Adenosine stimulation of proliferation of breast carcinoma cell lines: Evaluation of the [3H]thymidine assay system and modulatory effects of the cellular microenvironment in vitro

Cobalt/Bioglass Nanoparticles Enhanced Dermal Regeneration in a 3-Layered Electrospun Scaffold

Purpose

Due to the multilayered structure of the skin tissue, the architecture of its engineered scaffolds needs to be improved. In the present study, 45s5 bioglass nanoparticles were selected to induce fibroblast proliferation and their protein secretion, although cobalt ions were added to increase their potency.

Methods

A 3-layer scaffold was designed as polyurethane (PU) - polycaprolactone (PCL)/ collagen/nanoparticles-PCL/collagen. The scaffolds examined by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), tensile, surface hydrophilicity and weight loss. Biological tests were performed to assess cell survival, adhesion and the pattern of gene expression.

Results

The mechanical assay showed the highest young modulus for the scaffold with the doped nanoparticles and the water contact angle of this scaffold after chemical crosslinking of collagen was reduced to 52.34±7.7°. In both assessments, the values were statistically compared to other groups. The weight loss of the corresponding scaffold was the highest value of 82.35±4.3 % due to the alkaline effect of metal ions and indicated significant relations in contrast to the scaffold with non-doped particles and bare one (P value<0.05). Moreover, better cell expansion, greater cell confluence and a lower degree of toxicity were confirmed. The up-regulation of TGF β1 and VEGF genes introduced this scaffold as a better model for the fibroblasts commitment to a new skin tissue among bare and nondoped scaffold (P value<0.05).

Conclusion

The 3-layered scaffold which is loaded with cobalt ions-bonded bioglass nanoparticles, is a better substrate for the culture of the fibroblasts.

EGFR-targeted bacteriophage lambda penetrates model stromal and colorectal carcinoma tissues, is taken up into carcinoma cells, and interferes with 3-dimensional tumor formation

Introduction

Colorectal cancer and other adult solid cancers pose a significant challenge for successful treatment because the tumor microenvironment both hinders the action of conventional therapeutics and suppresses the immune activities of infiltrating leukocytes. The immune suppression is largely the effect of enhanced local mediators such as purine nucleosides and eicosanoids. Genetic approaches have the promise of interfering with these mechanisms of local immunosuppression to allow both intrinsic and therapeutic immunological anticancer processes. Bacterial phages offer a novel means of enabling access into tissues for therapeutic genetic manipulations.

Methods

We generated spheroids of fibroblastic and CRC cancer cells to model the 3-dimensional stromal and parenchymal components of colorectal tumours. We used these to examine the access and effects of both wildtype (WT) and epidermal growth factor (EGF)-presenting bacteriophage λ (WT- λ and EGF-λ) as a means of delivery of targeted genetic interventions in solid cancers. We used both confocal microscopy of spheroids exposed to AF488-tagged phages, and the recovery of viable phages as measured by plaque-forming assays to evaluate access; and measures of mitochondrial enzyme activity and cellular ATP to evaluate the outcome on the constituent cells.

Results

Using flourescence-tagged derivatives of these bacteriophages (AF488-WT-λ and AF488-EGF-λ) we showed that phage entry into these tumour microenvironments was possible and that the EGF ligand enabled efficient and persistent uptake into the cancer cell mass. EGF-λ became localized in the intracellular portion of cancer cells and was subjected to subsequent cellular processing. The targeted λ phage had no independent effect upon mature tumour spheroids, but interfered with the early formation and growth of cancer tissues without the need for addition of a toxic payload, suggesting that it might have beneficial effects by itself in addition to any genetic intervention delivered to the tumour. Interference with spheroid formation persisted over the duration of culture.

Discussion

We conclude that targeted phage technology is a feasible strategy to facilitate delivery into colorectal cancer tumour tissue (and by extension other solid carcinomas) and provides an appropriate delivery vehicle for a gene therapeutic that can reduce local immunosuppression and/or deliver an additional direct anticancer activity.

Seeding metastases: The role and clinical utility of circulating tumour cells

Peripheral human blood is a readily-accessible source of patient material in which circulating tumour cells (CTCs) can be found. Their isolation and characterization holds the potential to provide prognostic value for various solid cancers. Enumeration of CTCs from blood is becoming a common practice in informing prognosis and may guide therapy decisions. It is further recognized that enumeration alone does not capture perspective on the heterogeneity of tumours and varying functional abilities of the CTCs to interact with the secondary microenvironment. Characterizing the isolated CTCs further, in particular assessing their functional abilities, can track molecular changes in the disease progress. As a step towards identifying a suite of functional features of CTCs that could aid in clinical decisions, developing a CTC isolation technique based on extracellular matrix (ECM) interactions may provide a more solid foundation for isolating the cells of interest. Techniques based on size, charge, density, and single biomarkers are not sufficient as they underutilize other characteristics of cancer cells. The ability of cancer cells to interact with ECM proteins presents an opportunity to utilize their full character in capturing, and also allows assessment of the features that reveal how cells might behave at secondary sites during metastasis. This article will review some common techniques and recent advances in CTC capture technologies. It will further explore the heterogeneity of the CTC population, challenges they experience in their metastatic journey, and the advantages of utilizing an ECM-based platform for CTC capture. Lastly, we will discuss how tailored ECM approaches may present an optimal platform to capture an influential heterogeneous population of CTCs.

Differential effect of adenosine on rhabdomyosarcoma migration and proliferation

INTRODUCTION

Adenosine and its receptors are involved deeply in the regulation of tumour biology. Purine nucleotides are released from stressed cells in states of hypoxia or radiochemotherapy-induced cell damage. Adenosine exerts its effect through the P1 family of selective receptors. The purpose of the study was to evaluate the exact role of extracellular role on biology of Rhabdomyosarcoma (RMS) cells.

MATERIAL AND METHODS

Series of in vitro studies accompanied by immunohistochemical, RQ-PCR and shRNA methods have characterised adenosine receptor expression on Rhabdomyosarcoma cell lines, normal skeletal muscle and effect of adenosine on Rhabdomyosarcoma growth and migration.

RESULTS

Extracellular adenosine (highest at 50 μM, p < 0.05) and AMP (highest at 300 μM, p < 0.05) markedly enhanced chemotaxis in the Boyden chamber assay The reaction is mostly governed by the A1 receptor, which is greatly overexpressed in Rhabdomyosarcoma as compared with normal skeletal muscle. Cell migration induced by adenosine and AMP is blocked by pertussis toxin, phospholipase C and MAP kinase inhibitor, which demonstrates the importance of these signalling pathways. High doses of adenosine have a detrimental effect on cellular proliferation, in a receptor-independent manner (≥ 500 μM; p < 0.05). The blockage of adenosine transporter by dipyridamole abolishes this effect, indicating involvement of an intrinsic pathway. Further increase of adenosine concentration, induced by deaminase inhibitors, augment the effect.

CONCLUSIONS

Our results suggest that adenosine and AMP trigger cell migration by binding to P1 receptors and directing cancer cells to the sites of hypoxia or cellular damage. Specifically by A1 receptor which is overexpressed in RMS.

Purinergic Signalling: Therapeutic Developments

Purinergic signalling, i.e., the role of nucleotides as extracellular signalling molecules, was proposed in 1972. However, this concept was not well accepted until the early 1990's when receptor subtypes for purines and pyrimidines were cloned and characterised, which includes four subtypes of the P1 (adenosine) receptor, seven subtypes of P2X ion channel receptors and 8 subtypes of the P2Y G protein-coupled receptor. Early studies were largely concerned with the physiology, pharmacology and biochemistry of purinergic signalling. More recently, the focus has been on the pathophysiology and therapeutic potential. There was early recognition of the use of P1 receptor agonists for the treatment of supraventricular tachycardia and A2A receptor antagonists are promising for the treatment of Parkinson's disease. Clopidogrel, a P2Y12 antagonist, is widely used for the treatment of thrombosis and stroke, blocking P2Y12 receptor-mediated platelet aggregation. Diquafosol, a long acting P2Y2 receptor agonist, is being used for the treatment of dry eye. P2X3 receptor antagonists have been developed that are orally bioavailable and stable in vivo and are currently in clinical trials for the treatment of chronic cough, bladder incontinence, visceral pain and hypertension. Antagonists to P2X7 receptors are being investigated for the treatment of inflammatory disorders, including neurodegenerative diseases. Other investigations are in progress for the use of purinergic agents for the treatment of osteoporosis, myocardial infarction, irritable bowel syndrome, epilepsy, atherosclerosis, depression, autism, diabetes, and cancer.

Tiamulin inhibits breast cancer growth and pulmonary metastasis by decreasing the activity of CD73

BACKGROUND

Metastasis is the leading cause of death in breast cancer patients. CD73, also known as ecto-5'-nucleotidase, plays a critical role in cancer development including metastasis. The existing researches indicate that overexpression of CD73 promotes growth and metastasis of breast cancer. Therefore, CD73 inhibitor can offer a promising treatment for breast cancer. Here, we determined whether tiamulin, which was found to inhibit CD73, was able to suppress breast cancer development and explored the related mechanisms.

METHODS

We firstly measured the effect of tiamulin hydrogen fumarate (THF) on CD73 using high performance liquid chromatography (HPLC). Then, we investigated cell proliferation, migration and invasion in MDA-MB-231 human breast cancer cell line and 4 T1 mouse breast cancer cell line treated with THF by migration assay, invasion assay and activity assay. Besides, we examined the effect of THF on syngeneic mammary tumors of mice by immunohistochemistry.

RESULTS

Our data demonstrated that THF inhibited CD73 by decreasing the activity instead of the expression of CD73. In vitro, THF inhibited the proliferation, migration and invasion of MDA-MB-231 and 4 T1 cells by suppressing CD73 activity. In vivo, animal experiments showed that THF treatment resulted in significant reduction in syngeneic tumor growth, microvascular density and lung metastasis rate.

CONCLUSIONS

Our results indicate that THF inhibits growth and metastasis of breast cancer by blocking the activity of CD73, which may offer a promising treatment for breast cancer therapy.

Adenosine Stimulate Proliferation and Migration in Triple Negative Breast Cancer Cells

Emerging evidence suggests that the adenosine (Ado) receptors may play crucial roles in tumor progression. Here, we show that Ado increases proliferation and migration in a triple negative breast cancer model, the MDA-MB 231 cell line. The use of specific agonists and antagonists evidenced that these effects depend on the activation of the A_2B receptor, which then triggers an intracellular response mediated by the adenylate cyclase/PKA/cAMP signaling pathway. Ado also increases the expression of Na_V1.5 channels, a potential biomarker in breast cancer. Together, these data suggest important roles of the A_2B receptors and Na_V1.5 channels in the Ado-induced increase in proliferation and migration of the MDA-MB 231 cells.

Adenosine A2b receptor promotes progression of human oral cancer

BACKGROUND

Adenosine A2b receptor (ADORA2B) encodes an adenosine receptor that is a member of the G protein-coupled receptor superfamily. This integral membrane protein stimulates adenylate cyclase activity in the presence of adenosine. Little is known about the relevance of ADORA2B to human malignancy including oral squamous cell carcinoma (OSCC). We aimed to characterize the expression state and function of ADORA2B in OSCC.

METHODS

The ADORA2B expression levels in nine OSCC-derived cells were analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Using an ADORA2B knockdown model, we assessed cellular proliferation and expression of hypoxia-inducible factor1α (HIF-1α). We examined the adenosine receptor expression profile under both normoxic and hypoxic conditions in the OSCC-derived cells. In addition to in vitro data, the clinical correlation between the ADORA2B expression levels in primary OSCCs (n = 100 patients) and the clinicopathological status by immunohistochemistry (IHC) also was evaluated.

RESULTS

ADORA2B mRNA and protein were up-regulated significantly (p < 0.05) in seven OSCC-derived cells compared with human normal oral keratinocytes. Suppression of ADORA2B expression with shRNA significantly (p < 0.05) inhibited cellular proliferation compared with the control cells. HIF-1α also was down-regulated in ADORA2B knockdown OSCC cells. During hypoxia, ADORA2B expression was induced significantly (p < 0.05) in the mRNA and protein after 24 hours of incubation in OSCC-derived cells. IHC showed that ADORA2B expression in primary OSCCs was significantly (p < 0.05) greater than in the normal oral counterparts and that ADORA2B-positive OSCCs were correlated closely (p < 0.05) with tumoral size.

CONCLUSION

Our results suggested that ADORA2B controls cellular proliferation via HIF-1α activation, indicating that ADORA2B may be a key regulator of tumoral progression in OSCCs.

Static magnetic field inhibits 5' nucleotidase activity in cancerous and non-cancerous human gastric tissues

The aim of the present study is to investigate possible effects of static magnetic field (SMF) on 5' nucleotidase (5'NT-CD73) and xanthine oxidase (XO) activities in cancerous and non-cancerous human gastric tissues in order to contribute to the elucidation of the anticancer activity of SMF. Cancerous and non-cancerous human gastric tissues removed from patients by surgical operations were used in the studies. SMF was created using two static magnets. Before and after treatment with SMF, 5'NT and XO activities in the tissue samples were measured. 5'NT activity was found to be lowered, but no significant change was observed in XO activity in the gastric tissues treated with the SMF. Our results suggest that SMF inhibits 5'NT enzyme in gastric tissues significantly. It is supposed that in addition to other proposed mechanisms, inhibition of purine catabolic activity due to inhibition of some key enzymes in the DNA turn-over like 5'NT might also play part in the anticancer activity of SMF.

Purinergic signalling and cancer

Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.

Adenosine A2A and A2B receptor expression in neuroendocrine tumours: potential targets for therapy

The clinical management of neuroendocrine tumours is complex. Such tumours are highly vascular suggesting tumour-related angiogenesis. Adenosine, released during cellular stress, damage and hypoxia, is a major regulator of angiogenesis. Herein, we describe the expression and function of adenosine receptors (A(1), A(2A), A(2B) and A(3)) in neuroendocrine tumours. Expression of adenosine receptors was investigated in archival human neuroendocrine tumour sections and in two human tumour cell lines, BON-1 (pancreatic) and KRJ-I (intestinal). Their function, with respect to growth and chromogranin A secretion was carried out in vitro. Immunocytochemical data showed that A(2A) and A(2B) receptors were strongly expressed in 15/15 and 13/18 archival tumour sections. Staining for A(1) (4/18) and A(3) (6/18) receptors was either very weak or absent. In vitro data showed that adenosine stimulated a three- to fourfold increase in cAMP levels in BON-1 and KRJ-1 cells. The non-selective adenosine receptor agonist (adenosine-5'N-ethylcarboxamide, NECA) and the A(2A)R agonist (CGS21680) stimulated cell proliferation by up to 20-40% which was attenuated by A(2B) (PSB603 and MRS1754) and A(2A) (SCH442416) receptor selective antagonists but not by the A(1) receptor antagonist (PSB36). Adenosine and NECA stimulated a twofold increase in chromogranin A secretion in BON-1 cells. Our data suggest that neuroendocrine tumours predominantly express A(2A) and A(2B) adenosine receptors; their activation leads to increased proliferation and secretion of chromogranin A. Targeting adenosine signal pathways, specifically inhibition of A(2) receptors, may thus be a useful addition to the therapeutic management of neuroendocrine tumours.

The dietary flavonoid apigenin enhances the activities of the anti-metastatic protein CD26 on human colon carcinoma cells

There is accumulating evidence that secondary plant metabolites such as flavonoids may have anti-cancer properties, and yet the molecular pathways that lead to alterations in cancer cell behaviour remain unclear. We investigated the possible actions of apigenin, a flavone present in leafy vegetables like parsley, on the levels of CD26 in carcinoma cells. CD26 is a multifunctional cell-surface protein that through its associated dipeptidyl peptidase (DPPIV) and ecto-adenosine deaminase (eADA) enzyme activities is able to suppress pathways involved in tumour metastasis. CD26 is down-regulated in various cancers including colorectal carcinoma. Apigenin substantially up-regulated cell-surface CD26 on HT-29 and HRT-18 human colorectal cancer cells. Levels of CD26 protein, along with its associated DPPIV enzyme activity, capacity to bind eADA, and ability to link cells to fibronectin, were increased with a maximum after 24-48 h. Elevation of CD26 occurred at concentrations that were at least 10-fold less than those shown to affect cell growth, and 100-fold below those that could affect cell viability. Furthermore, the CD26 effect was enhanced when apigenin was paired with chemotherapeutic agents utilized in the treatment of advanced colorectal cancer including irinotecan, 5-fluorouracil and oxaliplatin. For irinotecan, apigenin caused a 4-fold increase in the potency of the drug. These results demonstrate that apigenin can increase the cellular levels of CD26 and its multiple functions, and may oppose the predicted effect of decreased DPPIV and eADA activities on carcinoma cells, which is to facilitate tumour growth and metastasis.

Hypoxia-inducible adenosine A2B receptor modulates proliferation of colon carcinoma cells

Extracellular adenosine regulates a wide variety of physiological processes by interacting with 4 adenosine receptor subtypes: A1, A2A, A2B, and A3. However, little is known of their pathophysiological roles in human cancers. In this study, we examined the expression pattern of adenosine receptors in various colorectal tissues and human colon carcinoma cell lines and investigated the biologic functions regarding colon carcinogenesis. Using reverse transcriptase polymerase chain reaction and Western blotting, we found that adenosine receptor A2B (ADORA2B) was consistently up-regulated in colorectal carcinoma tissues and colon cancer cell lines compared with normal colorectal mucosa. In immunohistochemistry, we observed diffuse immunopositivity of ADORA2B in 67% of colorectal adenocarcinomas (39/58), 17% of tubular adenomas (5/30), and 0% of normal colon glands (0/62). During a hypoxic state, there was also a significant induction of ADORA2B expression in the messenger RNA level at 8 hours of incubation and in the protein level at 24 hours of incubation in colon carcinoma cell lines. To examine the function of ADORA2B, we applied an ADORA2B-selective antagonist (MRS1754) to the colon carcinoma cells, which significantly inhibited cell growth in a dose-dependent manner as demonstrated with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assay. In conclusions, ADORA2B was overexpressed in colorectal carcinomas grown under a hypoxic state, presumably promoting cancer cell growth. Our data suggest that this adenosine receptor is a potential therapeutic target for colorectal cancer.

Functional analysis of LOXL2 in pancreatic carcinoma

OBJECTIVES

Lysyl oxidase-like 2 (LOXL2) plays a part in epithelial-mesenchymal transition (EMT) by stabilizing the transcription factor SNAI1. Previous studies showed that LOXL2 is one of the most highly and specifically upregulated genes in pancreatic cancer. LOXL2 was also found to be strongly upregulated in the secretome of established pancreatic cancer cell lines. To get more insight into the aggressive growth and infiltrating nature of pancreatic cancer, we evaluated the functional role of LOXL2 in pancreatic cancer cells.

METHODS

Gene inhibition by small interfering RNAs was used to silence LOXL2 in pancreatic cancer cell lines MiaPaCa-2 and Panc1. Cell death, proliferation, and morphology of transfected cells were determined. Cell characteristics under cell stress and gemcitabine treatment were analyzed. Gene expression analysis of transfected cells by DNA microarray was used to understand the processes of chemosensitization.

RESULTS

Silencing of LOXL2 in pancreatic cancer cells resulted in an augmented sensitivity toward gemcitabine treatment, with significantly elevated cell death and reduced viable cells. However, transfection had no direct effect on morphology or growth pattern of Mia PaCa-2 and Panc1 cell lines. Gene expression analysis identified among others the transcription factor E2F5 as possible target of LOXL2.

CONCLUSIONS

Gene inhibition of the EMT regulatory gene LOXL2 resulted in a distinct sensitization toward gemcitabine. Additionally, gene expression analysis showed a role for LOXL2 in the regulation of different transcription factors associated with invasion and metastasis. Our results suggest that the improved response toward chemotherapy in LOLX2-silenced pancreatic cancer cells is possibly mediated by the transcription factor E2F5.

Ecto-5'-nucleotidase promotes invasion, migration and adhesion of human breast cancer cells

PURPOSE

Associated with many molecules, metastasis includes cell adhesion to extracellular matrix, migration towards specific direction and invasion into local vessel of distant organs. The purpose of the present study was to evaluate the role of ecto-5'-nucleotidase (eN, ecto-5-NT, CD73) generated extracellular adenosine in biologically malignant behaviors of human breast cancer cell lines.

MATERIALS AND METHODS

Two human breast cancer cell lines, T-47D with lower expression of CD73 and MB-MDA-231 with higher expression of CD73, were used to investigate the functions of CD73. The effects of CD73 over-expression on invasion, migration and adhesion were observed in T-47D transfected with pcDNA-NT5E plasmid. The effects of specific CD73 inhibitor, alpha, ss-methylene ADP (APCP), were observed in MB-MDA-231 cells.

RESULTS

The results showed CD-73 overexpression increased invasion, migration and adhesion to ECM of the pcDNA-NT5E transfected T-47D cells compared to the saline and mock vector controls. The increased cell mobility of CD-73-overexpressed T-47D cells was blocked by APCP. Adenosine increased the mobility of wild type T-47D cells. APCP inhibited the mobility of the MB-MDA-231 cells.

CONCLUSION

Taken together, our results indicated that CD73 may facilitate the adhesion, migration and invasion of human breast cancer cells through its enzyme activity of generating adenosine. This study provided a possibly molecular mechanism of metastasis of breast carcinoma.

RNA interference of ecto-5'-nucleotidase (CD73) inhibits human breast cancer cell growth and invasion

Metastasis is a leading cause of mortality and morbidity in breast cancer. Recently, dramatic overexpression of ecto-5'-nucleotidase (CD73), a glycosylphosphatidylinositol-anchored cell surface protein has been found in estrogen receptor-negative [ER (-)] breast cancer cell lines and in clinical samples. In this study, CD73 small interfering RNA (siRNA) plasmid was constructed and stably transfected into breast cancer cell MB-MDA-231 to determine the role of CD73 in breast cancer metastasis and the possible mechanism. Our study demonstrates that CD73 siRNA effectively inhibits CD73 gene expression at mRNA and protein level in MB-MDA-231 cells, leading to in vivo and in vitro growth suppression, prevention of adhesion to extracellular matrix (ECM), and inhibition of invasion and migration. These properties correlate with inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 expression and activity as well as reduction of epidermal growth factor receptor (EGFR) expression. Demonstration of the role of CD73 in breast cancer may lead to new targeted therapies for breast cancer.

Adenosine receptors in colon carcinoma tissues and colon tumoral cell lines: focus on the A(3) adenosine subtype

Adenosine may affect several pathophysiological processes, including cellular proliferation, through interaction with A(1), A(2A), A(2B), and A(3) receptors. In this study we characterized adenosine receptors in human colon cancer tissues and in colon cancer cell lines Caco2, DLD1, HT29. mRNA of all adenosine subtypes was detected in cancer tissues and cell lines. At a protein levels low amount of A(1), A(2A), and A(2B) receptors were detected, whilst the A(3) was the most abundant subtype in both cancer tissues and cells, with a pharmacological profile typical of the A(3) subtype. All the receptors were coupled to stimulation/inhibition of adenylyl-cyclase in cancer cells, with the exception of A(1) subtype. Adenosine increased cell proliferation with an EC(50) of 3-12 microM in cancer cells. This effect was not essentially reduced by adenosine receptor antagonists. However dypiridamol, an adenosine transport inhibitor, increased the stimulatory effect induced by adenosine, suggesting an action at the cell surface. Addition of adenosine deaminase makes the A(3) agonist 2-chloro-N6-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine (Cl-IB-MECA) able to stimulate cell proliferation with an EC(50) of 0.5-0.9 nM in cancer cells, suggesting a tonic proliferative effect induced by endogenous adenosine. This effect was antagonized by 5-N-(4-methoxyphenyl-carbamoyl)amino-8-propyl-2(2furyl)-pyrazolo-[4,3e]-1,2,4-triazolo [1,5-c] pyrimidine (MRE 3008F20) 10 nM. Cl-IB-MECA-stimulated cell proliferation involved extracellular-signal-regulated-kinases (ERK1/2) pathway, as demonstrated by reduction of proliferation with 1,4-diamino-2,3-dicyano-1,4-bis-[2-amino-phenylthio]-butadiene (U0126) and by ERK1/2 phosphorylation. In conclusion this study indicates for the first time that in colon cancer cell lines endogenous adenosine, through the interaction with A(3) receptors, mediates a tonic proliferative effect.

Palmitate and oleate have distinct effects on the inflammatory phenotype of human endothelial cells

Free fatty acids may create a state of continuous and progressive damaging to the vascular wall manifested by endothelial dysfunction. In this study we determine the mechanisms by which fatty acids palmitate (C16:0) and oleate (C18:1) affect intracellular long chain acyl-CoA (LCAC) content, energy metabolism, cell survival and proliferation and activation of NF-kappaB in cultured endothelial cells. A 48-h exposure of human umbilical vein endothelial cells (HUVEC) to 0.5 mM palmitate or 0.5 mM oleate increased total long chain acyl-CoA (LCAC) content 1.7 and 2 fold, respectively and decreased ATP(total)/ADP(total) ratio by 26+/-5% (mean+/-SEM) and 15+/-2%, respectively, which was prevented by the acyl-CoA synthetase inhibitor triacsin C. Furthermore, palmitate inhibited cell proliferation by 34+/-5%, while oleate stimulated it by 12+/-2%. alpha-Tocopherol fully and triacsin C partially abolished the effect of palmitate on cell proliferation. Palmitate and oleate increased caspase-3 activity 3.2 and 1.4 fold, respectively. Palmitate-induced caspase-3 activation was prevented by triacsin C and slightly reduced by alpha-tocopherol and by the de novo ceramide synthesis inhibitor fumonisin B(1). Both fatty acids induced antioxidant-sensitive nuclear translocation of NF-kappaB after 72 h, but not after 48 h. In conclusion, we showed that fatty acids influence different aspects of HUVEC function resulting in amongst other activation of apoptotic and inflammatory pathways. Our results indicate that the effects depend on the fatty acid type and may be related to accumulation of LCAC.

Adenosine upregulates CXCR4 and enhances the proliferative and migratory responses of human carcinoma cells to CXCL12/SDF-1alpha

The level of expression of the chemokine receptor CXCR4 has been shown to play a crucial role in determining the ability of cancer cells to metastasize from the primary tumor and become established in tissue sites that are rich in the CXCR4 ligand CXCL12/SDF-1alpha. High CXCR4 expression on cancer cells is associated with an increased risk of recurrence and poorer overall survival. We propose that local tissue mediators within the primary tumor or at secondary sites may modulate the level of CXCR4 expression and, therefore, potentially affect the ability of the cancer cells to metastasize. The purine nucleoside adenine-9-beta-D-ribofuranoside (adenosine) is generated at high concentrations within the extracellular fluid of solid tumors because of their hypoxia. We show here that adenosine acts through A(2A) and A(2B) adenosine receptors on human colorectal carcinoma cells to upregulate CXCR4 mRNA expression up to 10-fold and selectively increases cell-surface CXCR4 protein up to 3-fold. This increase in cell-surface CXCR4 enables the carcinoma cells to migrate toward CXCL12, and enhances their proliferation in response to CXCL12. Adenosine may therefore be one of the factors within the tumor microenvironment that facilitates tumor dissemination, by upregulating CXCR4 on certain cancer cells and enhancing cellular responses to CXCL12.

Neuro-bioenergetic concepts in cancer prevention and treatment

Cancer remains one of the most difficult and elusive disorders to prevent and treat, despite great efforts in research and treatment over the last 30 years. Researchers have tried to understand the pathogenesis of cancer by discovering the single cellular mechanism or pathway derived from a genetic mutation. There are limited efforts made toward discovering a unified concept of cancer. We propose a neuro-bioenergetic concept of cancer pathogenesis based on the central mechanism of cellular hyperexcitability via inducible overexpression of voltage-gated ion channels, ligand-gated channels and neurotransmitters. Exploration of this concept could lead to a better understanding of the cause of cancer as well as developing more effective and specific strategies toward cancer prevention and treatment.

Adenosine downregulates DPPIV on HT-29 colon cancer cells by stimulating protein tyrosine phosphatase(s) and reducing ERK1/2 activity via a novel pathway

The multifunctional cell-surface protein dipeptidyl peptidase IV (DPPIV/CD26) is aberrantly expressed in many cancers and plays a key role in tumorigenesis and metastasis. Its diverse cellular roles include modulation of chemokine activity by cleaving dipeptides from the chemokine NH(2)-terminus, perturbation of extracellular nucleoside metabolism by binding the ecto-enzyme adenosine deaminase, and interaction with the extracellular matrix by binding proteins such as collagen and fibronectin. We have recently shown that DPPIV can be downregulated from the cell surface of HT-29 colorectal carcinoma cells by adenosine, which is a metabolite that becomes concentrated in the extracellular fluid of hypoxic solid tumors. Most of the known responses to adenosine are mediated through four different subtypes of G protein-coupled adenosine receptors: A(1), A(2A), A(2B), and A(3). We report here that adenosine downregulation of DPPIV from the surface of HT-29 cells occurs independently of these classic receptor subtypes, and is mediated by a novel cell-surface mechanism that induces an increase in protein tyrosine phosphatase activity. The increase in protein tyrosine phosphatase activity leads to a decrease in the tyrosine phosphorylation of ERK1/2 MAP kinase that in turn links to the decline in DPPIV mRNA and protein. The downregulation of DPPIV occurs independently of changes in the activities of protein kinases A or C, phosphatidylinositol 3-kinase, other serine/threonine phosphatases, or the p38 or JNK MAP kinases. This novel action of adenosine has implications for our ability to manipulate adenosine-dependent events within the solid tumor microenvironment.

Immunohistochemical analysis of the expression of FATE/BJ-HCC-2 antigen in normal and malignant tissues

FATE/BJ-HCC-2 is a newly identified cancer/testis (CT) antigen, which was detected in tumor tissues and testis. As previous studies of FATE/BJ-HCC-2 expression pattern were mainly based on messenger RNA (mRNA) analysis, it is necessary to investigate its actual protein expression pattern in tumor tissues for the evaluation of its application value. In this study, we produced specific polyclonal antibody (pAb) to the recombinant FATE/BJ-HCC-2 protein and analyzed the FATE/BJ-HCC-2 antigen expression in normal and malignant tissues by the immunohistochemical approach. The results showed that there was no detectable FATE/BJ-HCC-2 antigen expressed in normal tissues except testis. In hepatocellular carcinoma (HCC) tissues, the FATE/BJ-HCC-2 antigen was detected in 20% (7/35) specimens. All samples that expressed the FATE/BJ-HCC-2 antigen were of poorly or moderately differentiated HCC. The stained antigen was located in the cytoplasm and the staining pattern showed heterogeneity from focal to more than 40% of the tumor cells. The FATE/BJ-HCC-2 antigen was also expressed in other tumor tissues. The results of [3H]thymidine incorporation showed that FATE/BJ-HCC-2 protein enhanced tumor cell proliferation after transfection of FATE/BJ-HCC-2 gene in HCC cell line (P<0.01). This effect could be specifically blocked by anti-FATE/BJ-HCC-2 pAb. Serological screening showed that the antibody specific to the FATE/BJ-HCC-2 antigen was detected in 7.7% (4/52) patients. Notably, the four positive patients bore poorly or moderately differentiated HCC. FATE/BJ-HCC-2 mRNA transcript was detected in the peripheral blood mononuclear cells (PBMCs) of 46.67% patients whose resected HCC tissue samples were positive for FATE/BJ-HCC-2 mRNA, which implicated tumor cell dissemination in blood circulation and may relate to the metastasis of HCC. Thus, FATE/BJ-HCC-2 may be a valuable candidate CT antigen for polyvalent vaccines in tumor immunotherapy and an assisting diagnostic marker for prognosis of the disease.