Chemokines, chemokine receptors and the gastrointestinal system

Alterations in chemokine receptor CCR5 activity influence tumor cell biology in human cholangiocarcinoma cell lines

INTRODUCTION AND OBJECTIVES

Intrahepatic (I-CCA) and extrahepatic (E-CCA) cholangiocarcinoma (CCA) have different growth patterns and risks for tumor metastasis. Inhibition and/or activation of the chemokine receptor CCR subclasses have been reported to alter tumor cell biology in non-CCA cancers. In this study we documented CCR expression profiles in representative human I-CCA and E-CCA cell lines and the in vitro effects of CCR antagonists and agonists on tumor cell biology.

MATERIALS AND METHODS

CCR expression profiles were documented by real-time reverse transcription polymerase chain reaction; cell proliferation by WST-1; spheroid formation by sphere dimensions in anchorage-free medium; cell migration by wound healing and invasion by Transwell invasion chambers.

RESULTS

All 10 CCR motifs (CCR1-10) were expressed in the I-CCA, HuCCT1 cell line and six (CCR4, 5, 6, 8, 9 and 10) in the E-CCA, KMBC cell line. In HuCCT1 cells, CCR5 expression was most abundant whereas in KMBC cells, CCR6 followed by CCR5 were most abundant. The CCR5 antagonist Maraviroc significantly inhibited cell proliferation, migration and invasion in HuCCT1 cells, and spheroid formation and invasion in KMBC cells. The CCR5 agonist RANTES had no effect on HuCCT1 cells but increased cell proliferation, migration and invasion of KMBC cells.

CONCLUSION

These results suggest that CCR expression profiles differ in I-CCA and E-CCA. They also indicate that CCR5 antagonists and agonists have cell-specific effects but in general, CCR5 inactivation inhibits CCA tumor cell aggressiveness. Additional research is required to determine whether CCR5 inactivation is of value in the treatment of CCA in humans.

CXCL12/CXCR4 promotes proliferation, migration, and invasion of adamantinomatous craniopharyngiomas via PI3K/AKT signal pathway

OBJECTIVES

Adamantinomatous craniopharyngiomas (adaCP) accounts for 5.6% to 15% of intracranial tumors. High expression of chemokine (C-X-C motif) ligand 12 (CXCL12, also known as stromal cell-derived factor 1 [SDF1]) and its receptor CXC receptor type 4 (CXCR4) are widespread in various malignancy via multiple signal transduction pathways. This study aims to investigate the mechanism of CXCL12/CXCR4 promoting proliferation, migration, and invasion of adaCP.

METHODS

Quantitative real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry were used to evaluate the expression of CXCL12/CXCR4 mRNA and protein in 10 human adaCP tissues. Three successfully primary cell lines were obtained from native mainly solid tumor specimens, and confirmed by the means of inverted contrast microscope directly and following hematoxylin and eosin staining. Immunofluorescence was used to detect protein expression in vivo for the verification of primary cell line. Proliferation, migration, and invasion assays were performed to assess the biological functional role of CXCL12/CXCR4 in adaCP. The signal pathways involved in the action of CXCL12/CXCR4 in adaCP were also evaluated.

RESULTS

CXCL12 and CXCR4 were highly expressed in human adaCP samples. Primary adaCP cells were isolated and detected by the means of immunofluorescence for the detection of pan cytokeratin (pan-CK) and vimentin (VIM). Overexpression of CXCL12/CXCR4 significantly promoted the proliferation, migration, and invasion of primary adaCP cells. Moreover, cancer-promoting activity of CXCL12/CXCR4 is partially through its facilitation of PI3K/AKT signal pathway.

CONCLUSIONS

Our data showed that CXCL12/CXCR4 promotes adaCP proliferation, migration, and invasion through PI3K/AKT signal pathway. These findings suggested that therapeutic strategies regulating CXCL12/CXCR4 expression may provide an effective treatment of adaCP.

Regulation of the intestinal immune system by flavonoids and its utility in chronic inflammatory bowel disease

Flavonoids are phytochemicals which can regulate the activity of the intestinal immune system. In patients with chronic inflammatory bowel disease (IBD) there is an overexpression and imbalance of the components of the inflammatory immune reactions which are chronically activated. Suppression of inflammation can be achieved by anti-inflammatory drugs which are used in clinical medicine but these can cause serious side effects. Flavonoids can have natural immunosuppressive properties and inhibit the activation of immune cells and its effectors (chemokines, TNF-, cytokines). Phytochemicals such as flavonoids bind to the nuclear Ah (aryl hydrocarbon) -receptor thereby stimulating protective enzyme activities. As shown by clinical evidence in patients and by experimental work some flavonoids (apigenin, epigallocatechin gallate) were effective in the inhibition of inflammation. Instead of or additionally to anti-inflammatory drugs flavonoids can be used in IBD patients to treat the over-reactive immunologic system. This is accomplished by upregulation of the Ah-receptor. Flavonoids interact with toll-like receptors expressing on the surface of immune cells, then they were internalized to the cytosol and transferred into the nucleus, where they were attached to the Ah-receptor. The Ah-receptor binds to the Ah-R nuclear translocator and via Ah response element beneficial protective enzymes and cytokines are induced, leading to upregulation of the anti-inflammatory system.

Role of G protein-coupled receptors-microRNA interactions in gastrointestinal pathophysiology

G protein-coupled receptors (GPCRs) make up the largest transmembrane receptor superfamily in the human genome and are expressed in nearly all gastrointestinal cell types. Coupling of GPCRs and their respective ligands activates various phosphotransferases in the cytoplasm, and, thus, activation of GPCR signaling in intestine regulates many cellular and physiological processes. Studies in microRNAs (miRNAs) demonstrate that they represent critical epigenetic regulators of different pathophysiological responses in different organs and cell types in humans and animals. Here, we reviewed recent research on GPCR-miRNA interactions related to gastrointestinal pathophysiology, such as inflammatory bowel diseases, irritable bowel syndrome, and gastrointestinal cancers. Given that the presence of different types of cells in the gastrointestinal tract suggests the importance of cell-cell interactions in maintaining gastrointestinal homeostasis, we also discuss how GPCR-miRNA interactions regulate gene expression at the cellular level and subsequently modulate gastrointestinal pathophysiology through molecular regulatory circuits and cell-cell interactions. These studies helped identify novel molecular pathways leading to the discovery of potential biomarkers for gastrointestinal diseases.

CCR7 enhances TGF-β1-induced epithelial-mesenchymal transition and is associated with lymph node metastasis and poor overall survival in gastric cancer

CCR7 is a G protein-coupled chemokine receptor. In this study, we used immunohistochemistry with tissue microarrays to measure CCR7 expression in tumor specimens from 122 patients with gastric cancer. We show that CCR7 expression is associated with lymph node metastasis (P = 0.022) and overall survival (OS; P = 0.025), and is an independent factor associated with poorer overall survival (P = 0.032). The CCR7 mechanism was predicted based on bioinformatic analysis and verified in gastric cancer cell lines and primary tumor samples. The data show that CCR7 contributes to TGF-β1-induced epithelial-mesenchymal transition (EMT) and that the effects of TGF-β1 are inhibited by a CCR7 neutralizing antibody or a NF-κB inhibitor. Increased TGF-β1 expression was accompanied by nuclear localization of NF-κB-p65 and higher levels of the mesenchymal marker vimentin in human gastric cancer samples. We conclude that the CCR7 axis mediates TGF-β1-induced EMT via crosstalk with NF-κB signaling, facilitating lymph node metastasis and poorer overall survival in patients with gastric cancer. These findings suggest CCR7 is a novel prognostic indicator and a potential target for gastric cancer therapy.

C-X-C motif receptor 7 in gastrointestinal cancer

Chemokine receptors are key mediators of normal physiology and numerous pathological conditions, including inflammation and cancer. This receptor family is an emerging target for anticancer drug development. C-X-C motif receptor 7 (CXCR7) is an atypical chemokine receptor that was first cloned from a canine cDNA library as an orphan receptor and was initially named receptor dog cDNA 1 (RDC1). Shortly after demonstrating that RDC1 binds with its ligand, stromal cell-derived factor-1α and interferon-inducible T-cell α chemoattractant, RDC1 was officially deorphanized and renamed CXCR7, as the seventh receptor in the CXC class of the chemokine receptor family. Recent accumulating evidence has demonstrated that CXCR7 expression is augmented in the majority of tumor cells compared with their normal counterparts and is involved in cell proliferation, survival, migration, invasion and angiogenesis during the initiation and progression of breast, lung and prostate cancer. In the present review, the expression and role of CXCR7, as well as its clinical relevance in cancer of the gastrointestinal system, were investigated. In addition, the potential of this chemokine receptor as a therapeutic target in the treatment of gastrointestinal cancer was discussed.

Design, synthesis and SAR study of novel trisubstituted pyrimidine amide derivatives as CCR4 antagonists

The design, synthesis and structure-activity relationship studies of some novel trisubstituted pyrimidine amide derivatives prepared as CCR4 antagonists are described. The activities of these compounds were evaluated by the CCR4-MDC chemotaxis inhibition assay. Compound 1, which we have previously reported as a potent antagonist of CCR4, was employed as the positive control. The results indicated that most of the synthesized compounds exhibited some chemotaxis inhibition activity against CCR4. Of these new compounds, compounds 6c, 12a and 12b, with IC₅₀ values of 0.064, 0.077 and 0.069 μM, respectively, showed higher or similar activity compared with compound 1 (IC₅₀ of 0.078 μM). These compounds provide a basis for further structural modifications. The systematic structure-activity relationship of these trisubstituted pyrimidine amide derivatives was discussed based on the obtained experimental data. The results from the SAR study may be useful for identifying more potent CCR4 antagonists.

CXC chemokines and chemokine receptors in gastric cancer: From basic findings towards therapeutic targeting

Gastric cancer is the fourth most common cancer, and the second-highest cause of cancer-related deaths worldwide. Despite extensive research to identify novel diagnostic and therapeutic agents, patients with advanced gastric cancer suffer from a poor quality of life and poor prognosis, and treatment is dependent mainly on conventional cytotoxic chemotherapy. To improve the quality of life and survival of gastric cancer patients, a better understanding of the underlying molecular pathologies, and their application towards the development of novel targeted therapies, is urgently needed. Chemokines are a group of small proteins associated with cytoskeletal rearrangements, the directional migration of several cell types during development and physiology, and the host immune response via interactions with G-protein coupled receptors. There is also growing evidence to suggest that chemokines not only play a role in the immune system, but are also involved in the development and progression of tumors. In gastric cancer, CXC chemokines and chemokine receptors regulate the trafficking of cells in and out of the tumor microenvironment. CXC chemokines and their receptors can also directly influence tumorigenesis by modulating tumor transformation, survival, growth, invasion and metastasis, as well as indirectly by regulating angiogenesis, and tumor-leukocyte interactions. In this review, we will focus on the roles of CXC chemokines and their receptors in the development, progression, and metastasis of gastric tumors, and discuss their therapeutic potential for gastric cancer.

p53 mutation in the genesis of metastasis

Development of metastatic cancer is a complex series of events that includes genesis of tumor-related vascular and lymphatic systems, enhanced cellular motility, and the capacity to invade and survive at distant sites, as well as evasion of host defences. The wild-type p53 protein plays key roles in controlling these facets of tumor progression, and loss of normal p53 function can be sufficient to predispose tumor cells to gain metastatic properties. In contrast, dominant p53 mutants that have gained oncogenic functions can actively drive metastasis through a variety of mechanisms. This chapter aims to highlight these processes.

Epigenetic silencing of CXCL14 induced colorectal cancer migration and invasion

To explore epigenetic regulation and the impact of chemokine CXCL14 on colorectal cancer, 7 colorectal cancer cell lines, 107 cases of primary colorectal cancer, and 10 cases of normal colorectal mucosa were evaluated in this study. Methylation specific PCR (MSP), semi-quantitative reverse-transcription PCR (RT-PCR), cell proliferation assay, colony formation, and transwell assay were performed for the evaluation. Complete methylation and loss of CXCL14 expression were found in 5 colorectal cancer cell lines. Partial methylation and weak expression were found in two cell lines. CXCL14 was methylated in 79.4% (85/107) of primary human colorectal cancer. No methylation was found in 10 cases of normal colorectal mucosa. Restoration of CXCL14 expression was induced by the 5-aza-2'-deoxycytidine (DAC) treatment. The cell viability was reduced and colony formation was inhibited by restoration of CXCL14 expression in HCT116 cells, a colorectal cancer cell line. The number of invasive and migration cells was reduced by CXCL14. The expression of MMP-2, Vimentin, and NF-κB was suppressed, and the expression of E-cadherin and IκB-α was induced by CXCL14. In conclusion, CXCL14 is frequently methylated in human colorectal cancer and promoter region hypermethylation silenced CXCL14 expression in colorectal cancer cells. Restoration of CXCL14 expression suppressed colorectal cancer proliferation. CXCL14 inhibits colorectal cancer migration, invasion, and epithelial-to-mesenchymal transition (EMT) by suppressing NF-κB signaling.