Reduced expression of the CXC chemokine hIRH/SDF-1alpha mRNA in hepatoma and digestive tract cancer

Five Critical Gene-Based Biomarkers With Optimal Performance for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most fatal cancers in the world. There is an urgent need to understand the molecular background of HCC to facilitate the identification of biomarkers and discover effective therapeutic targets. Published transcriptomic studies have reported a large number of genes that are individually significant for HCC. However, reliable biomarkers remain to be determined. In this study, built on max-linear competing risk factor models, we developed a machine learning analytical framework to analyze transcriptomic data to identify the most miniature set of differentially expressed genes (DEGs). By analyzing 9 public whole-transcriptome datasets (containing 1184 HCC samples and 672 nontumor controls), we identified 5 critical differentially expressed genes (DEGs) (ie, CCDC107, CXCL12, GIGYF1, GMNN, and IFFO1) between HCC and control samples. The classifiers built on these 5 DEGs reached nearly perfect performance in identification of HCC. The performance of the 5 DEGs was further validated in a US Caucasian cohort that we collected (containing 17 HCC with paired nontumor tissue). The conceptual advance of our work lies in modeling gene-gene interactions and correcting batch effect in the analytic framework. The classifiers built on the 5 DEGs demonstrated clear signature patterns for HCC. The results are interpretable, robust, and reproducible across diverse cohorts/populations with various disease etiologies, indicating the 5 DEGs are intrinsic variables that can describe the overall features of HCC at the genomic level. The analytical framework applied in this study may pave a new way for improving transcriptome profiling analysis of human cancers.

Adipocytes contribute to tumor progression and invasion of peritoneal metastasis by interacting with gastric cancer cells as cancer associated fibroblasts

BACKGROUND

Peritoneal metastasis (PM) is one of the most common causes of noncurative surgery and the most frequent recurrence pattern in gastric cancer (GC). During the process of PM, GC cells detached from primary tumor interact with human peritoneal mesothelial cells (HPMC) overlapped with adipose tissues such as the omentum or mesentery. Although the interaction with HPMC promotes the malignancy of GC, the role of adipose tissues remains unclear.

AIMS

We aimed to clarify how adipose tissue are affected by adjacent primary tumors during the expression of adipokines and to elucidate whether GC cells transform adipocytes into CAFs in vitro. In addition, we investigated whether GC cells are affected by adipocytes in their ability to infiltrate.

METHODS

We investigated the phenotypic conversion of adipocytes during the malignant process of GC cells in vivo and in vitro. We evaluated the expression levels of adiponectin in the omental adipose tissue of gastric cancer patients by western blotting. Following adipocytes/gastric cancer cells coculture, adipocyte markers, adiponectin receptors, and inflammatory cytokine markers were detected by real-time PCR and/or western blotting in the single-cultured and co-cultured adipocytes; cancer-associated fibroblast (CAF) markers were detected by immunofluorescence and western blotting in the single-cultured and co-cultured adipocytes; invasion assays were performed in single cultured and co-cultured MKN45 and OCUM.

RESULTS

In omental adipose tissues that are situated close to the primary tumors, the expression of adiponectin tended to decrease in patients with subserosal or serosal invasion. By co-culturing with GC cells, adipocytes were dedifferentiated and the expression levels of CAF marker FSP1 and inflammatory cytokines, PAI-1 and IL-6, significantly increased (p < 0.05). Furthermore, GC cells co-cultured with adipocytes showed enhanced invasion ability.

CONCLUSION

Our findings suggest that the phenotypic conversion of adipocytes may promote the malignancy of GC in the construction of the cancer microenvironment of PM.

The CXCL12 Crossroads in Cancer Stem Cells and Their Niche

Simple Summary

CXCL12 and its receptors have been extensively studied in cancer, including their influence on cancer stem cells (CSCs) and their niche. This intensive research has led to a better understanding of the crosstalk between CXCL12 and CSCs, which has aided in designing several drugs that are currently being tested in clinical trials. However, a comprehensive review has not been published to date. The aim of this review is to provide an overview on how CXCL12 axes are involved in the regulation and maintenance of CSCs, their presence and influence at different cellular levels within the CSC niche, and the current state-of-the-art of therapeutic approaches aimed to target the CXCL12 crossroads.

Abstract

Cancer stem cells (CSCs) are defined as a subpopulation of “stem”-like cells within the tumor with unique characteristics that allow them to maintain tumor growth, escape standard anti-tumor therapies and drive subsequent repopulation of the tumor. This is the result of their intrinsic “stem”-like features and the strong driving influence of the CSC niche, a subcompartment within the tumor microenvironment that includes a diverse group of cells focused on maintaining and supporting the CSC. CXCL12 is a chemokine that plays a crucial role in hematopoietic stem cell support and has been extensively reported to be involved in several cancer-related processes. In this review, we will provide the latest evidence about the interactions between CSC niche-derived CXCL12 and its receptors—CXCR4 and CXCR7—present on CSC populations across different tumor entities. The interactions facilitated by CXCL12/CXCR4/CXCR7 axes seem to be strongly linked to CSC “stem”-like features, tumor progression, and metastasis promotion. Altogether, this suggests a role for CXCL12 and its receptors in the maintenance of CSCs and the components of their niche. Moreover, we will also provide an update of the therapeutic options being currently tested to disrupt the CXCL12 axes in order to target, directly or indirectly, the CSC subpopulation.

Stromal-cell-derived Factor 1-α Promotes Tumor Progression in Colorectal Cancer

PURPOSE

Although stromal-cell-derived factor (SDF)-1α is suggested to be involved in tumorigenicity and tumor angiogenesis, the clinicopathological significance of its expression in colorectal cancers is not fully understood. We examined SDF-1α expression in colorectal cancers and investigated its relationship to clinicopathological features such as tumor staging, lymph-node metastasis, vascular invasion (VI), lymphatic invasion (LI) and neural invasion (NI).

METHODS

Specimens of 83 primary colorectal cancers were examined immunohistochemically, and the relationships between clinicopathological features and SDF-1α expression were analyzed. To compare the expressions between the normal colon tissue and colorectal cancer tissues, we performed Western blot analyses.

RESULTS

According to the Western blot analyses, SDF-1α was more highly expressed in colorectal carcinoma tissues than in normal colonic mucosa (20/21). According to the immunohistochemical stain, SDF-1α was associated with nodal status, distant metastasis, tumor staging, VI and LI. SDF-1α expression had a significant prognostic value for overall survival. Kaplan-Meier plots of survival in patients with high SDF-1α showed that high SDF-1α expression was associated with a shorter overall survival. However, no association was found between SDF-1α expression and other pathologic or clinical variables, including age, gender, degree of differentiation, and presence of perineural invasion.

CONCLUSION

The expression of SDF-1α might be associated with tumor progression in colorectal cancer. Inhibition of SDF-1α could be a therapeutic option in colorectal cancer patients.

The role of CXC chemokines in the transition of chronic inflammation to esophageal and gastric cancer

Chronic inflammation may increase the risk to develop cancer, for instance esophagitis or gastritis may lead to development of esophageal or gastric cancer, respectively. The key molecules attracting leukocytes to local inflammatory sites are chemokines. We here provide a systematic review on the impact of CXC chemokines (binding the receptors CXCR1, CXCR2, CXCR3 and CXCR4) on the transition of chronic inflammation in the upper gastrointestinal tract to neoplasia. CXCR2 ligands, including GRO-α,β,γ/CXCL1,2,3, ENA-78/CXCL5 and IL-8/CXCL8 chemoattract pro-tumoral neutrophils. In addition, angiogenic CXCR2 ligands stimulate the formation of new blood vessels, facilitating tumor progression. The CXCR4 ligand SDF-1/CXCL12 also promotes tumor development by stimulating angiogenesis and by favoring metastasis of CXCR4-positive tumor cells to distant organs producing SDF-1/CXCL12. Furthermore, these angiogenic chemokines also directly enhance tumor cell survival and proliferation. In contrast, the CXCR3 ligands Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 are angiostatic and attract anti-tumoral T lymphocytes and may therefore mediate tumor growth retardation and regression. Thus, chemokines exert diverging, sometimes dual roles in tumor biology as described for esophageal and gastric cancer. Therefore extensive research is needed to completely unravel the complex chemokine code in specific cancers. Possibly, chemokine-targeted cancer therapy will have to be adapted to the individual's chemokine profile.

The expression and role of CXC chemokines in colorectal cancer

Cancer is a life-threatening disease world-wide and colorectal cancer is the second common cause of cancer mortality. The interaction between tumor cells and stromal cells plays a crucial role in tumor initiation and progression and is partially mediated by chemokines. Chemokines predominantly participate in the chemoattraction of leukocytes to inflammatory sites. Nowadays, it is clear that CXC chemokines and their receptors (CXCR) may also modulate tumor behavior by several important mechanisms: regulation of angiogenesis, activation of a tumor-specific immune response by attracting leukocytes, stimulation of tumor cell proliferation and metastasis. Here, we review the expression and complex roles of CXC chemokines (CXCL1 to CXCL16) and their receptors (CXCR1 to CXCR6) in colorectal cancer. Overall, increased expression levels of CXC chemokines correlate with poor prognosis.

Expression of SDF-1 alpha and nuclear CXCR4 predicts lymph node metastasis in colorectal cancer

Although stromal cell-derived factor (SDF)-1 alpha and its receptor CXCR4 are experimentally suggested to be involved in tumorigenicity, the clinicopathological significance of their expression in human disease is not fully understood. We examined SDF-1 alpha and CXCR4 expression in colorectal cancers (CRCs) and their related lymph nodes (LNs), and investigated its relationship to clinicopathological features. Specimens of 60 primary CRCs and 27 related LNs were examined immunohistochemically for not only positivity but also immunostaining patterns for SDF-1 alpha and CXCR4. The relationships between clinicopathological features and SDF-1 alpha or CXCR4 expression were then analysed. Stromal cell-derived factor-1 alpha and CXCR4 expression were significantly associated with LN metastasis, tumour stage, and survival of CRC patients. Twenty-nine of 47 CXCR4-positive CRCs (61.7%) showed clear CXCR4 immunoreactivity in the nucleus and a weak signal in the cytoplasm (nuclear type), whereas others showed no nuclear immunoreactivity but a diffuse signal in the cytoplasm and at the plasma membrane (cytomembrane type). Colorectal cancer patients with nuclear CXCR4 expression showed significantly more frequent LN metastasis than did those with cytomembrane expression. Colorectal cancer patients with nuclear CXCR4 expression in the primary lesion frequently had cytomembrane CXCR4-positive tumours in their LNs. In conclusion, expression of SDF-1 alpha and nuclear CXCR4 predicts LN metastasis in CRCs.

[Identification of colorectal cancer, adenoma, and inflammatory bowel disease specific gene expression patterns using whole genomic oligonucleotide microarray system]

BACKGROUND

Discrimination and classification of colorectal diseases (adenoma, colorectal cancer, inflammatory bowel disease) using biopsy samples and expression microarrays, has not been solved yet, nevertheless, it can contribute to the understanding of the colonic diseases.

METHODS

Total ribonucleic acid was extracted, amplified and biotinylated from frozen colonic biopsies of 15 patients with colorectal cancer, 15 with adenoma, 14 with inflammatory bowel disease and 8 normal controls. Genome-wide gene expression profile was evaluated by Human Genome U133 Plus 2.0 microarrays. Two independent methods were used for data normalization and "Prediction Analysis of Microarrays" was performed for feature selection. Leave one-out stepwise discriminant analysis was performed. The expression results were verified by real-time polymerase chain reaction.

RESULTS

Top validated genes included CD44 antigen, met proto-oncogene, chemokine ligand-12, ADAM-like decysin-1 and ATP-binding casette-A8 genes in adenoma; collagen IValpha1, lipocalin-2, calumenin, aquaporin-8 genes in colorectal cancer; and lipocalin-2, ubiquitin D and interferon induced transmembrane protein 2 genes in inflammatory bowel disease. The discriminant analysis was able to classify the samples in overall 96.2% using 7 discriminatory genes. The expression of 94% of the 52 genes measured by Taqman real-time polymerase chain reaction correlated with the results obtained using Affymetrix microarrays at a significance of p < 0.05.

CONCLUSIONS

We successfully performed whole genomic microarray analysis to identify discriminative signatures using routine biopsy samples. The results set up data warehouse which can be further mined.

Chemokines in hepatitis C virus infection: Pathogenesis, prognosis and therapeutics

Hepatitis C virus infection and its associated liver inflammatory disease is a major global health problem affecting over 170 million people worldwide. Following viral infection, multiple pro-inflammatory mediators contribute to recruitment of immune cells to the liver and to the generation of an anti-viral immune response. However, when this vigorous immune response fails to eliminate the virus, chronic infection is established. This in turn, results in an ongoing process of inflammation, regeneration and fibrosis that in many cases leads to the development of cirrhosis and of hepatocellular carcinoma. Multiple recent publications mark chemokines and their receptors as key players in leukocyte recirculation through the inflamed liver. Furthermore, chemokines may also be involved in liver regeneration, fibrosis, and in malignant transformation, which is induced by the persistence of inflammation. Accumulating data indicates that distinct chemokines and chemokine receptors may be associated with different stages of the chronic hepatitis C virus infection-associated liver disease. Multiple small molecules and peptide antagonizing chemokines and their receptors are in advanced phase 3 and phase 2 clinical trials. In the near future, such drugs are expected to enter clinical use raising the question whether they may be applicable for the treatment of chronic viral infection-associated liver disease. In this review, recent advances in understanding the role of chemokines and their receptors in the pathogenesis of chronic viral infection-associated liver disease are presented. Furthermore, the clinical implications of these novel findings, which mark chemokines as prognostic markers and therapeutic targets for immune-modulation during chronic liver viral infection, are documented.

Ganoderma lucidum polysaccharide peptide reduced the production of proinflammatory cytokines in activated rheumatoid synovial fibroblast

The aim of the current study was to elucidate the potential therapeutic effect of Ganoderma lucidum polysaccharide peptide (GL-PP) in rheumatoid arthritis (RA). The effects of GL-PP on cell proliferation and cytokine production were studied in RA synovial fibroblasts (RASF). GL-PP significantly inhibited the proliferation of RASF. Following the incubation with GL-PP, production of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 in RASF were significantly increased as expressed as percentage change from basal values. However, the actual effects were minimal due to the low basal values. When RASF were activated by IL-1beta or lipopolysaccharides, IL-8 and MCP-1 production increased many folds. GL-PP significantly suppressed their productions. The inhibitory effects of GL-PP on cytokine production in RASF were at least in part, by inhibiting the nuclear factor-kappa B (NF-kappaB) transcription pathway. Our results demonstrated that GL-PP had the unique ability to modulate cytokine production in RASF and warrants further investigation into its mechanism of action.

CXCR4 and CXCL12 are inversely expressed in colorectal cancer cells and modulate cancer cell migration, invasion and MMP-9 activation

Colorectal cancer (CRC) is characterized by a distinct metastatic pattern resembling chemokine-induced leukocyte trafficking. This prompted us to investigate expression, signal transduction and specific functions of the chemokine receptor CXCR4 in CRC cells and metastases. Using RT-PCR analysis and Western blotting, we demonstrated CXCR4 and CXCL12 expression in CRC and CRC metastases. Cell differentiation increases CXCL12 mRNA levels. Moreover, CXCR4 and its ligand are inversely expressed in CRC cell lines with high CXCR4 and low or not detectable CXCL12 expression. CXCL12 activates ERK-1/2, SAPK/JNK kinases, Akt and matrix metalloproteinase-9. These CXCL12-induced signals mediate reorganization of the actin cytoskeleton resulting in increased cancer cell migration and invasion. Moreover, CXCL12 increases vascular endothelial growth factor (VEGF) expression and cell proliferation but has no effect on CRC apoptosis. Therefore, the CXCL12/CXCR4 system is an important mediator of invasion and metastasis of CXCR4 expressing CRC cells.

Expression of CXCR4 and Its Down-Regulation by IFN-γ in Head and Neck Squamous Cell Carcinoma

PURPOSE

The functional expression of CXCR4, which plays roles in cell migration and proliferation in response to its unique ligand stromal cell-derived factor-1 (SDF-1), has been reported in variety of carcinomas. However, CXCR4 expression and its functional role in head and neck squamous cell carcinomas (HNSCC) remain unclear. In this study, we investigated CXCR4 expression and analyzed its functions in HNSCC cell lines. We also attempted to regulate CXCR4 expression using cytokines, such as interleukin-1beta, tumor necrosis factor-alpha, and IFN-gamma. Finally, we investigated correlation between CXCR4 expression and clinical features in patients with HNSCC.

EXPERIMENTAL DESIGN

Six HNSCC cell lines were used in this study. Reverse transcription-PCR and flow cytometry analysis were shown for CXCR4 expressions with or without stimulations of cytokines. SDF-1-mediated cell migration was assayed in Matrigel-coated chemotaxis chamber. The SDF-1-mediated cell proliferation was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The SDF-1-mediated signaling pathways were analyzed by Western blot analysis. Biopsy specimens from 56 patients with HNSCC were used for immunohistologic analysis.

RESULTS

The significant CXCR4 expression was found in HSQ-89, IMC-3, and Nakamura cells. The SDF-1-mediated cell migration and proliferation were observed in CXCR4-positive cells. SDF-1 also promoted rapid phosphorylation of extracellular signal-regulated kinase 1/2 and Akt signaling pathways in CXCR4-positive cells. The SDF-1-mediated cell migration and proliferation of CXCR4-positive cells were inhibited by neutralization of CXCR4. Among three cytokines tested, IFN-gamma significantly reduced CXCR4 expression and SDF-1-induced cell migration and proliferation of CXCR4-positive cells. Immunohistologic analysis revealed that patients with advanced neck status and patients who developed distant metastases showed significantly higher CXCR4 expression, and the cause-specific survival of patients with CXCR4-expression was significantly shorter. Furthermore, multivariate analysis confirmed that CXCR4 positive was the independent factor for cause-specific death.

CONCLUSION

Our results may provide an insight into future therapeutic agent that inhibits tumor metastasis and progression via down-regulating CXCR4 expression in patients with HNSCC.

Mechanisms regulating the recruitment of macrophages into hypoxic areas of tumors and other ischemic tissues

The mechanisms responsible for recruiting monocytes from the bloodstream into solid tumors are now well characterized. However, recent evidence has shown that these cells then differentiate into macrophages and accumulate in large numbers in avascular and necrotic areas where they are exposed to hypoxia. This parallels their tendency to congregate in ischemic areas of other diseased tissues such as atherosclerotic plaques and arthritic joints. In tumors, macrophages appear to undergo marked phenotypic changes when exposed to hypoxia and to switch on their expression of a number of mitogenic and proangiogenic cytokines and enzymes. This then promotes tumor growth, angiogenesis, and metastasis. Here, we compare the various mechanisms responsible for monocyte recruitment into tumors with those regulating the accumulation of macrophages in hypoxic/necrotic areas. Because the latter are best characterized in human tumors, we focus mainly on these but also discuss their relevance to macrophage migration in ischemic areas of other diseased tissues. Finally, we discuss the relevance of these mechanisms to the development of novel cancer therapies, both in providing targets to reduce the proangiogenic contribution made by hypoxic macrophages in tumors and in developing the use of macrophages to deliver therapeutic gene constructs to hypoxic areas of diseased tissues.

Differential expression of splicing variants of the human caldesmon gene (CALD1) in glioma neovascularization versus normal brain microvasculature

Caldesmon is a cytoskeleton-associated protein which has not yet been related to neoplastic angiogenesis. In this study we investigated the expression of the caldesmon gene (CALD1) splicing variants and the protein expression level in glioma microvessels versus normal brain microvasculature. To exclude sources of splice variant expression from non-vascular components all possible cellular components present in control and glioma samples were pre-screened by laser-capture microdissection followed by RT-PCR before the cohort study. We discovered differential expression of the splicing variants of CALD1 in the tumor microvessels in contrast to normal brain microvasculature. Missplicing of exons 1, 1 + 4, and 1' + 4 of the gene is exclusively found in glioma microvessels. To exclude the possibility that this missplicing results from splice-site mutations, mutation scanning was performed by a coupled in vitro transcription/translation assay (IVTT). No premature stop mutations were traced by the IVTT. The transcriptional changes consequently resulted in up-regulation at the protein expression level. The up-regulated expression of caldesmon was coincident with the down-regulated expression of tight junction proteins (occludin and ZO-1). The results support the notion that missplicing of the CALD1 gene in glioma microvasculature is an independent epigenetic event regulated at the transcriptional level. The event coexists with tight junction (TJ) breakdown of the endothelial cells in glioma microvasculature. The data reveal a novel mechanism contributing to dysfunctionality of glioma neovascularization.

CXCR4 antagonist inhibits stromal cell-derived factor 1-induced migration and invasion of human pancreatic cancer

The stromal cell-derived factor-1 (SDF-1)/CXCR4 system is implicated in various instances of cell migration in mammals, including the migration of lymphocytes and the formation of metastases. We have recently synthesized a potent novel CXCR4 antagonist, TN14003. The purpose of this study was to investigate the role of SDF-1/CXCR4 axis in the pancreatic cancer metastasis via cell migration and invasion, and the inhibitory effect of TN14003 on pancreatic cancer cell metastasis. The expression of CXCR4 was detected in six pancreatic cancer cell lines by Western blotting and immunocytochemistry. In migration and invasion assays, SDF-1 stimulated both migration and invasion of cancer cells in a dose-dependent manner. The maximal effect of SDF-1 was observed at 100 ng/ml. SDF-1-induced migration and invasion of cancer cells were completely blocked by 100 nm TN14003. The stimulatory effect of SDF-1 on cancer migration and the inhibitory effect of TN14003 were mediated via the alteration in phosphorylation of mitogen-activated protein kinases. Treatment of cancer cells with 100 ng/ml SDF-1 resulted in a significant increase of actin polymerization, which was reduced by 100 nm TN14003. SDF-1 enhanced cancer cell adhesion to laminin, which was not reversed by TN14003. Taken together, SDF-1/CXCR4 axis is involved in pancreatic cancer metastasis through migration and invasion. The small molecule antagonists against CXCR4 such as TN14003 might be an effective anti-metastatic agent for pancreatic cancer.

Osteoactivin expressed during cirrhosis development in rats fed a choline-deficient, L-amino acid-defined diet, accelerates motility of hepatoma cells

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is closely associated with chronic liver diseases, particularly cirrhosis. However, the genes involved in hepatocarcinogenesis in the context of developing cirrhosis remain unknown. This study aims to identify genes associated with early cirrhosis-associated hepatocarcinogenesis.

METHODS

We examined genes differentially expressed between the livers of normal rats and rats fed a choline-deficient, L-amino acid-defined (CDAA) diet using suppression subtractive hybridization. We examined both the expression in the liver and HCC tissues of osteoactivin (OA), isolated in this screen, and its effect on invasiveness and metastasis.

RESULTS

OA mRNA was strongly expressed in the livers of rats fed the CDAA diet for 1-3 months. Moderate expression was sustained for 18 months. OA overexpression increased the invasiveness and metastasis of rat hepatoma cells in vitro and in vivo. In humans, OA expression was not detectable in normal liver tissues. While OA transcripts were detectable in cirrhotic nontumorous liver tissues surrounding HCCs, the majority of HCC tissue samples exhibited higher levels of OA expression than the surrounding normal tissue.

CONCLUSIONS

These results indicate that OA is a novel factor involved in the progression of HCC via stimulation of tumor invasiveness and metastatic potential.

Role of chemokines in angiogenesis: CXCL12/SDF-1 and CXCR4 interaction, a key regulator of endothelial cell responses

Chemokines are small proteins that act as cell attractants via the activation of G protein-coupled receptors. Chemokines play an important role in several pathophysiological processes such as inflammation and immunity. Many proinflammatory chemokines also support the development of vascular blood supply at the site of inflammation. Similarly, tumor-generated chemokines can contribute to tumor growth by promoting angiogenesis. Recently, significant advances have been made in understanding the contribution of chemokines to the angiogenesis process. This review will discuss first the evidence supporting the direct contribution of different chemokine subfamily members, including CC, CXC, and CX3C chemokines, as positive or negative regulators of the angiogenesis process based on the expression of their cognate receptors on endothelial cells. Additionally, the relationship between classic angiogenic factors and chemokine receptor expression on endothelial cells, and the implications of chemokine production by cancer cells will be analyzed with particular emphasis on the CXCL12/stromal-cell derived factor-1 interaction with CXCR4.

Expression of CXCR4 and CXCL12 (SDF-1) in human prostate cancers (PCa) in vivo

Human prostate cancers (PCa) express great variability in their ability to metastasize to bone. The identification of molecules associated with aggressive phenotypes will help to define PCa subsets and will ultimately lead to better treatment strategies. The chemokine stromal-derived factor-1 (SDF-1 or CXCL12) and its receptor CXCR4 are now known to modulate the migration and survival of an increasing array of normal and malignant cell types including breast, pancreatic cancers, glioblastomas, and others. The present investigation extends our previous investigations by determining the expression of CXCR4 and CXCL12 in humans using high-density tissue microarrays constructed from clinical samples obtained from a cohort of over 600 patients. These data demonstrate that CXCR4 protein expression is significantly elevated in localized and metastastic cancers. At the RNA level, human PCa tumors also express CXCR4 and message, but overall, they were not significantly different suggesting post-transcriptional regulation of the receptor plays a major role in regulating protein expression. Similar observations were made for CXCL12 message, but in this case more CXCL12 message was expressed by metastastic lesions as compared to normal tissues. PCa cell lines also express CXCL12 mRNA, and regulate mRNA expression in response to CXCL12 and secrete biologically active protein. Furthermore, neutralizing antibody to CXCL12 decreased the proliferation of bone homing LNCaP C4-2B and PC3 metastastic tumor cells. These investigations provide important new information pertaining to the molecular basis of how tumors may 'home' to bone, and the mechanisms that may account for their growth in selected end organs.

Chemokines and antitumor immunity: walking the tightrope

Chemokines play an important role in the generation of the immune system and in virtually every aspect of an immune response. The role of chemokines in antitumor immunity has been less straightforward to discern. A dichotomy exists in the field. One area of research has focused on the impact of tumor-derived chemokines, implicating them in everything from metastases to immune suppression. Another area of research has been dedicated to the introduction of chemokines into tumor cells in order to facilitate immune cell recruitment. In this review these two areas of investigation will be explored.

Regional expression of CXCL12/CXCR4 in liver and hepatocellular carcinoma and cell-cycle variation during in vitro differentiation

The CXCL12 / CXCR4 system may be important in carcinoma. Expression of the alpha-chemokine SDF-1alpha (stromal cell derived factor-1alpha) / CXCL12 mRNA is reduced in many carcinomas, yet its tissue protein expression may guide metastasis. Here we first compare the mRNA and protein expression of CXCL12 and its receptor CXCR4 in human liver, hepatocellular carcinoma, and malignant cell lines, and then assess cell cycle variation in CXCR4 expression. CXCR4 mRNA was present in most normal human tissues and malignant cell lines; it was only marginally reduced in hepatomas, while CXCL12 was markedly reduced, P < 0.0001. Immuno-histochemical staining of adjacent non-malignant liver showed regional CXCR4 cytoplasmic and cell-surface staining, limited to those hepatocytes around the central vein, a distribution resembling that of CXCL12. CXCL12 protein was not present in hepatocellular carcinoma cells in vivo, nor was cytoplasmic CXCR4 staining; nuclear CXCR4 protein expression in some malignant hepatocytes and CXCR4 staining of capillary endothelial cells around tumor cells were noted. In some malignant cell lines that had no CXCL12 on northern blots CXCL12 was weakly detectable by RT-PCR or protein staining in the cytoplasm of a few cells. With a view to future manipulation of CXCL12 / CXCR4 expression and growth we noted that in HT-29 cells CXCR4 protein expression was less on confluent than on non-confluent cells and varied during the cell cycle. Higher expression was associated most closely with the percentage of cells in the S-phase and inversely with the percentage of cells in the G1-phase. Treatment of HT-29 cells with butyrate reduced CXCR4 cell surface expression and reduced the percentage of cells in S-phase. In summary, CXCL12 protein expression parallels its mRNA, being markedly reduced in malignant cell lines and hepatomas; in liver, the regional distributions of CXCL12 and cytoplasmic CXCR4 are similar; finally, in HT-29, CXCR4 expression correlates with the S-phase of the cell cycle and is reduced during butyrate-induced differentiation.

CXCR4/CXCL12 expression and signalling in kidney cancer

CXCL12 (SDF-1), a CXC-chemokine, and its specific receptor, CXCR4, have recently been shown to be involved in tumourgenesis, proliferation and angiogenesis. Therefore, we analysed CXCL12alpha/CXCR4 expression and function in four human kidney cancer cell lines (A-498, CAKI-1, CAKI-2, HA-7), 10 freshly harvested human tumour samples and corresponding normal kidney tissue. While none of the analysed tumour cell lines expressed CXCL12alpha, A-498 cells were found to express CXCR4. More importantly, real-time RT-PCR analysis of 10 tumour samples and respective adjacent normal kidney tissue disclosed a distinct and divergent downregulation of CXCL12alpha and upregulation of CXCR4 in primary tumour tissue. To prove that the CXCR4 protein is functionally active, rhCXCL12alpha was investigated for its ability to induce changes of intracellular calcium levels in A-498 cells. Moreover, we used cDNA expression arrays to evaluate the biological influence of CXCL12alpha. Comparing gene expression profiles in rhCXCL12alpha stimulated vs unstimulated A-498 kidney cancer cells revealed specific regulation of 31 out of 1176 genes tested on a selected human cancer array, with a prominent stimulation of genes involved in cell-cycle regulation and apoptosis. The genetic changes reported here should provide new insights into the developmental paths leading to tumour progression and may also aid the design of new approaches to therapeutic intervention.

Loss of transgelin in breast and colon tumors and in RIE-1 cells by Ras deregulation of gene expression through Raf-independent pathways

Activated Ras but not Raf can transform RIE-1 and other epithelial cells, indicating the critical importance of Raf-independent effector function in Ras transformation of epithelial cells. To elucidate the nature of these Raf-independent activities, we utilized representational difference analysis to identify genes aberrantly expressed by Ras through Raf-independent mechanisms in RIE-1 cells. We identified a total of 22 genes, both known and novel, whose expression was either activated or abolished by Ras but not Raf. The genes up-regulated encode proteins involved in protein or DNA synthesis, regulation of protease activity, or ligand binding, whereas those genes down-regulated encode actin cytoskeletal-, extracellular matrix-, and gap junction-associated proteins, and transmembrane receptor- or cytokine-like proteins. These results suggest that a key function of Raf-independent signaling involves deregulation of gene expression. We further characterized transgelin as a gene whose expression was abolished by Ras. Transgelin was identified previously as a protein whose expression was lost in virally transformed cell lines. We show that this loss is regulated at the level of gene expression and that both Raf-dependent and Raf-independent pathways are required to cause Ras down-regulation of transgelin in RIE-1 cells, whereas Raf alone is sufficient to cause its loss in NIH 3T3 fibroblasts. We also found that Ras-dependent and Ras-independent mechanisms can cause the down-regulation of transgelin in human breast and colon carcinoma cells lines and patient-derived tumor samples. We conclude that loss of transgelin gene expression may be an important early event in tumor progression and a diagnostic marker for breast and colon cancer development.

Loss of chemokine SDF-1alpha-mediated CXCR4 signalling and receptor internalization in human hepatoma cell line HepG2

Expression of the chemokine stromal cell-derived factor-1alpha (SDF-1alpha) is absent from many carcinomas, including hepatomas. We note an early signalling defect in the hepatocellular carcinoma (HCC) cell line HepG2 that expresses the CXCR4 receptor and binds biotin-labelled SDF, but fails to stimulate downstream signalling events after engagement with SDF. In HepG2, the SDF/CXCR4 interaction did not result in calcium influx, phosphorylation and internalization of CXCR4, nor in a rapid phosphorylation of p44/42 MAP kinase. There were no CXCR4 mutations in the second chemokine binding loop or C terminal phosphorylation and internalization domains. The downstream signalling machinery in HepG2 appears to be intact since transfection of wild-type CXCR4 restored functional responsiveness. We conclude that HepG2 is unresponsive to SDF stimulation because of a defect located after receptor binding but before the activation of the signalling cascade. A hypothetical blocking molecule could hinder receptor internalization or CXCR4 signalling.

Expression of functional CXCR4 chemokine receptors on human colonic epithelial cells

In addition to their role as regulators of leukocyte migration and activation, chemokines and their receptors also function in angiogenesis, growth regulation, and HIV-1 pathogenesis--effects that involve the action of chemokines on nonhematopoietic cells. To determine whether chemokine receptors are expressed in human colonic epithelium, HT-29 cells were examined by RT-PCR for the expression of the chemokine receptors for lymphotactin, fractalkine, CCR1-10, and CXCR1-5. The only receptor consistently detected was CXCR4 (fusin/LESTR), although HT-29 cells did not express mRNA for its ligand, stromal cell-derived factor (SDF-1alpha). Flow cytometric analysis with anti-CXCR4 antibody indicated that the CXCR4 protein was expressed on the surface of roughly half of HT-29 cells. CXCR4 was also expressed in colonic epithelial cells in vivo as shown by immunohistochemistry on biopsies from normal and inflamed human colonic mucosa. The mRNA for SDF-1alpha and other CC and CXC chemokines was present in normal colonic biopsies. The CXCR4 receptor in HT-29 cells was functionally coupled, as demonstrated by the elevation in [Ca2+]i, which occurred in response to 25 nM SDF-1alpha and by the SDF-1alpha-induced upregulation of ICAM-1 mRNA. Sodium butyrate downregulated CXCR4 expression and induced differentiation of HT-29 cells, suggesting a role for CXCR4 in maintenance and renewal of the colonic epithelium. This receptor, which also serves as a coreceptor for HIV, may mediate viral infection of colonic epithelial cells.

IFN-alpha receptor mRNA expression in a United States sample with predominantly genotype 1a/I chronic hepatitis C liver biopsies correlates with response to IFN therapy

Our aim was to assess whether, in the United States, with the predominant hepatitis C viral (HCV) genotypes 1a/I and 1b/II, hepatic interferon-alpha receptor (IFNAR) mRNA expression correlated with response to IFN therapy, levels of HCV RNA, or histologic activity index (HAI). Nine of 24 patients (38%) had an initial response to IFN treatment, 5 of whom (21%) had a sustained response. The corrected hepatic IFNAR mRNA expression (measured by RT-PCR) for the sustained responder group (mean +/- SE, 0.16 +/- 0.06, n = 5) was significantly higher than for the nonresponding group (0.059 +/- 0.01, n = 15) (p < 0.02). Patients who relapsed had an intermediate value (0.092 +/- 0.029, n = 4). Higher IFNAR expression was inversely correlated with a lower serum HCV RNA titer (p < 0.01), and responders to IFN treatment tended to have a lower titer of HCV RNA (p = 0.056). We found no significant correlation between the amounts of IFNAR with (1) the total HAI (low HAI < or = 7, IFNAR 0.076 +/- 0.013, n = 10; high HAI > or = 8, IFNAR 0.092 +/- 0.027, n = 14, ns) or (2) individual inflammation, necrosis, or fibrosis components of the HAI. As with Japanese HCV patients with genotypes 1b/II-2b/IV, higher hepatic IFNAR mRNA expression in the United States with predominant genotypes 1a/I and 1b/II appears to correlate with response to IFN therapy and a low HCV RNA titer but not with the total HAI or its components.

Monocyte-chemo-attractant-protein-1 (MCP-1)-gene expression in cervical intra-epithelial neoplasias and cervical carcinomas

Chemokines play a central role in the chemotactic activation of immunological effector cells. One of the currently best characterized chemokines is the monocyte-chemo-attractant protein-1 (MCP-1), which is involved in the cross-talk with cells of the monocyte-macrophage lineage. Since macrophages and macrophage-derived cytokines appear to be important in the transcriptional regulation of "high-risk" types of human papillomaviruses (HPV), we monitored MCP-1 expression by in situ hybridization (ISH) in histologically distinct stages of cervical intra-epithelial neoplasms (CIN), cervical cancer and non-HPV-associated cases of erosive endocervicitis. Here, we demonstrate that high-grade dysplasia (CIN III, n = 9) completely lacks both MCP-1 expression and CD68+-macrophage infiltration, while MCP-1-specific signals were occasionally detectable in one out of 5 CIN-II and in one out of 3 CIN-I lesions. Inspection of hyperplastic squamous epithelium adjacent to cervical carcinomas reveals high MCP-1 expression and accumulation of infiltrating macrophages. In contrast, no macrophages could be detected in corresponding hyperplastic tissue areas surrounding CIN-II and CIN-III lesions, although MCP-1 was found to be highly expressed. Finally, in agreement with our earlier in vitro data, invasive carcinomas of the cervix uteri showed MCP-1-specific hybridization signals and macrophage infiltration only in the stroma surrounding the carcinoma cells and in endothelial cells of capillaries, especially at the invasion front of the tumor, while the inner mass of the carcinomas was completely negative. On the other hand, ISH and histochemical evaluation of inflammatory, non-HPV-associated cases of erosive endocervicitis indicate strong MCP-1 expression, which is regularly accompanied by chemotactic appearance of macrophages. These observations indicate that dysregulation of MCP-1-gene expression may represent an important step during HPV-linked carcinogenesis, allowing the escape of virus-positive cells from local immune response.

Interleukin-8 and hIRH (SDF1-alpha/PBSF) mRNA expression and histological activity index in patients with chronic hepatitis C

Recombinant human intercrine reduced in hepatomas (hIRH)/stromal cell-derived factor 1 (SDF1-alpha)/pre-B-cell growth-stimulating factor (PBSF), a new chemokine, exhibits an in vitro chemotaxis to neutrophils and a mixed in vivo chemotactic activity to neutrophils, lymphocytes, and monocytes in a rat intradermal injection model. We have investigated the messenger RNA (mRNA) expression of interleukin-8 (IL-8) and hIRH, in chronic hepatitis C of differing severity. Levels of expression of IL-8 and hIRH mRNA obtained from 37 human liver biopsy samples were measured by reverse-transcription and semiquantitative polymerase chain reaction (RT-PCR) amplification. We examined the correlation between mRNA expression and components of the histological activity index (HAI). Patients with HAI > or = 8 had a significantly higher corrected IL-8 mRNA expression ratio (0.24 +/- 0.13 [mean +/- SD]; n = 20) than those with HAI < or = 7 (0.05 < or = 0.03; n = 17; P < .0001). Additionally, IL-8 mRNA expression was strongly associated with the severity of portal inflammation (PI) (high PI vs. low PI, 0.22 +/- 0.14 vs. 0.05 +/- 0.04; P < .0001) and with the presence of bile duct lesions (0.29 +/- 0.15 vs. 0.11 +/- 0.1; P < .01). In contrast, hIRH mRNA expression was not associated with the total HAI, any components of the HAI, or bile duct inflammation or injury. These results suggest that hIRH, although having the -CXC-, alpha chemokine motif, and exhibiting in vivo and in vitro inflammatory activity as does IL-8, plays a different role from IL-8 in hepatic inflammation and injury. IL-8 expression is directly associated with inflammation in patients with chronic hepatitis C, while hIRH expression does not correlate with histopathological severity of inflammation.