Phase II study of intravenous adenosine 5'-triphosphate in patients with previously untreated stage IIIB and stage IV non-small cell lung cancer

"Find Me" and "Eat Me" signals: tools to drive phagocytic processes for modulating antitumor immunity

Phagocytosis, a vital defense mechanism, involves the recognition and elimination of foreign substances by cells. Phagocytes, such as neutrophils and macrophages, rapidly respond to invaders; macrophages are especially important in later stages of the immune response. They detect "find me" signals to locate apoptotic cells and migrate toward them. Apoptotic cells then send "eat me" signals that are recognized by phagocytes via specific receptors. "Find me" and "eat me" signals can be strategically harnessed to modulate antitumor immunity in support of cancer therapy. These signals, such as calreticulin and phosphatidylserine, mediate potent pro-phagocytic effects, thereby promoting the engulfment of dying cells or their remnants by macrophages, neutrophils, and dendritic cells and inducing tumor cell death. This review summarizes the phagocytic "find me" and "eat me" signals, including their concepts, signaling mechanisms, involved ligands, and functions. Furthermore, we delineate the relationships between "find me" and "eat me" signaling molecules and tumors, especially the roles of these molecules in tumor initiation, progression, diagnosis, and patient prognosis. The interplay of these signals with tumor biology is elucidated, and specific approaches to modulate "find me" and "eat me" signals and enhance antitumor immunity are explored. Additionally, novel therapeutic strategies that combine "find me" and "eat me" signals to better bridge innate and adaptive immunity in the treatment of cancer patients are discussed.

Tumour immune escape via P2X7 receptor signalling

While P2X7 receptor expression on tumour cells has been characterized as a promotor of cancer growth and metastasis, its expression by the host immune system is central for orchestration of both innate and adaptive immune responses against cancer. The role of P2X7R in anti-tumour immunity is complex and preclinical studies have described opposing roles of the P2X7R in regulating immune responses against tumours. Therefore, few P2X7R modulators have reached clinical testing in cancer patients. Here, we review the prognostic value of P2X7R in cancer, how P2X7R have been targeted to date in tumour models, and we discuss four aspects of how tumours skew immune responses to promote immune escape via the P2X7R; non-pore functional P2X7Rs, mono-ADP-ribosyltransferases, ectonucleotidases, and immunoregulatory cells. Lastly, we discuss alternative approaches to offset tumour immune escape via P2X7R to enhance immunotherapeutic strategies in cancer patients.

P2X Receptors: Potential Therapeutic Targets for Symptoms Associated With Lung Cancer - A Mini Review

Symptoms associated with lung cancer mainly consist of cancer-associated pain, cough, fatigue, and dyspnea. However, underlying mechanisms of lung cancer symptom clusters remain unclear. There remains a paucity of effective treatment to ameliorate debilitating symptoms and improve the quality of life of lung cancer survivors. Recently, extracellular ATP and its receptors have attracted increasing attention among researchers in the field of oncology. Extracellular ATP in the tumor microenvironment is associated with tumor cell metabolism, proliferation, and metastasis by driving inflammation and neurotransmission via P2 purinergic signaling. Accordingly, ATP gated P2X receptors expressed on tumor cells, immune cells, and neurons play a vital role in modulating tumor development, invasion, progression, and related symptoms. P2 purinergic signaling is involved in the development of different lung cancer-related symptoms. In this review, we summarize recent findings to illustrate the role of P2X receptors in tumor proliferation, progression, metastasis, and lung cancer- related symptoms, providing an outline of potential anti-neoplastic activity of P2X receptor antagonists. Furthermore, compared with opioids, P2X receptor antagonists appear to be innovative therapeutic interventions for managing cancer symptom clusters with fewer side effects.

Extracellular ATP: A Feasible Target for Cancer Therapy

Adenosine triphosphate (ATP) is one of the main biochemical components of the tumor microenvironment (TME), where it can promote tumor progression or tumor suppression depending on its concentration and on the specific ecto-nucleotidases and receptors expressed by immune and cancer cells. ATP can be released from cells via both specific and nonspecific pathways. A non-regulated release occurs from dying and damaged cells, whereas active release involves exocytotic granules, plasma membrane-derived microvesicles, specific ATP-binding cassette (ABC) transporters and membrane channels (connexin hemichannels, pannexin 1 (PANX1), calcium homeostasis modulator 1 (CALHM1), volume-regulated anion channels (VRACs) and maxi-anion channels (MACs)). Extracellular ATP acts at P2 purinergic receptors, among which P2X7R is a key mediator of the final ATP-dependent biological effects. Over the years, P2 receptor- or ecto-nucleotidase-targeting for cancer therapy has been proposed and actively investigated, while comparatively fewer studies have explored the suitability of TME ATP as a target. In this review, we briefly summarize the available evidence suggesting that TME ATP has a central role in determining tumor fate and is, therefore, a suitable target for cancer therapy.

Extracellular adenosine 5'-triphosphate in pulmonary disorders

Adenosine 5'-triphosphate (ATP) is found in every cell of the human body where it plays a critical role in cellular energetics and metabolism. ATP is released from cells under physiologic and pathophysiologic condition; extracellular ATP is rapidly degraded to adenosine 5'-diphosphate (ADP) and adenosine by ecto-enzymes (mainly, CD39 and CD73). Before its degradation, ATP acts as an autocrine and paracrine agent exerting its effects on targeted cells by activating cell surface receptors named P2 Purinergic receptors. The latter are expressed by different cell types in the lungs, the activation of which is involved in multiple pulmonary disorders. This succinct review summarizes the role of ATP in inflammation processes associated with these disorders including bronchoconstriction, cough, mechanical ventilation-induced lung injury and idiopathic pulmonary fibrosis. All of these disorders still constitute unmet clinical needs. Therefore, the various ATP-signaling pathways in pulmonary inflammation constitute attractive targets for novel drug-candidates that would improve the management of patients with multiple pulmonary diseases.

The P2X7 purinergic receptor: a potential therapeutic target for lung cancer

PURPOSE

Purinergic P2X7 receptor (P2X7R) is a gated ion channel for which adenosine triphosphate (ATP) is a ligand. Activated P2X7R is widely expressed in a variety of immune cells and tissues and is involved in a variety of physiological and pathological processes. Studies have confirmed that P2X7R is involved in the regulation of tumor cell growth, stimulating cell proliferation or inducing apoptosis. Recent studies have found that P2X7R is abnormally expressed in lung cancer and is closely related to the carcinogenesis and development of lung cancer. In this paper, we comprehensively describe the structure, function, and genetic polymorphisms of P2X7R. In particular, the role and therapeutic potential of P2X7R in lung cancer are discussed to provide new targets and new strategies for the treatment and prognosis of clinical lung cancer.

METHODS

The relevant literature on P2X7R and lung cancer from PubMed databases is reviewed in this article.

RESULTS

P2X7R regulates the function of lung cancer cells by activating multiple intracellular signaling pathways (such as the JNK, Rho, HMGB1 and EMT pathways), thereby affecting cell survival, growth, invasion, and metastasis and patient prognosis. Targeting P2X7R with inhibitors effectively suppresses the growth and metastasis of lung cancer cells.

CONCLUSION

In summary, P2X7R is expected to become a potential target for the treatment of lung cancer, and more clinical research is needed in the future to explore the effectiveness of P2X7R antagonists as treatments.

Role of coenzymes in cancer metabolism

Cancer is a heterogeneous set of diseases characterized by the rewiring of cellular signaling and the reprogramming of metabolic pathways to sustain growth and proliferation. In past decades, studies were focused primarily on the genetic complexity of cancer. Recently, increasing number of studies have discovered several mutations among metabolic enzymes in different tumor cells. Most of the enzymes are regulated by coenzymes, organic cofactors, that function as intermediate carrier of electrons or functional groups that are transferred during the reaction. However, the precise role of cofactors is not well elucidated. In this review, we discuss several metabolic enzymes associated to cancer metabolism rewiring, whose inhibition may represent a therapeutic target. Such enzymes, upon expression or inhibition, may impact also the coenzymes levels, but only in few cases, it was possible to direct correlate coenzymes changes with a specific enzyme. In addition, we also summarize an up-to-date information on biological role of some coenzymes, preclinical and clinical studies, that have been carried out in various cancers and their outputs.

ATP-loaded biomimetic nanoparticles as controlled release system for extracellular drugs in cancer applications

Purpose

The antitumoral effect of ATP requires its accumulation in the extracellular space to interact with membrane receptors in target cells. We propose the use of albumin nanoparticles (ANPs) coated with erythrocyte membranes (EMs) to load, deliver, release, and enhance the extracellular anticancer activity of ATP.

Materials and methods

ANPs were synthesized by desolvation method and optimal values of pH, albumin concentration, and ethanol volume were determined. EMs were derived from erythrocyte lysates and were coated on to ANPs using an extruder. Size was determined by transmission electron microscopy (TEM) and hydrodynamic size and zeta potential were determined by dynamic light scattering. Coating of the ANPs with the EMs was verified by TEM and confocal microscopy. Nanoparticle cell uptake was analyzed by confocal microscopy using HeLa and HEK-293 cell cultures treated with nanoparticles stained with 1,1′-diocta-decyl-3,3,3′,3′-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt (DiD) for EM-ANPs and Alexa 488 for ANPs. Cell viability was analyzed by [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) and Annexin V/propidium iodide assays.

Results

Optimal values of ANP preparation were as follows: pH=9, 10 mg/mL albumin concentration, and 2.33±0.04 mL ethanol volume. Size distributions as analyzed by TEM were as follows: ANPs =91.9±4.3 nm and EM-ANPs =98.3±5.1 nm; hydrodynamic sizes: ANPs =180.5±6.8 nm and EM-ANPs =197.8±3.2 nm; and zeta potentials: ANPs =17.8±3.5 mV, ANPs+ATP =−13.60±0.48 and EM-ANPs =−13.7±2.9 mV. The EMs coating the ANPs were observed by TEM and confocal microscopy. A fewer number of internalized EM-ANPs+ATP compared to non-coated ANPs+ATP was observed in HeLa and HEK-293 cells. Cell viability decreased up to 48.6%±2.0% with a concentration of 400 µM ATP after 72 hours of treatment and cell death is caused mainly via apoptosis.

Conclusion

Our current results show that it is possible to obtain nanoparticles from highly biocompatible, biodegradable materials and that their coating with EMs allows the regulation of the internalization process in order to promote extracellular activity of ATP.

Targeted delivery of adenosine 5'-triphosphate using chitosan-coated mesoporous hydroxyapatite: A theranostic pH-sensitive nanoplatform with enhanced anti-cancer effect

In this Study, a pH-sensitive nanoplatform made up of chitosan (Cs) and mesoporous hydroxyapatite (HAP) was synthesized and employed for delivering of adenosine 5'-triphosphate (ATP). The fabricated system was decorated with folic acid (FA), providing both tumor targeting and imaging. The FA.Cs.ATP@HAP nanoparticles displayed enhanced colloidal stability and controlled drug release. In vitro biological experiments revealed that FA.Cs.ATP@HAP was internalized into the tumor cells with a high efficiency in a time-dependent manner and exhibited strong fluorescence within the cells. Compared with free ATP, the FA.Cs.ATP@HAP nanoparticles exhibited a significant inhibition effect against the proliferation of the tumor cells (Saos-2, T47D, and MCF7) in a dose-dependent manner, while no significant cytotoxic effect was observed in the normal cells (HEK-293), indicating the selective cytotoxicity of the fabricated nanosystem against the tumor cells. Also, the mechanism of action of FA.Cs.ATP@HAP was investigated, and it was found that it induces a high rate of apoptosis in the tumor cells through a decrease in mitochondrial membrane potential and caspase activation. Based on these findings, FA.Cs.ATP@HAP is a novel biomedical material with targeting, imaging, and high anticancer properties against tumor cells, and it could be considered as a promising candidate for cancer therapy.

Use of the lung cancer-specific Quality of Life Questionnaire EORTC QLQ-LC13 in clinical trials: A systematic review of the literature 20 years after its development

The European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Lung Cancer 13 (QLQ-LC13) covers 13 typical symptoms of lung cancer patients and was the first module developed in conjunction with the EORTC core quality-of-life (QL) questionnaire. This review investigates how the module has been used and reported in cancer clinical trials in the 20 years since its publication. Thirty-six databases were searched with a prespecified algorithm. This search plus an additional hand search generated 770 hits, 240 of which were clinical studies. Two raters extracted data using a coding scheme. Analyses focused on the randomized controlled trials (RCTs). Of the 240 clinical studies that were identified using the LC13, 109 (45%) were RCTs. More than half of the RCTs were phase 3 trials (n = 58). Twenty RCTs considered QL as the primary endpoint, and 68 considered it as a secondary endpoint. QL results were addressed in the results section of the article (n = 89) or in the abstract (n = 92); and, in half of the articles, QL results were presented in the form of tables (n = 53) or figures (n = 43). Furthermore, QL results had an impact on the evaluation of the therapy that could be clearly demonstrated in the 47 RCTs that yielded QL differences between treatment and control groups. The EORTC QLQ-LC13 fulfilled its mission to be used as a standard instrument in lung cancer clinical trials. An update of the LC13 is underway to keep up with new therapeutic trends and to ensure optimized and relevant QL assessment in future trials.

Altered purinergic signaling in the tumor associated immunologic microenvironment in metastasized non-small-cell lung cancer

OBJECTIVES

Purines are well-known as intracellular sources for energy but they also act as extracellular signaling molecules. In the recent years, there has been a growing interest in the therapeutic potential of purinergic signaling for cancer treatment. This is the first study to analyze lung purine levels and purinergic receptors in non-small-cell lung cancer (NSCLC) patients.

MATERIALS AND METHODS

In this prospective clinical trial we enrolled 26 patients with NSCLC and 21 patients with chronic obstructive pulmonary disease (COPD) without signs of malignancy. The purine concentrations were analyzed in bronchoalveolar lavage fluid (BALF) using fluorescent/luminescent assays. Expression of purinergic receptors and ectonucleotidases were analyzed using real time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Patients with NSCLC have significantly lower ATP and ADP concentrations in BALF than patients with COPD (p=0.006 and p=0.009). Expression of the ectonucleotidase CD39 is significantly higher in BAL cells from cancer patients compared to COPD (p=0.001) as well as in metastasized tumors compared to non-metastasized tumors (p=0.009). Receptor-analysis revealed a higher expression of P2X4 (p=0.03), P2X7 (p=0.001) and P2Y1 (p=0.003) in BAL cells of tumors with distant metastasis.

CONCLUSION

Our data suggests a role for CD39 in lung cancer tumor microenvironment, influencing tumor invasiveness and metastasization. Potentially the increased degradation of ATP and ADP leads to a subversion of their anti-neoplastic effects. Furthermore P2Y1, P2X4 and P2X7 receptors are upregulated in BAL cells in metastatic disease. Our findings might facilitate the identification of new therapeutic targets for cancer immunotherapy.

Expression and function of P2 receptors in hematopoietic stem and progenitor cells

Nucleotides have unambiguously emerged as a family of mediators of intercellular communication, which bind to a class of plasma membrane receptors, P2 receptors, to trigger intercellular signaling. P2 receptors can be further divided into P2X and P2Y subfamilies based on structure and function. Different hematopoietic cells express diverse spectrums of P2 receptors at different levels, including hematopoietic stem and progenitor cells (HSPCs). Extracellular adenosine triphosphate (ATP) exerts different effects on HSPCs, regulating cell proliferation, differentiation, migration, and chemotaxis, release of cytokines or lysosomal constituents, and generation of reactive oxygen or nitrogen species. The relationship between abnormal P2 receptor function and human diseases attracts more and more attention. This review summarizes the expression and function of P2 receptors in HSPCs and the relationship to hematopoietic diseases.

Role of ion channels in regulating Ca²⁺ homeostasis during the interplay between immune and cancer cells

Ion channels are abundantly expressed in both excitable and non-excitable cells, thereby regulating the Ca²⁺ influx and downstream signaling pathways of physiological processes. The immune system is specialized in the process of cancer cell recognition and elimination, and is regulated by different ion channels. In comparison with the immune cells, ion channels behave differently in cancer cells by making the tumor cells more hyperpolarized and influence cancer cell proliferation and metastasis. Therefore, ion channels comprise an important therapeutic target in anti-cancer treatment. In this review, we discuss the implication of ion channels in regulation of Ca²⁺ homeostasis during the crosstalk between immune and cancer cell as well as their role in cancer progression.

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.

The therapeutic promise of ATP antagonism at P2X3 receptors in respiratory and urological disorders

A sensory role for ATP was proposed long before general acceptance of its extracellular role. ATP activates and sensitizes signal transmission at multiple sites along the sensory axis, across multiple synapses. P2X and P2Y receptors mediate ATP modulation of sensory pathways and participate in dysregulation, where ATP action directly on primary afferent neurons (PANs), linking receptive field to CNS, has received much attention. Many PANs, especially C-fibers, are activated by ATP, via P2X3-containing trimers. P2X3 knock-out mice and knock-down in rats led to reduced nocifensive activity and visceral reflexes, suggesting that antagonism may offer benefit in sensory disorders. Recently, drug-like P2X3 antagonists, active in a many inflammatory and visceral pain models, have emerged. Significantly, these compounds have no overt CNS action and are inactive versus acute nociception. Selectively targeting ATP sensitization of PANs may lead to therapies that block inappropriate chronic signals at their source, decreasing drivers of peripheral and central wind-up, yet leaving defensive nociceptive and brain functions unperturbed. This article reviews this evidence, focusing on how ATP sensitization of PANs in visceral "hollow" organs primes them to chronic discomfort, irritation and pain (symptoms) as well as exacerbated autonomic reflexes (signs), and how the use of isolated organ-nerve preparations has revealed this mechanism. Urinary and airways systems share many features: dependence on continuous afferent traffic to brainstem centers to coordinate efferent autonomic outflow; loss of descending inhibitory influence in functional and sensory disorders; dependence on ATP in mediating sensory responses to diverse mechanical and chemical stimuli; a mechanistically overlapping array of existing medicines for pathological conditions. These similarities may also play out in terms of future treatment of signs and symptoms, in the potential for benefit of P2X3 antagonists.

P2Y2 receptor promotes intestinal microtubule stabilization and mucosal re-epithelization in experimental colitis

P2Y(2) receptor expression is increased in intestinal epithelial cells (IECs) during inflammatory bowel diseases (IBDs). In this context, P2Y(2) stimulates PGE(2) release by IECs, suggesting a role in wound healing. For this study, we have used the non-cancerous IEC-6 cell line. IEC-6 cell migration was determined using Boyden chambers and the single-edged razor blade model of wounding. The receptor was activated using ATP, UTP, or 2-thioUTP. Pharmacological inhibitors, a blocking peptide, a neutralizing antibody and interfering RNAs were used to characterize the signaling events. Focal adhesions and microtubule (MT) dynamics were determined by immunofluorescence using anti-vinculin and anti-acetylated-α-tubulin antibodies, respectively. In vivo, the dextran sodium sulfate mouse model of colitis was used to characterize the effects of P2Y(2) agonist 2-thioUTP on remission. We showed that P2Y(2) increased cell migration and wound closure by recruiting Go protein with the cooperation of integrin α(v) . Following P2Y(2) activation, we demonstrated that GSK3β activity was inhibited in response to Akt activation. This leads to MT stabilization and increased number of focal adhesions. In vivo, P2Y(2) activation stimulates remission, as illustrated by a reduction in the disease activity index values and histological scores as compared to control mice. These findings highlight a novel function for this receptor in IECs. They also illustrate that P2Y receptors could be targeted for the development of innovative therapies for the treatment of IBDs.

Purinergic signaling in the airways

Evidence for a significant role and impact of purinergic signaling in normal and diseased airways is now beyond dispute. The present review intends to provide the current state of knowledge of the involvement of purinergic pathways in the upper and lower airways and lungs, thereby differentiating the involvement of different tissues, such as the epithelial lining, immune cells, airway smooth muscle, vasculature, peripheral and central innervation, and neuroendocrine system. In addition to the vast number of well illustrated functions for purinergic signaling in the healthy respiratory tract, increasing data pointing to enhanced levels of ATP and/or adenosine in airway secretions of patients with airway damage and respiratory diseases corroborates the emerging view that purines act as clinically important mediators resulting in either proinflammatory or protective responses. Purinergic signaling has been implicated in lung injury and in the pathogenesis of a wide range of respiratory disorders and diseases, including asthma, chronic obstructive pulmonary disease, inflammation, cystic fibrosis, lung cancer, and pulmonary hypertension. These ostensibly enigmatic actions are based on widely different mechanisms, which are influenced by the cellular microenvironment, but especially the subtypes of purine receptors involved and the activity of distinct members of the ectonucleotidase family, the latter being potential protein targets for therapeutic implementation.

P2Y6 receptor contributes to neutrophil recruitment to inflamed intestinal mucosa by increasing CXC chemokine ligand 8 expression in an AP-1-dependent manner in epithelial cells

BACKGROUND

Inflammatory bowel diseases are characterized by the presence of CXCL8 at the site of lesions resulting in neutrophil recruitment and loss of tissue functions. We report that P2Y(6) receptor activation stimulates CXCL8 expression and release by intestinal epithelial cells (IECs). In this context, we investigated if uridine 5'-diphosphate (UDP) enemas stimulate neutrophil recruitment to the mucosa of mice suffering from colitis-like disease and we characterized the signaling events linking P2Y(6) to CXCL8 expression in IEC.

METHODS

Neutrophil recruitment was monitored by immunofluorescence and FACS analysis. Expression of Cxcl1, a mouse functional homolog of CXCL8, was determined by quantitative real-time polymerase chain reaction (qPCR). Pharmacological inhibitors and interfering RNAs were used to characterize the signaling pathway. The outcomes of these treatments on protein phosphorylation and on CXCL8 expression were characterized by western blots, qPCR, luciferase, and chromatin immunoprecipitation (ChIP) assays.

RESULTS

Mutation of the AP-1 site in the CXCL8 core promoter abolished the UDP-stimulating effect. The c-fos/c-jun dimer was identified as the AP-1 complex regulating CXCL8 in response to UDP stimulation. Regulation of CXCL8 expression by P2Y(6) required PKCδ activation upstream of the signaling pathway composed of MEK1/2-ERK1/2 and c-fos. UDP administration to mice suffering from colitis-like disease increased the number of neutrophil infiltrating the mucosa, correlating with Cxcl1 increased expression in IEC and the severity of inflammation.

CONCLUSIONS

This study not only describes the P2Y(6) signaling mechanism regulating CXCL8 expression in IEC, but it also illustrates the potential of targeting P2Y(6) to reduce intestinal inflammation.

Adenosine triphosphate regulates NADPH oxidase activity leading to hydrogen peroxide production and COX-2/PGE2 expression in A549 cells

Non-small cell lung carcinoma (NSCLC) accounts for most of all lung cancers, which is the leading cause of mortality in human beings. High level of cyclooxygenase-2 (COX-2) is one of the features of NSCLC and related to the low survival rate of NSCLC. However, whether extracellular nucleotides releasing from stressed resident tissues contributes to the expression of COX-2 remains unclear. Here, we showed that stimulation of A549 cells by adenosine 5'-O-(3-thiotriphosphate) (ATPγS) led to an increase in COX-2 gene expression and prostaglandin E(2) (PGE(2)) synthesis, revealed by Western blotting, RT-PCR, promoter assay, and enzyme-linked immunosorbent assay. In addition, ATPγS induced intracellular reactive oxygen species (ROS) generation through the activation of NADPH oxidase. The increase of ROS level resulted in activation of the c-Src/epidermal growth factor receptor (EGFR)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/nuclear factor (NF)-κB cascade. We also found that activated Akt was translocated into the nucleus and recruited with NF-κB and p300 to form a complex. Thus, activation of p300 modulated the acetylation of histone H4 via the NADPH oxidase/c-Src/EGFR/PI3K/Akt/NF-κB cascade stimulated by ATPγS. Our results are the first to show a novel role of NADPH oxidase-dependent Akt/p65/p300 complex formation that plays a key role in regulating COX-2/PGE(2) expression in ATPγS-treated A549 cells. Taken together, we demonstrated that ATPγS stimulated activation of NADPH oxidase, resulting in generation of ROS, which then activated the downstream c-Src/EGFR/PI3K/Akt/NF-κB/p300 cascade to regulate the expression of COX-2 and synthesis of PGE(2) in A549 cells. Understanding the regulation of COX-2 expression and PGE(2) release by ATPγS on A549 cells may provide potential therapeutic targets of NSCLC.

The therapeutic potential of adenosine triphosphate as an immune modulator in the treatment of HIV/AIDS: a combination approach with HAART

Extracellular adenosine triphosphate (eATP) is a potent molecule that has the capacity to modulate various aspects of cell functions including gene expression. This element of modulation is essential to the role of ATP as a therapeutic agent. The hypothesis presented is that ATP can have an important impact on the treatment of HIV infection. This is supported in part by published research, although a much greater role for ATP is suggested than prior authors ever thought possible. ATP has the ability to enhance the immune system and could thus improve the host's own defense mechanisms to eradicate the virus-infected cells and restore normal immune function. This could provide effective therapy when used in conjunction with highly active antiretroviral therapies (HAART) to eliminate the latently infected cells. The key lies in applying ATP through the methodology described. This article presents a strategy for using ATP therapeutically along with background evidence to substantiate the importance of using ATP in the treatment of HIV infection.

Oral bioavailability of ATP after prolonged administration

Purinergic receptors are important for the regulation of inflammation, muscle contraction, neurotransmission and nociception. Extracellular ATP and its metabolites are the main ligands for these receptors. Occasional reports on beneficial results of ATP administration in human and animal studies have suggested the bioavailability of oral ATP supplements. We investigated whether prolonged daily intake of oral ATP is indeed bioavailable. Thirty-two healthy subjects were randomised to receive 0, 250, 1250 or 5000 mg ATP per d for 28 d by means of enteric-coated pellets. In addition, on days 0 and 28, all thirty-two subjects received 5000 mg ATP to determine whether prolonged administration would induce adaptations in the bioavailability of ATP. ATP supplementation for 4 weeks did not lead to changes in blood or plasma ATP concentrations. Of all ATP metabolites, only plasma uric acid levels increased significantly after the administration of 5000 mg of ATP. Prolonged administration of ATP was safe as evidenced from liver and kidney parameters. We conclude that oral administration of ATP only resulted in increased uric acid concentrations. On the basis of these findings, we seriously question the claimed efficacy of oral ATP at dosages even lower than that used in the present study.

Randomized clinical trial on the effects of adenosine 5'-triphosphate infusions on quality of life, functional status, and fatigue in preterminal cancer patients

CONTEXT

One potential agent to improve symptoms and quality of life (QoL) in advanced cancer patients is adenosine 5'-triphosphate (ATP). Several reports suggest that ATP may positively affect QoL and survival in patients with advanced non-small-cell lung cancer.

OBJECTIVES

To investigate the effects of ATP infusions on QoL parameters in patients with preterminal cancer of mixed tumor types.

METHODS

Ninety-nine preterminal cancer patients were randomly allocated to receive either ATP intravenously weekly (8-10 hours/week, with maximum 50 μg/kg.minute) for eight weeks or receive no ATP (control group). QoL parameters were assessed until eight weeks and analyzed by repeated-measures analysis of covariance.

RESULTS

Fifty-one patients were randomized to the ATP group and 48 to the control group. Unexpectedly, in the untreated control group, most of the outcome parameters did not deteriorate but remained stable or even significantly improved over time. Between the ATP and control groups, no statistically significant differences were observed for the large majority of outcome parameters, except for the strength of elbow flexor muscles in favor of the control group.

CONCLUSION

ATP infusions, at the dose and schedule studied, did not have a significant effect on QoL, functional status, or fatigue in preterminal cancer patients of mixed tumor types.

Extracellular ATP enhances in vitro invasion of prostate cancer cells by activating Rho GTPase and upregulating MMPs expression

We previously found that in addition to anti-proliferation function, extracellular ATP had a pro-invasion effect on prostate cancer cells, and probably serves as an important regulator of invasion in local microenvironment. However, the underlying mechanism remains unclear. In this study, we demonstrated that ATP increased the motility of prostate cancer cells, and promoted formation of lamellipodia and filopodia. We also found that ATP induced activation of Rac1 and Cdc42, and promoted expression of MMP-3 and MMP-13. These data suggest that extracellular ATP enhances the invasion of prostate cancer cells by activating Rho GTPases Rac1 and Cdc42 and upregulating MMPs expression.

Treatment adherence and patients' acceptance of home infusions with adenosine 5'-triphosphate (ATP) in palliative home care

GOALS OF WORK

In preterminal cancer patients, provision of palliative care in the patients' own environment is preferred. The aim of the present study was to evaluate patients' and caregivers' treatment adherence and patients' acceptance of home infusions with adenosine 5'-triphosphate (ATP).

PATIENTS AND METHODS

Preterminal cancer patients (life expectancy <6 months) with mixed tumor types were eligible for the study. Patients received a maximum of eight weekly intravenous 8-10 h ATP infusions. Evaluation of treatment adherence was based on registration of protocol deviations and patients' acceptance by structured interviews with patients.

MAIN RESULTS

Fifty-one patients received a total of 266 intravenous ATP infusions. The infusion protocol was well executed: mean duration approximately 8.30 h, stepwise achievement of the maximum infusion rate within 30 min in 65% of the infusions, and almost no delay in weekly administration. All except one patient were not burdened by the administration of the infusions at home and none of them had felt afraid. The majority of patients found the advantages of the ATP infusions outweighing the disadvantages. However, an important bottleneck in the administration of ATP infusions at home was difficulty in establishing venous access.

CONCLUSION

ATP infusions at home are well accepted by patients. Difficulties in establishing venous access might be reduced by composing specialized home infusion teams working both at the day care center and at home or by adopting an alternative route of venous access.

Extracellular ATP and cancer: an overview with special reference to P2 purinergic receptors

Purinergic signal transduction mechanisms have been appreciated as a complex intercellular signalling network that plays an important regulatory role in both short- and long-term processes in practically every living cell. One of the most intriguing aspects of the field is the participation of ATP and other purine nucleotides in the determination of cell fate and the way they direct cells towards proliferation, differentiation or apoptosis, thereby possibly taking part in promoting or preventing malignant transformation. In this review, following a very brief introduction to the historical aspects of purinergic signalling and a concise overview of the structure of and signal transduction pathways coupled to P2 purinergic receptors, the current theories concerning the possible ways how extracellular ATP can alter the function of tumour cells and the effectiveness of anticancer therapies are discussed, including pharmacological, nutritional, vasoactive and 'anti-antioxidant' actions of the nucleotide. The effects of ATP on animals inoculated with human tumours and on patients with cancer are looked over next, and then an overview of the literature regarding the expression and presumed functions of P2 purinoceptors on tumour cells in vitro is presented, sorted out according to the relevant special clinical fields. The article is closed by reviewing the latest developments in the diagnostic use of P2 purinergic receptors as tumour markers and prognostic factors, while discussing some of the difficulties and pitfalls of the therapeutic use of ATP analogues.

Effect of extracellular ATP on the growth of hormone-refractory prostate cancer in vivo

OBJECTIVE

To investigate whether the antineoplastic action of ATP on hormone-refractory prostate carcinoma (HRPC) cells in vitro also occurs in vivo, by examining the effect of ATP in vivo on tumours resulting from implanted HRPC cells in mice.

MATERIALS AND METHODS

HRPC tumour cells DU145 and PC-3 were implanted into male nude athymic mice. The effect of daily intraperitoneal (i.p.) injections of ATP (25 mm) on the growth of freshly implanted and established HRPC tumours was assessed. Histological examination using light and electron microscopy was used to confirm retention of the original ultrastructure of the implanted tumours.

RESULTS

Daily i.p. injections of ATP significantly reduced the growth of freshly implanted DU145 tumour by 57.8% (P = 0.003), and reduced the rate of growth of established DU145 tumour by 69.0% (P = 0.006). ATP also significantly reduced the growth of freshly implanted PC-3 tumour by 68.9% (P < 0.001). ATP treatment had no adverse effects on the host mice.

CONCLUSION

Our results show, for the first time, that ATP effectively reduces the growth of advanced HRPC tumours in vivo. This may represent a step in establishing ATP as an effective agent for HRPC treatment.

Emerging drugs for cancer cachexia

Cachexia is a complex syndrome. The main components of this pathological state are anorexia and metabolic abnormalities such as glucose intolerance, fat depletion and muscle protein catabolism among others. The altered metabolic status generates a high degree of energetic inefficiency that results in weight loss, fatigue and a considerable loss of muscle and, therefore, asthenia. The aim of the present article is to review the different therapeutic approaches and emerging drugs that have been designed to fight and counteract cachexia associated with cancer.

Intravenous ATP infusions can be safely administered in the home setting: a study in pre-terminal cancer patients

The aim of the study was to investigate the safety of adenosine 5′-triphosphate (ATP) administration at home in pre-terminal cancer patients. Included were patients with cancer for whom medical treatment options were restricted to supportive care, who had a life expectancy of less than 6 months, a World Health Organization performance status 1 or 2, and suffered from at least one of the following complaints: fatigue, anorexia or weight loss >5% over the previous 6 months. Side effects were registered systematically on a standard form according to the National Cancer Institute (NCI) Common Toxicity Criteria. Fifty-one patients received a total of 266 intravenous ATP infusions. Of these, 11 infusions (4%) were given at the lowest dose of 20 μg kg⁻¹ min⁻¹, 85 infusions (32%) at 25–40 μg kg⁻¹ min⁻¹, and 170 (64%) at the highest dose of 45–50 μg kg⁻¹ min⁻¹ ATP. The majority of ATP infusions (63%) were without side effects. Dyspnea was the most common side effect (14% of infusions), followed by chest discomfort (12%) and the urge to take a deep breath (11%). No symptoms of cardiac ischemia occurred in any of the infusions. All side effects were transient and resolved within minutes after lowering the ATP infusion rate. Side effects were most frequent in the presence of cardiac disorders. We conclude that ATP at a maximum dose of 50 μg kg⁻¹ min⁻¹ can be safely administered in the home setting in patients with pre-terminal cancer.

Dyspnoea after antiplatelet agents: the AZD6140 controversy

Recent randomised studies suggest that experimental oral reversible platelet P2Y12 receptor inhibitor, AZD6140, causes dyspnoea. This also raises similar concerns about the parent compound, and another adenosine triphosphate (ATP) analogue (AR-69931MX or cangrelor), which is currently in Phase 3 trial in patients undergoing coronary interventions. We analysed package inserts, and available clinical trials safety data for antiplatelet agents with regard to the incidence of dyspnoea. We found that dyspnoea is a very rare complication of the presently approved platelet inhibitors, mostly caused by underlying disease, rather than antiplatelet therapy per se. The main reasons for respiratory distress after oral (AZD6140), and intravenous (cangrelor) agents may be the development of mild asymptomatic thrombotic thrombocytopenic purpura, fluid retention and dyspnoea because of the reversible nature of these drugs. Also, these agents are ATP analogues, which rapidly metabolise to adenosine, a well-known bronchoprovocator causing dyspnoea as well. In summary, dyspnoea is seldom considered, there are no treatment algorithms when it does occur, plausible mechanisms exist and despite these plausible mechanisms, the true cause of dyspnoea in these exposed individuals is unknown. Additional pulmonary function testing, immunological investigations and platelet receptor studies are urgently needed to determine the cause of dyspnoea after AZD6140, and to point out how such serious adverse reactions can be prevented, or at least minimised, raising potential concerns about this drug.

Molecular mechanisms of adenosine-induced apoptosis in human HepG2 cells

AIM

To investigate effects of adenosine on cell proliferation and apoptosis in human HepG2 cells.

METHODS

HepG2 cells were incubated in the presence of adenosine (0.1-5 mmol/L) for 12-48 h, and the effect of adenosine on cell proliferation was evaluated by using 3-(4,5-dimethyl-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Hoechst 33342 fluorescent staining, dUTP-fluorescein isothiocyanate (FITC) fluorescence and flow cytometric analysis techniques were used to observe cell apoptosis. The effects of adenosine receptor (A1, A2a, A3 and nonspecific receptor) antagonists (8-cpt, DMPX, MRS1191, and theophylline) and an adenosine transporter protein inhibitor (dipyridamole) on adenosine-induced cell apoptosis were observed. Mitochondrial membrane potential was analyzed using DePsipher fluorescent staining, and caspase activity was detected using a Fluorometric assay kit and a fluorescence microplate reader.

RESULTS

Adenosine significantly reduced cell viability in a dose- and time-dependent manner. The cytotoxicity of adenosine was related to the induction of cell apoptosis. Four adenosine receptor antagonists had no effect on cell apoptosis. However, dipyridamole significantly reduced the percentage of adenosine-induced apoptotic cells from 27.3% to 7.1% (P<0.05). At 48 h after treatment, 3 mmol/L adenosine increased caspase-3 activity 3.5-fold; dipyridamole markedly decreased caspase-3 activity 1.6-fold, and decreased apoptotic cell numbers. When HepG2 cells were treated with 3 mmol/L adenosine, mitochondrial membrane potential and the activity of caspase-8 or -9 remained unchanged.

CONCLUSION

Our results suggest that adenosine-induced apoptosis in HepG2 cells is related to intracellular events rather than cell surface receptors, and that a caspase-3 cascade activation is required, which is not mediated via a mitochondrial pathway.

P2 receptors and cancer

Purinergic signalling has been implicated in many biological processes, and ATP and other extracellular nucleotides might have therapeutic potential in the treatment of cancer by signalling through P2 receptors. Different P2 receptor subtypes have been identified in a variety of different cancer types, in both primary samples of human cancer tissue and cell lines. Recent evidence suggests that different receptor subtypes mediate different pathophysiological functions such as proliferation, differentiation and apoptosis. In vivo studies of the use of ATP suggest that it can decrease the rate of cancer growth, and the first clinical trials have been undertaken. Thus, agents acting at P2 receptors might provide novel therapeutic tools in the treatment of cancer. In this article, background information about purinergic signalling and purinoceptor subtypes will be provided and then the proposed role of ATP in different cancers will be discussed in detail, including a discussion of in vivo studies and animal models, clinical trials and the specific P2 receptor subtypes involved.

Randomized clinical trial of adenosine 5'-triphosphate on tumor growth and survival in advanced lung cancer patients

We recently reported that regular infusions of adenosine 5'-triphosphate (ATP) inhibited loss of body weight and quality of life in patients with non-small cell lung cancer (NSCLC). In the present paper we investigated whether ATP affects tumor growth and survival in the same group of patients. Fifty-eight NSCLC patients (stage IIIB or IV) were randomly assigned to receive either 10 i.v. 30-h ATP infusions every 2-4 weeks over a 24-week period (n = 28) or no ATP (control patients, n = 30). ATP was given for a median of 6.5 infusions. Differences in time to progression and survival between patients in both groups were tested by means of the log-rank test and Cox regression analysis. Forty-nine patients were evaluable for tumor response. None of the evaluable patients showed a complete or partial response. Median time to progression was 3.9 months [95% confidence interval (CI) = 2.3-5.5] in the ATP group compared to 3.0 months (95% CI = 2.4-3.7) in the control group (p = 0.71). Median survival was 5.6 months (95% CI = 1.1-10.1) for the ATP group and 4.7 months (95% CI = 2.6-6.8) for the control group (p = 0.68). ATP treatment was associated with a significant increase in survival in the subgroup of weight-losing patients with stage IIIB NSCLC: in this subgroup, median survival was 9.3 months (95% CI = 2.1-16.5) for ATP-treated patients versus 3.5 months (95% CI = 2.3-4.7) for control patients (between-group difference: p = 0.009). No significant effect of ATP was observed for weight-losing patients with stage IV NSCLC or for weight-stable NSCLC patients. Although ATP as a single therapy does not lead to tumor regression or increased survival in patients with advanced lung cancer, it may prolong survival in weight-losing patients with stage IIIB lung cancer. The latter finding is intriguing, but requires confirmation in larger clinical trials.

Cellular Distribution and Functions of P2 Receptor Subtypes in Different Systems

This review is aimed at providing readers with a comprehensive reference article about the distribution and function of P2 receptors in all the organs, tissues, and cells in the body. Each section provides an account of the early history of purinergic signaling in the organ?cell up to 1994, then summarizes subsequent evidence for the presence of P2X and P2Y receptor subtype mRNA and proteins as well as functional data, all fully referenced. A section is included describing the plasticity of expression of P2 receptors during development and aging as well as in various pathophysiological conditions. Finally, there is some discussion of possible future developments in the purinergic signaling field.

Adenosine triphosphate infusion increases liver energy status in advanced lung cancer patients: an in vivo 31P magnetic resonance spectroscopy study

We recently observed inhibition of weight loss in patients with advanced nonsmall-cell lung cancer after intravenous infusion of ATP. Because liver ATP levels were found to be decreased in lung cancer patients with weight loss, the present 31P magnetic resonance spectroscopy (MRS) study was aimed at investigating whether ATP infusion restores liver energy status in these patients. Nine patients with advanced nonsmall-cell lung cancer (stage IIIB/IV) were studied 1 week before (baseline) and at 22 to 24 hours of continuous ATP infusion (37-75 microg/kg/min). Localized hepatic 31P MR spectra (repetition time 15 seconds), obtained in the overnight-fasted state, were analyzed for ATP and P(i) content. Ten healthy subjects (without ATP infusion) served as control. Liver ATP levels in lung cancer patients increased from 8.8 +/- 0.7% (relative to total MR-detectable phosphate; mean +/- SE) at baseline to 12.2 +/- 0.9% during ATP infusion (P <.05), i.e., a level similar to that in healthy subjects (11.9 +/- 0.9%). The increase in ATP level during ATP infusion was most prominent in patients with > or = 5% weight loss (baseline: 7.9 +/- 0.7%, during ATP infusion: 12.8 +/- 1.0%, P < 0.01). In conclusion, ATP infusion restores hepatic energy levels in patients with advanced lung cancer, especially in weight-losing patients. These changes may contribute to the previously reported beneficial effects of ATP infusion on the nutritional status of lung cancer patients.

Beneficial effects of adenosine triphosphate on nutritional status in advanced lung cancer patients: a randomized clinical trial

PURPOSE

In a randomized clinical trial in patients with advanced non-small-cell lung cancer (NSCLC), infusion with adenosine 5'-triphosphate (ATP) inhibited loss of body weight and quality of life. In the present article, the effects of ATP on body composition, energy intake, and energy expenditure as secondary outcome measures in the same patients are reported.

PATIENTS AND METHODS

Patients with NSCLC, stage IIIB or IV, were randomized to receive either 10 intravenous, 30-hour ATP infusions every 2 to 4 weeks or no ATP. Fat mass (FM), fat-free mass (FFM), and arm muscle area were assessed at 4-week intervals for 28 weeks. Food intake, body cell mass (BCM), and resting energy expenditure (REE) were assessed at 8-week intervals for 16 weeks. Between-group differences were tested for statistical significance by repeated-measures analysis of covariance.

RESULTS

Fifty-eight patients were randomized (28 ATP, 30 control). No change in body composition over the 28-week follow-up period was found in the ATP group, whereas, per 4 weeks, the control group lost 0.6 kg of FM (P =.004), 0.5 kg of FFM (P =.02), 1.8% of arm muscle area (P =.02), and 0.6% of BCM/kg body weight (P =.054) and decreased 568 KJ/d in energy intake (P =.0001). Appetite also remained stable in the ATP group but decreased significantly in the control group (P =.0004). No significant differences in REE between the ATP and control groups were observed.

CONCLUSION

The inhibition of weight loss by ATP infusions in patients with advanced NSCLC is attributed to counteracting the loss of both metabolically active and inactive tissues. These effects are partly ascribed to maintenance of energy intake.

Do patients with nonmetastatic non-small cell lung cancer demonstrate altered resting energy expenditure?

BACKGROUND

The cancer cachexia syndrome occurs in patients with non-small cell lung cancer (NSCLC) and includes elevated resting energy expenditure (REE). This increase in REE leads to weight loss, which in turn confers a poor prognosis. This study was undertaken to determine whether the cancer cachexia syndrome occurs in patients with nonmetastatic NSCLC.

METHODS

In this case-control study, 18 patients with nonmetastatic NSCLC (stages IA to IIIB) were matched to healthy controls on age (+/- 5 years), gender, and body mass index (+/- 3 kg/m2). Only 4 cancer patients had experienced > 5% weight loss. Cancer patients and controls were compared on the basis of: (1) unadjusted REE, as measured by indirect calorimetry; (2) REE adjusted for lean body mass, as measured by dual x-ray absorptiometry; (3) REE adjusted for body cell mass, as measured by potassium-40 measurement; and (4) REE adjusted for total body water, as measured by tritiated water dilution.

RESULTS

We observed no significant difference in unadjusted REE or in REE adjusted for total body water. However, with separate adjustments for lean body mass and body cell mass, cancer patients manifested an increase in REE: mean difference +/- standard error of the mean: 140+/-35 kcal/day (p = 0.001) and 173+/-65 kcal/day (p = 0.032), respectively. Further adjustment for weight loss yielded similarly significant results.

CONCLUSIONS

These results suggest that the cancer cachexia syndrome occurs in patients with nonmetastatic NSCLC and raise the question of whether clinical trials that target cancer cachexia should be initiated before weight loss.

Biphasic cytotoxic mechanism of extracellular ATP on U-937 human histiocytic leukemia cells: involvement of adenosine generation

Since extracellular ATP can exhibit cytotoxic activity in vivo and in vitro, its application has been proposed as an alternative anticancer therapy. In this study we investigated the mechanisms of ATP-induced cytotoxicity in a human leukemic cell line (U-937). ATP added as a single dose exceeding 50 microM was cytostatic or even cytotoxic for U-937 cells. Interestingly, growth inhibition by ATP (50-3500 microM) showed a biphasic dose response. Up to 800 microM, ATP was cytotoxic in a dose-dependent manner (EC(50) 90 microM). In a range between 800 and 2500 microM, cell count was markedly higher despite the higher ATP concentrations. The cytotoxic effect of ATP could be antagonized by addition of uridine as a pyrimidine source and, alternatively, by addition of the nucleoside transmembrane inhibitor dipyridamole. The apoptosis-inducing adenosine A(3) receptor was not involved in measurable quantities, since (1) adenosine did not lead to an elevation of intracellular calcium levels, and (2) an unselective A(1-3) antagonist (ULS-II-80) could not abrogate the cytotoxic effect. Experiments monitoring extracellular nucleotide metabolism confirmed the assumption that the long-term production and continuous uptake of adenosine, which is extracellularly generated by degradation of ATP, led to an intracellular nucleotide imbalance with pyrimidine starvation. The biphasic dose response to higher ATP concentrations could be explained by the rapid degradation of lower ATP concentrations (300 microM) to adenosine by serum-derived enzymes, whereas higher concentrations (900 microM) only produced small amounts of adenosine due to forward inhibition of AMP hydrolysis by prolonged high ADP levels. FACS analysis revealed that at lower adenosine concentrations (300 microM) a reversible G(1) phase arrest of the cell cycle was induced, whereas higher concentrations (1000 microM) triggered apoptosis. Considering ATP as a potential cytostatic drug, our data have important implications concerning metabolic interactions of administered nucleotides.

Adenosine triphosphate: established and potential clinical applications

Adenosine 5'-triphosphate (ATP) is a purine nucleotide found in every cell of the human body. In addition to its well established role in cellular metabolism, extracellular ATP and its breakdown product adenosine, exert pronounced effects in a variety of biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation and liver glycogen metabolism. These effects are mediated by both P1 and P2 receptors. A cascade of ectonucleotidases plays a role in the effective regulation of these processes and may also have a protective function by keeping extracellular ATP and adenosine levels within physiological limits. In recent years several clinical applications of ATP and adenosine have been reported. In anaesthesia, low dose adenosine reduced neuropathic pain, hyperalgesia and ischaemic pain to a similar degree as morphine or ketamine. Postoperative opioid use was reduced. During surgery, ATP and adenosine have been used to induce hypotension. In patients with haemorrhagic shock, increased survival was observed after ATP treatment. In cardiology, ATP has been shown to be a well tolerated and effective pulmonary vasodilator in patients with pulmonary hypertension. Bolus injections of ATP and adenosine are useful in the diagnosis and treatment of paroxysmal supraventricular tachycardias. Adenosine also allowed highly accurate diagnosis of coronary artery disease. In pulmonology, nucleotides in combination with a sodium channel blocker improved mucociliary clearance from the airways to near normal in patients with cystic fibrosis. In oncology, there are indications that ATP may inhibit weight loss and tumour growth in patients with advanced lung cancer. There are also indications of potentiating effects of cytostatics and protective effects against radiation tissue damage. Further controlled clinical trials are warranted to determine the full beneficial potential of ATP, adenosine and uridine 5'-triphosphate.