnosis, and targeted therapies are the keys to success in better cancer control and treatment. A big challenge remains to identify biomarkers for predicting who may have higher cancer risk and are able to respond to certain chemopreventive agents as well as for assessing a patient's response during treatment. Although a large body of evidence indicates that chronic inflammation is a risk factor for cancer, it is unclear whether inflammatory biomarkers can be used to predict cancer risk, progression, and death.

PPARγ agonists target aromatase via both PGE2 and BRCA1.

Obesity is a well-recognized risk factor for postmenopausal breast cancer. Although the underlying mechanisms are not clearly defined, aromatase is thought to play a pivotal role in connecting obesity-associated inflammation with postmenopausal breast cancer. It has been well established that both the proinflammatory prostaglandin E(2) (PGE(2)) and the BRCA1 tumor-suppressor gene regulate aromatase expression.

The role of anti-inflammatory drugs in colorectal cancer.

A large body of evidence indicates that genetic mutations, epigenetic changes, chronic inflammation, diet, and lifestyle are key risk factors for colorectal cancer (CRC). Prevention of CRC has long been considered a plausible approach for the population and individuals at high risk for developing this disease. A significant effort has been made in the development of novel drugs for both prevention and treatment over the past two decades.